Studies on keeping-quality of vegetables and fruits. III. Changes in sugar and organic acid contents accompanying the chilling-injury of eggplant fruits

The mechanism of chiiling-injury in fruits of eggplants (Solanum melongena L. cultivar ‘Hyonaga’) was investigated by determining the sugar and organic acid content during cold storage and after exposure to low temperature for various periods. Fructose, glucose and maltose were detected, and totalled more than 96% of total sugar on the initial day. Total sugar content increased to 30% higher than the initial day after 2 days of cold storage, and after that decreased gradually, while in 20° C-stored fruits it decreased sharply. Fructose, glucose and maltose increased rapidly after transfer from 1° C to 20° C. Succinic, oxalic, malic and citric acid were detected before storage. Malic and citric acid were found to be the main organic acids. The ratio of malic/citric acid in fruits stored at 1°C decreased during storage, while after storage at 20°C it increased. The ratio in fruits after transfer from 1°C to 20°C increased rapidly during the time course. The ratio of malic/citric acid ranged from 6.0 to 6.8 in healthy fruits, while it was below 5.9 or above 7.3 in chilled fruits. It is suggested that according to this ratio the degree of chilling-injury of eggplant fruits might be foreseen.     

Effects of post-harvest salicylic acid treatment on fruit quality and anti-oxidant metabolism in pineapple during cold storage

Summary

Pineapple (Ananas comosus L. ‘Comte de Paris’) fruit at commercial maturity (180 fruit per treatment, three replicates) were immersed in 0, 1.0, 3.0, or 5.0 mM salicylic acid (SA) for 15 min, then stored at 10ºC and 90% relative humidity (RH) for 20 d. After 20 d in cold storage, they were moved to 20ºC for 2 d to simulate shelf-life. Physiological and biochemical responses were studied. The results showed that the 3.0 or 5.0 mM SA treatments lowered the internal browning (IB) index, while the 5.0 mM SA treatment decreased the soluble solids content (SSC), titratable acidity (TA), and soluble sugar content, but increased ascorbic acid (AsA) levels at the end of shelf-life. Furthermore, during cold storage, all SA treatments significantly decreased the rate of tissue respiration in pineapple fruit. SA at 5.0 mM significantly decreased the activities of peroxidase (POD), polyphenol oxidase (PPO), and phenylalanine ammonia-lyase (PAL), but increased the activities of superoxide dismutase (SOD) and ascorbate peroxidase (APX) compared with the non-SA treated (untreated) controls. Overall, these results indicate that post-harvest treatment with 5.0 mM SA delayed the occurrence of IB in pineapple, extended its shelf-life, and maintained fruit quality during cold storage.     

Effect of temperature manipulation during storage and ripening on firmness,extractable juice and woolliness in nectarines

‘Independence’ nectarines were stored at — 0.5°C for three or four weeks or at 3°C for four weeks or kept at room temperature for 18 h prior to storage for four weeks at -0.5°C. After cold storage, fruit from all treatments was ripened at 10°, 15°or20°C. In all treatments the percentage woolly fruit initially increased to high values and thereafter decreased with further ripening. The rate of increase and decrease in woolliness depended on the ripening temperature. A storage period of four weeks at — 0.5°C resulted more woolliness during subsequent ripening. Woolliness persisted longer after a four-week cold storage period than after a three-week one. When fruit was delayed at room temperature prior to cold storage, woolliness generally developed earlier and to a lesser extent during ripening. At all ripening temperatures initial storage at 3°C resulted in most woolliness extending over the longest period. In addition, browning of the meso- carp tissue occurred only in fruit cold stored at 3°C.-The delay period before cold storage decreased fruit firmness by 15.7 to 17.6 N. Except for fruit subjected to the delay period, the extractable juice in fruit of all treatments first decreased during ripening to low values then increased.     

Pre- and post-harvest salicylic acid treatments alleviate internal browning and maintain quality of winter pineapple fruit

The post-harvest internal browning (IB) and quality in pineapple (Ananas comosus L. ‘Comte de Paris’) fruit were studied in relation to pre-harvest salicylic acid (SA) spray (PSS) or/and post-harvest salicylic acid immersion (PSI) treatments at 10 °C for up to 20 days plus 2 days at 20 °C (shelf-life). In addition, the activities of polyphenol oxidase (PPO) and phenylalanine ammonia-lyase (PAL) were measured during cold storage. The results showed that all SA treatments significantly reduced IB incidence and intensity. Furthermore, SA did not affect soluble solids content (SSC), titratable acidity (TA) and total phenolics (TP) content, but delayed the decline of ascorbic acid (AsA) content. At the same time, SA significantly inhibited PPO and PAL activities. The study indicated the beneficial effect of SA by pre-harvest spray and/or post-harvest immersion on pineapple fruit quality and resistance to IB, and PSS + PSI treatment showed the best effect.     

The effects of storage temperature and fruit size on firmness,extractable juice,woolliness and browning in two nectarine cultivars

Fruit firmness, extractable juice, woolliness and browning of the mesocarp tissue in ‘Independence’ and ‘Flavortop’ nectarines stored at —0.5°, 3°, 5° and 7°C for four weeks were determined during ripening at 15°C. The firmness of both ‘Independence’ and ‘Flavortop’ during ripening decreased as storage temperatures increased. The percentage extractable juice after cold storage and during ripening varied considerably between cultivars and between the storage temperatures. The extractable juice of fruit stored at higher temperatures tended to increase during ripening, whereas fruit stored at lower temperatures tended to decrease first before increasing. At storage temperatures of —0.5° and 3°C both cultivars passed through a stage of woolliness during ripening, while less woolliness occurred after storage at 5° and 7°C. In both cultivars the percentage extractable juice during ripening was higher on average at storage temperatures of 5° and 7°C. Severe browning of mesocarp tissue in both cultivars occurred during ripening after storage at 3°C. The effect of fruit size on changes in firmness, development of woolliness and mesocarp browning in ‘Flavortop’ nectarines stored at — 0.5°C for four weeks and ripened at 15°C was also determined. Larger nectarines lost firmness more rapidly, woolliness occurred sooner and the mesocarp tissue was more prone to browning than smaller fruit during ripening.     

Preventing cold storage disorders in nectarines

A storage experiment was aimed at preventing low temperature storage disorders in nectarine fruits, of cvs July Red and Autumn Grand. Fruit was either cooled immediately after harvest or kept at 20°C for 48 h, before transfer to controlled atmosphere (CA) conditions at 0°C. Combinations of 0, 10, 15 and 20% C02 with 8 and 16% 02 were assayed. The fruit was evaluated following cold storage, 31 days after harvest, and after four and eight days under ‘shelf conditions’ (ripening at 15-18 °C). Warming of the fruit at 20°C before cold storage prevented woolliness in the absence of elevated C02 levels but did not affect internal browning and increased reddish discoloration; further, it enhanced water loss and ripening, increasing fruit softening markedly. Conversely, high C02 delayed fruit ripening in CA storage, keeping the fruit firmer, and preventing the development of woolliness, internal browning and reddish discoloration during ripening, the best results being mostly obtained with 20% C02. 02 levels assayed did not show clear effects, but decreased 02 concentration in absence of high C02 showed some benefit in ‘July Red’. No deleterious effect of C02 concentrations even as high as 20% could be detected. Thus, even though high C02 in CA conditions showed promise for controlling disorders and preventing over-ripening, further work is needed on other cultivars, and lower 02 concentrations should be investigated before making a general recommendation.     

White light prevents increased catechin synthesis by ultraviolet irradiation in banana fruits

Irradiation of green banana fruit (Musa AAA, Cavendish subgroup, ‘Williams’) with an ultraviolet (UV)-C fluence of 720 Jm'2 increased ethylene evolution five-fold compared with controls during the first 24 h in either dark or light. The activity of phenylalanine ammonia-lyase (PAL) in extracts from the outer peel of irradiated fruit increased at least two-fold in either light or dark, but at 20°C it took 1-2 d for PAL activity to increase above the rate in controls. Irradiation did not affect the content of total phenolic compounds in outer peel in either dark or light until 4-6 d later. The content of chlorogenic acid was also not increased in either dark or light by UV-C. The catechin content of outer peel doubled in the dark within 24 h of irradiation and continued to increase six-fold during the first three days after irradiation. Exposure to white light (13.2 Wm 2) after irradiation almost completely prevented this increase in catechin content. These results show a close metabolic relationship between catechin and the bronze pigment previously reported in bananas irradiated with UV-C.     

Effects of temperature and plant growth regulators on anthocyanin synthesis and phenylalanine ammonia-lyase activity in chicory (Cichorium intybus L.)

Summary

This study addresses the effects of air temperature and plant growth regulators on anthocyanin synthesis, sugar content and phenylalanine ammonia-lyase (PAL) activity in chicory (Cichorium intybus L.). Anthocyanin in chicory was synthesised at the highest level under 15°/10°C (day/night) temperatures, followed by 20°/15°C, and 25°/20°C; while synthesis was inhibited > 90% at 30°/25°C, resulting in an almost green colour. Sugar contents paralleled anthocyanin development under the same temperatures. The plant growth regulators, abscisic acid (ABA), ethephon and uniconazole all stimulated anthocyanin synthesis, with uniconazole treatment showing the greatest effect. Gibberellic acid (GA₃) inhibited anthocyanin development, while GA₃ in combination with uniconazole alleviated this inhibition.

PAL activity was higher at 15°/10°C or 20°/15°C (day/night) temperatures when plants were treated with ABA, ethephon or GA₃, than at 25°/20°C and 30°/25°C (day/night) temperatures. These results suggest that, under lower temperatures, plant growth regulators may play an important role in anthocyanin synthesis and PAL activity in chicory.     

Variations in contents of (−)-epicatechin and activities of phenylalanine ammonialyase and polyphenol oxidase of longan fruit during development

Longan fruit has attracted much attention by consumers over the world due to the unique sweet–sour taste. However, the fruit brown rapidly at ambient temperature during storage, due to enzyme-catalyzed reaction of phenolics. Experiments were conducted to understand the variations in the levels of total phenolics and (−)-epicatechin as a major substrate for polyphenol oxidase (PPO) in pericarp tissue of longan fruit during development. The activities of phenylalanine ammonialyase (PAL) and PPO, involved in the synthesis and oxidation of (−)-epicatechin, respectively, during longan fruit development were also measured. During fruit development, the content of total phenolics decreased rapidly and then increased while the content of (−)-epicatechin tended to decrease. Both PAL and PPO activities decreased rapidly at the early fruit development and increased later but the increase of the former appeared was 10 days earlier than the latter. Thus, the level of (−)-epicatechin depended largely on PAL activity but it could involve the conversion of (−)-epicatechin into other flavonoids. This study could help develop appropriate preharvest treatments to control pericarp browning of harvested longan fruit by understanding the variation in the level of the major browning substrate during development.     

砂梨果肉褐变与酚类物质及相关酶活性的相关分析

【目的】为了探明砂梨褐变的内在机制,为砂梨贮藏与加工过程中品种选择和褐变控制提供理论依据,【方法】以11个砂梨品种的成熟果实为试材,测定总酚与酚类物质组成及含量、GSH含量、PPO、SOD、CAT、PAL、POD酶活性等相关指标。【结果】结果表明,不同品种酶促褐变程度有很大差别,‘新兴’和‘早生黄金’褐变较重,而‘秋黄’和‘丰水’较轻。绿原酸、儿茶素、芦丁和没食子酸是梨果肉中含量较高的酚类物质。总酚含量与果实褐变度相关性最高,绿原酸次之,儿茶素最低。【结论】梨果肉褐变相关酶活性与酚类物质组分及含量对其酶促褐变的影响程度因品种不同而存在差异。梨果肉酶促褐变与总酚和绿原酸含量的相关度高于与酶类的相关度。     

外源草酸对冷藏绿竹笋的保鲜效果及其生理基础

 绿竹笋（Dendrocalamopsis oldhami）采后分别置于水和5 mmol · L^-1 草酸溶液中浸泡10 min, 晾干后在（4 ± 0.5）℃条件下贮藏。结果发现草酸处理抑制了竹笋切面的褐变,延缓了笋肉木质纤维化。 草酸处理降低了脂氧合酶（LOX）、多酚氧化酶（PPO）、过氧化物酶（POD）和苯丙氨酸解氨酶（PAL） 活性,提高了超氧化物歧化酶（SOD）和过氧化氢酶（CAT）活性,并降低了过氧化氢（H₂O₂）含量。     

Effect of low temperatures on pulp browning and endogenous abscisic acid and ethylene concentrations in peach (Prunus persica L.) fruit during post-harvest storage

Summary

Changes in the severity of pulp browning, endogenous abscisic acid (ABA) and ethylene concentrations, and related gene expression in peach (Prunus persica L. ‘Bayuecui’) fruit stored at the biological freezing-point temperature (BFT; 1ºC), at 4ºC, or at room temperature (20ºC; as a control) were investigated.The results showed that fruit stored at room temperature showed climacteric changes in ethylene and ABA concentrations and in levels of expression of the corresponding ethylene synthetase genes (PpACS1, PpACO1) and the gene for a key enzyme of ABA synthesis (PpNCED), concomitant with a significant decrease in fruit firmness and an increase in juice yield. Meanwhile, two sucrose synthase genes (PpSUS1 and PpSUS2) were expressed at relatively low levels. However, fruit firmness decreased slightly and chilling injury (CI) increased significantly 40 d after storage (DAS) at 4ºC, with a significant accumulation of proline [from 8.33 µg g^–1 (at t = 0 d) to 9.125 µg g^–1 (at t = 40 d)]. In contrast, fruit firmness decreased slowly and pulp browning increased slightly 80 DAS at the BFT ( 1ºC), with a lower accumulation of proline than in fruit stored at 4ºC. The concentrations of soluble sugars and titratable acidity decreased during storage at 1ºC, 4ºC, or 20ºC, but there was a peak of soluble sugars at a late stage of storage at the BFT ( 1ºC). The fruit browning index was significantly and positively correlated (R ² = 0.967) with ABA concentration. The decrease in ABA concentration in cold-stored fruit (at both 1ºC and 4ºC) inhibited ethylene production. Moreover, there was no significant correlation between CI in fruit and ethylene production. In conclusion, the decrease in ABA concentration reduced ethylene concentrations and inhibited the development of pulp browning, which resulted in an improved taste, but crisper fruit, when fruit were stored at the BFT (–1ºC).     

Maturity and water loss effects on avocado (Persea americana Mill.) postharvest physiology in cool environments

The influence of cold storage, increasing fruit maturity and water loss on the ripening physiology of ‘Fuerte’ avocado was investigated. Fruit cold stored for 28 d at 5.5°C always subsequently ripened faster than non-stored fruits of a similar maturity. Non-stored fruit showed an expected decrease in ripening time with increasing maturity. In cold stored fruit the relationship between ripening time and maturity was less clear. Cold stored fruit lost less water during ripening than non-stored fruit of similar maturity, but lost water faster than non-stored fruit. Increasing maturity reduced the total amount of water lost during ripening. Cold storage increased the incidence of mesocarp discoloration which became more severe with increasing fruit maturity. Passive water infusion into fruit had no effect on the rate of fruit ripening (and water is obviously not involved as a ‘ripening trigger’) but totally inhibited the manifestation of postharvest browning disorders.     

Changes in Ripening Behaviors of 1-MCP-Treated ‘d’Anjou' Pears After Storage

Abstract

1-Methylcyclopropene (1-MCP), an ethylene action inhibitor, was applied to ‘d’Anjou' pears (Pyrus communis L.) at 20°C between 2 and 5 days after harvest. Scald of ‘d’Anjou' pears was completely controlled by 1-MCP at a concentration between 0.05 and 0.3 µl l1 after a prolonged cold storage plus 7 days of exposure to an environment with or without 500 µl l1 ethylene at a temperature of 20°C or 25°C. 1-MCP inhibited the biosyntheses of α-farnesene and its oxidative products (conjugated trienes) and thus controlled scald. However, fruit treated with the above concentrations of 1-MCP did not ripen normally in an environment with or without ethylene. Ethylene production and fruit softening of 1-MCP-treated ‘d’Anjou' pears were inhibited during 7 and 15 days at 20°C. ‘d’Anjou' fruit treated with 0.01 and 0.02 µl l¹ 1-MCP ripened normally on day 7 at 20°C after 3 months of cold storage at ? 1°C, and ripened fruit did not develop any incidence of scald. Untreated fruit developed substantial scald. After 4 months of storage or longer, both untreated fruit and fruit treated with 0.01 and 0.02 µl l 1 1-MCP developed an unacceptable incidence of scald upon ripening. Thus, use of other scald control methods may be necessary in addition to treatment with a low dosage of 1-MCP to insure both normal ripening and scald control for d'Anjou pear fruit from the Mid-Columbia district.     

Variations in contents of browning substrates and activities of some related enzymes during litchi fruit development

Pericarp browning is a major factor to limit storage and transportation of postharvest litchi fruit. Experiments were conducted firstly to determine variations in contents of browning substrate (−)-epicatechin in pericarp tissues of litchi fruit during development. Changes in the activities of polyphenoloxidase (PPO), peroxidase (POD) and phenylalanine ammonialyase (PAL) in association with the synthesis or oxidation of (−)-epicatechin were also examined. (−)-Epicatechin content tended to decrease during fruit development. PAL activity had a high level at the initial stage of fruit development, then decreased rapidly, and finally increased slightly, which was in agreement with the variation in (−)-epicatechin content. The higher contents of total phenolics and (−)-epicatechin of fruit of ‘Nuomici’ than ‘Feizixiao’ were also related to the higher PAL activity. PPO had a similar change to PAL in activity, but POD activity slowly decreased at the early fruit development and then increased markedly. It is suggested that (−)-epicatechin content might be largely regulated by PAL activity. This study could help to understand the variations in the content of the browning substrate and the activities of some substrate-related enzymes of litchi fruit during development and then control better pericarp browning of harvested litchi fruit by the application of appropriate preharvest treatments.     

Changes in parameters of cell senescence in carnation flowers after cold storage

The effects of cold storage on vase life, ethylene (C₂H₄) production, and parameters of cell senescence, were measured in flowers of spray carnation (Dianthus caryophyllus L.), cultivar ‘Pink Royalette’. Storage for 6 or 12 days at 2°C led to a reduction in the subsequent vase life at 20°C. In addition, storage caused a reduction in the time between the rise in ethylene production and the end of vase life. That is, cold storage increased the sensitivity of the petal cells to endogenous C₂H₄.Normal aging of flowers for 6 days at 20°C led to decreased capacity of petals to take up [¹⁴C] sucrose, decreased activity of membrane ATPase, increased membrane microviscosity and decreased membrane phospholipid content, relative to the levels in fresh flowers. However, cold storage of flowers for 6 days at 2°C caused opposite changes in the levels of these senescence parameters (measured at constant temperature). It was concluded that cold storage does not simply lead to a slow rate of senescence, but has other effects on cell properties.     

Effects of polyethylene bags,ethylene absorbent and 1-methylcyclopropene on the storage of Japanese pears

Summary

Storage of the ‘Nijisseiki’ cultivar of Japanese pears was studied over three seasons for periods up to 36 weeks at 0°C. Storage in 50 μm thick low-density polyethylene (LDPE) bags at 0°C considerably delayed yellowing in all experiments, even after fruit was removed to 20°C for 1 week at the end of storage. The addition of an ethylene absorbent made from potassium permanganate on aluminium oxide (Purafil II) further delayed yellowing. Carbon dioxide levels in both treatments varied, but were generally in the range 2–3%. Oxygen levels remained high, generally 16–19%. In bags without Purafil, ethylene levels rose slightly during storage and were generally about 0.15 μl l^–1. When Purafil was included in the bags, the ethylene level was reduced 10-fold or more. A sensory test indicated that the use of LDPE bags and ethylene absorbent resulted in fruit with better eating quality than fruit stored in air. Disorders over the 3-year investigation were low even after long-term storage. The use of polyethylene bags reduced the severity of flesh browning, and flesh spot decay was virtually absent. The use of bags increased the severity of core browning. Inclusion of an ethylene absorbent in bags reduced the severity of disorders, particularly core browning. Treatment of the fruit with 1-methylcyclopropene (1-MCP), before or during storage, resulted in higher ethylene levels in the polyethylene bags. At the concentrations used, 1-MCP did not improve the storage of ‘Nijisseiki’ compared to the use of polyethylene bags with Purafil II.     

外源绿原酸对苹果抗病相关酶的影响

采用离体培养方法对富士、红星和八棱海棠进行绿原酸处理,研究苹果在外源绿原酸处理下POD、PPO、PAL活性的动态变化以及绿原酸含量的变化。结果表明,富士以0.0001%绿原酸、红星以0.0008%绿原酸、八棱海棠以0.0004%绿原酸处理后,其PAL活性均显著提高,苹果体内也因此而提高了绿原酸水平。     

Erh?hung der Temperatur bei der Apfellagerung durch Einsatz von 1-MCP

The investigations should purify whether the temperature during apple storage can be increased by application of 1-MCP to decrease energy consumption and costs. The investigations were carried out over 2 years with the following treatments: Year 1: The apple cultivars ‘Elstar, Elshof’ and ‘Gala, Must’ were investigated. For both cultivars 3 different storage temperatures (1, 2 and 4°C) with and without application of 1-MCP were examined. Each temperature and 1-MCP treatment was investigated both under CA-/ULO-conditions with 1.5% O₂ and 2% CO₂ and in cold storage with normal atmosphere. Year 2: The apple cultivars ‘Jonagold, Jonica’ und ‘Golden Delicious, Weinsberg’ were investigated. For both cultivars 3 different storage temperatures (1, 2 and 4°C) with and without application of 1-MCP were examined. Each temperature and 1-MCP treatment was investigated both under CA-/ULO-conditions with 1.5% O₂ and 3% CO₂ and in cold storage with normal atmosphere. The influence of temperature, storage atmosphere and 1-MCP application on fruit firmness, soluble dry matter (sugar) and fruit acid was investigated on 6 dates (September to October in the first year) respectively on 5 dates (October to March) during the storage period. Following results were obtained:

1. In the first year storage temperature did not influence the content of soluble dry matter of both cultivars. Application of 1-MCP led to a less decomposition of soluble dry matter. In the second year the content of soluble dry matter decreased slightly with increasing temperatures. A clear positive effect of 1-MCP-application was not noticeable. Altogether an increase of storage temperature has no or only a small influence of the content of soluble dry matter. 1-MCP can slow down the decomposition of soluble dry matter.
2. An increase of storage temperature had no or only a small influence of fruit firmness. With increasing storage temperature fruit firmness decreased slightly.1-MCP application led to a higher fruit firmness, especially during cold storage in normal atmosphere. In both years all cultivars showed a same or higher fruit firmness at 4°C with 1-MCP application under CA-/ULO-conditions as at 1°C without 1-MCP application under CA-/ULO-conditions.
3. An increase of storage temperature had no or only a small influence of the content of fruit acid.1-MCP application under CA-/ULO-conditions reduced the decomposition of fruit acid. In both years usually all cultivars showed a same or higher content of fruit acid at 4°C with 1-MCP application under CA-/ULO-conditions as at 1°C without 1-MCP application under CA-/ULO-conditions.

The results show that an increasing of storage temperature under CA-/ULO-conditions and with 1-MCP application has no negative influence on fruit quality in comparison to fruits which were stored under CA-/ULO-conditions at low temperatures without 1-MCP application.     

Effects of nitric oxide fumigation on post-harvest core browning in ‘Yali’ pear (Pyrus bretschneideri Rehd.) during cold storage

Summary

Core browning often occurs as a physiological disorder in ‘Yali’ pear (Pyrus bretschneideri Rehd.) and results in a high losses during storage. In this study, the effects of fumigation with nitric oxide (NO) gas on the incidence of core browning in ‘Yali’ pears during cold storage were investigated. ‘Yali’ pear fruit were treated with 0, 10, 20, or 30 µl l^–1 NO at 25º ± 2ºC for 3 h under anaerobic conditions, then stored at 0º ± 1ºC under normal air for up to 120 d. The data showed that fumigation with 20 µl l^–1 NO was most effective at suppressing core browning. Thereafter, treatment with 20 µl l^–1 NO was used for comparisons with untreated control fruit in experiments to measure changes in total phenolics contents, polyphenol oxidase (PPO) activities, and the contents of glutathione (GSH), ascorbic acid (AsA), and NO in fruit core tissue during storage. The results showed that NO-fumigated fruit had lower PPO activity, but higher GSH and AsA contents in their core tissue compared with untreated control fruit. NO fumigation also maintained higher endogenous NO levels in core tissue after 60 d in storage, while the total phenolics contents of fruit remained at lower levels until day-100 of storage. These results indicate that the inhibitory effect of fumigation with

20 µl l^–1 NO on core browning was associated with its effects on reducing PPO activity and total phenolics contents, while maintaining the contents of GSH and AsA in core tissue of ‘Yali’ pear during cold storage.