Modified atmosphere packaging to extend the shelf life of tomatoes

An experimental retail packaging system was used to compare the atmospheric com-position and relative humidity which developed within packs sealed with a range of plastic films with different permeability properties, and to study the effects of these conditions on the rate of ripening (as indicated by colour change) and sensory quality of tomatoes. In packs sealed with several polyvinylchloride (PVC) films or with K-resin (a butadiene-styrene copolymer), an atmosphere containing 3–9% CO₂+3−9% 0₂ developed within circa 3–4 days at 10 or 12.5°C. Ripening of part ripe fruit was retarded, but continued normally after the packs were perforated, with no obvious adverse effects on the smell, flavour or texture of the fruit. In packs sealed with less permeable films (e.g. cellulose acetate), the internal atmosphere equilibrated to 10–18% CO₂+ < 2% O₂, resulting in complete inhibition of ripening, a high incidence of rotting and tainting of the fruit. Very high (98% or above) relative humidity within sealed packs also encouraged fungal spoilage. The possible commercial applications and benefits of this type of modified atmosphere (MA) packaging are discussed.     

The response of unripe Conference pears to modified atmosphere retail packaging

Unripe green Conference pears with initial firmness values of 46–55 N were sealed in modified atmosphere (MA) low density polyethylene (LDPE, 30μ) pillow packs and in perforated control packs on three dates during 1985–1986. Changes in pack atmosphere composition, skin chlorophyll content, flesh firmness and sensory quality were monitored during 14–20 days simulated shelf-life at 20°C. In MA packs, equilibrated atmospheres containing 5–9% CO₂ and < 5% O₂ developed within c. 3 days. Chlorophyll degradation was completely inhibited by MA and resumed when packs were perforated, but MA only partially retarded the rate of flesh softening. Variations in the rate of ripening changes in duplicate MA packs could not be explained simply by differences in pack atmospheres. Furthermore, pears retarded by MA packaging failed to develop the normal sweet, aromatic flavour and succulent, juicy texture of 'eating-ripe' fruit, even when the packs were perforated after 4 days.
The differences in the responses of pears and apples to MA packaging, and the limitations of using this technique for the commercial marketing of English pears are discussed.     

The effects of packaging film and storage temperature on the quality of a dry coleslaw mix packaged in a modified atmosphere

Summary The effects of six packaging treatments on the quality of dry coleslaw packaged in modified atmospheres and stored at 4 and 8 °C for 9 days were determined. The coleslaw was packaged within either oriented polypropylene (OPP) or one of four microperforated OPP films, PA‐120, PA‐160, PA‐190, and PA‐210. It was also stored within punctured OPP (i.e. in air). Packaging within OPP resulted in an atmosphere with very low O₂ (<1%) and extremely high CO₂ (25–35%) levels. These storage conditions had detrimental effects on the quality of coleslaw: loss of firmness, falling pH, high cell permeability and exudate, high surface moisture and poor acceptability of aroma. By contrast, the microperforated films generated less atmosphere modification; in some cases this was insufficiently modified to be technically useful. The relatively high O₂ levels in these microperforated packs resulted in lower appearance and colour scores, increased surface dryness and higher firmness values. Increasing storage temperature from 4 to 8 °C resulted in a reduction in shelf‐life for all film types. While still not optimal, packaging within microperforated films allowed better preservation of quality and reduced cell membrane damage.     

Storage Potential of Tomatoes Harvested at the Breaker Stage using Modified Atmosphere Packaging

Breaker tomatoes sealed in polymeric film (MAP) were stored at 15°C 23 days. A steady state of about 3.5-4.0 % O₂ and CO₂ was established. Mean concentrations of the gases within 24 hr of packaging were minimum 2.5 % O₂ and maximum 8.0% CO₂- Thereafter gas concentration moved gradually to a steady state; no evidence of anoxic conditions occurred. After 23 days of MAP storage fruit ripened normally under ambient conditions. Quality evaluations demonstrated that 15°C MAP storage permitted harvesting of breaker stage of ripeness tomatoes without reducing storage life to an unacceptable duration. MAP delayed changes in acidity, soluble solids, texture, color and polygalacturonase activity and resulted in substantial reduction in fruit weight loss and spoilage as compared to breaker fruit without film packaging.     

Suitability of Plastic Films for Modified Atmosphere Packaging of Fruits and Vegetables

Suitability of plastic films in standard configurations to maintain modified atmospheres was evaluated for common fruits and vegetables. Most films did not result in optimal O₂ and CO₂ atmospheres, especially when produce had high respiration. Produce with low and medium respiration could be matched with films considering O₂ permeability requirements alone. MA packaging systems designed to produce optimal oxygen at suitable temperatures could have complications from transient temperature increases during storage and/or transportation. Respiration rates of fruits and vegetables increase more with temperature than do gas permeabilities of films. Higher than optimum temperatures could cause anoxia and seriously damage produce. More permeable gas pathways and temperature compensation to equalize Q₁₀ values are needed for MA packaging systems to timction effectively.     

Use of passive and active modified atmosphere packaging to prolong the postharvest life of three varieties of apricot (Prunus armeniaca, L.)

The evolution of the atmospheric composition (O₂ and CO₂ and ethylene) passively produced by three varieties of apricots (Beliana, Rouge de Rousillon and Polonais) stored at 10 °C under four plastic films of different permeabilities was studied. The results corresponding to respiratory intensity (IR) revealed that, while the IR decreased during the storage period under modified-atmosphere packaging, it increased again with the opening of the bags and the exposure of the fruits to air. The modified atmosphere inside the bags (O₂ and CO₂) and the time necessary to reach equilibrium depended on the IR of the fruits and the permeability of the film. The ethylene concentration decreased from the second day onwards in all the cases studied; this decrease being more pronounced in the films of least permeability due to a combination of its diffusion through the film and the inhibition of its synthesis as the CO₂ concentration increased and O₂ concentration decreased. Partial deviations in the metabolism of the three varieties were detected in the two films of lowest permeability (6060 and 12100 cm³ of O₂ and CO₂ m⁻²/24 h⁻¹ atm⁻¹ at 25°C) due to anoxia. The use of the active modified atmosphere, replacing the initial atmosphere of the bags with an atmosphere enriched with CO₂ (20% CO₂ and 80% air), did not modify the gas composition at equilibrium, although it shortened the time necessary for it to be reached. For the Beliana variety a slight decrease in ethylene concentration was observed inside the bags with an active modified atmosphere in relation to that of the bags with a passive modified atmosphere. The accumulation of ethanol in the tissues was not higher under the active modified atmosphere than under the passive modified atmosphere. Received: 19 July 1999 / Revised version: 29 September 1999     

Effects of packaging type, gas atmosphere and storage temperature on survival and growth of Listeria spp. in shredded dry coleslaw and its components

The survival and growth of Listeria populations inoculated on to dry coleslaw mix and its components were investigated, focusing on effects of storage temperatures and gas atmospheres within packaging films or storage chambers. There were few significant effects of packaging film at 3 °C, but at 8 °C the elevated CO₂/low O₂ atmospheres generated within orientated polypropylene (OPP) packages and used in controlled atmosphere chambers were inhibitory. Although two strains of Listeria monocytogenes had survival characteristics comparable with Listeria innocua, L. monocytogenes ATCC 19114 survived better at 3 °C and also in the elevated CO₂/low O₂ atmospheres within OPP at 8 °C. The effects of product components on the survival of L. innocua were linked to storage temperature. Shredded carrot reduced initial counts and at 8 °C inhibited survival of L. innocua in comparison with shredded cabbage.     

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.     

THE SHELF-LIFE EXTENSION OF HADDOCK IN CARBON DIOXIDE-OXYGEN ATMOSPHERES WITH AND WITHOUT POTASSIUM SORBATE

Fresh haddock, whole fish or fillets, treated or not with various potassium sorbate dips, were sealed in gas impermeable bags containing gas atmospheres of 60% CO₂, 20% O₂ and 20% N₂, air or vacuum, stored on ice in insulated AIRBOX containers at 0°C and subsequently assessed using the Torry freshness scale after 11 to 18 days storage. The trends in the data suggested higher freshness scores for gas and gas plus dip compared with the air and vacuum packs. The dip alone was not effective. It was important to maintain the fish at 0° C.     

Mathematical Model for Perforation Effect on Oxygen and Water Vapor Dynamics in Modified-Atmosphere Packages

A mathematical model was developed to study the influence of film perforations on O₂ concentration and relative humidity in the atmosphere in a package containing fresh fruits. The model included equations describing fruit respiration and transpiration as well as permeation of oxygen and water vapor through the perforated film. Closed-system experiments with mango fruit revealed a linear dependence of respiration rate on O₂ concentration. The model allowed analytical computation of the time course of in-package O₂ concentration and relative humidity, and the results were in good agreement with experimentally measured values. Perforations had a much more pronounced effect on O₂ concentration than on relative humidity. The model enabled practical predictions for designing modified-atmosphere packaging.     

The sensory and microbiological quality of fresh sliced mushroom (Agaricus bisporus L.) packaged in modified atmospheres

The effect of modified atmospheres, generated by using different packaging films, on the quality of sliced mushrooms was evaluated. The carbon dioxide and oxygen content inside the packages as well as the colour, texture, weight loss, sensory attributes, mesophiles, psychrotrophs, Pseudomonas fluorescens, faecal coliforms, Escherichia coli and anaerobic spores were determined. Modified atmospheres containing 2.5% CO₂ and 10–20% O₂ reduced the microbial counts and improved the mushrooms’ appearance when compared with an air atmosphere. Modified atmospheres containing 15% CO₂ and <0.1% O₂ inhibited mushroom development and toughening and reduced microbial growth. Although these atmospheres had no effect on colour, they did allow the development of off odours and anaerobic spores were detected. No differences in microbial growth or mushroom spoilage were observed under the different moisture contents generated in the packages at 4 °C. Aerobic bacteria counts were considered very high even at the beginning.     

Changes in Sensory Quality of Sterile Cantaloupe Dice Stored in Controlled Atmospheres

Diced cantaloupe flesh that was microbiologically sterile was prepared to study the physiological deterioration of fruit when stored under a range of controlled atmospheres at 4.5°C. Sterile fruit pieces were prepared by boiling whole melons for 3 min, then dicing aseptically. Storage atmospheres were in continuous flow and contained from 0 to 26% CO₂ and 3.5 to 17% O₂. Sensory assessments were carried out by a highly trained panel at 14 day intervals. Acceptable product up to 28 days was obtained for three treatments: 6% CO₂ and 6% O₂, 9.5% CO₂ and 3.5% O₂, and 15% CO₂ and 6% O₂. Overall treatment with 0, 19.5 or 26% CO₂ (irrespective of O₂ concentration) caused significant deterioration in sensory characteristics.     

METHOD FOR MEASURING CO2 ABSORPTION IN CO2 and N2 PACKAGED FRESH MEAT1

Headspace gas composition of meat stored in modified atmosphere packaging (MAP) undergoes dynamic changes as a result of packaging film permeability, postmortem metabolic activity, CO₂ absorption in water and lipid, and bacteria growth and respiration. A combined analytical and experimental method was developed to investigate CO₂ absorption by packaged fresh meat in a gas-impermeable environment and during isothermal storage. the ideal gas law was used as a theoretical basis and a gas-impermeable and constant-volume chamber was constructed to evaluate the theoretical derivation. Changes in headspace pressure caused by dynamic interactions between beef and MAP atmospheres were monitored to predict concentration changes of CO₂ within the chamber. the proposed methodology for measuring CO₂ concentration changes was confirmed by gas analysis and proved valid for prediction of headspace CO₂ concentration changes in MAP gas-impermeable systems within the range of initial gas composition 20% to 100% CO₂ balanced with N₂, at temperatures ranging from 3 to 13C, and an initial headspace pressure of 155 kPa.     

Responses of CA-stored Bramley's Seedling and Cox's Orange Pippin apples to modified atmosphere retail packaging

The responses of Bramleys and Coxs apples to modified atmosphere (MA) retail packaging were studied in samples of fruit removed from controlled-atmosphere (CA) storage at monthly intervals through the marketing season, packed in MA or perforated control packs and held under simulated marketing conditions at 15C. The degree of modification of the pack atmospheres and the effects of MA packaging on fruit ripening changes were influenced by the duration and conditions of storage prior to packing. In addition, differential effects of MA packaging on the extent of retardation of flesh softening and skin yellowing were found as the storage period was extended. During 2 or 4 weeks at 15C, however, MA packs made from low density polyethylene (LDPE, 30 p) were effective in retarding changes in firmness and skin colour of Bramleys, previously stored for < 22 weeks (October-March) in 8% C02+ 13% O2 or for < 30 weeks (October-May) in 6% C02+3% 02. Similarly, during a 2-week marketing period at 15C, LDPE or ethylenevinylacetate (EVA, 30 II.) MA packs were effective in retarding some ripening changes in Coxs previously stored for < 31 weeks (Oc- tober-May) in < 1% C02+1.25% 02. The practical benefits of MA retail packaging for the marketing of apples are also discussed.     

Design of Modified Atmosphere Packaging Systems: Modeling Oxygen Concentrations Within Sealed Packages of Tomato Fruits

A method was developed for determination of O₂ consumption as a function of O₂ concentration by mathematical characterization of O₂ depletion by a tomato fruit in a closed system with time. Mathematical equations were developed describing O₂ consumption as a function of O₂ concentration for breaker, pink and red tomato fruit and were used to model film permeability characteristics (O₂ permeability coefficient, surface area, thickness) as a function of fruit weight to achieve desired sealed package concentrations of O₂ in modified atmosphere packages. Equations were also developed to describe the time for initial O₂ establishment as affected by void volume. Calculations are presented for optimizing package parameters for tomato fruit.     

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.     

Chemical and biochemical study of industrially produced San Simón da Costa smoked semi-hard cow's milk cheeses: Effects of storage under vacuum and different modified atmospheres

Two batches of smoked, semi-hard (ripened for 45 d) San Simón da Costa cow's milk cheeses with Protected Designation of Origin were used to investigate the chemical, biochemical, and sensorial parameters that may be affected by modified-atmosphere packaging. Cheeses were packaged for 45 d as follows: vacuum packaging, packaging in 100% N₂, packaging in a gas mixture of 20% CO₂/80% N₂, and packaging in a gas mixture of 50% CO₂/50% N₂. The San Simón da Costa cheeses were characterized by high contents of lactic, oxalic, and citric organic acids. The main free amino acids found were isoleucine, phenylalanine, serine, valine, lysine, and glutamic acid, and the most abundant volatile compounds included ethanol, diacetyl, 2-butanol, isopropyl alcohol, furfural, acetaldehyde, 2-butanone, acetone, and 2-methylfuran. Modified atmospheres appeared to alter the ripening processes by affecting lipolysis, as indicated by the lower concentrations of butyric and propionic acids compared with control cheeses. In addition, modified-atmosphere packaging altered the proteolysis processes, yielding higher amounts of branched-chain alcohols. The results revealed that storage under modified atmosphere contributes to the accumulation of several compounds probably derived from smoke, including aldehydes such as 2-furancarboxaldehyde (furfural), alcohols such as 2-methoxyphenol (guaiacol), ketones such as 2-cyclopenten-1-one, and esters such as methyl furancarboxylate, which were negatively correlated with flavor. Vacuum packaging was the most useful technique in terms of preserving the sensory quality of San Simón da Costa Protected Designation of Origin cheeses. Considering the current demands for packaged portions of food at the distribution and retail levels and the potential health risks associated with some smoke-derived compounds usually present in some smoked foods, the results obtained in this study may be of special interest to the cheese industry.     

Sensory comparison of commercial low and high oxygen modified atmosphere packed sirloin beef steaks

The objectives of this study were to investigate the effects of using commercially low and high modified atmosphere packaging (MAP) on quality characteristics of sirloin beef steaks. Gas mixtures used included 80% O₂:20% CO₂ (O₂80), 70% O₂/30% CO₂ (O₂70) and 50% O₂/30% CO₂:20% N₂ (O₂50) and for commercial packs O₂75 ± 5%, CO₂25 ± 5%, < 5% N₂-(O₂Com). All samples were packed in similar tray and packaging film formats. The experimental parameters monitored included microbiological, physiochemical and sensory measurements (naïve assessors). Microbial counts did not exceed the recommended legal ranges over the storage period. However the numbers of LAB (lactic acid bacteria) were the highest for commercially-packed samples (O₂Com) in comparison to laboratory packaged samples (O₂80, O₂70 and O₂50). Commercially-packaged samples eventually spoiled due to the occurrence of off-flavours and off-odours and subsequently were the least acceptable to sensory naïve assessors.     

Nondestructive and Continuous Monitoring of Oxygen Levels in Modified Atmosphere Packaged Ready‐to‐Eat Mixed Salad Products Using Optical Oxygen Sensors,and Its Effects on Sensory and Microbiological Counts during Storage

The objective of this study was to determine the percentage oxygen consumption of fresh, respiring ready‐to‐eat (RTE) mixed leaf salad products (Iceberg salad leaf, Caesar salad leaf, and Italian salad leaf). These were held under different modified atmosphere packaging (MAP) conditions (5% O₂, 5% CO₂, 90% N₂ (MAPC—commercial control), 21% O₂, 5% CO₂, 74% N₂ (MAP 1), 45% O₂, 5% CO₂, 50% N₂ (MAP 2), and 60% O₂, 5% CO₂, 35% N₂ (MAP 3)) and 4 °C for up to 10 d. The quality and shelf‐life stability of all packaged salad products were evaluated using sensory, physiochemical, and microbial assessment. Oxygen levels in all MAP packs were measured on each day of analysis using optical oxygen sensors allowing for nondestructive assessment of packs. Analysis showed that with the exception of control packs, oxygen levels for all MAP treatments decreased by approximately 10% after 7 d of storage. Oxygen levels in control packs were depleted after 7 d of storage. This appears to have had no detrimental effect on either the sensory quality or shelf‐life stability of any of the salad products investigated. Additionally, the presence of higher levels of oxygen in modified atmosphere packs did not significantly improve product quality or shelf‐life stability; however, these additional levels of oxygen were freely available to fresh respiring produce if required. This study shows that the application of optical sensors in MAP packs was successful in nondestructively monitoring oxygen level, or changes in oxygen level, during refrigerated storage of RTE salad products.     

Production and Regeneration of Principal Volatiles in Apples Stored in Modified Atmospheres and Air

In a series of exploratory experiments, storage of McIntosh apples (Malus domestica Borkh.) in modified atmospheres (MA) (5% CO₂+ 3% O₂ at 2.8°C) suppressed the development of headspace ethanol and acetaldehyde from that in apples stored in air at 0°C (RA). Acetaldehyde, ethanol, ethyl butyrate and hexanal production from intact fruit was further suppressed when the apples were stored in 1.5% CO₂+ 1.5% O₂ or 1.5% CO₂+ 1.0% O₂ at 2.8°C. Placement of fruit in RA following MA storage initially regenerated ethyl butyrate and hexanal in preference to ethanol and acetaldehyde. However storage of fruit in 1.5% CO₂+ 1.0% O₂ for 320 days completely suppressed the principal headspace volatiles and blocked their subsequent regeneration in RA.