A Multi‐functional Biofilm Used as an Active Insert in Modified Atmosphere Packaging for Fresh Produce

We developed a multi‐functional agar‐based biofilm for fresh produce packaging by modulating its CO₂ absorption and water vapour absorption functions. The film was prepared from solutions containing agar as a matrix and a water vapour absorbent, glycerol as a plasticizer, and sodium carbonate (SC) and/or sodium glycinate (SG) as a CO₂ absorbent. The optical, mechanical, and CO₂ and water vapour absorption properties of SC, SG, and SC/SG films were investigated. Multi‐functional films tended to show poor mechanical properties, with a hard texture and an opaque and yellowish colour. The three films had different CO₂ absorption capacities and coefficients, with SC film showing the highest absorption, followed by SC/SG and SG films. The water absorption coefficients were much higher than those of CO₂, with the opposite dependence on the absorbent compound. The multi‐functional benefits of the developed film were shown by using the film for modified atmosphere packaging (MAP) of shiitake mushrooms as an insert label. A tailored MAP design for shiitake mushrooms was produced based on mass transfer mathematical models. The package attached with SC film label was capable of generating the desired internal atmosphere and thus showed the best quality preservation in terms of colour, firmness, flavour score, and bacterial growth after 5‐day storage. A tailored MAP system with our multi‐functional film can provide an optimal modified atmosphere for CO₂‐sensitive fresh commodities, preserve their quality, and extend their shelf life. Copyright © 2015 John Wiley & Sons, Ltd.     

Effect of hinokitiol impregnated sheets on shelf life and quality of “KEK‐1” tomatoes during storage

Hinokitiol (β‐thujaplicin, volatile oil extracted from the wood of Hiba arborvitae [Thujopsis dolabrata var. hondae], cypress family) is a natural preservative, antimicrobial, and chelating agent, used to prevent decay and extend the shelf life of fruits and vegetables. In the present study, we used nonwoven rayon sheets impregnated with hinokitiol to conduct packaging studies. Mature green tomatoes var. “KEK‐1” were packaged under three packaging conditions, ie, modified atmosphere packaging (MAP), MAP + hinokitiol (MH), and perforated film package (as control), and their quality attributes were compared during storage. The packaging materials used were low‐density polyethylene (LDPE) film (40 μm) and fresh sheets of nonwoven rayon impregnated with hinokitiol. O₂ in the MAP packaged tomatoes were retained throughout the storage period (3% to 5% O₂). Results showed that MH had slightly improved quality attributes throughout the storage period when compared with MAP alone. Expression levels of LeACS, LeADH, and LeTBG4 genes were higher in 5 and 9 days of control when compared with MAP and MH. “KEK‐1” tomatoes had longer shelf life under MAP and MH packaging and maintained the quality at 15°C. Hence, the effect of the MAP with bioactive packaging treatments could be effective in the future application for the extension of shelf life and quality of fruits and vegetables.     

Combined effects of hot water treatment (HWT) and modified atmosphere packaging (MAP) on quality of tomatoes

Effects of hot water treatment (HWT) and modified atmosphere packaging (MAP) on quality of tomatoes were studied. Prior to packaging with low‐density polyethylene (LDPE) film (0.02 mm in thickness), tomatoes were immersed in hot water (42.5°C) for 30 min. Control tomatoes were not treated and were stored for 2 weeks at 10°C and then for 3 days at 20°C without packaging. Steady states of O₂ and CO₂ concentrations inside the package were about 5 and 8%, respectively, and were reached after 6 and 4 days of storage, respectively. MAP reduced weight loss of tomatoes to about 41% of that of unpackaged fruit during a 2‐week storage period. The use of a combination of HWT and MAP reduced weight loss and decay, inhibited color development and maintained firmness of tomatoes but had no effect on soluble solids content or titratable acidity. HWT slightly reduced mold growth of tomatoes stored in MAP. Packaging of control fruit in MAP resulted in stimulation of mold growth around the stem end of the fruit after about 1 week of storage and also resulted in cracking and decay. HWT could be used as disinfectant for tomatoes prior to storage in MAP in order to reduce microbial growth, cracking and decay that may be caused by excessive water vapor inside the package. Copyright © 2003 John Wiley & Sons, Ltd.     

Effect of oxygen concentration on the shelf‐life of fresh pork packed in a modified atmosphere

Freshly slaughtered meat was packed in modified atmosphere packs (MAP) containing 5%, 15%, 25%, 35%, 45% and 55% O₂ along with 20% CO₂ in each package and stored for 8 days at 4°C. The samples were evaluated on the 8th day in terms of TVBN total volatile base nitrogen (TVBN) value, thiobarbituric acid reactive substances (TBARs) value, colour acceptability score, overall acceptability score and total microbial count. The result indicated better effects for 45% and 55% O₂‐containing MAP; however, the TBARs value of 45% O₂ atmosphere was significantly lower, without having significant differences in other evaluation criteria, than in the 55% O₂ package; hence 45% O₂ and 20% CO₂ gas mixture were selected as the most appropriate gas composition for fresh pork packaging. Copyright © 2005 John Wiley & Sons, Ltd.     

Porous Ultrahigh Gas‐Permeable Polypropylene Film and Application in Controlling In‐pack Atmosphere for Asparagus

Porous polypropylene (PP) films with greater gas permeability and lower permeability ratios (β) than existing commercial films were developed for fresh produce packaging. PP containing high content of beta‐form crystal was biaxially stretched under controlled conditions. Resulting porous films with uniquely high oxygen transmission rate (OTR) of 2 659 000 cm³?m^?2?d^?1, water vapor transmission rate of 67 g?m^?2?d^?1, and β value of 0.76 was used as a “breathable window” attached to the less permeable commercial BOPP (biaxially oriented PP) lidding film. Various sizes/areas of the breathable windows were designed and tested on packaging asparagus of 400 g, at 5°C. Results demonstrated that in‐pack O₂ and CO₂ concentrations could be practically controlled and modified by changing areas of the breathable windows. Altered porous high OTR area directly affected total gas permeation of the package. Optimum gas composition of Ο₂ and CΟ₂ within the recommended controlled atmosphere for asparagus, stored at 5°C, was effectively created and maintained in the package containing 25 cm² breathable window (15% of total film lid's area). The shelf life of asparagus under optimum modified atmosphere was extended to 29 days, as compared with <3 days in the normal, low OTR tray sealed with BOPP lidding film. Clearly, these developed porous ultrahigh permeable PP films can be useful materials in designing high OTR package with desirable in‐pack O₂ and CO₂ concentrations. Copyright © 2013 John Wiley & Sons, Ltd.     

Modelling a modified atmosphere packaging system for fresh scallops (Argopecten purpuratus)

Seafood is a highly perishable food, which has a relative short shelf‐life. Modified atmosphere packaging (MAP) is a system that offers a way of extending the shelf‐life of seafood products, maintaining quality and inhibiting bacterial growth. The objective of this research was to study and determine the optimal conditions for packaging scallops in a modified atmosphere system, which includes CO₂/O₂/N₂ mixture, headspace:food ratio and storage temperature, utilizing an integrated mathematical model for MAP systems with its respective experimental validation. For validation purposes, two experiments were conducted, using gas mixtures of: (a) 45% CO₂/10% O₂/45% N₂; and (b) 60% CO₂/10% O₂/30% N₂. In addition, two experiments, at 6°C and 20°C, were conducted to obtain the shelf‐life model, utilizing the following gas mixtures: 30% CO₂/10% O₂/60% N₂; 45% CO₂/10% O₂/45% N₂; 60% CO₂/10% O₂/30% N₂; and 75% CO₂/10% O₂/15% N₂. Gas mixtures with CO₂ concentrations between 30% and 70% and different headspace:food ratios were tested during simulations. The optimal conditions for scallop storage were a 60% CO₂/10% O₂/30% N₂ gas mixture and a headspace:food ratio of 2:1. With these conditions, a simulated shelf‐life of 21 days was obtained. Optimal conditions consider maximum shelf‐life, an adequate film collapse criterion, and time to reach the pseudo‐equilibrium condition. The predictive mathematical model, coupled with experimental studies for specific products, can be efficiently utilized to evaluate packaging alternatives (size, material and selected thickness) for different temperatures and initial gas concentration scenarios of MAP products. Copyright © 2006 John Wiley & Sons, Ltd.     

Quality changes of treated fresh‐cut tropical fruits in rigid modified atmosphere packaging containers

There has been increasing demand for various fresh‐cut tropical fruits. However, their short shelf‐life has limited the market increase of this product. Quality changes (firmness, colour, total soluble solids (TSS), titratable acidity (TA), sensory quality and microbial safety) of fresh‐cut mangoes, pineapples, melons and mixes of these fruits were evaluated. Chemical treatments to reduce browning, firmness loss and decay of fresh‐cut tropical fruits were investigated. The most effective agents for fresh‐cut mangoes, pineapples and melons were 0.1m ascorbic acid, 0.2m ascorbic acid and 0.2m ascorbic acid + 0.2m calcium chloride, respectively. Fresh‐cut tropical fruits were packaged in various rigid containers (PET, OPS and OPLA). Gas composition in the package headspace and time to reach steady‐state condition varied among fresh‐cut packaging systems and affected their quality and shelf‐life. The effects of package permeability of O₂ and CO₂ on quality and shelf‐life of the fresh‐cut products are discussed. Extended shelf‐life was observed in fresh‐cut mangoes, pineapples and mixes packaged in PET due to reduced O₂ and elevated CO₂ atmosphere. A modified atmosphere of 6% O₂ and 14% CO₂ achieved in PET extended the shelf‐life of fresh‐cut pineapples from 6 to 13 days. Accumulation of CO₂ may impart an off‐odour of fresh‐cut fruits. The results suggested that the shelf‐life of fresh‐cut fruits could be extended by using proper rigid containers. Suitable mixes to create optimal equilibrium modified atmosphere had a potential to extend shelf‐life of short shelf‐life fresh‐cut tropical fruits. Copyright © 2006 John Wiley & Sons, Ltd.     

Evaluation of plastic packages for guava refrigerated preservation

Guavas cv. ‘Kumagai’ were packed in several plastic materials and stored at 10°C and 85–90% relative humidity (RH) for 7, 14, 21 and 28 days (+3 days at 25°C). The plastic materials studied were: multilayer co‐extruded polyolephine film with selective permeability (PSP), low‐density polyethylene film (LDPE), LDPE film with mineral incorporation (LDPEm) and heat‐shrinkable polyolephine film (SHR). Guavas not packed were taken as control samples. The physicochemical characteristics of the fruits, O₂ and CO₂ transmission rates of the packaging materials and gas composition at the package headspace were evaluated. The LDPE film, 69 µm in thickness, with the lowest permeability to both O₂ and CO₂, led to anaerobiosis and high CO₂ concentration inside the packages and promoted physiological disturbances and changes in fruit flavour. The SHR film, 15 µm in thickness, was the most permeable to CO₂ and had quite high O₂ transmission, which modified the inner atmosphere of the packages slightly. The fruits packed in this film showed a poorer quality than the controls, possibly due to the heat produced during the shrinking of the film. The LDPEm film, 24 µm in thickness, was almost as permeable to CO₂ but had reduced O₂ transmission, promoting an atmosphere of equilibrium of 3% O₂ and 4.5% CO₂. Fruits packed in this film kept their skin colour and pulp firmness, suitable for consumption up to 14 days. The PSP film, 35 µm in thickness, had the greatest O₂ transmission but just over half of the CO₂ transmission of LDPEm, promoting an atmosphere of equilibrium of 0.5% O₂ and 4.5% CO₂ inside the packages. Fruits packed in such packages kept their physicochemical characteristics up to 21 days. Copyright © 2001 John Wiley & Sons, Ltd.     

Effectiveness of modified atmosphere packaging in preserving a prepared ready‐to‐eat food

The effectiveness of modified atmosphere packaging (MAP) was evaluated for a combination prepared food (Korean braised green peppers with dry anchovies). From a preliminary storage test of the ready‐to‐eat dish at 10°C, the aerobic bacterial count on the green peppers was selected as a primary quality index. The effect of MAP with different CO₂ concentrations on the product quality at 10°C was also studied. MAP with a CO₂ concentration of ≥30% extended the lag time and/or reduced the growth rate of bacteria. Finally, the effect of different storage temperatures (5, 10, 15 or 20°C) on the shelf life of the product was investigated. Mathematical modelling of bacterial growth curves under stretch‐wrap air packaging and MAP with 60% CO₂/40% N₂ showed that MAP increased the hypothetical minimum temperature in the square root model that describes the temperature dependence of the lag time and growth rate. MAP conditions of 60% CO₂/40% N₂ extended the shelf life at 10°C by 130% (to 18.4 days) relative to that achieved with stretch‐wrap air packaging (7.9 days) based on the time taken to reach the quality limit of an aerobic bacterial count of 10⁵ CFU/g. The relative extension of shelf life achieved with MAP was greater at lower temperatures. Copyright © 2008 John Wiley & Sons, Ltd.     

Preservation of cold‐stored guavas influenced by package materials

The objective of this study was to evaluate the influence of package materials on the preservation of cold‐stored ‘Kumagai’ guavas. The treatments were: PO2, co‐extruded polyolephinic film with gas injection (5% O₂/5% CO₂/N₂); PO3, co‐extruded polyolephinic film with gas injection (5% O₂/5% CO₂/N₂); LDPE, linear low density polyethylene film; LDPE‐gas, linear low density polyethylene film with gas injection (3% O₂/8% CO₂/N₂); PVC, polyvinylchloride stretch film; PO1, co‐extruded polyolephinic film and control: non‐packaged guavas. Guavas were stored at 10 ± 1°C/80–90% RH for 21 days, and then transferred to room temperature. Gas composition within the package headspace was analysed during storage and the physical and chemical characteristics of the guavas were evaluated daily during ripening. The modified atmosphere provided by PO1 film was insufficient to promote the benefit of senescence control. Although PVC provided an atmosphere close to that recommended, it did not preserve the colour and pulp firmness. PO2, PO3, LDPE and LDPE‐gas retarded the senescence process of the guavas during 21 days at 10°C plus 2 days at room temperature, but harmed the normal ripening of guavas in some aspects. This can be explained by reduced O₂ and elevated CO₂ levels within these four packages. None of the packages influenced the titratable acidity and the soluble solids, but they did harm ascorbic acid synthesis. Copyright © 2005 John Wiley & Sons, Ltd.     

Modified atmosphere packaging of fresh mushrooms

The storage life of harvested fruits and vegetables is influenced by their continued respiration and biochemical activity. Lowering the temperature, and modifying the atmosphere surrounding the product, can extend the shelf-life of the produce. Mushrooms (Agaricus bisporus) were placed into different structural containers covered with PVC films and stored at three temperatures. The effect of key variables, such as temperature, respiration rate, critical and optimal concentrations of O₂ and CO₂, package-weight/area ratio and film permeability, were studied. It was concluded that a highly perishable product, such as mushrooms, must be wrapped and refrigerated in order to prevent transpiration and shrivelling. Modified atmosphere packaging (MAP) may be beneficial but was not found to be essential. If a certain batch of mushrooms respires faster than predicted, or is exposed to large temperature fluctuations, MAP could have a damaging effect.     

Nanostructuring and Microstructuring of Materials from a Single Agropolymer for Sustainable MAP Preservation of Fresh Food

The main objective of the present work was to determine whether a single agropolymer [wheat gluten (WG)] could fit the modified atmosphere packaging (MAP) requirements of a range of six different fresh produce in key terms of oxygen permeation (Pe_O2) and CO₂/O₂ permselectivity (S) values. The required properties for optimal packaging of fresh fruits and vegetables were first evaluated using the Tailorpack MAP modelling software (UMR IATE, Montpellier, France) with packaging dimensions and respiratory and optimal atmosphere data as input parameters. Then, the modelled values obtained were compared with the properties of a range of WG composite films: monolayer self‐supported or multilayer at microscale or nanoscale, cast or thermoplasticised, with different formulations (percentage of plasticisers or nanofillers). The experimental gas transfer properties that could be covered by these materials ranged from 0.05 × 10^?10 to 2.00 × 10^?10 mol/m² s Pa for Pe_O2 and up to 18.0 for S. These ranges are much larger than conventional plastics that exhibit Pe_O2 from 0.10 × 10^?10 to 0.20 × 10^?10 mol/m² s Pa and S up to 4.5. It was demonstrated from a food‐requirements‐driven (Tailorpack modelling) and a multiscale film structuring (WG‐based composites) approaches, that transfer properties of WG‐based films would fit the requirements of the six selected fruits and vegetables better than conventional plastics. Copyright © 2012 John Wiley & Sons, Ltd.     

Comparison of Various Packaging Films for Mango Export

This study compared the effects of the use of various types of packaging films in maintaining quality, preserving bioactive compounds and extending shelf life of the ‘Nam Dok Mai’ mango. The principal techniques for maintaining the quality of mangoes are based on modified atmosphere packaging using highly gas‐permeable films and an ethylene‐removing mechanism. The films studied were non‐perforated highly gas‐permeable film, non‐perforated ethylene‐absorbing highly gas‐permeable film (HNPE), micro‐perforated highly gas‐permeable films (HMP) and common non‐perforated polyethylene film (LNP). These films were compared with non‐packaging treatment, which served as a control (C). Gas composition (O₂, CO₂ and C₂H₄) in the package headspace was monitored during storage at 12°C. The quality of mangoes were assessed by weight loss, colour (L* a* b*), texture, total soluble solids, titratable acidity, total phenolics, total flavonoids, ethanol concentration and sensory quality. Equilibrium‐modified atmospheres of 5 kPaO₂ + 5 kPaCO₂ and 4 kPaO₂ + 5 kPaCO₂ were achieved in the non‐perforated highly gas‐permeable film and HNPE packs, respectively. Carbon dioxide accumulation was observed in the HMP and LNP packs where CO₂ reached 17 and 10 kPa, respectively, after storage for 10 days. The shelf life of mangoes was extended to 40 days with HNPE, 35 days with HNP, and 30 days with HMP, as compared with 20 days with control and 5 days with LNP. HNPE, the film incorporated with fine particles of mordenite framework inverted‐type zeolite with ethylene‐absorbing ability, could further extend the shelf life of mangoes in addition to modified atmosphere packaging alone. Copyright © 2011 John Wiley & Sons, Ltd.     

Maintaining quality of fresh strawberries through various modified atmosphere packaging

The influence of various modified atmosphere packaging (MAP) (21/0.05, 4/8 and 60/20% O₂/% CO₂) on fresh strawberry qualities [pH, acidity, °Brix, colour ( L, a ) and texture profile analyses] was investigated and compared during storage. Among the gas combinations used, pH of fresh strawberry was 3.281 at 1 day, and increased to 3.561 for air [21/0.05% (O₂/CO₂)], 3.53 for low (4/8) and 3.538 high (60/20) at 12 days. At the end of the storage, °Brix had evolved from the initial 7.07 to 5.47, 5.65 and 5.62 for 21% O₂; 4% O₂ and 60% O₂, respectively. Storage in 60% O₂ or 4% O₂ delayed the decrease of °Brix, titratable acidity and increased pH compared with 21% O₂. At the end of the storage, the strawberry L values had slightly decreased. Initial values of the firmness were 1067 gf and reduced to 501 gf (21% O₂); 613 gf (4% O₂) and 575 gf (60% O₂) at 12 days storage. Higher O₂ resulted in better springiness and chewiness than those treated with 4% O₂ and 21% CO₂, but did not significantly affect resilience. These results show that the use of various MAP gas compositions, including high oxygen, could be a good alternative to maintain fresh strawberry qualities for at least 12 days. Copyright © 2008 John Wiley & Sons, Ltd.     

Effect of Different Packaging Methods on Quality and Shelf Life of Fresh Reindeer Meat

The impact of different packaging methods [vacuum, modified atmosphere packaging (MAP) (60% CO₂ and 40% N₂) and MAP + CO₂ emitter] on the quality of fresh reindeer meat (M. semimembranosus) stored at 4°C for 21 days was investigated. Colour and odour of the meat, drip loss, pH, microbial content, antioxidant capacity and cooking loss were measured. The MAP + CO₂ emitter resulted in prolonged microbial shelf life compared with vacuum and MAP without CO₂ emitter as lower level of total viable counts was detected after 13 and 17 days. Samples stored with CO₂ emitter also had lower drip loss. Samples stored in vacuum had significant lower L*‐value, higher a*‐value and lower intensity of freshness (odour and colour) compared with those stored in MAP and MAP with CO₂ emitter. However, MAP with a gas‐to‐product volume ratio of 1 : 1 seems to be too low in quality preserving. Increased partial pressure by adding a CO₂ emitter improved bacterial inhibition compared with vacuum and traditional MAP. Copyright © 2014 John Wiley & Sons, Ltd.     

Development of multilayer films with improved aroma barrier properties for durian packaging application

The symmetrical A/B/A structure of multilayer blown films was fabricated in this study. The immiscible low‐density polyethylene/polylactic acid (LDPE/PLA) blend was set as a core (B) layer and LDPE was used as skin (A) layers. The compositions of PLA in the core layer were varied from 20 to 50 wt%. The thickness of each layer was 10 μm (total film thickness of ~ 30 μm). In a blown film co‐extrusion process, the morphology of the fiber/ribbon‐like structures of LDPE/PLA blend was developed. Such structures had interesting effects on gas permeability and aroma barrier properties of the films. For instance, multilayer LDPE films containing 40 and 50 wt% PLA (P40 and P50) showed the reduction of oxygen permeability (PO₂) approximately 20% and 43%, respectively, compared with the neat LDPE film. A long tortuous path for gas and aroma transportation through film thickness was created from the developed ribbon‐like structures of the PLA minor phase. For durian packaging application, fresh‐cut durian of 300 g was packed in the developed multilayer films, LDPE, and HDPE (Control), stored at 4°C for 7 days. Results demonstrated that the steady‐state condition of 10% to 13% O₂ and 8% to 10% CO₂ was achieved in all packages except in the HDPE. Moreover, the P40 and P50 films exhibited an outstanding aroma barrier property for three major durian volatiles : diethyl sulfide, ethyl propanoate, and 2‐ethyl‐1‐hexanol. Overall results clearly indicated that the multilayer LDPE films containing PLA exhibited a significantly improved aroma barrier performance with optimum gas permeability desirable for modified atmosphere packaging to retain quality of fresh‐cut durian throughout the storage period.     

Effect of packaging film on the quality of ‘Chaoyang’ honey peach fruit in modified atmosphere packages

The quality of honey peach fruit stored at 2°C in modified atmosphere packages was studied. Three different thickness low‐density polyethylene (LDPE) films were used as packaging films. Honey peach fruits of ‘chaoyang’ were packaged in LDPE bags 15, 25 and 40µm thick and control (air). The respiration rate, O₂ and CO₂ concentrations in the packages, flesh colour, total soluble solid (TSS), titratable acidity (TA), flesh firmness (FF) and membrane integrity of the fruits were monitored. Compared to the control, MAP treatments inhibited the climacteric peak, avoided the increase of flesh colour, decreased the development of softness and retarded the reduction of TTS, TA and membrane integrity. Significant differences in the quality of the fruits were found between the three packages and the control (p ≤ 0.05). After 20 days at 2°C within the LDPE25 bags, a steady‐state atmosphere of 5% CO₂ + 4% O₂ was reached. Honey peaches stored in these bags showed the best quality at the end of the storage. Copyright copy; 2006 John Wiley & Sons, Ltd.     

Modified Atmosphere Packaging of Guava Fruit

Fully matured fresh guava fruits (Lucknow‐49) were precooled at 10 °C for 1 h and pretreated with 500‐ppm benomyl for 5 min. The fruits were packed in 25‐µm and 50‐µm LDPE bags with active modified atmosphere packaging of 3% O₂ + 5% CO₂, 6% O₂ + 5% CO₂ and 9% O₂ + 5% CO₂ gas concentrations and stored at 5 ± 1 °C and 10 ± 1 °C temperatures as well as non‐packaged as control. The shelf life of guava could be increased up to 42 days by packaging in 50‐µm LDPE bags with a gas concentration of 9% O₂ + 5% CO₂ and stored at 10 °C without much change in physical, biochemical and sensory characteristics. Physico‐chemical changes viz., PLW, pulp to peel ratio, firmness, TSS, total sugar, ascorbic acid and titratable acidity were observed minimum for fruits packed in 50‐µm LDPE bags at 3% O₂ + 5% CO₂ gas concentration at 5 °C storage temperature, but sensory score decreased drastically after 21 days of storage. Chilling injury was observed for the fruits packed at 5 °C storage temperature after 21 days of storage, and it was severe in 25‐µm LDPE bag at later stage. Control fruits over‐ripened with the highest weight loss (12.47%) on 6 days of storage and discarded from the storage. Copyright © 2014 John Wiley & Sons, Ltd.     

Packaging materials for fermented milk,part 2: solute‐induced changes and effects of material polarity and thickness on food quality

This work is a continuation of the application of a developed methodology for the selection of packaging material for a specific food product, in this case the ‘demanding’ food product: fermented milk. The effects of different packaging material parameters on the quality of fermented milk were studied. Food quality after storage was determined as a function of material polarity and pouch thickness by storing the liquid in pouches of different materials. The material polarity was varied by using laminates with polyethylene, poly(ethylene‐co‐vinyl alcohol) with two different ethylene contents and an aliphatic polyketone. The effects of pouch thickness were studied using high‐density polyethylene films of different thicknesses between 25 µm and 200 µm. The interactions between the milk product and the pouch material were analysed by oxygen and water permeability, gas chromatography–mass spectrometry and tensile testing. The CO₂ and O₂ contents in the headspace of the pouches were determined. The food quality was determined by measuring whey syneresis and the contents of Bifidobacteria, Enterobacteriaceae, yeast and mould. A trained taste panel determined the sensory properties. The content of CO₂, and consequently the sparkling taste, increased with increasing polarity and/or pouch thickness. The CO₂ content was affected more easily by changes in material polarity than by changes in pouch thickness. The increase in whey syneresis and the decrease in Bifidobacteria content with time were independent of material polarity and pouch thickness. The contents of Enterobacteriaceae, yeast and mould in the liquid were always below existing limits for foodstuffs. A newly developed method was used by which the CO₂ and O₂ permeabilities of the pouch/packaging could be estimated, using the kinetics of the gas composition in the pouch headspace. Permeability values, as estimated by the method, revealed that the CO₂ production and the O₂ consumption rates of the fermented milk were dependent on the CO₂ and O₂ headspace concentrations. An increase in permeability, determined by conventional methods, suggested that both the non‐polar and the polar polymers were plasticized by fermented milk. The plasticization was, however, modest and undetectable when the polyethylene tensile test data were analysed. Copyright © 2003 John Wiley & Sons, Ltd.     

Effect of Initial Gas Flushing or Vacuum Packaging on the Ripening Dynamics and Preference for Kimchi,a Korean Fermented Vegetable

The effects of vacuum or modified atmosphere packaging conditions on the ripening dynamics of kimchi and sensory preference were investigated to determine the potential of initial atmospheric flushing as a method for improving quality at consumption. In all the packaging treatments (control of air, vacuumizing, CO₂ flushing and N₂ flushing), the partial pressures of O₂ and N₂ remained at nearly constant initial levels; therefore, the increases of package pressures were dominantly caused by the increases in the CO₂ partial pressures as a result of kimchi fermentation. The CO₂ production from kimchi was greater in the vacuumed and CO₂‐flushed packages. The initial vacuumed treatment helped to maintain relatively lower pressure during extended storage, and the pressure of the CO₂‐flushed package could have been reduced as a result of the high solubility of CO₂ in the aqueous product. Initial CO₂ flushing also provided the packaged product with a pleasant cool flavour at the properly ripened state.