storage of fresh ginger rhizomes - university of hawaiʻi · 2018. 1. 18. · the ginger preserved...
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Storage of Fresh Ginger RhizomesERNEST K. AKAMINE
~. I
CREATING THE LAND-GRANT COLLEGE SYSTEM
CONTENTS
PAGE
Storage Decay 11
Physiological Breakdown 14
DISCUSSION . 20
ACKNOWLEDGMENTS
Without the cooperation and assistance of many individuals, institutions, and firms, this study could not have been accomplished. With grateful appre ciation the following acknowledgments are made:
N. Ikeda of Hilo Farmers' Exchange, Ltd., served as liaison between the ginger growers and the University of Hawaii and coordinated the shipping of the rhizomes from Hilo to Honolulu, where I. Shimizu of the Hawaii Farmers' Cooperative Association received the shipments.
K. Sunada and the other members of the Aloha Ginger Growers' Associa tion on the island of Hawaii supplied nearly all of the experimental rhizomes. Some rhizomes were also donated by A. Ikene, C. K. Higa, K. Tanaka, and S. Yogi, on Oahu. S. Takei, C. Maruyama, M. Ueda, and K. Mihata of the University of Hawaii Agricultural Extension Service assisted in contacting the growers and arranging for the procuring of the rhizomes for the tests.
F. Hisanaga of the State Department of Agriculture office in Hilo assisted in the grade aspects of exported ginger. M. Ishii of the Department of Plant Pathology of the Hawaii Agricultural Experiment Station identified the decay organisms on stored rhizomes. Gamma irradiation was administered by the Fruit Fly Laboratory of Entomology Research Branch, United States Depart ment of Agriculture. Sorbistat-K was donated by Chas. Pfizer and Co., Inc. Sta-Fresh Wax 920D was supplied by W. Yee of the University of Hawaii Agricultural Extension Service.
THE AUTHOR
ERNEST K. AKAMINE is Associate Plant Physiologist at the Hawaii Agricul tural Experiment Station.
Storage of Fresh Ginger Rhizomes
by Ernest K. Akamine
INTRODUCTION
Ginger is mentioned in the early literature of China and India as a spice. Thus it is one of the earliest of known spices . In the 16th century, the Spaniards introduced it into the West Indies and Mexico (5). The ginger of commerce is prepared from the underground stem or rhizome of Zingiber officinale Roscoe. It is marketed mostly in two forms : dried ginger and preserved ginger. While the ginger preserved in syrup is used as such, the dried ginger is employed in culinary preparations (soups, gingerbread, pickles, puddings, and curries) and in beverages (ginger ale and ginger beer ) . It is also used for medicinal pur poses (5). Major ginger-producing areas of the world are India, Malaya, China, West Africa, and the West Indies (3).
In Hawaii, ginger is marketed as fresh rhizomes which are also shipped to the mainland market. Two types of edible ginger are grown: the la rge type known locally as " Chinese" ginger and the small type known as "Japanese" ginger. Only the former type is grown to any great extent. Most of the plantings a re in small areas. Because of the prevalence of certain diseases on the island of Oahu, the ginger-growing areas seem to be shifting to the island of Hawaii, especially in the vicinity of Hilo from where most, if not all, of the ginger for the mainland market is exported. The total production for 1960 for the entire State as officially reported (9) was 905,000 pounds from a total of 32 acres. Of this production, 313,000 pounds (34.6 percent) were shipped to the Mainland by steamer without refrigeration. The wholesale value of the shipment was $61,588.00. It is estimated that shipment from Hawaii represents only about 7 percent of the total amount imported into the mainland United States annually, the remainder being supplied by foreign countries. Some for eign sources of ginger are: British Western Pacific Islands, Cuba, Hong Kon g, and Taiwan (Formosa) (8). It is reported that Hawaiian ginger, because of its higher quality, commands a better price on the mainland market than foreign importations.
In Hawaii, ginger is normally harvested from January to about April. At this time of the year, however, the prices are at the minimum because of the large imports by the United States from foreign sources. In order to obtain
higher prices, some farmers have delayed harvesting until the fall and later, but this has not been satisfactory because of the reduced quality of the rhi zomes due to epidermal peeling, disease and insect damage, sprouting, and disturbance to the new growth which is left in the ground to complete its growth cycle. Thus it appears that the highest quality rhizomes are those that are harvested immediately after they are mature, i.e., when the above-ground portions of the plants are dead. These rhizomes are plump and free from decay, insect damage, sprouting, and surface discoloration.
The object of this investigation was to develop a method which will per mit the storage of ginger rhizomes for several months without loss of quality and salability. The following are the factors that decrease the quality of rhizomes under ordinary storage: surface shrivelling and loss of weight due to desiccation; decay; physiological breakdown; sprouting; and surface dis coloration due to anthocyanin pigmentation (purple). This research therefore was directed toward the prevention of these factors in rhizomes stored for extended periods.
GENERAL PROCEDURE
Freshly harvested rhizomes obtained from various sources on the island of Hawaii were shipped by barge to Honolulu where the studies were con ducted. A few tests were conducted on rhizomes harvested on the island of Oahu. When received unwashed, and unless used otherwise, they were washed with water and air-dried in the laboratory before using in experiments. In most cases, these rhizomes were used in experiments no more than 2 or 3 days after harvest. Unless otherwise stated, the rhizomes used in the experiments were from the current growth, i.e., the so-called "1-year" rhizomes. ("2-year" rhizomes are those from the previous crop which were not harvested but al lowed to resprout.)
Reduced temperature conditions were obtained by storage in walk-in reefers. Room temperature (70°-83° F. ) conditions were effected by storage in the laboratory atmosphere. A sling psychrometer was employed to measure rel ative humidity in storage rooms. The polyethylene bags used in the tests were of gauge 0015 and two sizes (4" X 3" X 13" and 6" X 3" X 15") and sealed by tying the tops into knots. The paper bags ( Otter Kraft ) were of 5-pound size and were used unsealed. Controlled relative humidities were ob tained with solutions of sulfuric acid, which were adjusted to the required concentrations (10) each time the samples were removed for weighing and examining. The solutions were placed at the bottom of large desiccators, and the rhizomes were stored on false bottoms above the solutions. Treatments were replicated with sections of rhizomes, and unless otherwise stated, each section weighed approximately 4 ounces. All dipping treatments were effected at room temperature and the treated rhizomes were air-dried in the labora tory to remove surface moisture prior to storage. Wherever feasible, statistical analysis was employed to determine significance of differences 1 etween treat ment means at P = .05. Detailed procedures are given for the experiments described in the text.
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RESULTS
Surface Shrivelling and Weight Loss
In order to meet the grade standards of exported ginger ( 6) the rhizomes, among other things, must be free from surface shrivelling due to loss of moisture. An experiment (9 rhizomes per treatment) was conducted to compare the relative rate of loss in weight between I -year and 2-year rhizomes in stor age in paper bags at temperatures of 35°, 45° , 55°, 70°, and 70°-83° F., at average relative humidities of 82.9, 74.6, 85.6, 62.6, and 59.2 percent, respec tively. After 25 days of storage, the results indicated that the 1-year rhizomes lost significantly more weight than the older rhizomes at all storage conditions. The moisture content of the I-year and 2-year rhizomes was 88.7 and 81.4 percent, respectively. These facts emphasized the imprrtance of preventing the desiccation of the rhizomes from the current crop.
In the next experiment, an attempt was made to determine the areas of moisture loss on the rhizomes. Only young unsprouted tip sections, each with a single cut surface and weighing approximately 26 grams, were used. The treatments (4 rhizomes each) consisted of covering either the cut end only, surface only, or both the cut end and surface ( complete covering) with melted paraffin. An untreated lot was also maintained. After initial weighing, the rhizomes were stored in paper bags at room temperature. The loss in weight as determined by weighing at intervals is graphically presented in figure 1, which clearly shows the effects of differential covering. Of the two areas of moisture loss, more moisture was lost from the cut surface than from the intact surface. However, the minimum loss in weight was obtained by com pletely covering the rhizome.
Commercial fruit and vegetable waxes ( undiluted preparations) were next used in attempts to decrease loss of moisture in stored rhizomes. In table 1 are recorded results of exploratory experiments in which composite samples of treated and untreated rhizomes were stored in paper bags at room tempera ture. The durations of the tests were not long enough to determine the effect of the waxes on sprouting.
TABLE 1. Effect of commercial fruit and vegetable waxes on loss of weight in ginger rhizomes
No. of rhizome No. of days % loss Experiment Wax treatment sections in storage in weight
Brogdex None
12 12
1+ 14
19.7 12.8
None 4 4
' Cut End and Surface Paraffined (Sprouts 1.1 cm .)
2 4 10 12 14 16 18 20 22 26 28
DAYS IN STDRAGI;
FIGURE 1. Loss in weight and length of sprouts of ginger rhizomes in storage at room temperature as affected by differential covering with paraffin.
Data in table 1 indicated that waxing with commercial preparations accel erated the loss of weight. Replicated experiments were then conducted with these and other commercial waxes.
In a replicated test ( 5 rhizomes per treatment), there was no difference in the rate of weight loss between rhizomes waxed with Johnson's Potato Sprout Inhibitor Wax (full strength) and untreated rhizomes in storage in paper bags at room temperature for 2 weeks. In another test, dilutions ( Y2 , l/4 , and Ys strengths) of this preparation produced similar results.
In another test, two fruit waxes (Food Machiner y and Chemical Corp. ) were used full strength. Eight rhizomes received each treatment. They were stored in paper bags at room temperature. The results are recorded in table 2.
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TABLE 2. Effect of waxes on weight loss and sprouting in stored ginger rhizomes
A vera,ge % loss Percent sprouted Average% loss Average length in weight rhizomes in weight (cm. ) of sprout,
Treatment in 13 days in 36 days in 60 days in 60 days
Sta-Fresh \Vax #920 4.2 100.0 11.8* 1.4*
Sta-Fresh \Vax #920D 5.2 100.0 12.5* 1.2*
None 4.2 12.5 9.3 0.9
*Significantly greater than corresponding controls .
During the time previous to appea rance of sprouts ( the first 13 days ), there was no difference in the loss of weight between waxed and untreated lots (table 2 ) . At the end of the experiment (60 days), both waxed lots lost sig nificantly more weight than the untreated lot. However, sprouts in the waxed lots were also significantly longer than those in the untreated lot. This and the earlier sprouting of the waxed lots as shown by the data for the 36th day indicated that the greater loss in weight was due to the greater respiration rate accompanying elongation of the sprouts. Thus it seems that the waxes employed in this lot did not affect the percentage of loss in weight due to desiccation.
An effective method to reduce loss of weight is to store the rhizomes in poly ethylene bags. However, this induces mold growth' as indicated in the results of a typical experiment recorded in table 3. A relatively high percen tage of moisture loss occurred in the rhizomes stored at the two lowest tempera tures in spite of r elatively high storage humidities, especially in those stored in paper bags. This was due to tissue shrinkage as a result of physiological breakdown which was more pronounced at 35° than at 45° F. Physiological breakdown is characterized by softening, shrinkage, shrivelling, and oozing ( especially at cut ends) of the rhizome followed by mold growth as secondary infection.
Experiments with perforated polyethylene bags (20 to 100 pin-point per forations) produced results similar to those obtained with unperforated bags. Thus the beneficial effect of high humidity storage in preventing moisture loss obtained by the use of polyethylene bags was nullified by an increase in storage decay.
In the next experiment, an attempt was made to determine the lowest rela tive humidity at which loss of moisture from the rhizomes was prevented at room temperature. The results are recorded in table 4 .
10rganisms were identified as follows: Rhizopus sp., Penicillium sp., Tric/1oderma sp., Rhizoctonia sp., and Fusarium sp.
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TARLE 3. Effects of packaging on ginger rhizomes stored at various temperatures ( 6 rhizomes per treatment)
Average % Average Average % Storage weight loss mold status relative humidity
Package temperature ( °F.) in 37 days* in 37 days in storage rooms
Polyethylene Paper
35 35
0.4 13.0
Severe None 59.2
,v\JJ. differences between polyethylene bag and paper bag for all temperatures are statis- tically significant.
••Also physiological breakdown.
TABLE 4. Effects of relative humidity on ginger rhizomes stored at room temperature (8 rhizomes per treatment)
Average % Average Average % relative loss in weight Average sprout surface-shrivelling humidity in 26 days* mold status status status
10 18.9 None Dead** Severe 25 14.3 None Dead** Severe 35 10.8 None Alive Slight 65 10.7 None Alive None 75 0.0 Moderate Alive None 90 0.0 Severe Alive None
100 0.0 Severe Alive None
•Significant order: 18.9 > 14.3 > 10.8 = 10.7 > 0.0 = 0.0 = 0.0%. **Sprouted and died without making any further growth.
It is seen from the data in table 4 that the lowest relative humidity required for prevention of loss in weight at room temperature was 75 percent, which also prevented surface shrivelling. At this humidity, however, moderate mold development and sprouting occurred. Molding and sprouting are undesirable in grade standards ( 6) for ginger rhizomes intended for shipment.
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Storage Decay The removal of soil from ginger rhizomes is a quarantine as well as a grade
requirement for the export trade (6) . Commercially, soil is removed from the rhizomes either by washing with water or by brushing off the dry, loose soil particles. The effect of these two methods on mold development was deter mined. The results are recorded in table 5. With the exception of rhizomes stored at 35° and 45° F., at which temperatures physiological breakdown occurred in both washed and unwashed rhizomes stored in both polyethylene and paper bags, washed rhizomes stored under high humidity conditions in polyethylene bags at the other temperatures had much less mold development than corresponding brushed rhizomes ( table 5). Under lower humidity condi tions as existed in paper bags, however, there was no differrnce in the mold status between corresponding lots stored at different temperatures, there being only slight, if any, mold growth.
The use of a detergent as a possible mold control measure was next investi gated. The data presented in table 6 show doubtful advantage of using such a preparation for rhizomes stored in polyethylene bags at room temperature.
After washing, ginger rhizomes are normally cured at room temperature for various periods before being packed for shipment. In two replicated tests ( 4 rhizomes per treatment for both tests), rhizomes were cured for 4 and 7 days before storage in polyethylene bags at various temperatures (35°, 45°, 55°, 70°, and 70°-83° F.). Curing was of no advantage in terms of mold control, because all cured and uncured lots molded to the same degree.
All attempts made to control molding of ginger rhizomes by the use of hot water were unsuccessful. In two experiments ( 8 rhizomes per treatment for both experiments) in which hot water temperatures used ranged from ll0°- 1400 F. for dipping periods ranging from 5 to 40 minutes, treated rhizomes molded to the same degree as untreated ones in polyethylene bags at room temperature. Temperatures of 130° F. and higher injured the rhizome tissues. In another test ( 4 rhizomes per treatment), hot water-treated rhizomes in storage in paper bags did not have any lower incidence of molding than untreat ed lots when stored at temperatures of 35°, 45°, 55°, 70°, and 70°-83° F.
Ginger rhizomes were dipped in solutions of two commercial food preserva tives (sodium benzoate and potassium sorbate ) for 5 minutes, then stored in polyethylene bags at room temperature for 9 days. Sodium benzoate in con centrations from 0.05 to 1.0 percent ( two tests each with 7 rhizomes per treat ment) and potassium sorbate (Sorbistat-K ) (2) in concentrations from 1 to 8 percent (two tests each with 6 rhizomes per treatment ) were ineffective in controlling mold development.
In two tests ( each with 6 rhizomes per treatment) ginger rhizomes were dipped in solutions of sodium hypochlorite ( commercial "Bleachrex") for 10 minutes, then stored in polyethylene bags for 28 days at room temperature_ All concentrations used (125 to 10,000 p. p.m.) were ineffective in controlling mold growth. The highest concentration caused epidermal peeling. In another test ( 6 rhizomes per treatment ), rhizomes treated with sodium hypochlorite at concentrations varying from 2,500 to 10,000 p.p.m. and then stored in paper bags at room temperature for a month wern all bleached by the treatment.
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TABLE 5. Effect of brushing and washing on mold development in stored ginger rhizomes ( 8 rhizomes per treatment)
Stora,ge Average mold status
35 Polyethylene Severe Severe physiological breakdown 35 Paper Severe Severe physiological breakdown
45 Polyethylene Severe Light physiological breakdown Soil re- 45 Paper Severe Light physiological breakdown
moved by brushing 55 Polyethylene Severe
55 Paper Light
35 Polyethylene Moderate Severe physiolo,gical breakdo"'n 35 Paper Moderate Severe physiolo,gical breakdown
Soil re- 45 Polyethylene Severe Light physiological breakdown moved by 45 Paper Severe Light physiological breakdown washing with tap 55 Polyethylene None Purple pigmentation on cut ends water 55 Paper Light and intact surface
70 Polyethylene None Purple pigmentation on cut ends 70 Paper None and intact surface
70-83 Polyethylene Light 70-83 Paper None
Three commercial fungicides were employed in attempts to control mold growth in rhizomes stored in polyethylene bags at room temperature. The degree of effectiveness of these fungicides is shown in the combined data of two experiments (each with 8 rhizomes per treatment) recorded in table 7. The data indicate that Orthocide 50 and Zerlate have possibilities as mold inhib itors. However, these materials cannot be recommended for commercial use on ginger rhizomes without prior clearance for possible toxic residues.
The effects of modified atmosphere storage of ginger rhizomes were deter mined at room temperature. Modified atmospheres 'Vere obtained by propor-
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TABLE 6. Detergent as a mold inhibitor in stored ginger rhizomes ( 6 rhizomes per treatment}
Storage Average mold status Treatment temperature (°F.) Storage package after 29 days in storage
Washed only 3S Polyethylene Severe** \Vashed only 3S Paper Severe**
Washed + detergent* 3S Polyethylene Severe** Washed + detergent* 35 Paper Severe**
Washed only 70-83 Polye thylene Moderate \Vashed only 70-83 Paper Nooe
Washed + detergent* 70-83 Polyethylene Light Washed + detergent* 70-83 Paper Nooe
•New Pink Dr.eft (1 level tablespoon/ 2 qu,,~ts water, 5-minute dip). ••Also physiological breakdown.
TABLE 7. Fungicides as mold inhibitors in ginger rhizomes stored m polyethylene bags at room temperature
% concentration Average mold status Fungicide (water suspension)* after 14 days
Neo-Vita** Zerlate*** Zerlate Orthocide 50**** Orthocide 50 Orthocide 50 \Vater only None
1.5 o.s 1.0 0.5 0.75 1.0
Severe Severe Nooe Light Light Very light Severe Moderate
•5-minute dips. ••Re·mark Chemical Co.
***Zinc dimethyldithiocarbamate. ****Wettable preparation containing 50% Captan (N-trichloromethylmercapto·4-cyclo·
hexene·l , 2-dicarboximide).
tionately mixing carbon dioxide with air by means of flowmeters. The carbon dioxide-air mixture was humidified by bubbling through water and then passed into large glass jars (9% gallons) containing the rhizomes (10 per treatment) at atmospheric pressure. The results are shown in table 8.
That oxygen tensions lower than that in air were conducive to mold devel opment in stored ginger rhizomes is shown in table 8. In another test, seven rhizome sections stored in an airtight glass jar (1-gallon capacity) at room temperature developed severe molding in 21 days, whereas those stored in a non-airtight jar developed only a limited amount of mold.
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TABLE 8. Effects of modified atmosphere storage on ginger rhizomes at room temperature ( 17 days storage)
Assumed Average 0, tension Average sprout length
Treatment (%) mold status (cm.)
Air only 21.0 Slight 1.5* 1/2 Air+ 1h CO, 10.5 Moderate 0.5 'A A ir + ~ CO, 5.25 Severe 0.0** CO, only 0.0 Severe 0.0**
*Significantly greater than % Air + ~~ CO, treatment. ••When removed from the jars at the end of the storage period and exposed to atmos
pheric conditions, the rhizomes developed typical symptoms of physiological breakdown in 1 week. There was no sprouting.
Results reported in table 3, and those of an additional test ( 5 rhizomes per treatment ) in which rhizomes were stored in polyethylene bags at various temperatures, indicated that high humidities were conducive to mold develop ment at all temperatures between 35° F. and room temperature. Results of five experiments (each with 5 to 12 rhizomes per treatment ) in which rhizomes were stored under maintained humidities at various temperatures were combined and are recorded in table 9.
TABLE 9. Effect of relative humidity on average mold development in ginger rhizomes sto red at various temperatures (summary of five experiments in which the number of rhi zomes used per treatment varied from 5 to 12 and the storage period ranged from 26 to 31 days )
Tem perature (OF.) 10 25
Relative humidity (%)
35 45 55 70
Mold* Mold* Mold !\fold Mold Mold
•Also physiological breakdown.
At temperatures of 55° F. and above, humidities of 65 percent and lower prevented mold growth (table 9). At 35° and 45° F. storage, molding occurred probably as a result of secondary infection following physiological breakdown under both high and low relative humidities.
Physiological Breakdown
In experiments already described ( tables 3, 5, 6, and 9) and in others, storage temperatures of 45° F. and lower always resulted in physiological breakdown of the ginger rhizomes regardless of storage humidity. At these
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temperatures, rhizomes stored in polyethylene and paper bags were similarly affected. Freezing caused the rhizomes to break down and become soft upon thawing. That prolonged exposure to reduced oxygen tension may induce physiological breakdown even at room temperature was indicated in an experi ment in which after storage under controlled oxygen tension, the unsprouted rhizomes were exposed to air at room temperature. In 1 week, these rhizomes developed physiological breakdown without sprouting ( table 8).
Sprouting
The effect of certain wax preparations upon sprouting was discussed pre viously ( table 2 ) . Another wax preparation in which a sprout inhibitor is incorporated (Johnson's Sprout Inhibitor Wax for Potatoes) was used in attempts to control sprouting. The use of this material full strength reduced sprouting in rhizomes stored at room temperature, but it also increased mold ing. The results obtained by the use of various dilutions of this preparation are recorded in table 10.
According to table 10, the potato inhibitor wax at a concentration of one half strength reduced sprout growth, but it had no effect on the number of rhizomes which sprouted. Unlike the full-strength wax, the diluted prepara tions had no effect on mold growth.
TABLE 10. Effect of Johnson's Sprout Inhibitor Wax for Potatoes on sprouting in ginger rhizomes stored at room temperature for 34 days (5 rhizomes per treatment)
Average Average Wax Sprouted rhizomes longest sprout mold
concentration Package (%) (cm.) status
'h strength Polyethylene 100.0 o.s• Moderate 'h strength Paper 100.0 o.s• Slight
* strength Polyethylene 100.0 2.0 Moderate 'A strength Paper 100.0 1.9 None
Vii strength Polyethylene 100.0 2.2 Moderate Vii strength Paper 100.0 2.1 None
None Polyethylene 100.0 2.3 Moderate None Paper 100.0 1.6 None
•Significantly Jess than corresponding controls.
Maleic hydrazide has been used to control sprouting in potatoes, carrots, and onions (4). When used at a concentration of 1,000 p.p.m., this chemical had no effect on degree of sprouting of ginger rhizomes in storage at 70° F. and room temperature. At a concentration of 2,000 p.p.m., it significantly reduced sprout growth, although it had no effect on the percentage of sprouted rhizomes ( table ll).
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TABLE 11. Effect of maleic hydrazide on sprouting of ginger rhizomes in storage at room temperature for 29 days ( 6 rhizomes per treatment)
Average Sprouted rhizomes longest sprout
Treatment Package (%) (cm.)
Maleic hvdrazide* Polyethylene 100.0 0.8** Maleic hydrazide* Paper 100.0 0.5**
None Polyethylene 100.0 1.6 None Paper 100.0 1.1
*2,000 p.p.m., 2-hour dip at room temperature. **Significantly less than corresponding controls.
The use of naphthaleneacetic acid as a sprout inhibitor of various crops is well known (1, 4). Soaking ginger rhizomes (7 rhizomes per treatment) in a solution of sodium salt of naphthaleneacetic acid (100 mg/1) for 1 and 2 days at room temperature had no effect on sprouting of rhizomes when stored at room temperature. The effect of treating with higher concentrations of this chemical was next determined. According to the data obtained in this test (table 12), the effective concentration of naphthaleneacetic acid for the pre vention of sprouting was 200 mg/1. However, this treatment resulted in physi ological breakdown and severe molding.
TABLE 12. Effect of naphthaleneacetic acid (sodium salt) on sprouting of rhizomes in storage at room temperature for 27 days ( 6 rhizomes per treatment)
Average Average Sprouted rhizomes longest sprout mold
Treatment* Package (%) (cm.) status
Naphthaleneacetic acid (200 mg/I) Paper 0.0 Severe***
Naphthaleneacetic acid ( 150 mg/I) Polyethylene 100.0 1.0** Severe
Naphthaleneacetic acid (150 mg/I) Paper 100.0 0.6** Severe
Water only Polyethylene 100.0 4.5 Moderate Water only Paper 100.0 1.7 None
None Polyethylene 100.0 1.8 Moderate None Paper 100.0 0.8 None
*24-hour soaking at room temperature. **Significantly Jess than corresponding water control, but not significantly different from
dry control. ***Also physiological breakdown.
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Irradiation with gamma rays has been shown to prevent sprouting of potato tubers (7). In three experiments (each with 10 rhizomes per treatment ) the effect of gamma radiation (Co"0
) on sprouting of ginger rhizomes when stored in polyethylene and paper bags at room temperature for 28 days was determined. Dosages of 25,000 and 50,000 R. merely reduced the growth of the sprouts with concomitant increase in mold growth. Dosages of 75,000 and 100,000 R. completely inhibited sprouting but resulted in severe molding.
Three tests ( each with 14 rhizomes per treatment) were conducted to deter mine the effect of a fumigant upon sprouting of ginger rhizomes. Fumigation with methyl bromide at dosages of 2 and 2'/4 pounds per 1,000 cubic feet space for 2 hours at atmospheric temperature and pressure had no effect on sprouting of rhizomes stored in polyethylene and paper bags at room temperature for 28 days.
The effect of another fumigant, ethylene dibromide, on sprouting was tested in two experiments ( each with 12 rhizomes per treatment) . The results of one experiment, as shown in table 13, indicated that a low dosage (l/2 pound per 1,000 cubic feet) of the gas actually stimulated sprout growth in rhizomes when stored in polyethylene bags at 70° F. and room temperature; higher dosage ( 1 pound per 1,000 cubic feet) had no effect at room temperature storage. Similar results were produced in the other experiment.
TABLE 13. Effect of ethylene dibromide on sprouting of ginger rhizomes during storage for 32 days
Storage Average Ethylene dibromide dosage temperature Sprouted rhizomes longest sprout
( lb/ 1,000 cubic feet)* (OF.) ( %) (cm.)
1h 70 100.0 1.5** l/2 70-83 100.0 4.0**
I 70-83 100.0 2.8 None 70 100.0 0.9 None 70-83 100.0 2.7
• Fumigation for 2 hours at atmospheric temperature and pressure. ••Significantly greater than corresponding untreated lots.
The effect of modified atmosphere storage on mold development was dis cussed above. In the same experiment, the effect on sprouting was also studied (table 8). Among the treatments used, the lowest oxygen tension permitting sprouting was that afforded by a mixture of l/2 air and % CO 2 ( 10.5 percent 0 2 ). Lower oxygen tensions prevented sprouting completely in controlled storage, but upon exposure to room temperature conditions, the rhizomes developed symptoms of physiological breakdown similar to those manifested in rhizomes stored at low temperatures. In an additional test in which 10 rhizome sections were stored in an airtight glass jar (1-gallon capacity) at room temperatu re for 2 weeks, only limited sprouting occurred as compared to that in an open jar.
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The degree of sprouting in polyethylene and paper bags at different temper atures was determined in three tests. As indicated in the data of a representa tive experiment, sprouting occurred only at 70° F. and room temperature (table 14). At 70° F. there was less sprouting in both types of packaging than at room temperature. Furthermore, at both temperatures there was less sprout ing in polyethylene bags than in paper bags, in spite of the higher humidity in the former packaging than in the latter. This again may be a manifestation of low oxygen tension limiting sprouting as previously discussed ( table 8). A further support for this contention was observed in the results of an experi ment ( figure 1 ) already described. At the conclusion of this experiment, the average length of sprouts in the completely paraffined lot was significantly less than that of sprouts in the two partially paraffined lots. This was probably the result of an apparent differential interference with respiratory gas exchange caused by the different degrees of covering.
TABLE 14. Sprouting of ginger rhizomes in polyethylene and paper bags at different temperatures ( 10 rhizomes per treatment)
Sprouted rhizomes in 57 days
Temperature (OF.) Package (%)
35 Polyethylene 0.0 35 Paper 0.0
45 Polyethylene 0.0 45 Paper 0.0
55 Polyethylene 0.0 55 Paper 0.0
70 Polyethylene 40.0 70 Paper 80.0
70-83 Polyethylene 80.0 70-83 Paper 100.0
The effect of controlled relative humidity on sprouting at room temperature was previously discussed to some extent in connection with loss of weight in stored rhizomes ( table 4 ) . According to the data in table 4, the rhizomes sprouted and remained alive for 26 days even at 35 percent relative humidity at room temperature. At lower humidities, they sprouted but the sprouts were short-lived.
In another test ( 10 rhizomes per treatment), rhizomes stored at relative humidities from 90 to 35 percent at 70° F. sprouted and remained alive for at least 49 days, whereas those stored at 25 percent did not even sprout. In an additional experiment (6 rhizomes per treatment) conducted at 55° F., rhizomes were stored at relative humidities ranging from 90 to 35 percent.
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None of these rhizomes sprouted. Rhizomes stored at 45° and 35° F. (10 rhi zomes per treatment) were prevented from sprouting. However, at these temperatures physiological breakdown resulted regardless of storage humidity.
Reference is again made to a previous experiment ( figure 1) in which it was shown that due to excessive desiccation, the average length of sprouts of the nonparaffined rhizomes was significantly less than those of the two partially paraffined lots.
Discoloration
Grade stipulation for export ginger does not allow any form of discoloration on the surface of rhizomes (6). The most prominent discoloration is a purple pigmentation that occurs especially on cut surfaces. In several tests under favorable conditions, this purple pigmentation was observed to occur on rhi zomes stored in polyethylene bags at 55° and 70° F. after prolonged storage (60 days or longer). It was not observed on rhizomes stored in paper bags or in humidity-controlled chambers (up to 90 percent relative humidity) at these temperatures. At 45° and 35° F., visible pigmentation did not occur at any of the relative humidities studied. It· appeared in rhizomes stored in polyethylene bags, but not in·· those in paper bags at room temperature.
To follow up on these leads, 10 rhizome sections were placed in a shallow dish and kept partly submerged with tap water at room temperature. At the end of 36 days, the purple pigment completely covered the cut ends and very faintly appeared on the intact surface of the rhizomes. Twelve rhizomes were planted in a soil flat which was placed in the open and kept moist. After 29 days, they were dug up and examined. Again all cut surfaces of the rhi zomes were covered heavily with the purple pigment and the intact surface was only lightly pigmented.
These results seemed to indicate that free moisture must be present for visible pigmentation to occur on the rhizomes. Due to condensation of moisture on the inner surface of polyethylene bags, this treatment represented a condition similar to that of rhizomes being placed in water or planted in soil. At 70° F. and room temperature, the juvenile leaves (sheaths) of the sprouts showed anthocyanin pigmentation typical of new shoots of many plants. Therefore, it appears that the development of pigment on the rhizome surface was a manifestation of the biochemical changes associated with_ shoot development from a dormant organ. At 55° F., although no sprouting occurred, the rhi zomes were not injured because upon removal to room temperature, they sprouted normally. Since in polyethylene bags at 55° F. the pigment developed though no sprouting occurred, it seems that this temperature represented a threshhold condition which barely prevented sprouting. In fact some rhizomes in a few cases actually made some weak attempts to sprout.
Controlled Temperature and Humidity Storage
Using preliminary data gleaned during the progress of the experiments described above, another test was conducted m an attempt to determine the
19
optimum conditions required for prolonged storage of ginger rhizomes. The rhizomes (10 per treatment ) were stored under various controlled temperature and humidity conditions. At intervals loss in weight was determined. Obser vations were also made on factors used as some of the criteria for unmarket ability of rhizomes for the export trade as formulated by government regula tions (6) : shrivelling due to desiccation; softness and shrivelling due to physiological breakdown; decay of any form; sprouting; and discoloration. The treatments were continued in storage as long as the rhizomes were in a marketable condition. The data are presented graphically in figure 2, which shows, in addition to actual loss in weight with storage time, the basis for termination of each treatment at the time indicated.
In general, the results in thi s experiment ( figure 2) were in agreement with those obtained in the other experiments previously c!escribed. Room tempera ture in combination with any relative humidity was again demonstrated to be ineffective for prolonged ginger storage, because of its inability to prevent sprouting even at humidities sufficiently low to cause desiccation. At the high humidity, though desiccation was prevented, there was the additional factor of molding coupled to sprouting. Storage at 35° F. in combination with any relative humidity was again detrimental. Physiological breakdown fol lowed by shrivelling and molding occurred in all cases at this temperature. At 55° F., it was again shown that sprouting can be prevented at each humidity tested. However, high relative humidity caused molding, and desiccation was excessive in low humidity storage. At the intermediate relative humidity of 65 percent, rhizomes were kept in a marketable condition for 188 days. Al though the loss in weight of the rhizomes was 16.5 percent during this period, surface shrivelling did not occur to a degree sufficient to make the rhizomes unmarketable. Half of these rhizomes were removed from the storage chamber, air-dried long enough at room temperature to remove moisture condensed on the surface, packed in a commercial carton, and stored at room temperature for 2 weeks to simulate shipping conditions. At the end of this period, the rhizomes were still in a marketable condition. Rapid loss in weight occurred after about the 6th month of storage so that at the end of the 7th month when storage was terminated shrivelling was to the extent that the rhizomes were considered unmarketable. These data indicate the possibility of storing ginger rhizomes for at least 6 months in a marketable condition, provided the temperature and relative humidity are properly controlled in the storage medium.
DISCUSSION
According to the results of studies presented above, the best storage condi tion for ginger rhizomes among those tested seems to be the one in which the temperature is maintained at 55° F. and the relative humidity at 65 percent. Under this condition the rhizomes may be safely stored for at least 6 months. During this period nea rly all the requirements for long-time storage are ful filled, i .e., surface shrivelling, storage decay, physiological breakdown, sprout ing, and surface discoloration are inhibited. In view of these advantages, the
20
30 PB - Physiological breakdown M - Mold Sh(d) - ShriveII ing due to des iccotion Sh(F-B) - Shrivelling due to physiological breakdown S - Sprouting
25
... / lO
z / /
15 /"' "' 0 I,,:) ... 35° F ., 35% Relative Hufflidity ..... 35 ° F., 65% Relative Humidity ... 35° F ., 90% Relative Humidityz ...
55 ° F ., 35% Relative Hum idity 55° F ., 65% Relative Humidity....."'
u
Room Temperature, 35% Relative Humidity Room Temperature, 65% Relative Humidity
e Room Temperature, 90% Relative HumidityIii
30 50 70 90 110 no - 150 170 190 210
DAYS IH STORAGE
FIGURE 2. Effects of temperature and relative humidity on stored ginger rhizomes.
loss in weight ( 16.5 percent) in the 6-month period is not considered to be critical. The use of this method of storage will enable the grower to manip ulate his harvest schedule to suit his shipping and marketing schedule.
SUMMARY AND RECOMMENDATIONS
Factors affecting the longevity of ginger rhizomes in storage were investi gated. The studies resulted in the discovery of an optimum medium for the storage of rhizomes for periods of 6 months or more. Based upon the results of these studies and the prevalent commercial methods of handling harvested ginger rhizomes, the following procedure is recommended for the storage and shipping of this commodity:
1. Wash off soil with water immediately after harvest.
2. Air-dry in shade for 1 or 2 days to partially heal cut surfaces on the rhizomes.
3. Store in a room in which the temperature is maintained at 55° F. and the relative humidity at 65 percent.
4. For shipping, remove from storage room and air-dry in the shade long enough to remove moisture of condensation.
5. Pack in commercial cartons for shipping without refrigeration.
22
. LITERATURE CITED
(1) AVERY, G. S., JR., E. B. JoHNSON, R. M. ADDOMS, and B. F. THOMSON. 1947. HORMONES AND HORTICULTURE. McGraw-Hill Book Co., Inc., New
York and London. Pp. 267-272.
(2) CHAS. PFIZER and Co., INC. 1960. SORBISTAT, SORBISTAT-K. Technical
Bulletin No. 101. 29 pp.
(3) COBLEY, L. S. 1956. AN INTRODUCTION TO THE BOTANY OF TROPICAL CROPS. Longmans, Green and Co., Inc., New York. xv + 357 pp.
(4) LEOPOLD, A. C. 1955. AUXINS AND PLANT GROWTH. University of Cali
fornia Press, Berkeley and Los Angeles. Pp. ::63-273.
(5) SILLS, V. E. 1961. PROCESSING AND MARKETING GINGER PRODUCTS. South
Pacific Bulletin 11(3): 58-61.
(6) TERRITORY OF HAWAII, BOARD OF COMMISSIONERS OF AGRICULTURE AND FORESTRY, DIVISION OF MARKETING. 1959. PROPOSED STANDARDS FOR HAWAII-GROWN GINGER ROOT (REVISED SECOND DRAFT). 6 pp. (Mimeo.)
(7) THOMPSON, H. C., and W. C. KELLY. 1957. VEGETABLE CROPS, 5th ed. McGraw-Hill Book Co., Inc., New York, Toronto, and London. 402 pp.
(8) UNITED STATES DEPARTMENT OF AGRICULTURE, FOREIGN AGRICULTURAL TRADE OF THE U.S. 1961. IMPORTS OF FRUITS AND VEGETABLES UNDER QUARANTINE, FISCAL YEAR 1960-61. 11 pp. (Mimeo.)
(9) WALLRABENSTEIN, P. P., S. M. DouE, R. YAMAGUCHI, and E. NIHEI. 1961. STATISTICS OF HAWAIIAN AGRICULTURE 1960. Hawaii Coop~rative Extension Service, University of Hawaii, Agricultural Economics Report No. 53. 58 pp. (Mimeo.)
(10) WILSON, R. E. 1921. HUMIDITY CONTROL BY MEANS OF SULFURIC ACID SOLUTIONS, WITH CRITICAL COMPILATION OF VAPOR PRESSURE DATA. four. Ind. & Eng. Chem. 13: 326--331.
23
HAWAII AGRICULTURAL EXPERIMENT STATION HONOLULU, HAWAII
LAURENCE H. SNYDER President of the University
MORTON M. ROSENBERG Dean of the College and
Director of the Experiment Station
CTAHR_Exp. 130_2017-11-07_175335
CTAHR_Exp. 130_2017-11-07_175400
CTAHR_Exp. 130_2017-11-07_175434
~. I
CREATING THE LAND-GRANT COLLEGE SYSTEM
CONTENTS
PAGE
Storage Decay 11
Physiological Breakdown 14
DISCUSSION . 20
ACKNOWLEDGMENTS
Without the cooperation and assistance of many individuals, institutions, and firms, this study could not have been accomplished. With grateful appre ciation the following acknowledgments are made:
N. Ikeda of Hilo Farmers' Exchange, Ltd., served as liaison between the ginger growers and the University of Hawaii and coordinated the shipping of the rhizomes from Hilo to Honolulu, where I. Shimizu of the Hawaii Farmers' Cooperative Association received the shipments.
K. Sunada and the other members of the Aloha Ginger Growers' Associa tion on the island of Hawaii supplied nearly all of the experimental rhizomes. Some rhizomes were also donated by A. Ikene, C. K. Higa, K. Tanaka, and S. Yogi, on Oahu. S. Takei, C. Maruyama, M. Ueda, and K. Mihata of the University of Hawaii Agricultural Extension Service assisted in contacting the growers and arranging for the procuring of the rhizomes for the tests.
F. Hisanaga of the State Department of Agriculture office in Hilo assisted in the grade aspects of exported ginger. M. Ishii of the Department of Plant Pathology of the Hawaii Agricultural Experiment Station identified the decay organisms on stored rhizomes. Gamma irradiation was administered by the Fruit Fly Laboratory of Entomology Research Branch, United States Depart ment of Agriculture. Sorbistat-K was donated by Chas. Pfizer and Co., Inc. Sta-Fresh Wax 920D was supplied by W. Yee of the University of Hawaii Agricultural Extension Service.
THE AUTHOR
ERNEST K. AKAMINE is Associate Plant Physiologist at the Hawaii Agricul tural Experiment Station.
Storage of Fresh Ginger Rhizomes
by Ernest K. Akamine
INTRODUCTION
Ginger is mentioned in the early literature of China and India as a spice. Thus it is one of the earliest of known spices . In the 16th century, the Spaniards introduced it into the West Indies and Mexico (5). The ginger of commerce is prepared from the underground stem or rhizome of Zingiber officinale Roscoe. It is marketed mostly in two forms : dried ginger and preserved ginger. While the ginger preserved in syrup is used as such, the dried ginger is employed in culinary preparations (soups, gingerbread, pickles, puddings, and curries) and in beverages (ginger ale and ginger beer ) . It is also used for medicinal pur poses (5). Major ginger-producing areas of the world are India, Malaya, China, West Africa, and the West Indies (3).
In Hawaii, ginger is marketed as fresh rhizomes which are also shipped to the mainland market. Two types of edible ginger are grown: the la rge type known locally as " Chinese" ginger and the small type known as "Japanese" ginger. Only the former type is grown to any great extent. Most of the plantings a re in small areas. Because of the prevalence of certain diseases on the island of Oahu, the ginger-growing areas seem to be shifting to the island of Hawaii, especially in the vicinity of Hilo from where most, if not all, of the ginger for the mainland market is exported. The total production for 1960 for the entire State as officially reported (9) was 905,000 pounds from a total of 32 acres. Of this production, 313,000 pounds (34.6 percent) were shipped to the Mainland by steamer without refrigeration. The wholesale value of the shipment was $61,588.00. It is estimated that shipment from Hawaii represents only about 7 percent of the total amount imported into the mainland United States annually, the remainder being supplied by foreign countries. Some for eign sources of ginger are: British Western Pacific Islands, Cuba, Hong Kon g, and Taiwan (Formosa) (8). It is reported that Hawaiian ginger, because of its higher quality, commands a better price on the mainland market than foreign importations.
In Hawaii, ginger is normally harvested from January to about April. At this time of the year, however, the prices are at the minimum because of the large imports by the United States from foreign sources. In order to obtain
higher prices, some farmers have delayed harvesting until the fall and later, but this has not been satisfactory because of the reduced quality of the rhi zomes due to epidermal peeling, disease and insect damage, sprouting, and disturbance to the new growth which is left in the ground to complete its growth cycle. Thus it appears that the highest quality rhizomes are those that are harvested immediately after they are mature, i.e., when the above-ground portions of the plants are dead. These rhizomes are plump and free from decay, insect damage, sprouting, and surface discoloration.
The object of this investigation was to develop a method which will per mit the storage of ginger rhizomes for several months without loss of quality and salability. The following are the factors that decrease the quality of rhizomes under ordinary storage: surface shrivelling and loss of weight due to desiccation; decay; physiological breakdown; sprouting; and surface dis coloration due to anthocyanin pigmentation (purple). This research therefore was directed toward the prevention of these factors in rhizomes stored for extended periods.
GENERAL PROCEDURE
Freshly harvested rhizomes obtained from various sources on the island of Hawaii were shipped by barge to Honolulu where the studies were con ducted. A few tests were conducted on rhizomes harvested on the island of Oahu. When received unwashed, and unless used otherwise, they were washed with water and air-dried in the laboratory before using in experiments. In most cases, these rhizomes were used in experiments no more than 2 or 3 days after harvest. Unless otherwise stated, the rhizomes used in the experiments were from the current growth, i.e., the so-called "1-year" rhizomes. ("2-year" rhizomes are those from the previous crop which were not harvested but al lowed to resprout.)
Reduced temperature conditions were obtained by storage in walk-in reefers. Room temperature (70°-83° F. ) conditions were effected by storage in the laboratory atmosphere. A sling psychrometer was employed to measure rel ative humidity in storage rooms. The polyethylene bags used in the tests were of gauge 0015 and two sizes (4" X 3" X 13" and 6" X 3" X 15") and sealed by tying the tops into knots. The paper bags ( Otter Kraft ) were of 5-pound size and were used unsealed. Controlled relative humidities were ob tained with solutions of sulfuric acid, which were adjusted to the required concentrations (10) each time the samples were removed for weighing and examining. The solutions were placed at the bottom of large desiccators, and the rhizomes were stored on false bottoms above the solutions. Treatments were replicated with sections of rhizomes, and unless otherwise stated, each section weighed approximately 4 ounces. All dipping treatments were effected at room temperature and the treated rhizomes were air-dried in the labora tory to remove surface moisture prior to storage. Wherever feasible, statistical analysis was employed to determine significance of differences 1 etween treat ment means at P = .05. Detailed procedures are given for the experiments described in the text.
6
RESULTS
Surface Shrivelling and Weight Loss
In order to meet the grade standards of exported ginger ( 6) the rhizomes, among other things, must be free from surface shrivelling due to loss of moisture. An experiment (9 rhizomes per treatment) was conducted to compare the relative rate of loss in weight between I -year and 2-year rhizomes in stor age in paper bags at temperatures of 35°, 45° , 55°, 70°, and 70°-83° F., at average relative humidities of 82.9, 74.6, 85.6, 62.6, and 59.2 percent, respec tively. After 25 days of storage, the results indicated that the 1-year rhizomes lost significantly more weight than the older rhizomes at all storage conditions. The moisture content of the I-year and 2-year rhizomes was 88.7 and 81.4 percent, respectively. These facts emphasized the imprrtance of preventing the desiccation of the rhizomes from the current crop.
In the next experiment, an attempt was made to determine the areas of moisture loss on the rhizomes. Only young unsprouted tip sections, each with a single cut surface and weighing approximately 26 grams, were used. The treatments (4 rhizomes each) consisted of covering either the cut end only, surface only, or both the cut end and surface ( complete covering) with melted paraffin. An untreated lot was also maintained. After initial weighing, the rhizomes were stored in paper bags at room temperature. The loss in weight as determined by weighing at intervals is graphically presented in figure 1, which clearly shows the effects of differential covering. Of the two areas of moisture loss, more moisture was lost from the cut surface than from the intact surface. However, the minimum loss in weight was obtained by com pletely covering the rhizome.
Commercial fruit and vegetable waxes ( undiluted preparations) were next used in attempts to decrease loss of moisture in stored rhizomes. In table 1 are recorded results of exploratory experiments in which composite samples of treated and untreated rhizomes were stored in paper bags at room tempera ture. The durations of the tests were not long enough to determine the effect of the waxes on sprouting.
TABLE 1. Effect of commercial fruit and vegetable waxes on loss of weight in ginger rhizomes
No. of rhizome No. of days % loss Experiment Wax treatment sections in storage in weight
Brogdex None
12 12
1+ 14
19.7 12.8
None 4 4
' Cut End and Surface Paraffined (Sprouts 1.1 cm .)
2 4 10 12 14 16 18 20 22 26 28
DAYS IN STDRAGI;
FIGURE 1. Loss in weight and length of sprouts of ginger rhizomes in storage at room temperature as affected by differential covering with paraffin.
Data in table 1 indicated that waxing with commercial preparations accel erated the loss of weight. Replicated experiments were then conducted with these and other commercial waxes.
In a replicated test ( 5 rhizomes per treatment), there was no difference in the rate of weight loss between rhizomes waxed with Johnson's Potato Sprout Inhibitor Wax (full strength) and untreated rhizomes in storage in paper bags at room temperature for 2 weeks. In another test, dilutions ( Y2 , l/4 , and Ys strengths) of this preparation produced similar results.
In another test, two fruit waxes (Food Machiner y and Chemical Corp. ) were used full strength. Eight rhizomes received each treatment. They were stored in paper bags at room temperature. The results are recorded in table 2.
8
TABLE 2. Effect of waxes on weight loss and sprouting in stored ginger rhizomes
A vera,ge % loss Percent sprouted Average% loss Average length in weight rhizomes in weight (cm. ) of sprout,
Treatment in 13 days in 36 days in 60 days in 60 days
Sta-Fresh \Vax #920 4.2 100.0 11.8* 1.4*
Sta-Fresh \Vax #920D 5.2 100.0 12.5* 1.2*
None 4.2 12.5 9.3 0.9
*Significantly greater than corresponding controls .
During the time previous to appea rance of sprouts ( the first 13 days ), there was no difference in the loss of weight between waxed and untreated lots (table 2 ) . At the end of the experiment (60 days), both waxed lots lost sig nificantly more weight than the untreated lot. However, sprouts in the waxed lots were also significantly longer than those in the untreated lot. This and the earlier sprouting of the waxed lots as shown by the data for the 36th day indicated that the greater loss in weight was due to the greater respiration rate accompanying elongation of the sprouts. Thus it seems that the waxes employed in this lot did not affect the percentage of loss in weight due to desiccation.
An effective method to reduce loss of weight is to store the rhizomes in poly ethylene bags. However, this induces mold growth' as indicated in the results of a typical experiment recorded in table 3. A relatively high percen tage of moisture loss occurred in the rhizomes stored at the two lowest tempera tures in spite of r elatively high storage humidities, especially in those stored in paper bags. This was due to tissue shrinkage as a result of physiological breakdown which was more pronounced at 35° than at 45° F. Physiological breakdown is characterized by softening, shrinkage, shrivelling, and oozing ( especially at cut ends) of the rhizome followed by mold growth as secondary infection.
Experiments with perforated polyethylene bags (20 to 100 pin-point per forations) produced results similar to those obtained with unperforated bags. Thus the beneficial effect of high humidity storage in preventing moisture loss obtained by the use of polyethylene bags was nullified by an increase in storage decay.
In the next experiment, an attempt was made to determine the lowest rela tive humidity at which loss of moisture from the rhizomes was prevented at room temperature. The results are recorded in table 4 .
10rganisms were identified as follows: Rhizopus sp., Penicillium sp., Tric/1oderma sp., Rhizoctonia sp., and Fusarium sp.
9
TARLE 3. Effects of packaging on ginger rhizomes stored at various temperatures ( 6 rhizomes per treatment)
Average % Average Average % Storage weight loss mold status relative humidity
Package temperature ( °F.) in 37 days* in 37 days in storage rooms
Polyethylene Paper
35 35
0.4 13.0
Severe None 59.2
,v\JJ. differences between polyethylene bag and paper bag for all temperatures are statis- tically significant.
••Also physiological breakdown.
TABLE 4. Effects of relative humidity on ginger rhizomes stored at room temperature (8 rhizomes per treatment)
Average % Average Average % relative loss in weight Average sprout surface-shrivelling humidity in 26 days* mold status status status
10 18.9 None Dead** Severe 25 14.3 None Dead** Severe 35 10.8 None Alive Slight 65 10.7 None Alive None 75 0.0 Moderate Alive None 90 0.0 Severe Alive None
100 0.0 Severe Alive None
•Significant order: 18.9 > 14.3 > 10.8 = 10.7 > 0.0 = 0.0 = 0.0%. **Sprouted and died without making any further growth.
It is seen from the data in table 4 that the lowest relative humidity required for prevention of loss in weight at room temperature was 75 percent, which also prevented surface shrivelling. At this humidity, however, moderate mold development and sprouting occurred. Molding and sprouting are undesirable in grade standards ( 6) for ginger rhizomes intended for shipment.
10
Storage Decay The removal of soil from ginger rhizomes is a quarantine as well as a grade
requirement for the export trade (6) . Commercially, soil is removed from the rhizomes either by washing with water or by brushing off the dry, loose soil particles. The effect of these two methods on mold development was deter mined. The results are recorded in table 5. With the exception of rhizomes stored at 35° and 45° F., at which temperatures physiological breakdown occurred in both washed and unwashed rhizomes stored in both polyethylene and paper bags, washed rhizomes stored under high humidity conditions in polyethylene bags at the other temperatures had much less mold development than corresponding brushed rhizomes ( table 5). Under lower humidity condi tions as existed in paper bags, however, there was no differrnce in the mold status between corresponding lots stored at different temperatures, there being only slight, if any, mold growth.
The use of a detergent as a possible mold control measure was next investi gated. The data presented in table 6 show doubtful advantage of using such a preparation for rhizomes stored in polyethylene bags at room temperature.
After washing, ginger rhizomes are normally cured at room temperature for various periods before being packed for shipment. In two replicated tests ( 4 rhizomes per treatment for both tests), rhizomes were cured for 4 and 7 days before storage in polyethylene bags at various temperatures (35°, 45°, 55°, 70°, and 70°-83° F.). Curing was of no advantage in terms of mold control, because all cured and uncured lots molded to the same degree.
All attempts made to control molding of ginger rhizomes by the use of hot water were unsuccessful. In two experiments ( 8 rhizomes per treatment for both experiments) in which hot water temperatures used ranged from ll0°- 1400 F. for dipping periods ranging from 5 to 40 minutes, treated rhizomes molded to the same degree as untreated ones in polyethylene bags at room temperature. Temperatures of 130° F. and higher injured the rhizome tissues. In another test ( 4 rhizomes per treatment), hot water-treated rhizomes in storage in paper bags did not have any lower incidence of molding than untreat ed lots when stored at temperatures of 35°, 45°, 55°, 70°, and 70°-83° F.
Ginger rhizomes were dipped in solutions of two commercial food preserva tives (sodium benzoate and potassium sorbate ) for 5 minutes, then stored in polyethylene bags at room temperature for 9 days. Sodium benzoate in con centrations from 0.05 to 1.0 percent ( two tests each with 7 rhizomes per treat ment) and potassium sorbate (Sorbistat-K ) (2) in concentrations from 1 to 8 percent (two tests each with 6 rhizomes per treatment ) were ineffective in controlling mold development.
In two tests ( each with 6 rhizomes per treatment) ginger rhizomes were dipped in solutions of sodium hypochlorite ( commercial "Bleachrex") for 10 minutes, then stored in polyethylene bags for 28 days at room temperature_ All concentrations used (125 to 10,000 p. p.m.) were ineffective in controlling mold growth. The highest concentration caused epidermal peeling. In another test ( 6 rhizomes per treatment ), rhizomes treated with sodium hypochlorite at concentrations varying from 2,500 to 10,000 p.p.m. and then stored in paper bags at room temperature for a month wern all bleached by the treatment.
ll
TABLE 5. Effect of brushing and washing on mold development in stored ginger rhizomes ( 8 rhizomes per treatment)
Stora,ge Average mold status
35 Polyethylene Severe Severe physiological breakdown 35 Paper Severe Severe physiological breakdown
45 Polyethylene Severe Light physiological breakdown Soil re- 45 Paper Severe Light physiological breakdown
moved by brushing 55 Polyethylene Severe
55 Paper Light
35 Polyethylene Moderate Severe physiolo,gical breakdo"'n 35 Paper Moderate Severe physiolo,gical breakdown
Soil re- 45 Polyethylene Severe Light physiological breakdown moved by 45 Paper Severe Light physiological breakdown washing with tap 55 Polyethylene None Purple pigmentation on cut ends water 55 Paper Light and intact surface
70 Polyethylene None Purple pigmentation on cut ends 70 Paper None and intact surface
70-83 Polyethylene Light 70-83 Paper None
Three commercial fungicides were employed in attempts to control mold growth in rhizomes stored in polyethylene bags at room temperature. The degree of effectiveness of these fungicides is shown in the combined data of two experiments (each with 8 rhizomes per treatment) recorded in table 7. The data indicate that Orthocide 50 and Zerlate have possibilities as mold inhib itors. However, these materials cannot be recommended for commercial use on ginger rhizomes without prior clearance for possible toxic residues.
The effects of modified atmosphere storage of ginger rhizomes were deter mined at room temperature. Modified atmospheres 'Vere obtained by propor-
12
TABLE 6. Detergent as a mold inhibitor in stored ginger rhizomes ( 6 rhizomes per treatment}
Storage Average mold status Treatment temperature (°F.) Storage package after 29 days in storage
Washed only 3S Polyethylene Severe** \Vashed only 3S Paper Severe**
Washed + detergent* 3S Polyethylene Severe** Washed + detergent* 35 Paper Severe**
Washed only 70-83 Polye thylene Moderate \Vashed only 70-83 Paper Nooe
Washed + detergent* 70-83 Polyethylene Light Washed + detergent* 70-83 Paper Nooe
•New Pink Dr.eft (1 level tablespoon/ 2 qu,,~ts water, 5-minute dip). ••Also physiological breakdown.
TABLE 7. Fungicides as mold inhibitors in ginger rhizomes stored m polyethylene bags at room temperature
% concentration Average mold status Fungicide (water suspension)* after 14 days
Neo-Vita** Zerlate*** Zerlate Orthocide 50**** Orthocide 50 Orthocide 50 \Vater only None
1.5 o.s 1.0 0.5 0.75 1.0
Severe Severe Nooe Light Light Very light Severe Moderate
•5-minute dips. ••Re·mark Chemical Co.
***Zinc dimethyldithiocarbamate. ****Wettable preparation containing 50% Captan (N-trichloromethylmercapto·4-cyclo·
hexene·l , 2-dicarboximide).
tionately mixing carbon dioxide with air by means of flowmeters. The carbon dioxide-air mixture was humidified by bubbling through water and then passed into large glass jars (9% gallons) containing the rhizomes (10 per treatment) at atmospheric pressure. The results are shown in table 8.
That oxygen tensions lower than that in air were conducive to mold devel opment in stored ginger rhizomes is shown in table 8. In another test, seven rhizome sections stored in an airtight glass jar (1-gallon capacity) at room temperature developed severe molding in 21 days, whereas those stored in a non-airtight jar developed only a limited amount of mold.
1.3
TABLE 8. Effects of modified atmosphere storage on ginger rhizomes at room temperature ( 17 days storage)
Assumed Average 0, tension Average sprout length
Treatment (%) mold status (cm.)
Air only 21.0 Slight 1.5* 1/2 Air+ 1h CO, 10.5 Moderate 0.5 'A A ir + ~ CO, 5.25 Severe 0.0** CO, only 0.0 Severe 0.0**
*Significantly greater than % Air + ~~ CO, treatment. ••When removed from the jars at the end of the storage period and exposed to atmos
pheric conditions, the rhizomes developed typical symptoms of physiological breakdown in 1 week. There was no sprouting.
Results reported in table 3, and those of an additional test ( 5 rhizomes per treatment ) in which rhizomes were stored in polyethylene bags at various temperatures, indicated that high humidities were conducive to mold develop ment at all temperatures between 35° F. and room temperature. Results of five experiments (each with 5 to 12 rhizomes per treatment ) in which rhizomes were stored under maintained humidities at various temperatures were combined and are recorded in table 9.
TABLE 9. Effect of relative humidity on average mold development in ginger rhizomes sto red at various temperatures (summary of five experiments in which the number of rhi zomes used per treatment varied from 5 to 12 and the storage period ranged from 26 to 31 days )
Tem perature (OF.) 10 25
Relative humidity (%)
35 45 55 70
Mold* Mold* Mold !\fold Mold Mold
•Also physiological breakdown.
At temperatures of 55° F. and above, humidities of 65 percent and lower prevented mold growth (table 9). At 35° and 45° F. storage, molding occurred probably as a result of secondary infection following physiological breakdown under both high and low relative humidities.
Physiological Breakdown
In experiments already described ( tables 3, 5, 6, and 9) and in others, storage temperatures of 45° F. and lower always resulted in physiological breakdown of the ginger rhizomes regardless of storage humidity. At these
14
temperatures, rhizomes stored in polyethylene and paper bags were similarly affected. Freezing caused the rhizomes to break down and become soft upon thawing. That prolonged exposure to reduced oxygen tension may induce physiological breakdown even at room temperature was indicated in an experi ment in which after storage under controlled oxygen tension, the unsprouted rhizomes were exposed to air at room temperature. In 1 week, these rhizomes developed physiological breakdown without sprouting ( table 8).
Sprouting
The effect of certain wax preparations upon sprouting was discussed pre viously ( table 2 ) . Another wax preparation in which a sprout inhibitor is incorporated (Johnson's Sprout Inhibitor Wax for Potatoes) was used in attempts to control sprouting. The use of this material full strength reduced sprouting in rhizomes stored at room temperature, but it also increased mold ing. The results obtained by the use of various dilutions of this preparation are recorded in table 10.
According to table 10, the potato inhibitor wax at a concentration of one half strength reduced sprout growth, but it had no effect on the number of rhizomes which sprouted. Unlike the full-strength wax, the diluted prepara tions had no effect on mold growth.
TABLE 10. Effect of Johnson's Sprout Inhibitor Wax for Potatoes on sprouting in ginger rhizomes stored at room temperature for 34 days (5 rhizomes per treatment)
Average Average Wax Sprouted rhizomes longest sprout mold
concentration Package (%) (cm.) status
'h strength Polyethylene 100.0 o.s• Moderate 'h strength Paper 100.0 o.s• Slight
* strength Polyethylene 100.0 2.0 Moderate 'A strength Paper 100.0 1.9 None
Vii strength Polyethylene 100.0 2.2 Moderate Vii strength Paper 100.0 2.1 None
None Polyethylene 100.0 2.3 Moderate None Paper 100.0 1.6 None
•Significantly Jess than corresponding controls.
Maleic hydrazide has been used to control sprouting in potatoes, carrots, and onions (4). When used at a concentration of 1,000 p.p.m., this chemical had no effect on degree of sprouting of ginger rhizomes in storage at 70° F. and room temperature. At a concentration of 2,000 p.p.m., it significantly reduced sprout growth, although it had no effect on the percentage of sprouted rhizomes ( table ll).
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TABLE 11. Effect of maleic hydrazide on sprouting of ginger rhizomes in storage at room temperature for 29 days ( 6 rhizomes per treatment)
Average Sprouted rhizomes longest sprout
Treatment Package (%) (cm.)
Maleic hvdrazide* Polyethylene 100.0 0.8** Maleic hydrazide* Paper 100.0 0.5**
None Polyethylene 100.0 1.6 None Paper 100.0 1.1
*2,000 p.p.m., 2-hour dip at room temperature. **Significantly less than corresponding controls.
The use of naphthaleneacetic acid as a sprout inhibitor of various crops is well known (1, 4). Soaking ginger rhizomes (7 rhizomes per treatment) in a solution of sodium salt of naphthaleneacetic acid (100 mg/1) for 1 and 2 days at room temperature had no effect on sprouting of rhizomes when stored at room temperature. The effect of treating with higher concentrations of this chemical was next determined. According to the data obtained in this test (table 12), the effective concentration of naphthaleneacetic acid for the pre vention of sprouting was 200 mg/1. However, this treatment resulted in physi ological breakdown and severe molding.
TABLE 12. Effect of naphthaleneacetic acid (sodium salt) on sprouting of rhizomes in storage at room temperature for 27 days ( 6 rhizomes per treatment)
Average Average Sprouted rhizomes longest sprout mold
Treatment* Package (%) (cm.) status
Naphthaleneacetic acid (200 mg/I) Paper 0.0 Severe***
Naphthaleneacetic acid ( 150 mg/I) Polyethylene 100.0 1.0** Severe
Naphthaleneacetic acid (150 mg/I) Paper 100.0 0.6** Severe
Water only Polyethylene 100.0 4.5 Moderate Water only Paper 100.0 1.7 None
None Polyethylene 100.0 1.8 Moderate None Paper 100.0 0.8 None
*24-hour soaking at room temperature. **Significantly Jess than corresponding water control, but not significantly different from
dry control. ***Also physiological breakdown.
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Irradiation with gamma rays has been shown to prevent sprouting of potato tubers (7). In three experiments (each with 10 rhizomes per treatment ) the effect of gamma radiation (Co"0
) on sprouting of ginger rhizomes when stored in polyethylene and paper bags at room temperature for 28 days was determined. Dosages of 25,000 and 50,000 R. merely reduced the growth of the sprouts with concomitant increase in mold growth. Dosages of 75,000 and 100,000 R. completely inhibited sprouting but resulted in severe molding.
Three tests ( each with 14 rhizomes per treatment) were conducted to deter mine the effect of a fumigant upon sprouting of ginger rhizomes. Fumigation with methyl bromide at dosages of 2 and 2'/4 pounds per 1,000 cubic feet space for 2 hours at atmospheric temperature and pressure had no effect on sprouting of rhizomes stored in polyethylene and paper bags at room temperature for 28 days.
The effect of another fumigant, ethylene dibromide, on sprouting was tested in two experiments ( each with 12 rhizomes per treatment) . The results of one experiment, as shown in table 13, indicated that a low dosage (l/2 pound per 1,000 cubic feet) of the gas actually stimulated sprout growth in rhizomes when stored in polyethylene bags at 70° F. and room temperature; higher dosage ( 1 pound per 1,000 cubic feet) had no effect at room temperature storage. Similar results were produced in the other experiment.
TABLE 13. Effect of ethylene dibromide on sprouting of ginger rhizomes during storage for 32 days
Storage Average Ethylene dibromide dosage temperature Sprouted rhizomes longest sprout
( lb/ 1,000 cubic feet)* (OF.) ( %) (cm.)
1h 70 100.0 1.5** l/2 70-83 100.0 4.0**
I 70-83 100.0 2.8 None 70 100.0 0.9 None 70-83 100.0 2.7
• Fumigation for 2 hours at atmospheric temperature and pressure. ••Significantly greater than corresponding untreated lots.
The effect of modified atmosphere storage on mold development was dis cussed above. In the same experiment, the effect on sprouting was also studied (table 8). Among the treatments used, the lowest oxygen tension permitting sprouting was that afforded by a mixture of l/2 air and % CO 2 ( 10.5 percent 0 2 ). Lower oxygen tensions prevented sprouting completely in controlled storage, but upon exposure to room temperature conditions, the rhizomes developed symptoms of physiological breakdown similar to those manifested in rhizomes stored at low temperatures. In an additional test in which 10 rhizome sections were stored in an airtight glass jar (1-gallon capacity) at room temperatu re for 2 weeks, only limited sprouting occurred as compared to that in an open jar.
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The degree of sprouting in polyethylene and paper bags at different temper atures was determined in three tests. As indicated in the data of a representa tive experiment, sprouting occurred only at 70° F. and room temperature (table 14). At 70° F. there was less sprouting in both types of packaging than at room temperature. Furthermore, at both temperatures there was less sprout ing in polyethylene bags than in paper bags, in spite of the higher humidity in the former packaging than in the latter. This again may be a manifestation of low oxygen tension limiting sprouting as previously discussed ( table 8). A further support for this contention was observed in the results of an experi ment ( figure 1 ) already described. At the conclusion of this experiment, the average length of sprouts in the completely paraffined lot was significantly less than that of sprouts in the two partially paraffined lots. This was probably the result of an apparent differential interference with respiratory gas exchange caused by the different degrees of covering.
TABLE 14. Sprouting of ginger rhizomes in polyethylene and paper bags at different temperatures ( 10 rhizomes per treatment)
Sprouted rhizomes in 57 days
Temperature (OF.) Package (%)
35 Polyethylene 0.0 35 Paper 0.0
45 Polyethylene 0.0 45 Paper 0.0
55 Polyethylene 0.0 55 Paper 0.0
70 Polyethylene 40.0 70 Paper 80.0
70-83 Polyethylene 80.0 70-83 Paper 100.0
The effect of controlled relative humidity on sprouting at room temperature was previously discussed to some extent in connection with loss of weight in stored rhizomes ( table 4 ) . According to the data in table 4, the rhizomes sprouted and remained alive for 26 days even at 35 percent relative humidity at room temperature. At lower humidities, they sprouted but the sprouts were short-lived.
In another test ( 10 rhizomes per treatment), rhizomes stored at relative humidities from 90 to 35 percent at 70° F. sprouted and remained alive for at least 49 days, whereas those stored at 25 percent did not even sprout. In an additional experiment (6 rhizomes per treatment) conducted at 55° F., rhizomes were stored at relative humidities ranging from 90 to 35 percent.
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None of these rhizomes sprouted. Rhizomes stored at 45° and 35° F. (10 rhi zomes per treatment) were prevented from sprouting. However, at these temperatures physiological breakdown resulted regardless of storage humidity.
Reference is again made to a previous experiment ( figure 1) in which it was shown that due to excessive desiccation, the average length of sprouts of the nonparaffined rhizomes was significantly less than those of the two partially paraffined lots.
Discoloration
Grade stipulation for export ginger does not allow any form of discoloration on the surface of rhizomes (6). The most prominent discoloration is a purple pigmentation that occurs especially on cut surfaces. In several tests under favorable conditions, this purple pigmentation was observed to occur on rhi zomes stored in polyethylene bags at 55° and 70° F. after prolonged storage (60 days or longer). It was not observed on rhizomes stored in paper bags or in humidity-controlled chambers (up to 90 percent relative humidity) at these temperatures. At 45° and 35° F., visible pigmentation did not occur at any of the relative humidities studied. It· appeared in rhizomes stored in polyethylene bags, but not in·· those in paper bags at room temperature.
To follow up on these leads, 10 rhizome sections were placed in a shallow dish and kept partly submerged with tap water at room temperature. At the end of 36 days, the purple pigment completely covered the cut ends and very faintly appeared on the intact surface of the rhizomes. Twelve rhizomes were planted in a soil flat which was placed in the open and kept moist. After 29 days, they were dug up and examined. Again all cut surfaces of the rhi zomes were covered heavily with the purple pigment and the intact surface was only lightly pigmented.
These results seemed to indicate that free moisture must be present for visible pigmentation to occur on the rhizomes. Due to condensation of moisture on the inner surface of polyethylene bags, this treatment represented a condition similar to that of rhizomes being placed in water or planted in soil. At 70° F. and room temperature, the juvenile leaves (sheaths) of the sprouts showed anthocyanin pigmentation typical of new shoots of many plants. Therefore, it appears that the development of pigment on the rhizome surface was a manifestation of the biochemical changes associated with_ shoot development from a dormant organ. At 55° F., although no sprouting occurred, the rhi zomes were not injured because upon removal to room temperature, they sprouted normally. Since in polyethylene bags at 55° F. the pigment developed though no sprouting occurred, it seems that this temperature represented a threshhold condition which barely prevented sprouting. In fact some rhizomes in a few cases actually made some weak attempts to sprout.
Controlled Temperature and Humidity Storage
Using preliminary data gleaned during the progress of the experiments described above, another test was conducted m an attempt to determine the
19
optimum conditions required for prolonged storage of ginger rhizomes. The rhizomes (10 per treatment ) were stored under various controlled temperature and humidity conditions. At intervals loss in weight was determined. Obser vations were also made on factors used as some of the criteria for unmarket ability of rhizomes for the export trade as formulated by government regula tions (6) : shrivelling due to desiccation; softness and shrivelling due to physiological breakdown; decay of any form; sprouting; and discoloration. The treatments were continued in storage as long as the rhizomes were in a marketable condition. The data are presented graphically in figure 2, which shows, in addition to actual loss in weight with storage time, the basis for termination of each treatment at the time indicated.
In general, the results in thi s experiment ( figure 2) were in agreement with those obtained in the other experiments previously c!escribed. Room tempera ture in combination with any relative humidity was again demonstrated to be ineffective for prolonged ginger storage, because of its inability to prevent sprouting even at humidities sufficiently low to cause desiccation. At the high humidity, though desiccation was prevented, there was the additional factor of molding coupled to sprouting. Storage at 35° F. in combination with any relative humidity was again detrimental. Physiological breakdown fol lowed by shrivelling and molding occurred in all cases at this temperature. At 55° F., it was again shown that sprouting can be prevented at each humidity tested. However, high relative humidity caused molding, and desiccation was excessive in low humidity storage. At the intermediate relative humidity of 65 percent, rhizomes were kept in a marketable condition for 188 days. Al though the loss in weight of the rhizomes was 16.5 percent during this period, surface shrivelling did not occur to a degree sufficient to make the rhizomes unmarketable. Half of these rhizomes were removed from the storage chamber, air-dried long enough at room temperature to remove moisture condensed on the surface, packed in a commercial carton, and stored at room temperature for 2 weeks to simulate shipping conditions. At the end of this period, the rhizomes were still in a marketable condition. Rapid loss in weight occurred after about the 6th month of storage so that at the end of the 7th month when storage was terminated shrivelling was to the extent that the rhizomes were considered unmarketable. These data indicate the possibility of storing ginger rhizomes for at least 6 months in a marketable condition, provided the temperature and relative humidity are properly controlled in the storage medium.
DISCUSSION
According to the results of studies presented above, the best storage condi tion for ginger rhizomes among those tested seems to be the one in which the temperature is maintained at 55° F. and the relative humidity at 65 percent. Under this condition the rhizomes may be safely stored for at least 6 months. During this period nea rly all the requirements for long-time storage are ful filled, i .e., surface shrivelling, storage decay, physiological breakdown, sprout ing, and surface discoloration are inhibited. In view of these advantages, the
20
30 PB - Physiological breakdown M - Mold Sh(d) - ShriveII ing due to des iccotion Sh(F-B) - Shrivelling due to physiological breakdown S - Sprouting
25
... / lO
z / /
15 /"' "' 0 I,,:) ... 35° F ., 35% Relative Hufflidity ..... 35 ° F., 65% Relative Humidity ... 35° F ., 90% Relative Humidityz ...
55 ° F ., 35% Relative Hum idity 55° F ., 65% Relative Humidity....."'
u
Room Temperature, 35% Relative Humidity Room Temperature, 65% Relative Humidity
e Room Temperature, 90% Relative HumidityIii
30 50 70 90 110 no - 150 170 190 210
DAYS IH STORAGE
FIGURE 2. Effects of temperature and relative humidity on stored ginger rhizomes.
loss in weight ( 16.5 percent) in the 6-month period is not considered to be critical. The use of this method of storage will enable the grower to manip ulate his harvest schedule to suit his shipping and marketing schedule.
SUMMARY AND RECOMMENDATIONS
Factors affecting the longevity of ginger rhizomes in storage were investi gated. The studies resulted in the discovery of an optimum medium for the storage of rhizomes for periods of 6 months or more. Based upon the results of these studies and the prevalent commercial methods of handling harvested ginger rhizomes, the following procedure is recommended for the storage and shipping of this commodity:
1. Wash off soil with water immediately after harvest.
2. Air-dry in shade for 1 or 2 days to partially heal cut surfaces on the rhizomes.
3. Store in a room in which the temperature is maintained at 55° F. and the relative humidity at 65 percent.
4. For shipping, remove from storage room and air-dry in the shade long enough to remove moisture of condensation.
5. Pack in commercial cartons for shipping without refrigeration.
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. LITERATURE CITED
(1) AVERY, G. S., JR., E. B. JoHNSON, R. M. ADDOMS, and B. F. THOMSON. 1947. HORMONES AND HORTICULTURE. McGraw-Hill Book Co., Inc., New
York and London. Pp. 267-272.
(2) CHAS. PFIZER and Co., INC. 1960. SORBISTAT, SORBISTAT-K. Technical
Bulletin No. 101. 29 pp.
(3) COBLEY, L. S. 1956. AN INTRODUCTION TO THE BOTANY OF TROPICAL CROPS. Longmans, Green and Co., Inc., New York. xv + 357 pp.
(4) LEOPOLD, A. C. 1955. AUXINS AND PLANT GROWTH. University of Cali
fornia Press, Berkeley and Los Angeles. Pp. ::63-273.
(5) SILLS, V. E. 1961. PROCESSING AND MARKETING GINGER PRODUCTS. South
Pacific Bulletin 11(3): 58-61.
(6) TERRITORY OF HAWAII, BOARD OF COMMISSIONERS OF AGRICULTURE AND FORESTRY, DIVISION OF MARKETING. 1959. PROPOSED STANDARDS FOR HAWAII-GROWN GINGER ROOT (REVISED SECOND DRAFT). 6 pp. (Mimeo.)
(7) THOMPSON, H. C., and W. C. KELLY. 1957. VEGETABLE CROPS, 5th ed. McGraw-Hill Book Co., Inc., New York, Toronto, and London. 402 pp.
(8) UNITED STATES DEPARTMENT OF AGRICULTURE, FOREIGN AGRICULTURAL TRADE OF THE U.S. 1961. IMPORTS OF FRUITS AND VEGETABLES UNDER QUARANTINE, FISCAL YEAR 1960-61. 11 pp. (Mimeo.)
(9) WALLRABENSTEIN, P. P., S. M. DouE, R. YAMAGUCHI, and E. NIHEI. 1961. STATISTICS OF HAWAIIAN AGRICULTURE 1960. Hawaii Coop~rative Extension Service, University of Hawaii, Agricultural Economics Report No. 53. 58 pp. (Mimeo.)
(10) WILSON, R. E. 1921. HUMIDITY CONTROL BY MEANS OF SULFURIC ACID SOLUTIONS, WITH CRITICAL COMPILATION OF VAPOR PRESSURE DATA. four. Ind. & Eng. Chem. 13: 326--331.
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HAWAII AGRICULTURAL EXPERIMENT STATION HONOLULU, HAWAII
LAURENCE H. SNYDER President of the University
MORTON M. ROSENBERG Dean of the College and
Director of the Experiment Station
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