The Effect of Active Packaging on Microbial Stability and Quality of Chinese Steamed Bread

The present study was conducted to evaluate the effect of active packaging [oxygen absorber (OA) or oxygen absorber combined with ethanol emitter (OA + EE)] on microbial stability and quality of Chinese steamed bread (CSB) stored at 25 °C. Air‐packaged CSB was taken as control. Microbiological, sensory, physical, thermal and mechanical changes were monitored as a function of treatment and storage time. On day 2 of storage total plate count was reduced by 3.1, 3.7 and 4.4 cfu/g by OA, OA + EE (1% v/v) and OA + EE (3% v/v), respectively (p < 0.05). Yeasts and moulds were inhibited during the entire storage period. No detrimental effects of OA + EE (1% v/v) were observed on organoleptic parameters, whereas OA + EE (3% v/v) gave a strong objectionable flavour and taste. Active packaging significantly (p < 0.05) delayed the increase of potential of hydrogen as compared to the control. No significant effect of active packaging was found on moisture content, water activity, colour and specific volume. An increase in the melting enthalpy of amylopectin crystallite was observed in all samples during storage. The stored CSB samples packaged with OA showed higher values of hardness compared to samples packaged with OA + EE (1% v/v), indicating the potential of ethanol as plasticizer of the protein network. The results indicate the potential application of OA and OA + EE (1% v/v) as an antimicrobial packaging system for CSB preservation. Copyright © 2015 John Wiley & Sons, Ltd.     

Modified atmosphere packaging of pita (pocket) bread

Pita bread has a shelf-life of only a few hours, mainly due to its large surface to volume ratio. Hardening, caused by staling and drying, is the main factor affecting shelf-life. Extension of shelf-life by packaging pita in a high barrier laminate under modified atmosphere (MAP) of 99% CO₂ or 73% CO₂ with 27% N₂ was studied. A shelf-life of 14 days, as determined by microbial spoilage, was obtained for MAP pita bread. Staling, as determined by means of a penetrometer, was delayed in MAP pita. Organoleptic hedonic comparisons of MAP pita, against frozen defrosted pita from the same batch, gave almost identical results. Shelf-life was terminated by the appearance of microorganisms on bread.     

Effect of the gas/product ratio and CO2 concentration on the shelf-life of MA packed fish

Rainbow trout and Baltic herring fillets were gas packed at two different gas/product ratios and two different CO² concentrations. Two reference samples were used; one frozen and one vacuum packed. Changes in gas composition in the gas packages, microbial and sensory quality, K values and drip formation of the fillets were investigated during storage at 2°C. A gas/product ratio of 100 ml/100g gas package was as effective as a vacuum package in preserving the microbial quality of fish and a gas/product ratio of 40ml/100g gas package was as effective as a vacuum package in preserving the sensory quality of fish.     

Mass transfer from and through packaging materials

The use of polymer films for food packaging requires a knowledge of their transport properties under varying conditions. The permeability to gases and water vapour of the packaging films at the specific conditions of use, i.e. temperature, relative humidity and pressure gradient, are needed for selecting the optimum packaging system to ensure the required shelf-life of the packed product. Migration from, and absorption by, plastic films also play an important role in their selection. The 0₂ and CO₂ permeabilities of three plastic films at four different temperatures were evaluated and shown to follow the Arrhenius relationship in the range tested. The effects of four thicknesses of one film on its permeability are also reported. Three methods to evaluate migration from polymeric films were compared using different weight/volume ratios. The extraction method recommended by the FDA, using n-hexane in a stirred flask, was found to be best. The shelf-life of Matzoth (Jewish Passover bread) packed in polyethylene (stored at 25°C) was found to be longer than the shelf-life of those packed in the higher barrier PVDC/PE. This was apparently due to the absorption of undesirable oxidation compounds, given off from the Matzoth by the PE, which were not absorbed at detectable levels by the PVDC/PE.     

A rapid method to determine the barrier requirements for dehydrated oatmeal product using flexible packaging films

Product was packaged in two types of flexible packaging films, poor moisture-high oxygen barrier and high moisture-poor oxygen barrier, and stored under standard tropical conditions. Physical, chemical and biological changes were investigated regularly to find the shelf-life determining factors. Control samples were packaged in glass bottles and stored at 0°C. OTR and WVTR of packaging films were measured. Packaging film permeability and analytical data, obtained from storage tests, were used to determine the barrier requirements for dehydrated oatmeal product, intended for distribution and storage in a tropical climate for 9 months shelf-life. © 1997 John Wiley & Sons, Ltd.     

Effect of chitosan coating and vacuum packaging on the quality of refrigerated grilled pork

The effects of chitosan coating and vacuum packaging on the quality and shelf‐life of retail packaged grilled pork in a PVDC/nylon pouch during refrigerated storage at 2 ± 1°C were investigated. Grilled pork without chitosan coating and packaged in 100% air was used as the control sample. Firmness, pH, colour, peroxide values, microbial population and shelf‐life (as determined by sensory characteristics) of the samples were determined during the storage. The results showed that colour, peroxide values and microbial population coincided with sensory characteristics. The delayed growth of microbes in vacuum packaging can be attributed to inhibition by low levels of O₂. Chitosan coating was shown to minimize oxidation, as reflected by the peroxide values, colour changes and microbial counts of the samples. Vacuum‐packaged chitosan‐coated grilled pork showed negligible microbial growth and was found to be organoleptically acceptable throughout the storage period. Chitosan coating along with vacuum packaging provided a type of active packaging to maintain quality and extend the shelf‐life of grilled pork. Copyright © 2006 John Wiley & Sons, Ltd.     

Effect of Storage in a Low Oxygen Gas Atmosphere on Colour and Sensory Properties of Pork Loins

The objective of this study was to examine the quality characteristics of packaging materials and packaging units, and the viability and acceptability of the colour and sensorial properties of fresh pork meat during storage in low oxygen and high carbon dioxide modified atmosphere packaging up to 16 days at two temperatures (0°C and 4°C), as well as the sensorial properties of cooked meat. Packaging materials had good mechanical and barrier properties and were suitable for packaging in selected atmosphere. The concentration of oxygen during the whole storage period was less than 0.5% at both temperatures. The proportion of red colour (a*) was successfully maintained although the colour was slightly darker (L*) and the sensory value was lower when evaluated at the end of the storage period. Based on the obtained results and discussion, it can be concluded that samples packaged in a modified atmosphere with 40% CO₂ and 60% N₂ can be stored at 0°C for 15 days and at 4°C for 10 days. Samples had a good sensory quality until the 16th day, with the best results achieved on the 7th day. Copyright © 2013 John Wiley & Sons, Ltd.     

Active Packaging System Based on Ag/TiO2 Nanocomposite Used for Extending the Shelf Life of Bread. Chemical and Microbiological Investigations

This study was carried out to assess the shelf life and microbiological safety of wheat bread during storage in a packaging system made of Ag/TiO₂ nanocomposite (Ag/TiO₂‐P) in comparison with bread packed in high density polyethylene (HDP‐P) and bread not subject to packaging (CS). The Ag/TiO₂ nanocomposite was prepared by sol–gel procedure, and its morphostructural characterization was performed by X‐ray diffraction, Fourier transform infrared spectroscopy and transmission electron microscopy. The Ag/TiO₂‐P was prepared via inclusion of nanocomposite between the polyethylene layers to avoid bread–nanocomposite contact. Chemical and microbial stability of bread expressed in terms of total fat, protein, sugar, lipid hydroperoxides and yeasts, moulds, and Bacillus subtilis and Bacillus cereus counts, respectively, was monitored for 6 days. Experimental data indicate that Ag/TiO₂‐P considerably extends the shelf life and microbiological safety of bread in comparison with HDP‐P and CS. A possible mechanism involved in the preservation of the bread is hypothesized. Copyright © 2014 John Wiley & Sons, Ltd.     

不同包装方式对大米保鲜效果影响的研究

高温高湿条件下,不同包装方式对大米品质变化的影响进行分析研究,得出大米品质变化的影响规律.在贮藏初始阶段,环境高温是大米失水的诱因;在贮藏期间,包装材料的透湿性使包装内相对湿度上升,大米吸水.通过测定霉菌数量、分析包装袋内挥发性气体成分及浓度、测定大米光透差等,得出竹炭以其优越的吸附气体特性可以有效地调节包装袋内环境相对湿度和氧气含量等,确保贮藏期间大米的品质.     

乙醇气体发生剂在抗菌包装中的研究进展

综述了抗菌包装在食品包装中的研究进展,概括了乙醇的杀菌机理以及乙醇气体在控制食品质量和延长保质期方面的主要应用。重点介绍了一种释放型抗菌包装———乙醇气体发生剂,并对其在保鲜包装领域的应用前景与存在的问题进行了分析,为深入研究乙醇作为抗菌剂的特性,进一步开发气体型抗菌剂在食品抗菌包装中的应用,提供科学的研究基础。     

气调包装对冷鲜禽肉感官特性和保质期的影响

目的研究CO组、无氧组、真空组、低氧组、高氧组、普通组等6种包装方法对冷鲜禽肉感官特性和保质期的影响。方法测定禽肉在贮藏不同时间后的感官特性、理化指标(pH值、TVB-N值、TBA值、汁液损失率)和菌落种数的变化。结果随着贮藏时间的增加,各组的感官特性呈现下降趋势,CO组感官指标较好,12 d时保持新鲜;理化指标和菌落总数整体呈上升趋势,CO组、无氧组和真空组上升较慢,保持新鲜9~12 d。结论 CO组、无氧组和真空组保鲜效果较好,保鲜期达12 d,添加了CO(0.5%)对禽肉的感官特性有明显效果,总体保鲜效果为CO组无氧组真空组低氧组高氧组普通组。     

Effect of packaging materials and storage conditions on bacterial growth,off‐odour,pH and colour in chicken breast fillets

A comparison was made of the effect of different packaging materials on bacterial growth, off‐odour, pH and colour of chicken breast fillets stored at 4°C. For one of the packaging materials, the effects of temperature (4°C and 8°C) and initial oxygen present (0%, 2% and 4%) on bacterial growth, off‐odour, pH and colour in chicken breast fillets were also evaluated. Chicken breast fillets stored in the packaging material with the highest oxygen transmission rate (OTR) measured at actual storage conditions had the highest bacterial growth and the highest degree of off‐odour. Chicken breast fillets stored in packaging material mainly consisting of expanded PET had similar bacterial growth and off‐odour as in the barrier display film (BDF) packages, despite a smaller headspace volume and lower initial concentration of CO₂. No differences in discoloration and pH of the chicken breast fillets, due to storage temperature and amount of initial oxygen present, were found when one of the packaging materials was studied. In the early phase of the storage period, Pseudomonas spp. constituted the majority of the total viable counts, while after about 12 days, lactic acid bacteria dominated. At the end of the storage period, both Pseudomonas spp. and Enterobacteriaceae were present in high numbers. Significant differences in counts of Brochothrix thermosphacta were only obtained with initial presence of oxygen. The storage temperature had greater impact on microbial growth and off‐odour than the initial presence of oxygen in the packages. Copyright © 2004 John Wiley & Sons, Ltd.     

Efficacy of chitosan‐coated paper incorporated with vanillin and ethylene adsorbents on the control of anthracnose and the quality of Nam Dok Mai mango fruit

Mango fruit is perishable and susceptible to anthracnose. Active‐coated paper is proposed as potential packaging for commercial application in wrapping mango fruit to control anthracnose and delay the ripening process of fruit. The surface of white standard bleached paper was coated using a vanillin‐chitosan coating solution containing varying amounts of zeolite or activated carbon at 0% (vanillin paper), 0.1%, 0.2%, and 0.4%, w/v of ethylene absorbers. The first objective was to study the effect of absorber types and their amounts on ethylene removal. After that, the coating formulation that provided the highest ethylene removal was selected to wrap commercial Nam Dok Mai mango fruit to study the quality changes. The efficacy of active‐coated paper on the severity index of anthracnose disease, change in physicochemical properties, and sensory acceptability during storage (13°C, 90% relative humidity (RH) for 30 days) were investigated. It was found that vanillin‐chitosan coated paper containing 0.2% (w/v) of zeolite (zeolite paper) exhibited the highest capacity of ethylene adsorption. Zeolite paper could delay the disease incidence of wrapped mango fruit and provided the lowest severity index of anthracnose disease throughout storage. Moreover, changes in physicochemical qualities (weight loss, firmness, titratable acidity, total soluble solid, and color) of mango fruits wrapped in zeolite paper was quite low, compared with those wrapped with vanillin and uncoated papers. In addition, mango wrapped by zeolite paper had the highest sensory acceptance score. The results suggest that zeolite paper can efficiently be applied as wrapping to extend the postharvest life of mango fruit.     

Quality Evaluation of Grated Graviera Cheese Stored at 4 and 12°C using Active and Modified Atmosphere Packaging

The effect of active [oxygen absorber (OA) combined with an ethanol emitter (EE)] and modified atmosphere (100% Nitrogen) packaging in combination with a high barrier experimental polyethylene terephthalate‐silicon oxides//low density polyethelene film on shelf‐life extension of grated Graviera cheese stored at 4 and 12°C was investigated. Microbiological (total viable counts, Pseudomonads, lactic acid bacteria, Enterobacteriaceae and Yeasts/Moulds), physico‐chemical (pH, thiobarbituric acid and colour) and sensory (odour and taste) changes occurring in the product were monitored as a function of treatment and storage time (10 weeks). Sensory shelf‐life was approximately 1, 1.5, 4.5, 6, 9 and at least 10 weeks for control samples (12 and 4°C), for N2 packaged samples (12 and 4°C) and samples packaged with the OA + EE (12 and 4°C), respectively. At the point of sensory rejection, yeasts and moulds increased from 2.00 to 3.60 and 5.55 log CFU/g for control samples stored at 4 and 12°C, respectively. Similarly, for samples stored under nitrogen, yeasts and moulds reached 2.00 and 2.32 log CFU/g at 4 and 12°C, respectively. Yeasts and moulds in samples with the OA + EE remained below 2 log CFU/g throughout the entire storage period, irrespective of storage temperature. pH varied between 5.72 and 6.49 depending on specific treatment. Malondialdehyde absorbance ranged between 0.05 for fresh samples and 0.79 mg/kg at the time of sensory rejection of samples. Light parameters L and b decreased while parameter a increased during storage, reflecting a gradual discolouration of all samples and especially those stored at 12°C.     

Conservation of Bakery Products Through Cinnamaldehyde Antimicrobial Films

In this study, an antimicrobial film containing cinnamaldehyde was developed to pack bread and pastry made without preservatives. These products were wrapped with the antimicrobial films and packaged in low‐density polyethylene bags. The antimicrobial activity of the films, the migration of the cinnamaldehyde in the films to the products and product acceptance by consumers were evaluated. Samples of bread and pastry packaged with films without the antimicrobial were used as controls. When samples of bread packaged with the cinnamaldehyde films were analysed, the films were found to be effective in inhibiting the growth of aerobic mesophiles, yeast and mould. The control sample was observed to have twice as much growth (four log cycles) compared with the other treatments after 12 days of storage. After 60 days, the samples of pastry dough showed a reduction of two and three log cycles of growth for aerobic mesophiles and Staphylococcus spp. for the 5 and 10% films, respectively. However, the amounts of yeast and mould in samples packed in either 5 or 10% antimicrobial films did not increase over the storage period. In all evaluations, water activity did not influence the microbiological results. The content of cinnamaldehyde that migrated from the film (5%) to the pastry dough and bread were 0.005 g/g and 0.0025 g/g, respectively, after 3 days of storage at 23 ± 2 °C. This amount of the antimicrobial influenced the acceptance of the pastry dough compared with the control but did not influence the acceptance of the bread, possibly due to the smaller amount of cinnamaldehyde detected in samples of bread in relation to the samples of pastry dough. Copyright © 2013 John Wiley & Sons, Ltd.     

Effect of different modified atmosphere packaging on microbial quality,oxidation and colour of a seasoned ground beef product (meatball)

The effects of different modified atmosphere packaging (MAP) on microbial quality, oxidation and colour of meatballs were investigated. Meatballs were prepared in our laboratory and packaged in vacuum or in different gases: combinations of O₂ (0, 2, 21%) and CO₂ (0, 33, 66, 100%) with N₂ as balance gas. Total microbial count, thiobarbituric acid reactive substances and colour were determined during storage at 3°C for 3 weeks. Total microbial count remained unchanged at around 6.3 LogCFU/g in vacuum and 100% CO₂ packages after 7 days, and slightly increased afterwards. The microbial count was higher in other packages and increased to 7.6 LogCFU/g after 21 days storage. Oxidation was inhibited by reduced O₂ and increased CO₂ in the packages. Packages with low O₂ maintained colour (a‐values) to a greater extent than the packages with higher O₂ levels. MAP containing 1–3%O₂ with 33%CO₂ inhibited microbial growth, oxidation and colour change in meatballs. Copyright © 2009 John Wiley & Sons, Ltd.     

Assessment of oxygen levels in convenience‐style muscle‐based sous vide products through optical means and impact on shelf‐life stability

An optical oxygen analyser was used in two small‐scale industrial trials to non‐destructively assess the quality of packaged convenience foods and packaging process. Beef lasagne packed under 70% vacuum and cooked under standard sous vide conditions was monitored for residual oxygen, using disposable sensors incorporated in each pack and a benchtop optical oxygen analyser. High levels of residual oxygen close to ambient were determined in the majority of packs after packaging, as opposed to anticipated levels of 4–5%. Residual oxygen was monitored over product shelf‐life (4 weeks at +4–10°C) along with measurement of microbial growth and lipid oxidation in food by conventional destructive methods. Oxygen levels in packs went down to almost zero between weeks 2 and 3 indicating deterioration of packaged product. Correlation between oxygen profiles and the rate of microbial growth and lipid oxidation was established. The optical oxygen sensor system was shown to provide valuable information about performance of the packaging process, product storage conditions and food quality in a convenient and cost‐efficient fashion and non‐destructively. Copyright © 2004 John Wiley & Sons, Ltd.     

Metabolic profiling of liver from hypercholesterolemic pigs fed rye or wheat fiber and from normal pigs. High-resolution magic angle spinning 1H NMR spectroscopic study

This study presents the first application of a high-resolution magic angle spinning 1H NMR approach to elucidate the metabolic effects of a hypercholesterolemic condition and two high-fiber diets based on rye and wheat bread, respectively, in intact pig liver biopsy samples. Standard 1D and spin-echo 1H spectra were acquired on a total of 20 biopsy samples, and 2D total correlation spectroscopy experiments were carried out on selected samples for assignment of the observed resonances. Principal component analyses and partial least-squares regression discriminant analysis revealed differences in the hepatic lipid content and choline-containing compounds between normal and hypercholesterolemic pigs. In addition, the results demonstrated that the liver metabolite profile of hypercholesterolemic pigs fed a high-fiber rye bread differed from that of pigs fed high-fiber wheat bread with respect to both the lipoprotein fractions and the choline-containing compounds. These findings suggest that earlier reports on high-fiber rye diet-induced effects on plasma HDL/LDL content partially can be ascribed to effects on liver cholesterol metabolism and that the hepatic phospholipase pathways of phosphatidylcholine breakdown are affected by the high-fiber rye diet.     

Influence of packaging material on bread characteristics during ageing

One of the priorities of today's bread‐making industry is to find suitable packaging solutions to satisfy the peculiar requirements of bread, mostly appreciated by Italian consumers for its crispy crust. The packaging material should allow for both rapid heat exchange with the environment and water vapour evaporation to prevent condensation inside the package. Perforated orientated polypropylene (OPP) films are currently the best materials available for satisfying the industry's requirements. Recently, our group demonstrated that bread wrapping with perforated films is efficacious against bread contamination. The aim of this work was to verify whether these types of films could also influence the trend of phenomena related to product ageing. In particular, variations in the moisture inside the loaf during storage and their influence on changes in crumb softness were investigated. Three OPP films and one double‐layer film bag with different hole size characteristics were chosen for this study and their performances were compared with those of a paper bag. Because of the considerable differences in the hole size characteristics, the films showed very different barrier effects to water evaporation. The C250 OPP film (hole mean diameter = 0.54 mm and density = 21.4 holes/cm²) played an interesting role in modulating moisture variations. Wrapping bread in this film enabled both crust crispness and crumb softness to be maintained during 48h of storage. Such performances cannot effectively be obtained by using alternative industrial bread packaging materials, such as paper bags. Copyright © 2006 John Wiley & Sons, Ltd.