Mild heat and calcium treatment effects on fresh-cut cantaloupe melon during storage

The effect of mild heat fruit pre-treatment on some properties of fresh-cut cantaloupe melon during storage was determined. Whole fruit, previously held at 4 °C, was immersed in heated water (60 °C) with and without dissolved calcium lactate (1%). Fresh-cut processing was done immediately, either after treatment or after storage at 4 °C for 24 h. Headspace gas accumulation during storage indicated reduced respiration in heat-treated fruit. Reduced lipase activity occurred in heat treated fruit during storage at 10 °C, while the fruit that was cut 24 h after treatment had a reduced peroxidase activity, unlike fruit that was processed immediately after heating. Isoelectric focussing indicated production of heat shock proteins (PI = 5.1 and 6.5) as a result of heat-treatment. Textural measurements showed increased hardness, chewiness and cohesiveness, but springiness decreased in heat-treated fruit. Presence of calcium in the treatment solution did not affect respiration and textural changes caused by heat treatment. Lipase activity was, however, higher in fruit heated in calcium solutions. Results indicated the potential improvement of shelf life of cut cantaloupe melon by mild heat pre-treatment of the fruit, and that the addition of calcium to the treatment water did not further improve product quality.     

Modelling respiration of packaged fresh-cut ‘Rocha’ pear as affected by oxygen concentration and temperature

Respiration rates were measured in fresh-cut ‘Rocha’ pear (Pyrus communis L.) stored at four temperatures (0, 5, 10 and 15 °C) and with oxygen partial pressures ranging from 0 to 18 kPa. Respiratory quotient and ethanol production were used to determine the fermentation threshold. The oxygen concentration effect on the respiration rate was accurately described using Michaelis–Menten kinetics, without non-competitive inhibition by CO₂, and the effect of temperature on the respiration rate was well modelled by exponential functions. The oxygen level at which respiration was half its maximum (apparent _Km,O₂$K_{{\text{m,O}}_2}$) was similar to or only slightly greater than the fermentation threshold. The narrow range of oxygen between _Km,O₂$K_{{\text{m,O}}_2}$ and the fermentation threshold, suggests that modified atmosphere packaging technology has a limited applicability toward extension of the shelf-life of fresh-cut ‘Rocha’ pear.     

Modified atmosphere packaging confers additional chilling tolerance on ethylene-inhibited cantaloupe Charentais melon fruit

Cantaloupe Charentais melon fruits are subject to chilling injury when stored at low temperatures, around 2 °C. Ethylene-suppressed cantaloupe Charentais melon, expressing a 1-aminocyclopropane-1-carboxylic acid (ACC)-oxidase gene in antisense orientation, showed strong, but not total, resistance to chilling injury, allowing an extended storage at low temperatures. Modified atmosphere packaging (MAP) is known to alleviate chilling injury symptoms in a variety of chilling-sensitive horticultural commodities. In the present work, we have compared the effects of MAP in non-retractile plastic film and storage in air on ethylene production, respiratory activity, development of chilling injury symptoms, water loss, ion leakage and accumulation of ethanol and acetaldehyde in wild-type and ethylene-suppressed melons, during storage at 2 °C and after re-warming at 22 °C. MAP reduced chilling injury and extended the postharvest life of wild-type fruit and conferred additional chilling resistance on ethylene-suppressed melons. Reduction of ethylene production and water loss are necessary to prevent chilling injury symptoms in melon.     

Microbial,Physical, Chemical and Sensory Qualities of Minimally Processed and Modified Atmosphere Packaged “Ready To Eat” Orange Segments

Oranges were sanitized, dried, peeled and segmented. Undamaged segments were packed under passive and active MAP with low and high oxygen in PP trays sealed with CPP/OPP film. Overall quality of the segments were monitored for 25 days at 4°C. The results showed that orange segments could be stored under passive and active MAP without significant microbial growth. There were slight changes in acidity and Brix (p ≤ 0.05) with no significant changes in pH and sugar. The hardness increased and color (L, a, b) decreased during storage. Orange segments remained in a commercially viable condition for 10 days under MAP.     

高氧气调包装对鲜切胡萝卜的保鲜效果

研究了不同氧分压条件对鲜切胡萝卜保鲜效果的影响,评定其在贮藏过程中感官品质、呼吸强度、PPO、POD、PAL活性的变化。结果表明,40%氧气包装不适合鲜切胡萝卜贮藏保鲜。100%氧气包装的保鲜效果最好,可有效抑制鲜切胡萝卜呼吸强度以及PPO、POD、PAL的活性。60%、80%氧气包装的保鲜效果次之,但均可起到保鲜的作用。      

Effect of initial headspace oxygen level on growth and volatile metabolite production by the specific spoilage microorganisms of fresh-cut pineapple

The effect of initial headspace (IH) O₂ level on the shelf-life of fresh-cut pineapple was evaluated in this study. The results showed that although the IH O₂ level had a minor effect on the growth of Candida argentea, Candida sake and Meyerozyma caribbica on pineapple agar, the quantities of the volatile organic metabolites produced by these yeasts was generally smaller the lower the IH O₂ level. The only exception was the production of ethyl acetate by C. argentea, which was higher at low IH O₂ levels. In triangle tests performed with trained panellists, pineapple cubes packaged in an IH of 5% O₂ were determined to be significantly different (P < 0.05) to those packaged in 21% O₂ from day 5 of storage. Preference was shown for the pineapple cubes packaged in an IH of 5% O₂. The results imply that packaging in an IH O₂ level of 5% could be used to extend the shelf-life of fresh-cut pineapple.     

Growth kinetics of Listeria monocytogenes and spoilage microorganisms in fresh-cut cantaloupe

The main objective of this study was to investigate the growth kinetics of Listeria monocytogenes and background microorganisms in fresh-cut cantaloupe. Fresh-cut cantaloupe samples, inoculated with three main serotypes (1/2a, 1/2b, and 4b) of L. monocytogenes, were incubated at different temperatures, ranging from 4 to 43 °C, to develop kinetic growth models. During storage studies, the population of both background microorganisms and L. monocytogenes began to increase almost immediately, with little or no lag phase for most growth curves. All growth curves, except for two growth curves of L. monocytogenes 1/2a at 4 °C, developed to full curves (containing exponential and stationary phases), and can be described by a 3-parameter logistic model. There was no significant difference (P = 0.28) in the growth behaviors and the specific growth rates of three different serotypes of L. monocytogenes inoculated to fresh-cut cantaloupe. The effect of temperature on the growth of L. monocytogenes and spoilage microorganisms was evaluated using three secondary models. For L. monocytogenes, the minimum and maximum growth temperatures were estimated by both the Ratkowsky square-root and Cardinal parameter models, and the optimum temperature and the optimum specific growth rate by the Cardinal parameter model. An Arrhenius-type model provided more accurate estimation of the specific growth rate of L. monocytogenes at temperatures <4 °C. The kinetic models developed in this study can be used by regulatory agencies and food processors for conducting risk assessment of L. monocytogenes in fresh-cut cantaloupe, and for estimating the shelf-life of fresh-cut products.     

Effects of electron-beam irradiation on the shelf life, microbial populations and sensory characteristics of summer truffles (Tuber aestivum) packaged under modified atmospheres

The effects of two doses of electron-beam irradiation (1.5 kGy and 2.5 kGy) on the microbial populations (total mesophilic aerobes, Pseudomonas genus, Enterobacteriaceae family, molds and yeasts) and sensory characteristics of Tuber aestivum packaged under modified atmospheres were monitored immediately after treatment, and weekly during 42 days of storage at 4 °C. Treatment with 1.5 and 2.5 kGy reduced the pseudomonads populations by 4.3 and 5.5 logs, respectively. Enterobacteriaceae counts decreased by 5.4 logs with the 1.5 kGy dose and counts below the detection limit (<1.0 log cfu/g) were obtained with the 2.5 kGy dose. Lactic acid bacteria and yeasts were less affected by the ionizing radiation treatments and they became the dominant microbial populations throughout storage with microbial counts up to 7.1 log cfu/g. The carbon dioxide levels inside the packages containing irradiated truffles were lower than those of the non-irradiated ones, suggesting a decrease in the respiration rate of the treated ascocarps. The treatments with 1.5 and 2.5 kGy e-beam did not negatively affect the sensory characteristics of truffles, but a visible superficial yeast growth was detected in truffles irradiated with 1.5 kGy at the end of their shelf life (day 28). Treatment with 2.5 kGy e-beam has prolonged the shelf life to 42 days, compared with 21 days for the untreated samples.     

Flavonoids changes in fresh-cut onions during storage in different packaging systems

Consumers demand healthy, natural and fresh foods, which require only a minimum amount of effort and time for preparation. This was the reason for comparing the effects of different mild preservation technologies on onion flavonoids. Onions were minimally processed to produce fresh-sliced onions, which were packed either in closed plastic cups or under vacuum conditions, taking into account the effect of light exposure. In all cases, the commodity was acceptable after the storage period, with the exception of vacuum packaging (score 5, fair/poor, on a 1–9 scale), due to water loss (about 4%) colour loss and a glassy appearance. In general, after storage in the dark, a slight increase in flavonols was observed, whereas a clear decrease in the relatively low amounts of anthocyanins was evident. However, the best performance was obtained when the more transparent polystyrene cups were stored under light. Both types of flavonoids increased, with an enhanced increase of total flavonols by 58%, and an increase in total anthocyanins of 39%.     

Effect of modified atmosphere and vacuum packaging on some quality characteristics and the shelf-life of “morcilla”, a typical cooked blood sausage

The effect of modified atmosphere and vacuum packaging on the shelf-life of “morcilla”, a traditional cooked blood sausage, was investigated. A total of 99 “morcillas” were packaged under vacuum and in modified atmosphere using three different gas mixtures: 15:35:50/O₂:N₂:CO₂ (atmosphere 1), 60:40/N₂:CO₂ (atmosphere 2) and 40:60/N₂:CO₂ (atmosphere 3), and stored during 2, 4, 6 and 8 weeks at 4 °C. Shelf life evaluation was based on pH, water activity (a_w), colour (CIE L*, a*, b*, C* and h*), TBARS formation and microbial counts. The results indicated that, in general, storage time affected (P < 0.05) all parameters whereas no significant differences were observed (P > 0.05) among packaging conditions. Based on the microbial counts, the shelf-life of “morcilla” would be greater than 8 weeks for all packaging conditions. Samples packaged with high CO₂ concentrations (40:60/N₂:CO₂) showed the lowest values of TBARS at the end of storage.     

Critical effect of oxygen on aroma compound production by Proteus vulgaris

Aroma compound production by Proteus vulgaris was studied in a liquid medium under two culture conditions, static or shaken. By using a dynamic headspace technique coupled with gas chromatography–mass spectrometry, 30 volatile components, aldehydes, alcohols, esters, ketones, sulphur compounds and other miscellaneous compounds were identified. P. vulgaris produced a variety of volatile compounds in different amounts, depending on its culture condition. Sensory analysis has shown that the aroma characteristics of each culture condition were clearly differently perceived. The volatile composition was in agreement with the aroma perception. The culture medium obtained without agitation was characterised by a sulphur/rotten egg note and by a high level of H₂S. The culture medium obtained with agitation was characterised by fruity/fresh and cheese notes and by a high level of alcohols and volatile sulphur compounds. Thus, P. vulgaris could be a useful microorganism to produce various and numerous natural aroma compounds, depending on the culture conditions during fermentation.     

Effect of modified atmosphere packaging on quality factors and shelf-life of surface mould ripened cheese: Part I constant temperature

In the present study, packaging of a surface mould ripened cheese under 2 atm: MAP-A (0% O₂, 27 ± 6% CO₂) and MAP-B (2 ± 1% O₂, 19 ± 2% CO₂) was studied at 12 °C and the results were compared with the existing commercial packaging system (wrapped with waxed paper and inserted in cardboard box). Quality parameters such as colour, texture, pH and moisture content were evaluated after 0, 7 and 14 days of storage, together with a sensory evaluation. Tuckey test and principal components analysis showed that after 14 days of storage, the best conditions for the preservation of the cheeses corresponded to MAP-B. The predicted shelf-life was found to be 14, 6 and 17 days for control, MAP-A and MAP-B respectively. It was concluded that modified atmosphere packaging of surface mould ripened cheese with low levels of O₂ (1-3%) and relatively high levels of CO₂ (17-21%) can be used to extend the shelf-life of soft cheese; however the package has to be suitably designed, as total loss of O₂ (as in MAP-A) would shorten the shelf-life.     

Effect of time before storage and storage temperature on survival of Salmonella inoculated on fresh-cut melons

The effects of a waiting period at room temperature ( approximately 22 degrees C) before refrigerating fresh-cut watermelon, cantaloupe and honeydew pieces contaminated with Salmonella on survival of the inoculated pathogen were investigated. Whole cantaloupes, honeydew melons and watermelons were washed with water, and fresh-cut pieces from individual melons were prepared and inoculated with a five strain cocktail of Salmonella at 10(5)cfu/ml. Populations of aerobic mesophilic bacteria, yeast and mold and Pseudomonas spp. were higher for fresh-cut cantaloupe than for fresh-cut watermelon and honeydew immediately after preparation. Populations of Salmonella, aerobic mesophilic bacteria, yeast and mold and Pseudomonas ssp. in fresh-cut melons left at room temperature for up to 5h before refrigeration were significantly (P<0.05) higher than populations in fresh-cut melons stored at 5 degrees C immediately after preparation. Populations of Salmonella recovered in fresh-cut melon after inoculation with the cocktail of Salmonella strains averaged 2 log(10)cfu/g for all three types of melons. Populations in fresh-cut watermelon and honeydew pieces declined by 1 log when stored immediately at 5 degrees C for 12 days, while the populations in fresh-cut cantaloupe did not show significant (P>0.05) changes. Populations of Salmonella in fresh-cut melons stored immediately at 10 degrees C for 12 days increased significantly (P<0.05) from 2.0 to 3.0 log(10)cfu/g in watermelon, 1.9 to 3.0 log(10)cfu/g in honeydew and 2.0 to 3.6 log(10)cfu/g in cantaloupe pieces. Holding freshly prepared, contaminated fresh-cut melon pieces at 22 degrees C for 3h or more prior to refrigerated storage would increase the chances of Salmonella proliferation, especially if the fresh-cut melons were subsequently stored at an abusive temperature.     

Hot water treatment and peracetic acid to maintain fresh-cut Galia melon quality

The aim of the present study was to investigate if the use of hot water immersion dipping (HWD) alone or combined with other ecofriendly methods, could replace the use of chlorine in fresh-cut fruits such as melon. Melon pieces were subjected to hot (60 °C) or cold (5 °C) water dipping (60, 90, 120 s or 60 s, respectively) followed by immersion in 80 mg L^{− 1} peracetic acid (PAA) for 60 s at 5 °C or in water, packed in polypropylene trays under passive modified atmosphere (7.4 kPa O₂ and 7.4 kPa CO₂ at steady state), and stored up to 10 days at 5 °C. Respiration rate, ethylene emission, microbial load, flesh firmness, polyamine content and sensorial quality were determined. As main conclusions the longer HWD treatment times (90 and 120 s) followed by PAA dip, provided the lowest metabolic activity and helped to control microbial load without affecting the sensorial quality. In addition, both treatments increased the polyamine content helping to maintain the cell membranes integrity.

Industrial relevance

Maintaining quality and microbial safety are the most important concerns of the fresh-cut fruit and vegetables industry. The present study focused on assessing the effect of HWD treatments alone or in combination with PAA, on the respiration rate, ethylene emission, microbial load, flesh firmness, polyamines content and quality retention of fresh-cut Galia melon. According to our results, the use of a heat treatment alone or combined with PAA could replace the use of chlorine, and could be a feasible alternative for fresh-cut industry as a sanitizing method, as or more effective as chlorine.     

The influence of headspace and dissolved oxygen level on growth and haemolytic BL enterotoxin production of a psychrotolerant Bacillus weihenstephanensis isolate on potato based ready-to-eat food products

The major objective of this study was to determine the influence of the initial headspace and dissolved O₂ level and vacuum packaging on growth and diarrhoeal enterotoxin production by Bacillus weihenstephanensis on potato based ready-to-eat food products. In general, the lower the initial headspace or dissolved O₂ level the slower the maximum growth rate (μ_max, log₁₀ CFU g⁻¹ d⁻¹), the longer the lag phase duration (λ, d) and the smaller the maximum population density (N_max, log₁₀ CFU g⁻¹) became. The slowest μ_max, the longest λ and the smallest N_max were generally found for growth under vacuum packaging. This implies shorter shelf-lives will occur at higher initial headspace or dissolved O₂ levels as the growth of B. weihenstephanensis to the infective dose of 10⁵ CFU g⁻¹ in such atmospheres takes a shorter time. Significant consumption of dissolved O₂ only occurred when growth shifted from the lag to the exponential phase and growth generally transitioned from the exponential to the stationary phase when the dissolved O₂ levels fell below ca. 75 ppb. Diarrhoeal enterotoxin production (determined via detection of the L2 component of haemolytic BL) was similar for growth under initial headspace O₂ levels of 1-20.9%, and was only reduced when growth took place under vacuum packaging. The reduction in L2 production when growth took place under vacuum was most probably related to the low final cell densities observed under this condition. Both growth and L2 production were inhibited over a 32-day incubation period at 7 °C by 40% CO₂ irrespective of the headspace or dissolved O₂ levels. The results illustrate the importance of residual O₂ and CO₂ on the shelf-stability and safety of modified atmosphere packaged potato based ready-to-eat food products with regards to B. weihenstephanensis.     

Effect of exposure to light on physico-chemical quality attributes of sliced dry-cured Iberian ham under different packaging systems

Dry-cured Iberian ham slices were stored under vacuum and under two different atmospheres (N₂ = 70% N₂ + 30% CO₂; Ar = 70% Ar + 30% CO₂) and exposed to lightness or darkness. Physico-chemical, sensory and microbial analysis was carried out throughout 60 days storage. Vacuum samples showed the highest a*-value compared to N₂ and Ar after 30 (P < 0.05) and 60 days (P < 0.05). The influence of illumination during storage was evident after 60 days of storage, L* and a*-values being lower (P < 0.01) in hams exposed to light than those kept in darkness, which can be ascribed to the lower nitrosylmioglobin content in samples exposed to light after 60 days (P = 0.001). Ham slices stored in darkness showed the lowest TBARS values (P < 0.05) and hexanal content (P < 0.05) after 60 days. Slices of ham packed in vacuum showed lower TBARS values than N₂ and Ar batches (P = 0.001), these samples being perceived as more rancid (P < 0.05). The rest of the sensory attributes were not generally affected by gas mixture or illumination (P > 0.05).     

Storage behaviour of minimally processed pumpkin (Cucurbita maxima) under modified atmosphere packaging conditions

 Minimally processed vegetables in fresh, ready-to-cook form are gaining the confidence of both the trader and the consumer. This has led to a need to develop technology for increasing shelf life while maintaining the microbial, nutritional and sensory quality of minimally processed vegetables. This investigation was carried out on pumpkin in minimally processed form, packed in different polymeric film bags of varying permeabilities, creating an active equilibrium modified atmosphere within the package for the extention of storage life. It was observed that minimally processed pumpkin, which has a high respiratory rate at room temperature (155.7 mg CO₂/kg/h) could be stored for a period of 25 days at 5±2  °C under modified atmosphere packaging conditions with a minimum physiological loss in weight of 0.06% and marginally low changes in biochemical constituents, such as vitamin C, total soluble solids, moisture, carotenoids and titrable acidity, enabling the retention of near-fresh quality. The microbial loads of mesophilic aerobes and coliforms, which were log 5.5 and log 4.3 were less than threshold level. There was no growth of yeasts and moulds or mesophilic spore formers at the end of the storage period. Received: 24 January 2000 / Revised version: 4 April 2000     

Effects of electron-beam and gamma irradiation treatments on the microbial populations, respiratory activity and sensory characteristics of Tuber melanosporum truffles packaged under modified atmospheres

The effects of electron-beam or gamma irradiation (doses of 1.5 kGy and 2.5 kGy of either one) on the microbial populations, respiratory activity and sensory characteristics of Tuber melanosporum packaged under modified atmospheres were monitored immediately after treatment, and subsequently every seven days during 35 days of storage at 4 °C. Treatments with 1.5 and 2.5 kGy reduced the total mesophilic aerobes counts respectively by 4.3 and 5.6 log cfu/g for electron-beam treatment, and by 6.4 and 6.6 log cfu/g for gamma irradiation. Other microbial groups studied (Pseudomonas genus, Enterobacteriaceae family, lactic acid bacteria, mesophilic aerobic spores, molds and yeasts) were not detected after the treatments. A decrease in the respiratory activity was detected in all the irradiated batches, indicating that the carbon dioxide levels were lower and the oxygen levels higher than those of the non-irradiated ones. Two species of yeasts, Candida sake and Candida membranifaciens var. santamariae, survived the irradiation treatments and became the dominant microbial populations with counts of up to 7.0 log cfu/g. The growth of these microorganisms was visible on the surface of irradiated truffles from day 21 onwards, affecting the flavor and the general acceptability of the ascocarps. Moreover, a watery exudate was detected in the treated truffles from the third week onwards, so the application of irradiation treatments in doses equal to or above 1.5 kGy did not preserve the quality characteristics of T. melanosporum truffles beyond 28 days.     

Effect of temperature and modified atmosphere packaging on overall quality of fresh-cut bell peppers

The effect of vacuum packaging (VP) and modified atmosphere packaging without vacuum (MAP) on shelf-life of fresh-cut green bell pepper stored at 5°C and 10°C were evaluated. In-package atmosphere, overall quality, percentage of leaked juice, texture, ascorbic acid content, ethanol and acetaldehyde, and microbial growth, were evaluated at different intervals of storage. MAP-fresh-cut peppers presented better visual quality, less leaked juice and higher firmness than those stored under VP. Microbiological and quality analysis revealed a limit of shelf-life of 14 and 21 days, when fresh-cut peppers were stored at 10°C and 5°C, respectively. We conclude that MAP could be used to maintain quality attributes of fresh-cut peppers for up 21 days at 5°C.     

Effects of hypobaric and temperature-dependent storage on headspace aroma-active volatiles in common squid miso

The purpose of this study was to elucidate the effects of storage at hypobaric (10 kPa) atmosphere at room temperature (25 °C) and at a low temperature of 10 °C at atmospheric pressure on the headspace volatiles of miso prepared from common squid meat during 270 days of storage. Based on the odor active values of the volatiles detected, 2-methylpropanal, 3-methylbutanal, 3-methyl-1-butanol, n-ethyl decanoate, 2,3-butanedione, dimethyl disulfide, methional, and 2-methyl butanoic acid were identified as key aroma compounds in squid miso. Low-temperature storage appeared to retard volatile compound formation and extent the shelf life. Hypobaric storage induced a significant reduction in lipid oxidation products, particularly aldehydes and ketones. The contents of sulfur-containing compounds and acids were significantly low; however, esters had relatively higher levels in hypobaric conditions. Production of furans and their derivatives were also found to be controlled by hypobaric storage. Therefore, hypobaric storage can be considered as an effective means of preserving squid miso and related fish paste products to prolong shelf-life in order to maintain aroma attributes.