[Comment]

Practical Study of Jelly Processing to Utilize Immature

Satsuma Mandarin Fruits

Tadao Inazu and Yoshio Makino

Immature Satsuma mandarin fruits, containing larger amount of organic acids (citric acid ca. 3times, malic acid ca. 5 times) than the mature ones, were used for making jelly. The jelly was

produced by controlling concentrations of organic acid, sugar and gelling agent (carrageenan). Theratio of the gelling agent to the total weight of the jelly was mathematically determined from therelationship between carrageenan concentrations and breaking stress values of the jelly. There wasno significant different of the taste between immature and mature mandarin fruit jellies. Theutilization of the immature fruits is effective for saving amount of the juice needed for the jellymaking. Jelly making is a feasible method to employ the immature Satsuma mandarin fruit.

Keywords: Immature fruit, Citrus, Jelly, Satsuma mandarin

INTRODUCTION

Satsuma mandarin is one of the most favorable

fruits in Japan. In general, 90% of the mandarin

fruits have been thinned during growing process to

obtain high quality fruits and to maintain produc-

tion yield1'2). Yield of thinned immature mandarin

fruits is estimated to be 18 ton per hectare, which

have been wasted as a useless material. The wasted

fruits have been desirable to be used as a bio-

material resource from a point of material utiliza-

tion.

Dohi et al .3) reported that the immature mandarin

fruits were useful as a flavoring resource for sponge

cake and citrus vinegar. They suggested the possi-

bility of application of the immature mandarin for

food processing. However, to utilize a large amount

of the immature mandarin fruits as a food resource,

the other application methods are needed to be

found.

In the present study, the immature Satsuma mandarin juice was applied to jelly making which is

one of the most important application methods of

fruit juice by controlling concentrations of chemical

components and by adding gelling agent. Concentra-tion of the gelling agent was mathematically deter-

mined from the relationship between carrageenan

concentrations and breaking stress values of a jelly.

Usefulness of immature Satsuma mandarin for jelly

processing was discussed.

MATERIALS AND METHODS

1. Test fruits Three kinds of the immature Satsuma mandarin

fruits, Okitsu (early maturing variety, 32 years old) ,

Kuno (medium maturing variety, 27 years old) ,

Hayashi (late maturing variety, 36 years old) were

sampled as test plots at Kagawa Agricultural Experiment Station (Fuchu branch, Kagawa Prefec-

tural Government, Japan) on August 15th, 1995. The

mature mandarin fruits of the same types of variety

as described above were sampled as control plots at

the same Station (harvest date : Okitsu November

* Food Research Institute , Kagawa Prefectural Government ** Kagawa Prefectural Fermentation & Food Experimental

Station

68 (272)

Practical Study of Jelly Processing to Utilize Immature Satsuma Mandarin Fruits

17th, Kuno November 27th, Hayashi December 13

th) .

2. Preparation of fruit juice

One hundred immature Satsuma mandarin fruits

were washed by water, cut in two pieces, and sque-ezed to extract juice with a throttle (VITAM

PRESS 2, made in Italy) . The obtained juice was

centrifuged (10 min, 5,000 rpm) and filtrated

through a membrane (average pore size 5 pm) to remove suspended pulp. Thirty mature Satsuma

mandarin fruits were also treated by the same

method as above. This treatment was conducted on

each variety. The six types of the juice obtained

were presented for chemical analysis and jelly making.

3. Chemical analysis

Mean weight per fruit and extract juice yield

(weight ratio of extracted juice to a fruit) were determined. pH (HM-30 V, TOA Electronics, Inc.,

Tokyo, Japan) , Brix (PR-100, measurable range :

Brix 0-32%, ATAGO, Inc., Tokyo, Japan) , organic

acid concentration, and sugar concentration of the

juice obtained from six types of mandarin fruit were also determined. Organic acid concentration was

measured by high pressure liquid chromatography

(HPLC) system (Shodex LC DG-1, Showa Denko, Inc., Tokyo, Japan) , Shodex M 315 UV/VIS detec-

tor (Showa Denko, Inc.,) under the following condi-

tions : Shodex KC-811 column (Showa Denko,

Inc.,) , column temperature of 50°C, developer of

3 mM-HCI04, linear flow rate of 1 ml/min, and wavelength of 430nm, respectively. Sugar concen-

tration was also measured by HPLC system with

GLC-611 column (Hitachi, Inc., Tokyo, Japan) , R 401 differential refractometer (Waters Japan,

Inc., Tokyo, Japan) under the following conditions

column temperatue of 60°C, developer of 1 x 10 N-

NaOH, and flow rate of 1 ml/ min, respectively. 4. Jelly making

Before jelly making, sugar concentration of each

juice was adjusted to Brix value of 19.0% by controlling weight ratio of juice, sucrose, fructose,

and glucose to total weight of solution because that

commercial jelly with carrageenan was reported to have 19g sucrose per 100g jelly4). Organic acid

concentration (citric acid plus malic acid) of each

immature mandarin juice was adjusted to the same

concentrations as each mature one by dilution with distilled water. Carrageenan concentration was

determined by the procedure described in the later

sub-section "Concentration of carrageenen". Mix-

ture of each juice and carrageenan were heated up to 80°C to dissolve the carrageenan. 40 ml portions

of the heated mixture were divided into pudding

cases and cooled at 6°C in a refrigerator for gela-

tion. 5. Concentration of carrageenan

To determine the carrageenan concentration in

jellies, 0.66%, 0.72%, 0.78%, or 0.84% (w/w) of the carrageenan agent (Oruno CW8, Takeda Chemical

Industries, Inc., Tokyo, Japan) was added to a sugar

solution (adjusted to Brix value 19.0% using

granulated sugar) . The four types of carrageenan solution were heated up to 80°C, and then cooled in

a refrigerator for gelation. The jelly prepared was

cut in a rectangular prism (area 400 mm', thickness 10 mm) , and the prism was presented to breaking

stress measurement with a creep meter (Rheoner

RE-33005, Yamaden, Inc., Tokyo, Japan) by the

compression method according to Kohyama and Nishinari5). This rheological measurement was con-

ducted under the following conditions : diameter of

circular plunger was 40 mm ; compression speed

was 1mm/sec ; and clearance was 1 mm, respective-ly. The carrageenan concentration and breaking

stress data were analyzed by a least squares method

using a microcomputer with Delta graph® Pro 3

(Nippon Polaroid, Inc., Tokyo, Japan) . Statistical analysis was conducted by Fisher's z-transforma-tion method using Stat View® 4.02 (Abacus con-

cepts, Inc., Berkeley, USA) . The breaking stress of

a standard carrageenan jelly which is widely dis-

tributed to commercial market in Japan (mandarin orange taste, Morinaga Nyugyo, Inc., Tokyo,

Japan) was measured according to the same method as described above. These measurements were

repeated 16 times. 6. Sensory test

Sensory test was done to evaluate differences of

sweetness, sourness, and synthetic taste between the

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J. Cookery Sci. Jpn. Vol. 30 No. 3 (1997)

immature and mature fruit jellies by the two step

rank method with fifteen panelers (in our Institute) .

The jellies stored at 6°C were submitted to the test,

and the rank sum data obtained was analyzed according to Kramer's method°.

RESULTS AND DISCUSSION

1. Chemical component of juice

The mean weight per fruit and the extract juice

yield were presented in Table 1. The concentrations of organic acids and sugars in the six types of the

juice were also indicated in Table 1. The mean weight data per immature fruit were in the range of

14.7 to 21.2g, which were 80.0-106.8g lighter than

those per mature one. The extract yield data of the immature fruit juice were in the range of ca. 27 to 34

%, which were 13.5-18.1% lower than those of the mature one. This is because the mature mandarin

fruit possesses a larger amount of bulk sap than the

immature one (the amount of the sap per fruit is

proportional to largeness of the fruit). The concen-trations of citric acid and malic acid in the im-

mature mandarin juice were in the range of 3.69 to

3.98% and 0.16 to 0.18%, respectively, which were

about 3 times and 4-6 times higher than those in the mature one, respectively. The pH values of the

immature mandarin juice were in the range of 2.57

to 2.65, which were 0.65-0.83 lower than those of

the mature one. Kakiuchi et al.') reported that Satsuma mandarin fruit had much free acid chiefly

composed of the citric acid (over 90%) and the

malic acid. They also presented that the concentra-

tions of these organic acids rapidly rises at early stage of fruit growth (from August to September in

Japan) , and rapidly falls at medium stage of fruit

growth (from the end of September to the beginning of October) . The organic acid concentration falls

down to ca. 1% at late stage (from November to December) of fruit growth'. The great difference of

organic acid concentrations between the immature

and mature mandarin juice in the present study was

probably due to the difference of the growing stage when the fruits were harvested (August and Decem-ber, respectively).

Sucrose, fructose and glucose, which are the main

sugars in a mandarin fruit, were reported to

increase rapidly with accumulation of fruit sap". Kakiuchi et al. presented that the fructose and the

glucose in the mandarin fruit increased before the medium stage of fruit growth (beginning of Octo-

ber) , and that sucrose increases after the medium

stage. In the present experiment, sucrose concentra-tions in mature mandarin juice were 3-4 times

higher than those in the immature one as presented

in Table 1. The concentrations of the fructose and

the glucose in the mature mandarin juice were 1.7- 2.0, and 1.5-1.9 times higher than those in the

immature one, respectively. This indicates that the

sucrose increases more rapidly than the fructose

and the glucose in the mandarin fruit, and that the

sugar components are dependent on the harvest time of the mandarin fruit.

2. Jelly making

Table 2 indicates the weight component per 100g

jelly produced and the concentrations of sugar and organic acid after mixing. To adjust the sugar

concentration to be equal (Brix value 19.0%)

between the immature and the mature fruit jellies,

Table 1. Characteristics of Satsuma mandarin juice

* Weight ratio of extracted juice to a fruit.

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Practical Study of Jelly Processing to Utilize Immature Satsuma Mandarin Fruits

Table 2. Materials used for jelly making

* Carrageenan. ** Except carrageenen.

more sucrose, fructose and glucose were added to

immature mandarin juice than those to mature one.

Gordon') and Owada et a1.° reported that taste of fruit juice was affected by ratio of sugar concentra-

tion to organic acid concentration in juice, and that

high concentration of the organic acid in the juice

caused depression of preference of the juice. The

sugar and organic acid concentrations in each im-mature mandarin juice therefore are controlled to

the same concentrations as the mature one before

gelation from a taste point of view. 3. Concentration of carrageenan and break-

ing stress of a jelly

Rheological property of various polysaccharide

gels, such as pectiC), agarose, K-and A-car-rageenan, curdlan"), and agar12), is generally char-

acterized by a brittle breaking. The statement is

applied to the result obtained in the present experi-

ment as shown in Fig. 1. When the breaking load

g (x) [N], the deformation x [m], the thickness of sample L [m], and the cross section area A [m2] are

obtained, the breaking strain E[m/m] and the brea-

king stress P (e) [N/m2] can be expressed by Eq. (1)

and (2) as follows: E= X / L Eq. ( 1 )

P (E) =g(x)/ A Eq. ( 2 )

Omura et a1.'2 presented that the breaking stress

increased with an increase in the agar concetration

or with a rise in the compression speed. In the

present experiment, the breaking stress was mea-sured under the constant compression speed in-

dependent of the carrageenan concentretion in a

Fig. 1 A typical stress-strain curve of a carrageenan gel under the carrageenan concentration of 0.77% and

compression speed of lmm/sec. Symbol (0) breaking point, E breaking strain, P (E) breaking stress.

jelly. Fig. 2 shows the relationship between the carrageenan concentrations and breaking stress

values of jellies produced by the method presented in sub-section "Concentration of carrageenan". The

breking stress increased with an increase in the

carrageenan concentration in the jelly. This sug-

gests that the breaking stress is a function of the carrageenan concentration. We propose the follow-ing exponential type equation to express the rela-

tionship between the breaking stress and car-

rageenan concentration: P (E) BexP (k . c) Eq. ( 3 )

where c is the carrageenan concentration in a jelly

PAL B[N/m2] and Ic[%-'] are the constants. The

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J. Cookay Sci. Jpn. Vol. 30 No. 3 (1997)

Fig. 2 Relationship between carrageenan concentration and breaking stress of jellies. Symbols

(0) denote experimental data as a mean±standard deviation of 16 breaking stress values. Solid line

denotes the best fit line.

experimental data agreed with the calculated values

as shown in Fig. 2 (correlation coefficient 0.938,

statistically significant over 99.9% level) when B and k were 59.1 N/m2 and 6.92%-', respectively.

The values of the constants were calculated by the

least squares method. To determine the car-

rageenan concentration of the jelly in the present

experiment, the breaking stress of a marketing jelly was measured. The mean value of the breaking

stress of the marketing jelly was 12.5 x 103N/m2

which corresponded to the carrageenan concentra-

tion of 0.77% according to Eq. (3) . This value of carrageenan concentration was applied to the fruit

jelly making in this experiment. 4. Sensory test and suitable jelly component

Sensory scores of the mandarin fruit jelly were

presented in Table 3. A significant difference of the sensory scores expressing sweetness, sourness, or

synthetic taste between immature and mature man-

darin fruit jellies was not found. This suggests that

a jelly made from an immature mandarin juice has almost equal taste to that from a mature one, and

that the immature mandarin fruit may be useful for

jelly making as well as the mature one. The difference between Brix value and sum of concen-tration of sucrose, fructose and glucose is presumed

to be mainly caused by starch. The difference is

Table 3. Sensory score (rank sum) for

Satsuma mandarin jelly*

* All scores have no significant difference between the immature and mature mandarin jelly.

assumed to be sensuously neglected because sweet-

ness of starch is much weaker than that of the

sugars. The breaking stress of mandarin fruit jelly including sugar and organic acid may be different

from the stress of the jelly made in sub-section "Concentration of carrageenan" 13) However, the

lifference does not affect the results of sensory test. The breaking stress values between the immature

and the mature fruit jellies are equal because both

jellies include the same concentrations of sugar and

prganic acid. The suitable weight of the mature and

mmature mandarin juice and that of the mandarin ruits for making 100g jelly estimated from the

2xtract yield (Table 1) were presented in Table 4.

The weights of the immature mandarin juice and 'ruits needed for jelly making are ca . 1/3 (30.1-34.6

)/) and ca . 1/2 (46.3-57.7%) of the weights of the nature one, respectively. The extract yield of the

mmature mandarin juice is lower than that of the

Table 4. Weights of Satsuma mandarin juice and fruit needed for production of 100g jelly*

The values designated in parentheses indicate the

ratios in %.

72 (276)

Practical Study of Jelly Processing to Utilize Immature Satsuma Mandarin Fruits

mature one as shown in Table 1. However, high

concentration of the organic acid in the immature

fruit is useful for saving the amount of juice needed

for the jelly making. The sugar concentration in the

immature mandarin juice is lower than that of the

mature one. This does not seems to be a disadvanta-

geous factor in the jelly making process because sugar is generally added to the mandarin fruit juice

in the industrial procedure of the jelly making.

From a practical point of view, the immature

mandarin fruit may be more useful for the jelly

making than the mature one because the cost of

organic acid is higher than tht of sugar. Moreover,

the utilization of the wasted material like immature

fruits is desirable from an economical point of view.

From these results and discussion, we concluded

that the immature Satsuma mandarin fruits was

useful enough for the jelly making.

ACKNOWLEDGMENTS

Thanks to Dr. Ken-ichi Iwasaki in our institute

for the support to this study.

REFERENCES

1) Iwasaki, T.: J. Jpn. Soc. Hort. Sci., 30, 103 (1961)

2) Jones, W. W., Embleton, T. W., Barnhart, E. L. and Cree, C. B.: Hilgardia., 42, 441 (1974)

3) Dohi, S., Tezuka, M., Motosugi, M., Shimono, K. and Furuhashi, M.: Reports of the Shizuoka Prefec-

tural Industrial Technology Center., 31, 125 (1986) 4) Resources council, Science and technology agency,

Japan. : Standard tables of food composition in Japan. 4th ed, p. 70 (1982) Printing bureau ministry

of finance. 5) Kohyama, K. and Nishinari, K.: J. Jpn. Soc. Food

Sci. Technol., 39, 715 (1992) 6) Kahan, G., Coorer, D., Papavasiliou, A. and

Kramer, A.: Food Technol., 27, 61 (1973) 7) Kakiuchi, N., Iba, Y. and Ito, S.: Bulletin of the

Horticultural research station., B10, 149 (1970) 8) Gordon, J.: J. Food Sci., 30, 903 (1965) 9) Owada, T., lino, K., Ishima, T. and Yoshikawa, S. :

J. Jpn. Soc. Food Sci. Technol., 25, 147 (1978) 10) Watoson, E. L.: J. Food Sci., 31, 373 (1966) 11) Aizawa, M., Suzuki, S., Suzuki, T. and Toyama,

H.: Bull. Chem. Soc. Jpn., 46, 1638 (1973) 12) Omura, K., Akabane, H. and Nakahama, N.: J.

Home Econ. Jpn., 29, 22 (1978) 13) Kawamura, F., Nakajima, S. and Mori, K.: J.

Home Econ. Jpn., 27, 329 (1976) (Received Feb. 28, 1997)

摘果 ミカンを利用 したゼ リーの製造

稲津忠雄　牧野義雄

キ ー ワ ー ド : 摘 果 果 実 , か ん き つ , ゼ リ ー , 温 州 ミ カ ン

廃棄物 であ る摘 果 ミカ ンの有効 利 用 を図 るため に,そ

の果 汁 を用 い てゼ リー の試作 を行 った。温州 ミカ ンは

早生 品種(興 津),中 生 品種(久 能),晩 生 品種(林)

の3種 類 を用 いた。 試作 ゼ リー のゲ ル強度 は,ゲ ル化

剤 の添加率 と破 断応 力値 か ら構築 した関係 式 に よ り,

市販 品 と同 じ強度 に調整 した。摘 果 ミカン果 汁は完 熟

果 汁に比べ て糖 含 量が低 か った(シ ョ糖 で1/4,果 糖 で

1/2,ブドウ糖で1/2)が,逆に酸含量は高かった(ク

エ ン酸 で3倍,リ ン ゴ酸 で5倍)。 摘果 及 び完熟 果汁 か

ら成分 調整 して作 られ たゼ リー は,甘 さ,酸 っぱ さ,

お い しさの3項 目につ い て比較 した。 その結果,両 者

の 間に有 意差 は認 め られず,同 等の 品質 を持つ ゼ リー

が製 造 で きた。摘 果 ミカンは高 い酸含 量 の ため に,ゼ

リー 製造 に要 す る使 用 果 汁量 を節約 で き,こ れ を利 用

した方 が製造効 率 の 点 で有 利 で あ り,未 利用 資源 の活

用 に もな るこ とが明 らか に なっ た。

(平成9年2月28日 受理)*香 川県食品試験場

**香 川県発酵食品試験場

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