EFFECT OF OXYGEN CONCENTRATION ON THE BIOCHEMICAL AND CHEMICAL CHANGES OF STORED LONGAN FRUIT

ABSTRACT

Longan fruits were stored for 6 days in atmosphere of 5, 21 (air) or 60% O₂ (balance N₂) at 28C and 90–95% relative humidity to examine effects of low and high O₂ concentration on enzymatic browning and quality attributes of the fruit. Changes in pericarp browning, pulp breakdown, disease development, total phenol content, activities of phenol metabolism‐associated enzymes, relative leakage rate, α,α‐diphenyl‐β‐picrylhydrazy (DPPH) radical scavenging activity, and contents of total soluble solids, titratable acidity and ascorbic acid were evaluated. Storage of fruit in a 5% O₂ atmosphere markedly delayed pericarp browning in association with maintenance of high total phenolic content and reduced activities of polyphenol oxidase (PPO), peroxidase (POD) and phenylalanine ammonia lyase. Moreover, the fruit stored in a 5% O₂ atmosphere exhibited a lower relative leakage rate and higher DPPH radical scavenging activity than fruit stored in air. This presumably was beneficial in maintaining compartmentation of enzymes and substrates, and thus, reducing pericarp browning. Pulp breakdown and disease development were also reduced by exposure to a 5% oxygenatmosphere. On the contrary, exposure of longan fruit to a 60% O₂ atmosphere accelerated pericarp browning, pulp breakdown and decay development. PPO and POD activities and relative leakage rate were similar for control and 60% O₂‐treated fruit after 4 and 6 days of storage. Furthermore, treatment with 60% O₂ significantly decreased the phenolic content and DPPH scavenging activity of fruit. In addition, exposure to 5 or 60% O₂ resulted in a higher level of total soluble solids, but a lower level of ascorbic acid of longan fruit flesh. In conclusion, exposure to a 5% O₂ atmosphere showed great potential to reduce pericarp browning and extend shelf life of longan fruit.

PRACTICAL APPLICATIONS

Pericarp browning and pulp breakdown are the major causes of deterioration in postharvest longan. Conventional controlled atmosphere with low O₂ and high CO₂ is effective in maintaining quality and extending shelf life of fruits and vegetables, including inhibition of tissue browning. In this study, 5%‐controlled atmosphere reduced significantly pericarp browning, pulp breakdown and rot development. It could potentially be useful as a postharvest technology of longan fruit for reducing or replacing the use of chemicals such as SO₂ and fungicides, but it requires further investigation.     

Fruit quality and physiological responses of litchi cultivar McLean's Red to 1-methylcyclopropene pre-treatment and controlled atmosphere storage conditions

The effect of 1-MCP pre-treatment and two different controlled atmosphere storage conditions (CA-1, 17% O₂ + 6% CO₂; CA-2, 7% O₂ + 3% CO₂) on fruit quality parameters and physiological changes with respect to pericarp browning in ‘McLean's Red’ litchi were investigated. Fruits were pre-treated with 1-MCP (500 nl/l) and held at CA-1 or CA-2 for 21 d at 2 °C and at 90% RH. Stand-alone CA-1 or stand-alone CA-2 and the commercially adopted sulphur dioxide (SO₂) treatment were included in this study for comparison. Of the five treatments 1-MCP + CA-1 was most effective in preventing browning, loss of red colour (colour value a*) of the pericarp, ascorbic acid content; and retaining acceptable SSC/TA and taste. Fruit from 1-MCP + CA-1 showed higher overall acceptance after 21 d storage without any off-flavour according to the sensory panel data.1-MCP + CA-1 reduced the polyphenol oxidase (PPO) and peroxidase (POD) activity, retained membrane integrity and anthocyanin content during storage. Although SO₂ treatment prevents browning it showed negative effects on SSC/TA, taste and membrane integrity. Stand-alone CA-2 condition indicated higher pericarp browning, PPO, POD activity and loss of membrane integrity. Therefore, 1-MCP pre-treatment and CA-1 retains overall fruit quality for up to 21 d.     

Identification of (−)-epicatechin as the direct substrate for polyphenol oxidase from longan fruit pericarp

Postharvest browning of longan fruit results in a short life and a reduced commercial value. The experiments were conducted to separate, then purify and finally identify the polyphenol oxidase (PPO) substrates that cause longan fruit to brown. PPO and its substrates were, respectively, extracted from longan fruit pericarp tissues. The substrate for longan PPO was separated and purified using polyamide column chromatography, Sephadex LH-20 column chromatography and silica gel column chromatography, respectively. The substrate was further identified by 0.5% FeCl₃ solution and enzymatic reaction with longan PPO. On the bases of UV, ¹H NMR, ¹³C NMR, and ESI-MS data, the direct substrate for the PPO from pericarp tissues of longan fruit was identified to be (−)-epicatechin. Furthermore, the contents of (−)-epicatechin of pericarp tissues of longan fruit of two major cultivars were determined by high performance liquid chromatography (HPLC). The HPLC analysis exhibited that the contents of (−)-epicatechin of fruit pericarp of ‘Shixia’ and ‘Chuliang’ were 0.26 and 0.56 mg/g on fresh weight (FW) basis at harvest and 0.15 and 0.09 mg/g FW after 3 days of storage. The more rapid decrease in the (−)-epicatechin content of ‘Chuliang’ was due to the oxidization catalyzed by PPO, which was in agreement with the higher browning index.     

Combined effects of natural substances and modified atmosphere packaging on reducing enzymatic browning and postharvest decay of longan fruit

An integrated control strategy on preventing pericarp browning (BI) and decay incidence (DI) of longan fruit was investigated to replace sulphur dioxide (SO₂) fumigation. Fruit was treated with 5% ascorbic acid (AA), citric acid (CA), oxalic acid (OA), thymol (TH) and 2% chitosan (CH) for 5 min; sealed under modified atmosphere packaging (MAP) using high permeable film; and stored at 5 °C. Fruit treated with distilled water and sealed under MAP condition (MAPC) and air condition (AIRC) was used as controls. Combined effects of chemical treatments and MAP maintained quality of longan for 56 and 49 days in CH and TH, respectively, as compared to 28 days in MAPC and 21 days in AIRC. AA, CA and OA prevented BI, restrained enzyme activities and maintained high phenols. AA, CA and OA were most potent BI inhibitors; however, DI was the limitation of these treatments, while CH and TH effectively inhibited DI.     

Optimum controlled atmospheres minimise respiration rate and quality losses while increase phenolic compounds of baby carrots

Baby carrot is a very perishable product mainly due to the abrasion of the cylindrical carrot root segments. The influence of four different controlled atmospheres (CA) (air, 2 kPa O₂ + 15 kPa CO₂, 5 kPa O₂ + 5 kPa CO₂ and 10 kPa O₂ + 10 kPa CO₂) was studied to maintain quality and prolong the shelf life of baby carrots. Respiration rate (RR), the content of vitamin C, carotenoids and phenolics by HPLC as well as the sensory quality of baby carrots during storage at 4 °C were evaluated. The lowest RR was observed in baby carrots stored under CA containing the lowest O₂ concentrations. Baby carrots under low O₂ atmospheres preserved the highest vitamin C content, as well as the individual carotenoids. The wound-induced phenolic compounds, mainly trans chlorogenic acid, increased two fold in baby carrots stored under 5 kPa O₂ + 5 kPa CO₂. In general, CA maintained the overall visual quality of baby carrots up to 8 days. Controlled atmosphere of 5 kPa O₂ + 5 kPa CO₂ can be recommended as an optimum atmosphere to maintain quality of baby carrots, increasing bioactive compounds such as chlorogenic acid and avoiding anaerobic fermentation in case of temperature abuse.     

Purification and some properties of polyphenol oxidase of longan fruit

Polyphenol oxidase (PPO) was isolated from longan (Dimocarpus longan Lour.) fruit peel, with a 46-fold purification of PPO by ammonium sulfate, Sephadex G-200 and Phenyl Sepharose being achieved. Pyrogallol, 4-methylcatechol, and catechol were good substrates for the enzyme, and activity with chlorogenic acid, p-cresol, resorcinol, or tyrosine was not observed. The optimal pH for PPO activity was 6.5 with 4-methylcatechol. The enzyme had a remarkably temperature optimum (35°C) and was relatively stable, requiring a little more than 20 min at 50°C for 50% loss of activity. Reduced glutathione, l-cysteine, thiourea, FeSO₄ and SnCl₂ markedly inhibited PPO activity, whereas MnSO₄ and CaCl₂ enhanced PPO activity. Data obtained in this study might help to better understand longan fruit peel browning.     

Controlled and modified atmospheres influence chilling injury,fruit quality and antioxidative system of Japanese plums (Prunus salicina Lindell)

Our objective was to compare the effects of controlled atmosphere (CA) and modified atmosphere packaging (MAP) on fruit quality, chilling injury (CI) and pro‐ and antioxidative systems in ‘Blackamber’ Japanese plums. Matured fruit were stored for 5 and 8 weeks at 0–1 °C in normal air, CA‐1 (1% O₂ + 3% CO₂), CA‐2 (2.5% O₂ + 3% CO₂) and MAP (~10% O₂ and 3.8% CO₂). CA was more effective than MAP in retention of flesh firmness and titratable acidity during cold storage. Fruit stored in CA‐1 showed reduced CI and membrane lipid peroxidation after 5 and 8 weeks of cold storage. Low O₂ atmospheres appeared to limit the generation of reactive oxygen species (ROS) and their efficient scavenging through the concerted action of superoxide dismutase and peroxidase. The role of ascorbate–glutathione (AsA–GSH) cycle in the regulation of oxidative stress was also studied during and after storage in different atmospheres. In conclusion, optimum CA conditions delayed fruit ripening and CI through augmentation of antioxidative metabolism and suppression of oxidative processes.     

Impact of controlled atmosphere storage on physiological quality of soybean seed

Soybean seed tends to lose its quality property if kept in inappropriate storage conditions. The aim of this work was to evaluate the effect of different oxygen (O₂) and carbon dioxide (CO₂) partial pressures, combined with different temperatures on the soybean seed physiological potential maintenance. In 2017, seed of the cultivars 8473 RSF and TECIRGA 6070RR were stored for 7 months under: [1] ambient air; controlled atmosphere (CA) with [2] 1 kPa O₂ + 0.04 kPa CO₂; [3] 2 kPa O₂ + 0.04 kPa CO₂; [4] 2 kPa O₂ + 30 kPa CO₂; and [5] 2 kPa O₂ + 80 kPa CO₂. In 2018, seed of NA 5909 RG and FEPAGRO 37RR were stored for 7 months under the following conditions: [1] ambient air; and CA with [2] 1 kPa O₂ + 0.04 kPa CO₂; [3] 1 kPa O₂ + 15 kPa CO₂; [4] 1 kPa O₂ + 30 kPa CO₂; [5] 2 kPa O₂ + 0.04 kPa CO_2. In both years the storage conditions were conducted at three temperatures (20, 25 and 30 °C). The seed were stored with moisture content between 11 and 11.5. The reduction of the O₂ until 1.0 kPa maintained higher germination, however, storage above 25 °C is not recommended. High CO₂ partial pressure did not have additional effects on physiological quality conservation compared to solely low O₂. Seed of 8473 RSF stored at 25 and 30 °C resulted in low germination, regardless of the CA condition. NA 5909 RG reached 80% of germination, when CA was used, regardless of temperature. The ambient air did not maintain the seed physiological quality when stored at 25 and 30 °C and CA may efficiently maintain the physiological quality of soybean seed after 7 months, even in the higher temperature for NA5909 RG, but not for the other cultivars.     

Physiological responses and quality attributes of ‘Kyoho’ grapes to controlled atmosphere storage

This research studied the physiological responses and quality attributes of Kyoho grapes (Vitis vinifera X V. labrusca) to controlled atmosphere storage. The grapes were stored for up to 60 days in 95% relative humidity with four different conditions, 4% O₂+9% CO₂, 4% O₂+30% CO₂, 80% O_2, and air, as control. The examined physiological responses and quality attributes included polyphenol oxidase (PPO) activity, ethanol concentration, fruit detachment force (FDF), firmness, color, soluble solid content (SSC), titratable acidity (TA), ascorbic acid concentration (Vc), and sensory quality. PPO activity, FDF drop and decay incidence when stored in 4% O₂+30% CO₂ were more effectively controlled, but unacceptable alcoholic flavor and browning were detected after 45 days, compared with those stored in 4% O₂+9% CO₂ or 80% O₂. The fruits kept in 4% O₂+9% CO₂ or 80% O₂ had good quality during 60 days of storage. The results suggested that high O₂ atmosphere exhibited a potential for maintaining the quality of ‘Kyoho’ grapes during long-term storage.     

Browning characteristics of fresh-cut ‘Tsugaru’ apples as affected by pre-slicing storage atmospheres

The change in browning characteristics of the slices processed from ‘Tsugaru’ apples stored at 0 °C for 5 months under controlled atmosphere (CA, 1 kPa O₂ + 1 kPa CO₂, 3 kPa O₂ + 3 kPa CO₂) or air has been investigated for 5 days at 20 °C. Respiration and ethylene production of the slices from apples stored in CA were retarded. Electrolyte leakage and browning index were lower in the slices from apples stored under CA than air. Vitamin C and phenolic contents in the slices from apples stored under air were maintained at higher level compared to the slices from apples stored under CA. Polyphenol oxidase activity in the slices was not affected by pre-slicing storage atmospheres. Therefore, the atmospheres of pre-slicing storage affected browning development in fresh-cut products of ‘Tsugaru’ apples and browning was found to be correlated with the levels of electrolyte leakage and phenolic compounds.     

Effect of nitric oxide on pericarp browning of harvested longan fruit in relation to phenolic metabolism

The effects of nitric oxide (NO) on enzymatic browning of harvested longan fruit in relation to phenolic metabolisms were investigated. Fruits were dipped for 5 min in 1 mM sodium nitroprusside (SNP), a nitric oxide donor, then packed in 0.03 mm thick polyethylene bags, and finally stored for 6 days at 28 °C. Changes in pericarp browning and pulp breakdown were evaluated, while total phenol content, activities of phenolic-associated enzymes, polyphenol oxidase (PPO), peroxidase (POD) and phenylalanine ammonia lyase (PAL), and concentrations of total soluble solids, titratable acidity and ascorbic acid were measured. SNP treatment delayed pericarp browning, inhibited activities of PPO, POD and PAL and maintained a high total phenol content of longan fruit during storage. Furthermore, NO showed a significant inhibition of the in vitro activities of PPO and POD, indicating that the beneficial effect of NO was direct. Moreover, application of NO resulted in a lower pulp breakdown and maintained relatively high levels of total soluble solids and ascorbic acid.     

Quality of fresh-cut tomato as affected by type of cut,packaging, temperature and storage time

Long-life Calibra tomatoes (Lycopersicum esculentum Mill.) were minimally fresh processed in slices or wedges and packaged in polypropylene (PP) trays. Passive and active (3 kPa O₂+0 kPa CO₂ and 3 kPa O₂+4 kPa CO₂) modified atmosphere packages (MAP) were used at 0 and 5 °C. After 14 days, the gas composition within passive MAP packages was 11–13 kPa O₂+5.5–6 kPa CO₂ and 8–9.5 kPa O₂+10.5–11.5 kPa CO₂ at 0 and 5 °C, respectively. The gas composition reached in active MAP at both temperatures for both types of cuts was around 7–10.5 kPa O₂ and 7–9 kPa CO₂. The highest C₂H₄ level (15 L L^–1) was found in passive MAP at 5 °C, while in active MAP at both temperatures about 6 L L^–1 C₂H₄ accumulated. After 7 days of storage at 0 °C, the tomato pieces showed better aroma, appearance and overall quality than those stored at 5 °C. No difference between MAP treatments was found, although both led to a better appearance and overall quality than controls in air. After 14 days at 0 °C, only MAP treatments kept a good flavour, overall quality and texture, with no differences between them. After 14 days at 5 °C in all treatments, the flavour fell below a fair condition and the slices showed a slight senescence. MAP significantly reduced total plate counts (TPC) of slices at 5 °C, although only active MAP reduced TPC in wedges after 14 days at 5 °C. A visibly better appearance and overall quality was found in slices than in wedges. The main factors influencing the quality of tomato pieces were the storage duration and temperature. To keep the quality of fresh-cut tomatoes, one should consider three factors for selection: a suitable low chilling sensitive tomato cultivar, an adherent placenta and optimal maturity stage at harvest.     

Preservation of precut white cheese by modified atmosphere packaging

Effects of modified atmosphere packaging (MAP) on storage stability and quality of precut fresh and aged white cheese were investigated. Fresh or aged white cheese was cut into small cubes and packaged in five different atmospheres [0% O₂ + 0% CO₂ + 100% N₂ (MAP1), 10% O₂ + 0% CO₂ + 90% N₂ (MAP2), 0% O₂ + 75% CO₂ + 25% N₂ (MAP3), 10% O₂ + 75% CO₂ + 15% N₂ (MAP4) and aerobic (air)]. Control samples were packaged in brine and vacuum for fresh and aged white cheese, respectively. Changes in gas composition, total plate count, lactococci, lactobacilli, yeast and mould counts, proteolysis, lipolysis, pH, colour, texture and sensory properties were investigated during refrigerated storage. The best packaging treatment for the fresh cheese was MAP3, as it inhibited mould growth and protected the hardness. MAP2 can be recommended for the packaging of the aged cheese, as it decreased lipolysis.     

Effects of O2 and CO2 concentrations on physiology and quality of litchi fruit in storage

Litchi (Litchi chinensis Sonn. cv Heiye) fruit were stored in air, modified atmosphere packaging (MAP) and controlled atmospheres (CA) at 3 °C to determine the effects of different O₂ and CO₂ atmospheres on physiology, quality and decay during the storage periods. The results indicated that CA conditions were more effective in reducing total phenol content, delaying anthocyanidin decomposition, preventing pericarp browning, and decreasing fruit decay in comparison with MAP treatment. Polyphenol oxidase (PPO), peroxidase (POD), anthocyanin and total phenols were involved in cellular browning. High O₂ treatment significantly limited ethanol production of litchi flesh in the early period of storage. The fruit stored in CA conditions for 42 days maintained good quality without any off-flavour.     

Control of internal browning and quality improvement of ‘Fuji’ apples by stepwise increase of CO2 level during controlled atmosphere storage

To control internal browning injury and to reduce quality loss in ‘Fuji’ apples during storage, a stepwise controlled atmosphere (CA) method was applied in this study. Both non‐bagged and bagged apples during maturation were stored at 0 °C under 1% O₂ + 1% CO₂, 1% O₂ + 3% CO₂ or air for 10 months, and 1% O₂ + 1% CO₂ for 2 months followed by 1% O₂ + 3% CO₂ for 8 months (stepwise CA). The concentrations of internal ethylene and carbon dioxide in apples kept for 24 h at 20 °C after storage under CA conditions were maintained at low level, but there was no effect of stepwise CO₂ increase on internal gas concentrations. The non‐bagged and bagged apples stored under stepwise CA were not significantly different from those stored under 1% O₂ + 3% CO₂ continuously for 10 months in term of flesh firmness, titratable acidity and yellowing index. However, the apples stored under stepwise CA were firmer, more acid and greener than those stored under 1% O₂ + 1% CO₂ continuously for 10 months. Internal browning injury occurred in apples stored under 1% O₂ + 3% CO₂ continuously for 10 months, but it was suppressed completely by stepwise CA storage. The stepwise CA, increasing of CO₂ level after holding at 1% CO₂ for the first 2 months of storage, was effective in maintaining the quality and controlling the internal browning injury in non‐bagged and bagged ‘Fuji’ apples. Copyright © 2005 Society of Chemical Industry     

Effect of lactate-enhancement, modified atmosphere packaging, and muscle source on the internal cooked colour of beef steaks

Earlier studies on lactate-mediated colour stability in beef did not address the possible influence on cooked colour. Our objective was to examine the effect of lactate-enhancement, muscle source, and modified atmosphere packaging (MAP) on the internal cooked colour of beef steaks. Longissimus lumborum (LL) and Psoas major (PM) muscles from 16 (n = 16) beef carcasses (USDA Select) were randomly assigned to 4 enhancement treatments (non-injected control, distilled water-enhanced control, 1.25% and 2.5% lactate), and fabricated into 2.54-cm steaks. Steaks were individually packaged in either vacuum (VP), high-oxygen MAP (HIOX; 80% O₂ + 20% CO₂), or carbon monoxide MAP (CO; 0.4% CO + 19.6% CO₂ + 80% N₂), and stored for 0, 5, or 9 days at 1 °C. At the end of storage, surface and internal colour (visual and instrumental) was measured on raw steaks. Steaks were cooked to an internal temperature of 71 °C, and internal cooked colour (visual and instrumental) was evaluated. Lactate-enhancement at 2.5% level resulted in darker (P < 0.05) cooked interiors than other treatments. Interior cooked redness decreased (P < 0.05) during storage for steaks in VP and HIOX, whereas it was stable for steaks in CO. Our findings indicated that the beef industry could utilise a combination of lactate-enhancement and CO MAP to minimise premature browning in whole-muscle beef steaks.     

Inactivation of polyphenol oxidase in muscadine grape juice by dense phase-CO2 processing

The effect of dense phase-CO₂ processing (DP-CO₂) on polyphenol oxidase (PPO) activity, polyphenolic and antioxidant changes in muscadine grape juice under different processing pressures (27.6, 38.3, and 48.3 MPa) and CO₂ concentrations (0, 7.5, and 15%) were measured. Subsequently two DP-CO₂ conditions (48.3 MPa at 0 or 15% CO₂) were evaluated for polyphenolic and antioxidant changes during storage (4 °C, four weeks). Pressure alone was responsible for a 40% decrease in PPO activity that resulted in 16–40% polyphenolic and antioxidant losses. Increasing CO₂ from 0 to 7.5% was responsible for an additional 35% decrease in enzyme activity and a two-fold greater polyphenolic retention. However, insignificant changes in PPO activity or polyphenolic retention were observed when CO₂ was increased to 15%. During storage, juices with residual PPO activity following processing resulted in greater polyphenolic (8- to 10-fold) and antioxidant capacity (four-fold) degradation compared to control juices with no PPO activity. This study demonstrated that partial PPO inactivation can be obtained by DP-CO₂ and that CO₂ level was the primary variable influencing PPO activity and polyphenolics and antioxidant capacity retention in muscadine grape juice.     

Combined effect of carbon monoxide mixed with carbon dioxide in air on the mortality of stored-grain insects

A study to determine the effect of carbon monoxide (CO) mixed with carbon dioxide (CO₂) in air on controlling stored-grain insects was conducted in the laboratory. Within modified airtight gas exposure units containing wheat at 15% moisture content wet basis (w.b.), mixed-age adults of rusty grain beetle, Cryptolestes ferrugineus (Stephens), red flour beetle, Tribolium castaneum (Herbst), and granary weevil, Sitophilus granarius (L.) were exposed for 48, 96, 144 or 192 h to three types of gas mixtures in air, 5% CO, or 30% CO₂, or 5% CO + 30% CO₂ at 20 °C and 30 °C, the balance of the gas being air in each case.Carbon monoxide alone had no effect on the mortality of adults of the three insect species. For C. ferrugineus, there was no difference in mortality between by CO₂ alone and the CO₂ + CO mixture at either temperature for all exposures. However, both T. castaneum and S. granarius had higher mortality in the CO₂ + CO mixture than the CO₂ alone at both temperatures. Moreover, S. granarius was more susceptible to CO₂ + CO mixture than T. castaneum. These results suggest that for certain species, CO could be used to increase the efficiency of CO₂, especially at high temperatures.     

Effect of different levels of CO2 on the antioxidant content and the polyphenol oxidase activity of ‘Rocha’ pears during cold storage

Pears (Pyrus communis L. cv. ‘Rocha’) were exposed to air or controlled atmosphere (CA) containing various concentrations of CO₂: 0, 0.5 and 5 kPa, all with 2 kPa O₂. After 4 months of storage at 2 °C, the fruits were transferred to air at room temperature, and assessed in terms of soluble solids, titratable acidity, pH, incidence of brown heart and flesh browning, phenolic content, vitamin C content and polyphenol oxidase activity. By 4 months of storage, soluble solids and pH increased, and acidity decreased relative to harvest, but no differences were detected between pears stored under air or any of the CA tested. Higher contents of hydroxycinnamic derivatives and flavan‐3‐ols in the peel than in the flesh were recorded. However, the content of arbutin was higher in the flesh than in the peel, whereas flavonols were only detected in the peel. In general, hydroxycinnamic derivatives and flavonols were stable throughout storage, but flavan‐3‐ols decreased in concentration under air or CA. Arbutin was the only phenolic compound that increased in concentration as time elapsed. No clear relation was found between the storage conditions tested and the phenolic concentration in pears. Regarding ascorbic acid (AA) and dehydroascorbic acid (DHA), their concentrations were higher in the peel than in the flesh. Furthermore, AA and DHA were strongly affected by storage: the former decreased, whereas the latter increased in content. A decrease in PPO activity was apparent after harvest and during storage, particularly under higher levels of CO₂. The combination 2 kPa O₂ + 5 kPa CO₂ increased the incidence of internal disorders (viz. brown heart and flesh browning) after storage. Copyright © 2005 Society of Chemical Industry     

Mechanical parameters to assess quality changes in cherimoya fruit

 Several mechanical parameters obtained by means of compression and penetration tests, and changes in cherimoya (Annona cherimola Mill.) fruit quality during storage in air and two controlled atmospheres (CA), (3% O₂+0% CO₂ and 3% O₂+3% CO₂) were analysed. A gradient of softening was found among the equatorial and the apical areas of the flesh during CA storage, as assessed by localized penetration tests. The combination of low O₂/elevated CO₂ (3% O₂+3% CO₂) increased this gradient and had a greater inhibiting effect on skin softening than low O₂. It appeared that the prevention of softening by CA was stronger in the less mature tissues (equatorial and outer areas) than in the more mature tissues (apical and inner areas around the longitudinal axis). CA delayed or inhibited changes in fruit quality observed during air storage: increases in total soluble solids (TSS), titratable acidity (TA), and yellowness of the flesh (b), and diminution in flesh lightness of colour (L). A good relationship between an objective quality index (QI, where QI=TSS+TA+L/b) and the compression slope (CS) was found during storage under all the conditions tested. It is suggested that the relationship, QI=29.25+0.04×CS–0.0023×CS² could be useful when assessing stages of cherimoya fruit quality during storage under different conditions by performing a nondestructive, compression test. Received: 23 April 1998