REFRIGERATION SCIENCE AND TECHNOLOGYPROCEEDINGS

IMPROVING POSTHARVESTTECHNOLOGIES OF FRUITS,

VEGETABLES AND ORNAMENTALSVolume II

"AMELIORATION DES TECHNOLOGIES.•.. "" APRES RECOLTE DES FRUITS,

LEGUMES ET PLANTES ORNEMENTALES

•INTERNATIONAL INSTITUTE OF REFRIGERATIONINSTITUT INTERNATIONAL DU FROID

Commissions C2, D 1

EditorsF. Art(~s, M.l. Gil, M.A. Conesa

SCIENCE ET TECHNIQUE DU FROIDCOMPTES REND US

RESPONSE DIFFERENCES TO HOT AIR TREATMENTSBETWEEN TOLERANT (MANGO) AND SENSITIVE (GUAVA)

FRUITS AND THE ROLE OF SUGAR CONTENT ANDTREHALASE ACTIVITY

E.M. Yahia, M. BalderasFacultad de Qufmica, Universidad Aut6noma de Queretaro, Queretaro, Qro., 76010,

Mexico. yahia@sunserver.uaq.mx

Heat treatments have several advantages during the postharvest handling of fruitsandvegetables, including amelioration of chilling injury, control of decay and insects, andretardation of ripening. Fruits and vegetables show major differences in tolerance to heat.Mangoes are among the tolerant fruits, while guavas are among the sensitive fruits.Theobjective of this work was to investigate the difference in responses between the 2 fruitsandthe role of sugar content (glucose, fructose, sucrose, trehalose) and the activity of trehalasein the tolerance/sensitivity to heat. 'Manila' mangoes were heated at 43°C or 48°C and50%RH for 160 min, and then stored at 10°C and 85% RH for up to 12 days. Guavas wereheatedat 38°C for 120 min or 43°C for 160 min and then stored at l2°C for up to 12 days.Therewas no injury in mango, while there was a slight and severe injuries in guava heated at38°Cand 43°C, respectively. Trehalase activity was not detected in mango and increased inguavafruit. There was higher sucrose content in mango than in guava fruit.

Heat treatments are widely investigated in the last few years (Lurie, 1998a; 1998b;Paull, 1990; 1994), due to their potential use as an alternative for insect and decay control,retardation of ripening, and amelioration of chilling injury (CI).

Fruits and vegetables are known to respond differently to different types of stress(Paull, 1990, Lurie, 1998a, 1998b). There are significant differences between the responsesof different fruits and vegetables to heat treatments. For example, our previous studies(Yahia, 1997; Yahia et al. 1997) indicated that mango fruit is very tolerant to heat,whileguava fruit is very sensitive. The mechanism(s) for heat tolerance/sensitivity is(are)notwellknown. Very little work has been done to investigate the relative tolerance of differentfruitsand vegetables to heat. The basis for response to heat stress include synthesis of heatshockand other proteins, effect on wall degrading enzymes, electrolyte leakage, ethylenesynthesis, etc (Paull, 1990; Lurie 1998a; 1998b).

Some sugars, such as sucrose, are known to ameliorate some forms of stress tJ\unget aI., 1998). Back et al. (1979) indicated that glucose, sucrose and rafinose stabilizeproteins. The accumulation of trehalose, a non-reducing disaccharide consisting of twou-glycosidically linked glucose units, has been associated with different forms of stress,andit may serve as a protectant of enzymes and membranes, particularly under conditionsofheat and desiccation stress (Muller et al., 1995). Degradation of trehalose in yeast isprimarily controlled by a neutral trehalase in the cytosol (Muller et al., 1995). A highly

specific trehalase actIvity has been described in many plants, but none in fruits andvegetables. The enzyme does not cleave other common a-glycosides, and it is highlysensitiveto the inhibitor validamycin A. It is possible that the sensitivity of plant tissues tosomeforms of stress might be due to their incapacity to accumulate some sugars includingtrehalose,and/or to an increased activity of trehalase in these tissues.

The objective of this work was to investigate the differences in sensitivityltolerance ofmangoand guava fruits to heat treatments (38°C for 120 min or 43°C for 160 min in guava,and43°C or 48°C for 160 min in mango, all at 50% RH), and to con'elate that with thechangesin some sugars and the activity of the enzyme trehalase.

'Manila' fruit were harvested at the mature-green stage from the Cotaxla ExperimentalStationin Veracruz. Mature-green guava fruit were harvested from a commercial orchard inMichoacan.Fruits were brought immediately to the laboratory, selected for uniformity ofsize,color and freedom of defects, and classified into different groups. Mango fruit weredividedinto 4 groups of 90 fruit each, and another 39 fruit were used for initial evaluation.Onegroup of 90 fruit were heated at 43°C and another lot at 48°C, both for 160 min and ata RH of 50%. Guava fruit were divided to 3 homogenous groups of 160 fruit each, andanother40 fruit were used for initial evaluation. One lot was heated at 38°C, the other at43°C,both for 160 min and at 50% RH. Immediately after treatment, fruits were cooled inwaterat ambient temperature for 30 min, and one sample of these was evaluated. Heatedandnon-heated guava fruit were then stored at 12°C and 85% RH. Heated and non-heatedmangofruit were held (after heat treatment) at 10°C and 85% RH. Ten mango fruit (fromeachof the heated and non-heated lots) were evaluated after"4, 8, 24 and 48 h, and 4, 6, 9,and 12 days after heat treatment. Twenty guava fruit (from each of the heated and non-heatedlots) were evaluated after 4, 8, 24 and 48 h, and after 4, 6, 9 and 12 days after heattreatment. Fruit evaluated after 4 days or more were held at room temperature for 12 h,beforeanalysis.

Heat treatments were conducted inside a purpose built gas-tight, temperature-controlled, and forced-air chamber (Ortega and Yahia; 2000a; Ortega and Yahia, 2000b;Yahiaand Ortega, 2000; Yahia et at., 1997). The chamber (156 cm high, 70 cm wide, and132cm deep) is constructed from stainless steel. Chamber temperature is elevated aboveroom temperature by means of an electric strip heater that is energized using timeproportionedcontrol technique, and temperature is maintained within ±O.I °C over the rangeof20 to 60°C by automatically energizing four 1000W finned, 230V electric heater elementsas required. Humidity is provided through four atomizing nozzles, each has 2 ports; one forcompressedgas and one for water. When the compressed gas passes through the nozzle itdraws distilled water from the humidification water reservoir into the nozzle using theVenturieffect. When more humidity is required, 2 selenoid valves turn on simultaneously;eachallowing compressed air to flow through the nozzles. Air entrance to the chamber hada velocityof 5 m/sec and air velocity inside the chamber averaged 2.5-3.5 m/sec (dependingon location). Length of treatment was measured from the time of sealing the chamber andturning-onof the treatment.

Fruits were evaluated for incidence and intensity of heat injury, weight loss, texture andcolor.Injury was evaluated on the basis of the following subjective system: 0 = no injury,I = very slight injury (1-10%), 3 = slight injury (1l-20%), 5 = medium injury (21-30%),

ImprovingPostharvestTechnologies of Fruits, Vegetables and OrnamentalsEds. FAnes, MI Gil, MA ConesaIIR Conference, Murcia 2000

7 = severe injury (> 40%). Texture was evaluate using a stable micro system TA-HD textureanalyzer (Texture Technologies Corp, NY). Color was evaluated using a Minolta colorimeter(CM-2002). Total sugars were analyzed according to the AOAC (1970). Sucrose, glucoseandfructose were analyzed according to the method reported by Medlicott et al. (1985),Trehalase activity was determined according to the method of Goddijn et ai. (1997).

The desired temperature in the chamber (Figure 1) is usually achieved in about 10 min,Fruit surface Uust below the skin) and pulp temperatures are usually very slow to be achieved,

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Figure 1. Changes in Chamber (entrance and exit) and fruit (surface and pulp) temperatures duringheat-treatment of mango fruit, at 43°C for 160 min (a) or 48°C for 160 min (b),

Heat treatments caused more external injury in guava than in mango fruits (Figure2),Treatment at 38°C for 120 min caused the same external injury in guava fruit, as theheatingat 43°C for 160 min in mango. Heat treatments caused internal injury in guava, butnotinmango fruit (results not shown).

Total sugars were higher in mango than in guava fruit, but there were no differencesamong heated and non-heated fruits (data not shown). Fructose content was slightlyhigherin mango than in guava fruit, but there was no effect by heat treatments (data not presented),There are no differences in glucose content between the two types of fruits, neithertherewasan effect by heat treatments (data not presented). Sucrose content was higher in mangothanin guava fruit, but there was no effect by heat treatments (Figure 3). Trehalose contentwasvery low in both fruits (~ 2 mg/ml), and there were no differences due to the heat treatments(Figure 4). Trehalase activity was not detected in mango fruit, but was detected inguavafruit (Figure 5). Trehalase activity slightly increased after about 2 days from heat treatmentin the heated and non-heated guava fruit, and increased significantly after about 9 daysfromheat treatment in the non-heated and fruit heated at 38°C for 120 min.

7 ---- Control

6 ----- 43°C for 160 minon --- 48°C for 160 mine 50 4".•, ()on

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0

0 50 100 150 200 250 300

Hours at 10°C---- Control7 ----- 38°C for 120 min6 --- 43°C for 160 min

one 50 4()on;>, 3•...

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0

0 50 100 ISO 200 250 300

Hours at 12°C

Figure 2. External injury scores in mango (a) and guava (b) fruit after heat-treatments.

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....l 50

~ 40a 30 ------ Control

20 ----- 43°C for 160 min

10 ------ 48°C for 160 min

00 50 100 150 200 250 300

Hours at 10°C

8070 ------ Control60 ----- 38°C for 120 min....l 50 ------ 43°C for 160 mina 40bba 3020100

0 50 100 150 200 250 300

Hours at 12°C

Figure 3. Sucrose content in mango (a) and guava (b) fruit after heat treatments.

Improving Postharvest Technologies of Fruits. Vegetables and OrnamentalsEds. F Artes, MI Gil, MA Cones aIlR Conference, Murcia 2000

1000 (a)

800 -- Control600 43°C for 160 min

400 48°C for 160 min

:0 200..,,~ 0 ~ I •2u • • •"0 0 0 50 lOO 150 200 250 300>-or-..c:«)..,

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400200

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Figure 5. Changes in trehalase activity in mango (a) and guava (b) fruit after heat treatments,

We conclude that guava fruit is more sensitive to hot air treatments (38°C for 120 minor 43°C for 160 min, 50% RH) than the mango fruit (43°C or 48°C for 160 min, 50% RH).These differences were correlated with a higher sucrose content in mango fruit and highertrehalase activity in guava fruit.

As far as we know, this is the first work to report the presence of trehalase and trehalosein fruits.

AOAC., 1997. Association of Official Analytical Chemists. Official methods of analysis. 7th

edition, Washington, D.C.Aung, L.H.; Obenland, D.M.; Houck, L.G.; 1998. Conditioning and heat treatments

influence flavedo soluble sugars of lemon. J. Hort. Sci. & Biotechnol. 73(3):399-402.Back,1.F.; Oakenfull, D.; Smith, M.B.; 1979. Increased thermal stability of proteins in the

presence of sugars and polyols. Biochemistry 18:5191-5196.Goddijn, OJ.M.; Verwierdm, T.C.; Voogd, E.; Krutwagen, H.W.W.; De Graaf, P.T.H.M.;

Poels, 1.; Ponstein, A.S.; Damm, B.; 1997. Inhibition of trehalse activity enhancestrehalose accumulation in transgenic plants. Plant Physiol. 113: 181-190.

Lurie,S.; 1998a. Postharvest heat treatments. Postharvest Bio!. & techno!. 14:257-269.Lurie,S.; 1998b. Postharvest heat treatments of horticultural crops. Hort. Rev. 22:91-111.Medlicott, A.P.; Thompson, A.; 1985. Analysis of sugars and organic acids in ripening

mango fruits (Mangifera indica L. var Keitt) by high performance liquidchromatography. J. Sci. Food Agric. 36:561-566.

Ortega,D.; Yahia, E.M.; 2000a. Mortality of eggs and larvae of Anastrepha oblique and A.ludens in 'Manila' mango with controlled at~9spheres .at high temperatures (InSpanish). Folia entomologica 109: 43-53.

Ortega,D.; Yahia, E.M.; 2000b. tolerance and quality of mango fruit exposed to controlledatmospheres at high temperatures. Postharvest Bio!. & Techno!. 20(4): xxx-xxx. Inpress.

Paull,R.; 1990. Postharvest heat treatments and fruit ripening. Postharvest News & Info.1:355-363.

Yahia,E.M.; 1997. Avocado and guava fruits are sensitive to insecticidal MA and/or heat.CA'97. Proceedings Volume 1: CA Technology and Disinfestation Studies, Edited byJ.E Thompson and E.J. Mitcham, July 13-18, 1997, University of California, Davis,pp. 132-136.

Yahia,E.M.; Mondragon, A.; Balderas, M.; Santiago, P.; Lagunez, L.; 1999. Effects of hotair treatments on the postharvest physiology and quality of mango fruit. Acta Hort.509:419-527.

Yahia,E.M.; Ortega, D.; 2000. Mortality of eggs and third instar larvae of Anastrephaludens and A. oblique with insecticidal controlled atmospheres at high temperature.PostharvestBioI. & Technol. 20(3): 295-302.

Yahia,E.M.;Ortega, D.; Santiago, P.; Lagunez, L.; 1997. Responses of mango and mortalityof Anastrepha ludens and A. oblique in modified atmospheres at high temperature.CA'97. Proceedings. Volume 1: CA technology and disinfestations studies, edited byJ.E Thompson and EJ. Mitcham, University of California, Davis, July 13-18, 1997,pp. 105-112.

Improving Postharvest Technologies of Fruits. Vegetables and OrnamentalsEds. F Artis, MI Oil, MA ConesaIIR Conference, Murcia 2000

DIFFERENCE DE REPONSE AUX TRAITEMENTS A L'AIRCHAUD ENTRE LES FRUITS TOLERANTS (MANGUE) ET

SENSIBLES (GUAVA) ET LE ROLE DE LA TENEUR EN SUCREDE L'ACTIVITE DE LA TREHALASE

Resume: Les traitements a la chaleur presentent plusieurs avantages pendant lamanipulation apres-recolte des fruits et legumes, qui incluent l' amelioration des troublesaufroid, Ie contr61e de la degradation et des insectes, et Ie ralentissement du murissement. Lesfruits et legumes presentent de grandes differences en tolerance a la chaleur. La manguecompte parmi les fruits tolerants, alors que les guavas font partie des fruits sensibles.L'objectif de ce travail etait d'etudier les differences des reponses entre les 2 fruits et Ierolede la teneur en sucres (glucose, fructose, saccharose, trehalose) et I'activite de la trehalasedans la tolerance / sensibilite a la chaleur. Les mangues 'Manila' ont ete chauffees a 43°Cou a 48°e et a 50% H.R. pendant 160 min, puis stockees a lOoe et a 85% H.R. jusqu'a 12jours. Les Guavas ont ete chauffees a 38°e pendant 120 min ou a 43°e pendant 160min,puis stockees a 12°e jusqu'a 12 jours. Les mangues ne presentaient aucune blessure, alorsqu'il y avait des blessures legeres et graves sur les guavas chauffees a 38°C et a 43°C,respectivement. L'activite de la trehalase n'etait pas detectee chez Ja mangue et augmentaitchez la guava. La mangue presentait une plus haute teneur en saccharose que la guava.