Effect of 1-methylcyclopropene (1-MCP) on softening of fresh-cut kiwifruit,mango and persimmon slices

Ethylene production is enhanced by wounding during fresh-cut processing and the accumulation of this gas within the packages of fresh-cut fruit can be detrimental to their quality and shelf-life. The effect of 1-methylcyclopropene (1-MCP), an ethylene action blocker, applied before or after processing, on the quality of fresh-cut kiwifruit, mangoes and persimmons was evaluated during storage at 5 °C. Fresh-cut ‘Hayward’ kiwifruit slices softened at a slower rate and their ethylene production rate was decreased in response to 1-MCP application (1 μL L⁻¹ for 6 h at 10 °C) either before or after processing. A 2-min dip in 0.09 M (1%, w/v) CaCl₂ synergistically increased the effect of 1-MCP on firmness retention and 1-MCP did not affect the color (L* value) of fresh-cut kiwifruit slices. Softening and browning (decreasing L* value) were delayed when 1-MCP was applied directly on fresh-cut ‘Kent’ and ‘Keitt’ mango slices. Respiration rate of mango slices was not influenced by 1-MCP whereas the ethylene production was affected only towards the end of their shelf-life. Fresh-cut ‘Fuyu’ persimmons treated with 1-MCP after processing presented higher ethylene production rate, slower softening rate and slower darkening of color (decrease in L* value), whereas the respiration rate was not affected.     

Induction of ripening capacity in ‘Packham's Triumph’ and ‘Gebhard Red D’Anjou’ Pears by temperature and ethylene conditioning

Methods were tested for rapid induction of ripening capacity in ‘Packham's Triumph’ and ‘Gebhard Red D’Anjou’ pears in order to facilitate early marketing. Fruit of each cultivar were harvested at the onset of maturity and conditioned to develop ripening capacity by exposure to 100 μL L⁻¹ ethylene at 20 °C for 0, 24, 48, or 72 h, followed by varying durations of temperature conditioning at −0.5 or 10 °C. Ripening capacity was tested by measuring fruit firmness after 7 d at 20 °C after completion of conditioning treatments. Fruit firmness was also measured after conditioning but before ripening, and was designated “shipping firmness,” indicative of the potential for the fruit to withstand transport conditions without physical injury. With temperature conditioning at −0.5 °C only, ‘Packham's Triumph’ pears needed 45 d to develop ripening capacity, while ‘Gebhard Red D’Anjou’ pears were not capable of fully ripening after 60 d, the longest duration tested. Using ethylene only, 72 h exposure was necessary to develop full ripening capacity in both cultivars, and adequate shipping firmness was maintained. Using temperature conditioning at 10 °C, ripening capacity in ‘Packham's Triumph’ and ‘Gebhard Red D’Anjou’ developed within 10 and 20 d, respectively, but shipping firmness in ‘Gebhard Red D’Anjou’ was compromised at 20 d. In both cultivars, 24 or 48 h in ethylene followed by 5 d at 10 °C induced ripening capacity while maintaining adequate shipping firmness.     

Physiology of fresh-cut ‘Galia’ (Cucumis melo var. reticulatus) from ripe fruit treated with 1-methylcyclopropene

‘Galia’ (Cucumis melo var. reticulatus L. Naud. cv. Galia) fruit were harvested at the three-quarter slip stage and treated with 1 μL L⁻¹ 1-methylcyclopropene (1-MCP) at 20 °C for 24 h. The fruit were processed and stored as fresh-cut cubes and intact fruit for 10 d at 5 °C. Ethylene production of fresh-cut cubes was approximately 4–5-fold higher than intact fruit at day 1. Afterward, the ethylene production of fresh-cut cubes declined significantly whereas that of intact fruit remained relatively constant at about 0.69–1.04 ng kg⁻¹ s⁻¹. 1-MCP delayed mesocarp softening in both fresh-cut and intact fruit and the symptoms of watersoaking in fresh-cut fruit. Continuously stored fresh-cut cubes and cubes derived from intact fruit not treated with the ethylene antagonist softened 27% and 25.6%, respectively, during 10 d storage at 5 °C while cubes derived from 1-MCP-treated fruit softened 9% and 17%, respectively. Fresh-cut tissue from 1-MCP-treated fruit exhibited slightly reduced populations of both total aerobic organisms and Enterobacterium, although the differences did not appear to be sufficient to explain the differences in keeping quality between 1-MCP-treated and control fruit. Based primarily on firmness retention and reduced watersoaking, 1-MCP treatment deferred loss of physical deterioration of fresh-cut ‘Galia’ cubes at 5 °C by 2–3 d compared with controls.     

Effectiveness of 1-MCP treatments on ‘Bartlett’ pears as influenced by the cooling method and the bin material

Wooden bin-stored ‘Bartlett’ pears (Pyrus communis L.) were hydrocooled (HC) or forced-air cooled (FAC) and immediately treated or not with 1-methylcyclopropene (1-MCP) for 24 h. 1-MCP gas concentrations used were 0, 0.3 or 0.6 μL L^?1 (called 0, 0.3 and 0.6, respectively). Fruit were subsequently kept at 20 °C for 20 d or stored at ?0.5 °C and 95% RH for 60, 90, 120 or 150 d. After cold storage, fruit were kept at 20 °C for up to 16 d for further ripening. In another experiment, pears stored in wooden bins (W) or plastic bins (P) were all hydrocooled, treated or not with 0.5 μL L^?1 1-MCP (called 0.5 and 0, respectively), stored at ?0.5 °C and 95% RH for 0, 30, 60, 90 or 120 d, and transferred to 20 °C for further ripening. In FAC pears, increasing 1-MCP concentrations usually resulted in delayed increases in ethylene production and lower ethylene production rates, as well as delayed softening. In contrast, HC-0.3 pear firmness did not differ from that of HC-0 fruit after cold storage. Generally, HC-0.3 pears displayed higher ethylene production and lower firmness values than FAC-0.3 pears after a 7-d exposure to 20 °C, regardless the length of cold storage. FAC-0.6 pears always showed lower ethylene production rates and higher flesh firmness values than HC-0.6 fruit. Soluble solids concentration was not consistently affected by 1-MCP. FAC-0.3 and HC-0.6 fruit showed higher titratable acidity values than HC-0 fruit after 0, 60, 120 and 150 d of cold storage plus 7 d at 20 °C. Effectiveness of 1-MCP treatments on HC pears was influenced by the bin material; P-0.5 pears were firmer than W-0.5 pears after 7 d at 20 °C, regardless the length of the cold storage. HC-0.5 fruit exposed to ?0.5 °C for 90 d reached eating quality (firmness ≤23 N) by day 7 if placed in W, and by day 21 when stored in P. Results and previous evidence suggest that wet wooden bin material may represent a major though unpredictable source of 1-MCP sorption that could bind a significant percentage of the 1-MCP applied. When used at relatively low doses 1-MCP partial removal by wet wooden bins can compromise the application effectiveness for controlling ethylene action.     

Postharvest nitric oxide fumigation delays fruit ripening and alleviates chilling injury during cold storage of Japanese plums (Prunus salicina Lindell)

We investigated the effects of nitric oxide (NO) fumigation on fruit ripening, chilling injury, and quality of Japanese plums cv. ‘Amber Jewel’. Commercially mature fruit were fumigated with 0, 5, 10, and 20 μL L⁻¹ NO gas at 20 °C for 2 h. Post-fumigation, fruit were either allowed to ripen at 21 ± 1 °C or were stored at 0 °C for 5, 6, and 7 weeks followed by ripening for 5 d at 21 ± 1 °C. NO-fumigation, irrespective of concentration applied, significantly (P ≤ 0.5) suppressed respiration and ethylene production rates during ripening at 21 ± 1 °C. At 21 ± 1 °C, the delay in ripening caused by NO-fumigation was evident from the restricted skin colour changes and retarded softening in fumigated fruit. NO treatments (10 and 20 μL L⁻¹) delayed the decrease in titratable acidity (TA) without a significant (P ≤ 0.5) effect on soluble solids concentration (SSC) during ripening. During 5, 6, and 7 weeks of storage at 0 °C, NO-fumigation was effective towards restricting changes in the ripening related parameters, skin colour, firmness, and TA. The individual sugar (fructose, glucose, sucrose, and sorbitol) profiles of NO-fumigated fruit were significantly different from those of non-fumigated fruit after cold storage and ripening at 21 ± 1 °C. CI symptoms, manifest in the form of flesh browning and translucency, were significantly lower in NO-fumigated fruit than in non-fumigated fruit after 5, 6, and 7 weeks storage followed by ripening for 5 d at 21 ± 1 °C. NO-fumigation was effective in reducing decay incidence in plums during ripening without storage and after cold storage at 0 °C for 5, 6, and 7 weeks. In conclusion, the postharvest exposure of ‘Amber Jewel’ plums to NO gas (10 μL L⁻¹) delayed ripening by 3–4 d at 21 ± 1 °C, and also alleviated chilling injury symptoms during cold storage at 0 °C for 6 weeks.     

Integrated ethylene and temperature conditioning for induction of ripening capacity in ‘Anjou’ and ‘Comice’ pears

‘Anjou’ and ‘Comice’ pears from three harvest dates were conditioned to develop ripening capacity by exposure to 100 μL L⁻¹ ethylene at 20 °C for 0, 24, 48, or 72 h, followed by varying durations of temperature conditioning at −0.5 or 10 °C. Ripening capacity was tested by measuring fruit firmness after 7 d at 20 °C after completion of conditioning treatments. Fruit firmness was also measured after conditioning but before ripening, and was designated “shipping firmness”, indicative of the potential for the fruit to withstand transport conditions without physical injury. Ripening capacity in both cultivars developed more rapidly with later harvest date, increasing duration of ethylene conditioning, and increasing duration of temperature conditioning. Ripening capacity developed much more rapidly at 10 °C than at −0.5 °C. Useful durations of temperature conditioning at 10 °C were limited by fruit softening below acceptable values of shipping firmness. However, sequential combinations of ethylene and temperature conditioning at both −0.5 and 10 °C were identified wherein post-conditioning shipping firmness was acceptable.     

Effects of 1-methylcyclopropene on ripening of greenhouse tomatoes at three storage temperatures

Tomatoes (Lycopersicon esculentum Mill., cv. Rapsodie) were harvested at the mature green stage and treated with 250 nl l⁻¹ 1-methylcyclopropene (1-MCP) for 24 h at 20 °C. The fruit were then stored for 24 days at 15, 20 or 25 °C at 90–95% relative humidity. Sampling was carried out at 0, 6, 12, 18 and 24 days after treatment. Treatment with 1-MCP delayed ripening as measured by changes in lycopene, chlorophyll, hue angle, polygalacturonase (PG) activity and tissue firmness. Ripening was delayed by 6 days at 25 °C, by 12 days at 20 °C, and by 18 days at 15 °C in 1-MCP-treated fruit. In general, 1-MCP only delayed the onset of ripening-related changes and did not significantly alter final values for measures of firmness, color (hue angle), PG activity, and lycopene and chlorophyll contents at a particular storage temperature. The results suggest that 1-MCP is most effective at delaying ripening of mature-green tomatoes when they are stored near the currently recommended temperature range of 12.5–15 °C.     

Volatile profiles of ripening West Indian and Guatemalan-West Indian avocado cultivars as affected by aqueous 1-methylcyclopropene

Separate experiments were conducted with three major commercial avocado (Persea americana Mill.) cultivars grown in Florida: ‘Simmonds’ (early-season, West Indian race); ‘Booth 7’ (mid-season, Guatemalan-West Indian hybrid); and ‘Monroe’ (late-season, Guatemalan-West Indian hybrid). Fruit were harvested at preclimacteric stage and left untreated (Control) or treated 24 h after harvest with aqueous 1-methylcyclopropene (1-MCP) at 1.39 (treatment M1) or 2.77 μmol L⁻¹ a.i. (treatment M2) (75 or 150 μg L⁻¹) for 1 min at 20 °C. Whole fruit ripening was monitored at 20 °C/92% ± 3% R.H. and based on whole fruit firmness, respiration and ethylene evolution. Fruit volatiles were assessed at preclimacteric (24 h after harvest), mid-ripe (half of initial fruit firmness) and ripe maturity stages, from 100 g of chopped pulp using a purge and trap system. Untreated, firmer fruit ‘Monroe’ (268 N at harvest) ripened within 12 d of harvest while softer fruit ‘Simmonds’ (118 N) ripened within only 6 d. 1-MCP treatment extended ripening time from 33% (M1) to 83% (M2). All fruit softened normally, indicating the potential benefits of aqueous 1-MCP as a postharvest treatment for avocado when applied at these concentrations. Volatile profiles differed among the three cultivars with several compounds detected in only one cultivar, results that may contribute to a potential identification of the origin of the cultivar based on fruit volatile composition. The West Indian cultivar ‘Simmonds’ had much higher emission of hexanal (preclimacteric fruit) and cis-3-hexenal and cis-3-hexen-1-ol (ripe fruit) than the Guatemalan-West Indian hybrids ‘Booth 7’ and ‘Monroe’. On the other hand, these latter hybrids had much higher levels of alkanes than ‘Simmonds’. Treatment with 1-MCP increased emissions of alkanes during ripening of ‘Booth 7’ and ‘Monroe’. Total volatiles of avocado decreased during ripening mainly due to the significant reduction of sesquiterpenes, the main group of volatiles in all cultivars at harvest (‘Simmonds’, 53%; ‘Booth 7’, 78%; ‘Monroe’, 66%). β-Caryophyllene was the major compound at harvest, but decreased to less than 2% in ripe fruit, at which point most sesquiterpenes were not detected. Among the 10 sesquiterpenes commonly found in the avocado cultivars in this study, only α-Copaene had significantly higher emissions in mid-ripe fruit treated with the higher concentration of 1-MCP (2.77 μmol L⁻¹ a.i.), suggesting that ethylene participates in the regulation of this sesquiterpene.     

Effect of atmospheric modification, 1-MCP and chemicals on quality of fresh-cut banana

Fresh-cut banana slices have a short shelf-life due to fast browning and softening after processing. The effects of atmospheric modification, exposure to 1-MCP, and chemical dips on the quality of fresh-cut bananas were determined. Low levels of O₂ (2 and 4 kPa) and high levels of CO₂ (5 and 10 kPa), alone or in combination, did not prevent browning and softening of fresh-cut banana slices. Softening and respiration rates were decreased in response to 1-MCP treatment (1 μL L⁻¹ for 6 h at 14 °C) of fresh-cut banana slices (after processing), but their ethylene production and browning rates were not influenced. A 2-min dip in a mixture of 1% (w/v) CaCl₂ + 1% (w/v) ascorbic acid + 0.5% (w/v) cysteine effectively prevented browning and softening of the slices for 6 days at 5 °C. Dips in less than 0.5% cysteine promoted pinking of fresh-cut banana slices, while concentrations between 0.5 and 1.0% cysteine delayed browning and softening and extended the post-cutting life to 7 days at 5 °C.     

Ripening and sensory analysis of Guatemalan-West Indian hybrid avocado following ethylene pretreatment and/or exposure to gaseous or aqueous 1-methylcyclopropene

Previous reports showed that both gaseous and aqueous 1-methylcyclopropene (1-MCP) delay ripening of avocado (Persea americana Mill.), but there are no reports of the influence of 1-MCP on its sensory attributes. The objective of this study was to evaluate the effects of ethylene pretreatment and/or exposure to gaseous or aqueous 1-MCP on fruit ripening and sensory attributes of ‘Booth 7’ avocado, a Guatemalan-West Indian hybrid. Separate experiments were conducted during two seasons (2008 and 2009) with fruit harvested at preclimacteric stage in October (early season) and in November (late season). Fruit from Season 1 were exposed to ethylene (4.07 μmol L⁻¹) for 12 h at 20 °C, and stored for more 12 h at 20 °C in an ethylene-free (ethylene, <0.1 μL L⁻¹) room prior to treatment with either aqueous (1.39 or 2.77 μmol L⁻¹ a.i.) or gaseous (3.15 or 6.31 nmol L⁻¹ a.i.) 1-MCP. Ripening was monitored and firmness, respiration, ethylene production and weight loss were measured. Texture profile analysis and sensory analysis were performed on ripe fruit only (firmness, 10–15 N). Fruit from Season 2 were not exposed to ethylene pretreatment but treated only with aqueous 1-MCP 24 h after harvest. Fruit were assessed exclusively for sensory analysis when ripe (firmness, 10–15 N). Treatment with either 1-MCP formulation effectively delayed ripening from 4 to 10 d for early-season fruit, and from 4 to 6 d for late-season fruit. Higher concentrations of 1-MCP of either formulation had the greatest effect on selected pulp textural parameters of early-season fruit; the gaseous formulation had greater effect on late-season fruit quality than the aqueous formulation. In general, sensory panelists ratings of overall liking were not affected by 1-MCP treatment. Both aqueous and gaseous 1-MCP formulations delayed ripening of the Guatemalan-West Indian ‘Booth 7’ avocado without significant loss in appearance or in sensory attributes and, therefore, could be considered for use as a postharvest treatment for this hybrid.     

Physiology and quality response of harvested banana fruit to cold shock

Experiments were conducted to examine softening and quality responses of harvested banana fruit to cold shock treatment intended to extend shelf-life. Fruit were immersed in ice-water for 1 h, then treated with or without 100 μL L^?1 ethylene for 24 h at 24 °C, and finally stored at 20 °C. Fruit firmness, chlorophyll content, ethylene production, respiration rates, contents of pectin, starch and sugar, and the activities of the cell wall modifying enzymes polygalacturonase (PG), pectin methylesterase (PME) and CMCase (cellulase, endo-1,4-β-glucanase) were analyzed. Total amylase activity was also measured. Immersion in ice-water for 1 h effectively inhibited ripening-associated processes, including peel de-greening and pulp softening during storage or ripening. The delay in ripening was also manifest in reduced ethylene production and respiration rates. The inhibition of softening by cold shock treatment was related to decreased PG and PME activities, that is, retardation of pectin solubilization/degradation. Reduced activities of CMCase and total amylase and conversion of starch to sugar by ice-water immersion also contributed to the delay in softening of harvested banana fruit.     

Effect of harvest maturity on quality of fresh-cut pear salad

Texture of an unripe pear is firm and crisp, similar to an apple. However, at the crisp stage, the flavor of pears is flat. This study evaluated the effect of harvest maturity on the quality of fresh-cut pear salad. Fruit were harvested at commercial maturity and 1-month delayed. After 2 and 5 months (1 and 4 months for delayed-harvest fruit) storage at ?1 °C, fruit were sliced into 8–12 wedges per fruit, dipped in an antibrowning solution, packaged in Ziploc bags and stored at 1 °C for up to 21 d. Delayed-harvest fruit were larger in size (≈20% increase in weight), had lower flesh firmness (≈17% decrease), lower titratable acidity content (≈20% decrease), and lower phenolic content (≈45% and 13% decreases in pulp and peel, respectively). There was no significant difference in soluble solids content. After 2 months storage, ethylene production and respiration rate were initially lower in the slices from delayed-harvest fruit, but tended to become similar after 7 d in storage at 1 °C. Delayed-harvest fruit had lower hydroxycinnamic acids and flavanols, and higher ester, alcohol, and aldehyde volatile compounds after 2–5 months storage. The results indicated that fruit salad produced with delayed-harvest pears had less browning potential and better flavor. Sensory evaluation results showed that about 80% of the panel liked slices from delayed-harvest fruit over commercial harvested, especially in terms of visual quality (65–85%), sweetness (75–95%), taste (70–80%), and overall quality (75–80%) during 21 d storage at 1 °C. The cut surface of slices appeared dry in delayed-harvest fruit when processed after 5 months in storage. However, sensory evaluation showed that panels still preferred the delayed-harvest fruit.     

Effect of 1-MCP treatment and N2O MAP on physiological and quality changes of fresh-cut pineapple

The effects of both 1-MCP treatment of pineapples and packaging of their fresh-cut products with an alternative modified atmosphere (MA: 86.13 kPa N₂O, 10.13 kPa O₂ and 5.07 kPa CO₂) on physiological and quality changes of these minimally processed products were investigated. Fresh-cut fruit treated or not with 1-MCP were packed in Air or in MA and were stored at 4 °C for 10 d. The following parameters were monitored during storage: ripening index; O₂, CO₂ and C₂H₄ in the package headspace; firmness and colour. Microbial spoilage of MP pineapple samples was also investigated and a mathematical model based on the Zwietering modified Gompertz equation was used to obtain growth parameters of mesophilic bacteria, yeasts and moulds.The results showed that 1-MCP treatment and MAP in a N₂O enriched atmosphere had a positive combined effect on the inhibition of respiration and ethylene production of fresh-cut pineapple and on its softening delay, confirming previous findings about 1-MCP and N₂O preservative effects on fresh-cut fruit quality. This combined effect was not extended to the ripening index and colour maintenance, as MAP at 86.13 kPa of N₂O did not add any benefit to that of the 1-MCP treatment. From a microbiological point of view, N₂O MAP extended the shelf-life of the products of 3–4 d by increasing the lag phase of microbial growth.     

Effect of minimal processing on bioactive compounds and antioxidant activity of fresh-cut ‘Kent’ mango (Mangifera indica L.)

The influence of dipping in ascorbic acid, citric acid and calcium chloride (AA + CA + CaCl₂) solution and storage time on color, bioactive compounds content and antioxidant activity of fresh-cut mango ‘Kent’ stored at 5 °C was evaluated. The treated mangoes showed better color retention during storage than control mangoes. The dipping treatments with AA + CA + CaCl₂ significantly increased the vitamin C values compared with untreated mango cubes. β-Carotene was not affected by dipping treatments and vitamin E showed a significant decline over storage time for both treated and untreated mango cubes. However, higher vitamin E values were found in treated mangoes. Dipped cubes had higher antioxidant activity measured as TEAC and %RSA than controls. In general, addition of ascorbic acid as an anti-browning agent not only retarded quality loss of fresh-cut mango cubes but also promoted significant increases in antioxidant activity in comparison with control samples.     

Low-temperature induction of ripening capacity in ‘Comice’ and ‘Bosc’ pears as influenced by fruit maturity

The relationship between fruit maturity at harvest and the duration of postharvest exposure to ?1 °C required to induce ripening capacity was studied in ‘Comice’ and ‘Bosc’ pears. As fruit of both cultivars were harvested progressively later, shorter durations of exposure to ?1 °C were required to induce ripening capacity. The relationship between the duration of conditioning at ?1 °C and the fruit flesh firmness after 7 d at 20 °C was well-described by second-order polynomial equations. These equations were used to determine the number of days at ?1 °C required to induce ripening capacity for each harvest date. A linear relationship was observed between the number of days after fruit in the orchard reached maturity that fruit were harvested and the number of days of low-temperature conditioning needed to induce ripening capacity. This relationship may be used to predictively estimate the duration of low-temperature conditioning required to induce ripening based on harvest date.     

Effect of oxalic acid on ripening attributes of banana fruit during storage

The effect of exogenous oxalic acid treatment on ripening attributes of banana fruit during storage was investigated. Banana fruit were dipped into solutions of 0 (control) or 20 mM oxalic acid for 10 min and then stored at room temperature (23 ± 2 °C) and 75–90% relative humidity. The application of oxalic acid reduced fruit deterioration during storage. The oxalic acid treatment also reduced the rates of respiration and ethylene production, and delayed the decreases in firmness, hue angle, and maximal chlorophyll fluorescence (Fv/Fm) of banana fruit during storage. Furthermore, fruit treated with oxalic acid exhibited higher superoxide dismutase activity and antioxidant capability with a lower production of reactive oxygen species at the late storage period compared with non-oxalic acid-treated fruit. Overall, the oxalic acid treatment was effective in inhibiting postharvest ripening of banana fruit and exhibited the potential for commercial application to store the bananas at room temperature. It can be concluded that the delay in banana fruit ripening associated with oxalic acid treatment could be due to inhibition of respiration and ethylene production rates, and reduction of oxidative injury caused by reactive oxygen species through increased antioxidant activity.     

Effect of hyperbaric pressure and temperature on respiration rates and quality attributes of tomato

Previous work with hyperbaric treatment of tomato focused on application at lower temperature (13 °C). In this work, hyperbaric treatment at varying pressure levels (i.e., 0.1, 0.3, 0.5, 0.7 and 0.9 MPa) at ambient temperature (20 °C) was tested as a potential alternative to conventional refrigerated storage (0.1 MPa at 13 °C) to preserve tomato quality. The experiments were divided into 3 phases: (1) 4 day of hyperbaric treatment, (2) 5 day of post-treatment ripening, and (3) 10 day of post-treatment ripening. Respiration rate (RR) of the tomatoes was continuously monitored during the course of the hyperbaric treatments. Quality attributes were assessed immediately after removal from the hyperbaric treatments and after 5 and 10 day ripening at 20 °C after removal from the treatments. Hyperbaric treatments at ≥0.3 MPa resulted in RR equal or higher than the RR in control fruit (0.1 MPa at 20 °C). The lowest RR was obtained from tomato stored at 0.1 MPa at 13 °C. Hyperbaric treatment at 0.5, 0.7 and 0.9 MPa significantly reduced weight loss, retained color, firmness, total soluble solid (TSS), titratable acidity (TA) and TSS:TA ratio at similar levels as the tomato treated at 13 °C and 0.1 MPa. Firmness after treatment was highest for fruit from 0.1 MPa at 13 °C and from 0.5, 0.7 and 0.9 MPa at 20 °C. The higher firmness advantage declined by 5 day of ripening after treatment, with higher firmness only being retained for fruit from the 0.9 MPa at 20 °C and the 0.1 MPa at 13 °C treatments. After 10 day ripening, firmness was similar for all treatments. Lightness (L*) and hue angle were greater for all treatments compared with the 0.1 MPa at 20 °C treatment. However, only the greater hue angle difference was maintained after 5 day of ripening. After 10 day ripening, no significant differences were found in color attributes. Only 0.1 MPa at 13 °C retained higher soluble solids, lower titratable acidity and higher TSS:TA ratios after treatment and after 5 day ripening. At 10 day of ripening none of the quality attribute differences noted were retained for any of the treatments. These results show that the only consistent effect of hyperbaric treatment at 0.5, 0.7 and 0.9 MPa was to reduce weight loss and enhance firmness retention up to 5 day ripening after treatment.     

Sensory and analytical characteristics of a novel hybrid muskmelon fruit intended for the fresh-cut industry

A novel hybrid muskmelon has been bred specifically for use by the fresh-cut industry in winter. Quality characteristics of fresh-cut pieces from the hybrid were compared to those of its inbred parental lines and to those of a commercial netted muskmelon (cantaloupe) and a non-netted muskmelon (honeydew) fruit available in winter. Pieces from hybrid and female line fruit had higher soluble solids content (SSC) and firmness, and lower aromatic volatile concentrations compared to those from the male line fruit. Pieces from hybrid fruit also had higher SSC (>3%) and were firmer (>5 N) than commercial fruit available during the winter, and had twice the aromatic volatile concentration of commercial honeydew and a more intense orange hue than commercial muskmelon. Consumers rated the flavor, texture, sweetness and overall eating quality of the hybrid higher than its inbred parents and winter-available honeydew and as well as or better than winter-available muskmelon. Hybrid fruit stored 5 weeks at 1 °C under modified atmospheric conditions, then fresh-cut and stored 14 d in air at 5 °C maintained good quality (firmness = 51 N, SSC > 12%, β-carotene and ascorbic acid concentrations = 18 and 182 mg kg^?1, respectively), and showed no signs of tissue translucency or surface pitting despite microbial populations >11 log₁₀ kg^?1. The results indicate that the novel hybrid muskmelon is a promising new melon type for fresh-cut processing and marketing, at least during the winter season.     

Role of putrescine in regulating fruit softening and antioxidative enzyme systems in ‘Samar Bahisht Chaunsa’ mango

The role of putrescine (PUT) in regulating fruit softening, antioxidative enzymes and biochemical changes in fruit quality was investigated during ripening and cold storage of mango (Mangifera indica cv. Samar Bahisht Chaunsa). Fruit were treated with various PUT concentrations (0.0, 0.1, 1.0 and 2.0 mM) and were allowed to ripen at 32 ± 2 °C for 7 days, or stored at 11 ± 1 °C for up to 28 days. Respiration rate and ethylene production were measured daily during ripening and cold storage. Cell wall degrading enzymes such as exo-polygalacturonase (exo-PG), endo-polygalacturonase (endo-PG), pectin esterase (PE), endo-1,4-β-d-glucanase (EGase), antioxidative enzymes including superoxide dismutase (SOD), peroxidase (POX), and catalase (CAT), fruit firmness as well as biochemical fruit quality characteristics were estimated during ripening and cold storage at 2 and 7 day intervals, respectively. PUT treatments reduced respiration rate, ethylene production and maintained higher fruit firmness during ripening as well as cold storage. PUT-treated fruit exhibited significantly suppressed activities of cell wall enzymes (exo-, endo-PG and EGase), but retained higher PE activity during ripening and cold storage. Total phenolic and antioxidant contents were significantly higher in PUT-treated fruit during ripening as well in the cold storage period than in the controls. Activities of antioxidative enzymes (CAT, POX and SOD) were also significantly higher in PUT-treated fruit during ripening as well as cold storage. SSC and SSC:TA were lower in PUT-treated fruit, while TA and ascorbic acid content showed the reverse trend. In conclusion, pre-storage 2.0 mM PUT treatment inhibited ethylene production and suppressed the activities of cell wall enzymes, while resulting in higher activities of antioxidative enzymes and maintaining better fruit quality during ripening and cold storage.     

Controlled atmosphere storage of guava (Psidium guajava L.) fruit

The effects of controlled atmospheres (CA) on respiration, ethylene production, firmness, weight loss, quality, chilling injury, and decay incidence of three commercially important cultivars of guava fruit were studied during storage in atmospheres containing 2.5, 5, 8, and 10 kPa O₂ with 2.5, 5, and 10 kPa CO₂ (balance N₂) at 8 °C, a temperature normally inducing chilling injury. Mature light green fruit of cultivars, ‘Lucknow-49’, ‘Allahabad Safeda’ and ‘Apple Colour’, were stored for 30 days either in CA or normal air, and transferred to ambient conditions (25–28 °C and 60–70% R.H.) for ripening. CA storage delayed and suppressed respiratory and ethylene peaks during ripening. A greater suppression of respiration and ethylene production was observed in fruit stored in low O₂ (≤5 kPa) atmospheres compared to those stored in CA containing 8 or 10 kPa O₂ levels. High CO₂ (>5 kPa) was not beneficial, causing a reduction in ascorbic acid levels. CA storage was effective in reducing weight loss, and maintaining firmness of fruit. The changes in soluble solids content (SSC), titratable acidity (TA), ascorbic acid, and total phenols were retarded by CA, the extent of which was dependent upon cultivar and atmosphere composition. Higher amounts of fermentative metabolites, ethanol and acetaldehyde, accumulated in fruit held in atmospheres containing 2.5 kPa O₂. Chilling injury and decay incidence were reduced during ripening of fruit stored in optimal atmospheres compared to air-stored fruit. In conclusion, guava cultivars, ‘Lucknow-49’, ‘Allahabad Safeda’, and ‘Apple Colour’ may be stored for 30 days at low temperature (8 °C) supplemented with 5 kPa O₂ + 2.5 kPa CO₂, 5 kPa O₂ + 5 kPa CO₂, and 8 kPa O₂ + 5 kPa CO₂, respectively.