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Production and applications of biobased packaging materials for the food industry.

Materials based on renewable resources are being developed at an increasing rate. Today, the only biobased food-packaging materials used commercially on a major scale are based on cellulose. However, materials based on proteins, starch, polylactate and other renewable resources may be the food-packaging materials of tomorrow. The paper presents some of the different biobased materials and their potential as food-packaging materials.

Biodegradation, Environmental↗

Modelling permeation through porous polymeric films for modified atmosphere packaging.

The use of perforated packaging films is increasing with the application of modified atmosphere packaging for fresh produce. These films provide high to very high mass exchange rates. However, irrespective of the chemistry of the material, mass transport through such films cannot be described using conventional permeability equations (Henry's plus Fick's laws). Other expressions such as Knudsen's law, gas diffusivities or Poiseuille's hydrodynamic flow can be applicable. The application of these laws is discussed and their corresponding range of validity is provided. These laws were also applied to model experimental permeation rates of oxygen and water and were further used to describe the headspace evolution of two fruit products in modified atmosphere packaging. In the light of these results, the contribution of different factors to the headspace evolution is discussed.

Chromatography, Gas↗

Application of Finite Element Analysis (FEA) for the simulation of release of additives from multilayer polymeric packaging structures.

Computer programmes are available to predict, for consumer protection purposes, the migration of additives from a polymeric package during its contact with food. However most of these programs were developed to estimate migration only from single layer polymeric packaging under isothermal conditions. In this work a diffusion model was developed to simulate the migration from multilayer packaging and under non-isothermal temperature conditions, too. Finite Element Analysis (FEA) is used as a numerical approximation method to solve the diffusion equations describing such processes. The possibilities and limitations of the FEA method are presented and the correlation between experimental and computed results is discussed.

Algorithms↗

Active and intelligent packaging for food: is it the future?

This paper gives an overview of the legal consequences of a new EU framework regulation on food contact materials which includes controls on active and intelligent packaging. Recent developments in active and intelligent packaging systems are described, two examples of which aim at achieving improvements in quality and safety of food products. The first one is an on-command preservative-releasing packaging system. The second system is an intelligent concept, based on the development of a non-invasive microbial growth sensor to monitor the sterility of food products.

Environmental Exposure↗

Theoretical treatment of pollutant transfer in a finite volume of food from a polymer packaging made of a recycled film and a functional barrier.

The problem of pollutant transfer in food from a polymer packaging made of a recycled film and a functional barrier is studied from a theoretical point of view. In the present case, the process is controlled by Fickian diffusion through the two films of the polymer packaging in perfect contact and by convection into the food. A numerical model is built, taking all the facts into account: the diffusion of the pollutant through the two polymer films, a convective coefficient of mass transfer on the surface, a partition factor, the volume of the liquid and the thicknesses of the polymer films. The results are expressed by using dimensionless numbers so that they can be used for various cases, viz the kinetics of pollutant transferred into the food and the profiles of concentration of the pollutant through the packaging.

Diffusion↗

Prediction of worst case migration from packaging to food using mathematical models.

Prediction of migration from packaging to food is often made using equations which are not always designed specifically for the problem. At least, these equations should overestimate migration, in order to be on the safe side. Integration of Fick's equation under the assumption of 'infinite packaging' provides an equation which is very practical since it requires only a few experimental data. It is shown here that, unfortunately, the use of this equation leads to a systematic underestimation of the diffusivity, by the square of the percentage of migration at steady state. In contrast to widely accepted opinion, this model is not conservative. A conservative approach requires that the diffusivity is determined under 'finite packaging' assumptions, associated with very large volumes of food and with long term experiments. These equations are applied to the migration of a phenolic antioxidant from polypropylene.

Food Contamination↗

Overview of food packaging research in Hungary.

In the last 15 years, increasing demands for improvement in food quality, and for increased food choice have grown in Hungary. To meet these new requirements, packaging is of decisive importance. Considerable developments have been achieved as a result of wide-ranging R&D activities. A review compiled by the author is presented of the actual situation regarding Hungarian food packaging, covering the main domestic institutions for R&D activities dealing with packaging materials and methods, together with a discussion of trends and results.

Academies and Institutes↗

Food contamination with organic materials in perspective: packaging materials as the largest and least controlled source? A view focusing on the European situation.

The comparison of the various sources of food contamination with organic chemicals suggests that in the public, but also among experts, the perception of risk is often distorted. Firstly, neither pesticides nor environmental pollutants contribute the most; the amount of material migrating from food packaging into food may well be 100 times higher. Secondly, control of these large migrants is often lagging behind the standards set up for other sources, since many of the components (particularly those not being "starting materials") have not been identified and, thus, not toxicologically evaluated. Finally, attitudes towards different types of food contaminants are divergent, also reflected by the legal measures: for most sources of food contamination there are strict rules calling for minimization, whereas the European packaging industry has even requested a further increase in the tolerance to as close as possible to the limit set by the toxicologists. This paper calls for a more realistic perception and more coherent legal measures-and improvements in the control of migration from packaging material.

Europe↗

Migration of substances from food packaging materials to foods.

The employment of novel food packaging materials has increased the number of occurring hazards due to the migration from packaging material to the packaged food. Although polymers have mainly monopolized the interest of migration testing and experimentation, recent studies have revealed that migration also occurs from "traditional" materials generally considered to be safe, such as paper, carton, wood, ceramic, and metal. The regulations and the directives of the EU tend to become stricter in this respect. The emphasis is on reaching a consensus in terms of food simulants and testing conditions for migration studies. Furthermore, the list of hazardous monomers, oligomers, and additives continues to augment in order to ensure that the consumer safety is in current agreement with the HACCP, which is continuously gaining ground.

European Union↗

Physical polymer surface modification methods and applications in food packaging polymers.

Continued innovations in the polymer industry have made polymer surface modification methods a subject of intense research. The importance and necessity of surface modification of plastics are explained, and the advantages of physical surface treatments over the less-sophisticated chemical methods are outlined. Currently available physical surface modification methods for food packaging polymers are reviewed from the food packaging perspective. These physical surface modification methods include flame, corona discharge, UV, gamma-ray, electron beam, ion beam, plasma, and laser treatments. The principle of operation of each method is briefly described, and the advantages and disadvantages of each technique are cited. The extent to which each of these methods can produce the specific modifications desired is discussed. Furthermore, the effects of each treatment on barrier, mechanical, and adhesion properties of food packaging polymers are also examined. Finally, an overview of economic aspects of sophisticated surface modification techniques, including ion beam, plasma, and laser treatments, is presented.

Food Packaging↗

Consumer acceptance of stir-fry and kabobs from dark chicken meat and their packaging.

In a study of marketing opportunities for fresh, dark, chicken meat, focus group participants (n = 34) provided qualitative information concerning potential products and packaging concepts. Results of the focus groups indicated that the participants were willing to purchase new, convenient poultry products made from dark chicken meat. Specific dark meat products the participants were willing to by included boneless, skinless thighs, kabob cubes, and stir-fry strips. Consumers desired clear packaging for the products but did not want the packaging to be microwaveable or ovenproof. Acceptance of chicken kabob chunks and stir-fry strips of varying piece sizes (2.54, 3.81, and 5.08 cm) and seasoning concentrations (1.6, 2.1, and 2.6%) was evaluated by consumers (n = 83) using a nine-point hedonic scale. The most preferred products were a 5.08 cm (2 in) kabob with 2.6% seasoning and a stir-fry strip with 2.6% seasoning. A simulated supermarket setting test was conducted to verify findings from a mailed survey (n = 115) and actual purchase behavior by consumers (n = 121). A calculated desirability index indicated a ranked preference to be: breasts > kabobs > stir-fry > boneless, skinless thighs > bone-in, skin-on thighs.

Adult↗

Thermal inactivation D- and Z-values of Salmonella and Listeria innocua in fully cooked and vacuum packaged chicken breast meat during postcook heat treatment.

Studies were conducted to determine thermal inactivation D- and z-values of Salmonella and Listeria innocua in fully cooked and vacuum-packaged chicken breast meat. Fully cooked chicken breast meat products that were obtained from three different sources with differing formulations were uniformly inoculated with a cocktail of Salmonella (including Senftenberg, Typhimurium, Heidelberg, Mission, Montevideo, and California) or L. innocua at approximately 10(7) cfu/g. The inoculated meat samples were vacuum-packaged and then heat-treated at a temperature of 55 to 70 C for 5 to 90 min. After heat treatment, the samples were immediately cooled in an ice-water bath. Survivors of Salmonella and L. innocua were enumerated for each sample. D- and z-values of Salmonella and L. innocua were determined for each product and compared among the products. Source and formulation did not cause significant differences in the D- and z-values of Salmonella or L. innocua among the three fully cooked and vacuum-packaged chicken breast meat products.

Animals↗

D and z-values for Listeria monocytogenes and Salmonella typhimurium in packaged low-fat ready-to-eat turkey bologna subjected to a surface pasteurization treatment.

The D-values of Listeria monocytogenes and Salmonella Typhimurium at various surface pasteurization temperatures were determined for low-fat turkey bologna. Four cm2 meat squares were sterilized by irradiation prior to inoculation with 0.1 mL of a 10(8) cfu/mL culture, aseptically packaged in a linear low-density polyethylene pouch, and vacuum-sealed. Thermal treatments were administered by submerging packages in a heated water bath maintained at various set temperatures. At an 85 degrees C water bath temperature, no L. monocytogenes cells were detected (<10(2)) after 10 s of exposure, whereas at 61 degrees C cells viable were detected (>10(2)) up to 10 min of heating. No S. Typhimurium cells (<10(2)) were detected after 10 s at 70 degrees C, but cells survived up to 7 min at 60 degrees C. The D-values for L. monocytogenes at 61 and 65 degrees C were 124 and 16.2 s, respectively; whereas S. Typhimurium D-values were 278 s at 57 and 81 s at 60 degrees C. Z-values were 4.44 and 5.56 degrees C, respectively, for L. monocytogenes and S. Typhimurium. This study demonstrated that significant reductions in bacterial populations and complete inactivation of S. Typhimurium and L. monocytogenes cells can be achieved using an in-package thermal pasteurization process.

Animals↗

Thickness and compositional effects on surface heating rate of bologna during in-package pasteurization.

The surface heating rate (gamma) and final surface temperature (alpha) during in-package pasteurization were determined for different thickness levels of 2 types of bologna having different (13 and 18%) fat contents. Three thicknesses (4, 12, and 20 mm), corresponding to 1, 3, and 5 slices of bologna, were vacuum-packaged separately in a clear polymer pouch after placing a thermocouple on the surface. Refrigerated samples were immersed in a water bath set to 1 of 4 predetermined temperatures (60, 70, 80, and 90 degrees C), and time and temperature data were recorded for 10 min. Surface heating rate was fastest in the thinnest (4 mm) and slowest in the thickest (20 mm) samples for all 4 temperatures. Surface heating rate was slower in bologna with the higher fat content compared with the lower fat bologna. Final surface temperature attained after 3 min was lower with increased thickness levels for all temperatures. Thus, meat sample thickness and fat content significantly affect surface heating rate and final surface temperature during in-package pasteurization of bologna.

Animals↗

Biochemical survey on episodic localized darkening in turkey deboned thigh meat packaged in modified atmosphere.

The color of food, especially meat and meat products, is a parameter that strongly influences consumer choice. In Italy, repeated cases of darkening in deboned thigh meat of male turkeys packaged in modified atmosphere (MAP; 80% 02, 20% CO2) have been reported. The pH, lipid oxidation (TBARS), heme proteins, and iron content were investigated in MAP samples of turkey males, females, and in oxygen-permeable film-packaged males. Furthermore, the absorbance spectrum (400 to 700 nm) of the meat extracts was analyzed to better delineate the evolution and characteristics of the darkening process. Results showed that darkening occurred only in males with higher content of total iron, independently of the content of heme proteins, which differs only between males and females. Furthermore, pH was higher in muscles taken as controls, with respect to muscles involved in the darkening, as well as in females. Finally, TBARS values were found to be higher in darkened regions than in not darkened ones, as well as in MAP samples with respect to oxygen-permeable film-packaged samples. These findings suggest that darkening occurrence might depend on kind of muscle, sex, and individual characteristics of the animals raised under the same breeding conditions.

Animals↗

Development of polythene films for food packaging activated with an antilisterial bacteriocin from Lactobacillus curvatus 32Y.

AIMS: The aims of this work were to (i) use a bacteriocin produced by Lactobacillus curvatus 32Y active against Listeria monocytogenes to activate polythene films by different methods, (ii) implement a large-scale process for antilisterial polythene films production and (iii) verify the efficacy of the developed films in inhibiting the growth of L. monocytogenes during the storage of meat products. METHODS AND RESULTS: The film was made active by using the antilisterial bacteriocin 32Y by Lact. curvatus with three different procedures: soaking, spraying and coating. The antimicrobial activity of the activated films was tested in plate assays against the indicator strain L. monocytogenes V7. All the used procedures yielded active polythene films although the quality of the inhibition was different. The coating was therefore employed to develop active polythene films in an industrial plant. The antimicrobial activity of the industrially produced films was tested in experiments of food packaging involving pork steak and ground beef contaminated by L. monocytogenes V7 at roughly 10(3) CFU cm(-2) and gram respectively. The results of the challenge tests showed the highest antimicrobial activity after 24 h at 4 degrees C, with a decrease of about 1 log of the L. monocytogenes population. CONCLUSIONS: Antimicrobial packaging can play an important role in reducing the risk of pathogen development, as well as extending the shelf life of foods. SIGNIFICANCE AND IMPACT OF THE STUDY: Studies of new food-grade bacteriocins as preservatives and development of suitable systems of bacteriocin treatment of plastic films for food packaging are important issues in applied microbiology and biotechnology, both for implementing and improving effective hurdle technologies for a better preservation of food products.

Adsorption↗

Portal fusion protein constraints on function in DNA packaging of bacteriophage T4.

Architecturally conserved viral portal dodecamers are central to capsid assembly and DNA packaging. To examine bacteriophage T4 portal functions, we constructed, expressed and assembled portal gene 20 fusion proteins. C-terminally fused (gp20-GFP, gp20-HOC) and N-terminally fused (GFP-gp20 and HOC-gp20) portal fusion proteins assembled in vivo into active phage. Phage assembled C-terminal fusion proteins were inaccessible to trypsin whereas assembled N-terminal fusions were accessible to trypsin, consistent with locations inside and outside the capsid respectively. Both N- and C-terminal fusions required coassembly into portals with approximately 50% wild-type (WT) or near WT-sized 20am truncated portal proteins to yield active phage. Trypsin digestion of HOC-gp20 portal fusion phage showed comparable protection of the HOC and gp20 portions of the proteolysed HOC-gp20 fusion, suggesting both proteins occupy protected capsid positions, at both the portal and the proximal HOC capsid-binding sites. The external portal location of the HOC portion of the HOC-gp20 fusion phage was confirmed by anti-HOC immuno-gold labelling studies that showed a gold 'necklace' around the phage capsid portal. Analysis of HOC-gp20-containing proheads showed increased HOC protein protection from trypsin degradation only after prohead expansion, indicating incorporation of HOC-gp20 portal fusion protein to protective proximal HOC-binding sites following this maturation. These proheads also showed no DNA packaging defect in vitro as compared with WT. Retention of function of phage and prohead portals with bulky internal (C-terminal) and external (N-terminal) fusion protein extensions, particularly of apparently capsid tethered portals, challenges the portal rotation requirement of some hypothetical DNA packaging mechanisms.

Amino Acid Sequence↗

Antimicrobial activity of a nisin-activated plastic film for food packaging.

AIMS: To determine the effectiveness of a packaging film coated with nisin to inhibit Micrococcus luteus ATCC 10240 in tryptone soya broth (TSB) and the microbiota of raw milk during storage. A further aim was to examine the release of nisin from the activated film. METHODS AND RESULTS: An active package, obtained from nisin-treated film, was filled with 1 l of M. luteus ATCC 10240 (ML) suspension in TSB and stored at 4 and 25 degrees C for 2 days. After 24 h at 25 degrees C there was a remarkable reduction of M. luteus ATCC 10240 compared with the control, while at 4 degrees C a slight reduction was observed. Moreover, microbial growth was controlled when 1 l of three different kinds of milk was poured into the active package and stored at 4 degrees C for 7 days. The most significant results were observed in raw milk and pasteurized milk with a reduction of 0.9 log and 1.3 log, respectively. The release experiments showed that nisin release from the film was unpredictable, but it was favoured by low pH and high temperature. CONCLUSIONS: It appears that nisin-coated films were effective in inhibiting M. luteus ATCC 10240 in TSB and the bacterial flora in milk, and the release of nisin was pH and temperature dependent. SIGNIFICANCE AND IMPACT OF THE STUDY: Nisin-activated film may control bacterial growth, maintaining food quality, safety and extending the shelf-life of food products.

Animals↗