Radiolysis products and sensory properties of electron-beam-irradiated high-barrier food-packaging films containing a buried layer of recycled low-density polyethylene

The aim was to study the effect of electron-beam irradiation on the production of radiolysis products and sensory changes in experimental high-barrier packaging films composed of polyamide (PA), ethylene-vinyl alcohol (EVOH) and low-density polyethylene (LDPE). Films contained a middle buried layer of recycled LDPE, while films containing 100% virgin LDPE as the middle buried layer were taken as controls. Irradiation doses ranged between zero and 60 kGy. Generally, a large number of radiolysis products were produced during electron-beam irradiation, even at the lower absorbed doses of 5 and 10 kGy (approved doses for food ‘cold pasteurization’). The quantity of radiolysis products increased with irradiation dose. There were no significant differences in radiolysis products identified between samples containing a recycled layer of LDPE and those containing virgin LDPE (all absorbed doses), indicating the ‘functional barrier’ properties of external virgin polymer layers. Sensory properties (mainly taste) of potable water were affected after contact with irradiated as low as 5 kGy packaging films. This effect increased with increasing irradiation dose.     

Volatile and non-volatile radiolysis products in irradiated multilayer coextruded food-packaging films containing a buried layer of recycled low-density polyethylene.

The effects of gamma-irradiation (5-60 kGy) on radiolysis products and sensory changes of experimental five-layer food-packaging films were determined. Films contained a middle buried layer of recycled low-density polyethylene (LDPE) comprising 25-50% by weight (bw) of the multilayer structure. Respective films containing 100% virgin LDPE as the buried layer were used as controls. Under realistic polymer/food simulant contact conditions during irradiation, a large number of primary and secondary radiolysis products (hydrocarbons, aldehydes, ketones, alcohols, carboxylic acids) were produced. These compounds were detected in the food simulant after contact with all films tested, even at the lower absorbed doses of 5 and 10 kGy (approved doses for food preservation). The type and concentration of radiolysis products increased progressively with increasing dose. Generally, there were no significant differences in radiolysis products between samples containing a buried layer of recycled LDPE and those containing virgin LDPE (all absorbed doses), indicating the good barrier properties of external virgin polymer layers. Volatile and non-volatile compounds produced during irradiation affected the sensory properties of potable water after contact with packaging films. Taste transfer to water was observed mainly at higher doses and was more noticeable for multilayer structures containing recycled LDPE, even though differences were slight.     

Effect of packaging films on storage stability of intermediate-moisture deep-fried mackerel

A storage stability study was conducted on intermediate moisture deep-fried mackerel packed in polypropylene (PP), high density polyethylene (HDPE) and low density polyethylene (LDPE) for 12 weeks at 27°C. Water activity increased significantly ( P < 0.01) during 12 weeks storage from 0.80 to 0.86, 0.88 and 0.91 for PP-, HDPE- and LDPE-packed samples, respectively. Thiobarbituric acid values increased significantly ( P < 0.01) in all packaging films, most rapidly in the LDPE-packed samples. the physical firmness of the samples decreased similarly and was closely related to the amount of moisture absorbed during storage. Microbial count was low initially but increased most rapidly in LDPE-packed samples. Sensory evaluation showed that samples packed in PP and HDPE were acceptable for up to 8 weeks storage but for less than 4 weeks in LDPE.     

基于主成分分析法分析不同包装材料对双孢蘑菇品质的影响

采用主成分分析法定量分析5 种包装材料处理对双孢蘑菇品质影响,建立综合评价函数,筛选最佳包装材料。结果表明,9 个检测指标可简化成2 个主成分,累积方差贡献率达到86.224%,能够较好地反映原始数据的信息;不同包装膜处理双孢蘑菇的品质综合得分从高到低为：低压高密度聚乙烯＞高压低密度聚乙烯＞聚丙烯＞线性低密度聚乙烯＞乙烯-乙酸乙烯共聚物＞对照。由此可见,包装袋有利于双孢蘑菇贮藏保鲜,且低压高密度聚乙烯包装材料的保鲜效果最佳,为双孢蘑菇的贮藏保鲜提供了科学和直观的依据。     

Quality of packaged romaine lettuce hearts exposed to low-dose electron beam irradiation

We investigated the effects of low-dose electron beam irradiation (1.0, 1.5 and 3.2 kGy) on the quality of commercially prepackaged fresh romaine lettuce hearts. The impact of the irradiation treatment on the functionality of the package was also evaluated. Irradiated samples showed slight changes in color, but these changes were not significantly different (P >0.05) from the nonirradiated (control) samples. Sample firmness decreased by 49.58% (leaves) and 29.13% (ribs), as the dose level increased. Sensory attributes such as overall quality, color, sogginess, and off-flavor were found less acceptable at the higher dose level. Irradiation affected the respiration rates inside the packages, with lower (10.38%) O₂ and higher CO₂ levels than the control. Irradiation at 1.5 and 3.2 kGy dose levels improved the oxygen barrier capability of the low-density polyethylene (LDPE) bags (7.67% and 4.48%, respectively). Water vapor permeability was unaffected at all the irradiation dose levels. The stiffness of LPDE films did not change due to irradiation treatment. Results from sensory evaluation of produce overall quality suggest a potential fungicidal effect of low-dose irradiation (1.0 kGy) of packaged romaine lettuce hearts without altering the overall quality of the produce as well as the LDPE-packaging characteristics.     

Overall migration from commercial coextruded food packaging multilayer films and plastics containers into official EU food simulants

The overall migration from a wide range of commercial five-layer coextruded packaging films into aqueous food simulants (distilled water, 3% aqueous acetic acid) and alternative fatty food simulant (iso-octane) was studied. The overall migration from commercial plastics cups (PS, HIPS, and PP) used for ice-cream or yogurt packaging into distilled water and 3% aqueous acetic acid was also studied. Test conditions for packaging material/food simulant contact and method of overall migration analysis were according to the EU directives and CEN-standards. The results showed that for all tested five-layer films and plastics (PS, HIPS, and PP) cups values of overall migration into aqueous simulants (0.11-0.79 mg/dm², 2.3-15.9 mg/l) and (<0.10-0.41 mg/dm², <0.80-3.1 mg/l) were significantly lower than the upper limit (10 mg/dm²) for overall migration from plastic packaging materials and articles into food and food simulants set by the EU Directive 90/128/EEC and their revisions. The overall migration values from five-layer materials into iso-octane were significantly higher (0.94-8.23 mg/dm², 18.8-164.7 mg/l) than the above values but are still lower than the upper limit for overall migration. Global migration values of five-layer films into aqueous food simulants seems to be independent of material thickness. In contrast, overall migration into iso-octane increases with film thickness.     

The use of mechanical analyses,scanning electron microscopy and ultrasonic imaging to study the effects of high‐pressure processing on multilayer films

The effects of high‐pressure processing (HPP) on the mechanical and physical characteristics of eight high‐barrier multilayer films were investigated. These films were PET/SiO_x/LDPE, PET/Al₂O₃/LDPE, PET/PVDC/nylon/HDPE/PP, PE/nylon/EVOH/PE, PE/nylon/PE, metallised PET/EVA/LLDPE, PP/nylon/PP and PET/PVDC/EVA. In addition, PP was evaluated as a monolayer film for comparison purposes. Pouches made from these films were filled with distilled water, sealed, then pressure processed at 600 and 800 MPa for 5, 10 and 20 min at a process temperature of 45 °C. Pouches kept at atmospheric pressure were used as controls. Prior to and after HPP, all films were tested for tensile strength, percentage elongation and modulus of elasticity (at 50 cm min^?1) and imaged by scanning electron microscopy (SEM) and C‐mode scanning acoustic microscopy (C‐SAM). Results showed no significant changes in tensile strength, elongation and modulus of elasticity of all films after HPP. However, significant physical damage to metallised PET (MET‐PET) was identified by SEM and C‐SAM. Thus it could be concluded that MET‐PET is not suitable for batch‐type high‐pressure‐processed food packaging. It can also be concluded that the other materials investigated during this study are suitable for batch‐type high‐pressure‐processed food packaging. Copyright © 2003 Society of Chemical Industry     

Effect of food characteristics, storage conditions, and electron beam irradiation on active agent release from polyamide-coated LDPE films

ABSTRACT:  We investigated the effect of electron beam irradiation, storage conditions, and model food pH on the release characteristics of trans -cinnamaldehyde incorporated into polyamide-coated low-density polyethylene (LDPE) films. Active agent release rate on irradiated films (up to 20.0 kGy) decreased by 69% compared with the nonirradiated controls, from 0.252 to 0.086 μg/mL/h. Storage temperature (4, 21, and 35 °C) and pH (4, 7, and 10) of the food simulant solutions (10% aqueous ethanol) affected the release rate of trans -cinnamaldehyde. As expected, antimicrobial release rate decreased to 0.013 μg/mL/h at the refrigerated temperature (4 °C) compared to the higher temperatures (0.029 and 0.035 μg/mL/h at 21 and 35 °C). The fastest release rate occurred when exposed to the acidic food simulant solution (pH 4). In aqueous solution, trans -cinnamaldehyde was highly unstable to ionizing radiation, with loss in concentration from 24.50 to 1.36 μg/mL after exposure to 2.0 kGy. Fourier transform infrared (FTIR) analysis revealed that exposure to ionizing radiation up to 10.0 kGy did not affect the structural conformation of LDPE/polyamide films and the trans -cinnamaldehyde in the films, though it induced changes in the functional group of trans -cinnamaldehyde when dose increased up to 20.0 kGy. Studies with a radiation-stable compound (naphthalene) showed that ionizing radiation induced the crosslinking in polymer networks of LDPE/polyamide film and caused slow and gradual release of the compound. This study demonstrated that irradiation serves as a controlling factor for release of active compounds, with potential applications in the development of antimicrobial packaging systems.     

Migration of plasticizers phthalates, bisphenol A and alkylphenols from plastic containers and evaluation of risk

This study investigates the potential migration of plasticisers, plastic components and additives from several plastic water bottles. Compounds studied were phthalates (dimethyl phthalate, di-n-butyl phthalate, benzylbutyl phthalate, bis(2-ethylhexyl) phthalate), bis(2-ethylhexyl) adipate, octylphenol, 4-nonylphenol and bisphenol A. Polycarbonate (PC), high-density polyethylene (HDPE), low-density polyethylene (LDPE), polyethylene terephthalate (PET) and polystyrene (PS) plastics used in the water bottling sector were tested using three kinds of total or specific migration tests: (1) standard method UNE-EN ISO 177; (2) ultrasonic forced extraction; and (3) standard method UNE-EN 13130-1. In addition, bottled waters contained in different plastic materials were analysed to determine the potential migration of target compounds in real conditions. In all cases, samples were solid-phase extracted using Oasis HLB 200 mg cartridges and analysed using GC-MS in scan-acquisition mode. Bisphenol A and 4-nonylphenol were detected in incubated samples, indicating that migration from food plastics can occur at the experimental conditions tested. The total daily intake was calculated according to the levels detected in bottled water and the assessment of the consumers' risk was evaluated taking into consideration toxicological and legislative values.     

Feasibility study for the development of certified reference materials for specific migration testing. Part 1: Initial migrant concentration and specific migration

The paper describes a project with the main objective of developing the know how to produce certified reference materials (CRMs) for specific migration testing. Certification parameters discussed are the initial concentration of the migrant in the polymer (C_P,0) and the specific migration into a food simulant under certain temperature/time conditions. Sixteen preliminary candidate CRMs were defined and produced. The most important polymers (low- and high-density polyethylene (LDPE and HDPE), polypropylene (PP), polystyrene (PS), polyethylene terephtalate (PET), plasticized polyvinyl chloride (PVC), rigid PVC, polyamides (PA)) and additives as well as monomers representing different physicochemical properties as target substances for migration were chosen. The stability and homogeneity of the migrants in the materials were tested and methods for the determination of the certification parameters were developed and validated. From the 16 materials produced, the six most suitable CRM candidates (LDPE//Irganox 1076/Irgafos 168, LDPE//1,4-diphenyl-1,3-butadiene (DPBD), HDPE//Chimassorb 81/Uvitex OB, PP homo//Irganox 1076/Irgafos 168, HIPS, 1% mineral oil//styrene, PA 6//caprolactam) were selected. The feasibility of CRM production for the six candidate materials was demonstrated and a trial certification exercise was performed with participation of all four partner laboratories. All six materials showed suitable properties for future production as certified reference materials.     

The Influence of Electron Beam Irradiation on the Effectiveness of Trans-cinnamaldehyde-coated LDPE/Polyamide Films

ABSTRACT:  We have evaluated the effect of electron beam irradiation (up to 20 kGy) on the functional and barrier properties of trans-cinnamaldehyde-coated low-density polyethylene (LDPE)/polyamide films. Irradiation did not affect the tensile strength and toughness of the films, but the 20 kGy treatment increased the percent elongation-at-break significantly. The barrier properties were also enhanced (approximately 18.8%) when the films were exposed to 20 kGy. Addition of trans-cinnamaldehyde with 3% of polyamide coating solution (w/w) did not affect the tensile strength and barrier properties of the films, but significantly decreased the percent elongation-at-break and toughness. Films with 3% and 10% coating were used to wrap fresh-cut romaine lettuce samples to determine their antimicrobial activity. Total aerobic plate count (APC) and yeast and mold growth were determined as a function of dose (0, 0.5, and 1.0 kGy) for 14 d of storage at 4 °C. Irradiation reduced the total APC and yeast and mold counts (YMC) as dose increased. The 0.5- and 1.0-kGy treatments decreased initial APCs by 1.2- and 1.5-logs, and no YMCs were observed in the 1.0-kGy treated samples at day 0. Irradiation exposure significantly lowered APCs of lettuce samples by almost 1-log colony-forming unit (CFU)/g compared to the nonirradiated controls, though it only slightly reduced YMCs. The effectiveness of using irradiation with antimicrobial films was enhanced with increased radiation dose and trans-cinnamaldehyde concentration (3% to 10%).     

Gamma irradiation of cowpea (Vigna unguiculata L. Walp) seeds: effect on colour,cooking quality and pasting characteristics

Cowpea seeds were treated to various gamma irradiation doses, and their colour, cooking quality and pasting properties studied. Irradiation at 50 kGy resulted in significant browning (indicated by decreases in L colour value) of cowpea seeds. At 2 and 10 (but not at 50) kGy, irradiation led to significant reduction in cooking time of cowpea seeds possibly through irradiation‐induced degradation of starch and pectic substances (indicated by decreases in peak and final viscosities) leading possibly to enhanced heat and mass transfer within the seed cotyledon and cell wall, respectively. At 50 kGy, the cooking time of cowpea seeds was prolonged significantly owing possibly to extensive polymer cross‐linking occurring within the seeds at this high dose. Splitting of cowpea cotyledons during cooking decreased significantly at 50 kGy, but was unaffected at 2 and 10 kGy. Irradiation resulted in significant leaching of nutrients from cowpea seeds during cooking in a dose‐dependent manner.     

可食包装膜与合成包装膜综合性质的对比研究

研究了几种可食包装膜和合成包装膜的综合性质。结果表明:明胶膜、海藻酸钠复合膜和甲基纤维素复合膜综合性质较好。明胶膜的直角撕裂强度和断裂伸长率高于低密度聚乙烯膜(LDPE膜)和高密度聚乙烯膜(HDPE膜),但其抗拉强度稍低于HDPE膜而高于LDPE膜;海藻酸钠复合膜和甲基纤维素复合膜的抗拉强度高于HDPE膜和LDPE膜,海藻酸钠复合膜的直角撕裂强度和断裂伸长率以及甲基纤维素复合膜的断裂伸长率低于LDPE膜和HDPE膜,但甲基纤维素复合膜的直角撕裂强度却高于LDPE膜和HDPE膜;这3种膜都具有热封性,其热封强度接近HDPE膜,并具较高的阻气、阻油和阻湿性能,可以满足一些食品的包装要求。     

Release of Naturally Derived Antimicrobial Agents from LDPE Films

ABSTRACT: The migration of the naturally derived antimicrobial (AM) agents, linalool, carvacrol, and thymol, from low-density polyethylene (LDPE) films containing ethylene vinyl acetate (EVA) copolymer into the food simulants, isooctane and various ethanol/water mixtures, was studied with a view towards examining the applicability of a first-order kinetic approach as well as a diffusion model approach for describing these systems. The results suggest that the proposed models adequately describe the release of AM agents. The combination of kinetic and diffusion analyses can provide additional information about the release process using the same data set. The analyses suggest that the release of linalool from LDPE/EVA depends on the EVA content in the formulation and that an optimum level of EVA is required to minimize the rate of release. A modification of the existing “idealized diffusion” model is proposed that enables the model to be applied to systems that demonstrate a departure from linearity when subjected to conventional analysis. The applicability of the idealized diffusion model was compared with the “simulant-limited” model and the results suggest that the former model is appropriate for describing most real systems when the simulant (or foodstuff) is favored in the partitioning of the AM agent between the film and the simulant.     

Low-dose irradiation as a measure to improve microbial quality of ice cream

The present study was undertaken to investigate the efficacy of low-dose irradiation to improve the microbial safety of ice cream. Initially three different flavors (vanilla, strawberry and chocolate) of ice cream were exposed, at -72 degrees C, to doses of 1, 2, 5, 10 and 30 kGy to gamma-radiation. Irradiation at 1 kGy resulted in reduction of microbial population by one log cycle, thus meeting the requirement limits prescribed by Bureau of Indian Standards. Pathogens such as Listeria monocytogenes 036, Yersinia enterocoliticta 5692 and Escherichia coli O157:H19, respectively, showed the D10 values 0.38, 0.15 and 0.2 kGy in ice cream at -72 degrees C suggesting the efficacy of low doses (1 kGy) in eliminating them. Sensory evaluation studies of ice cream irradiated at 1, 2, 3 and 5 kGy by a 15 member panel demonstrated that doses higher than 2 kGy irradiation induced off-odour and an aftertaste was evident in vanilla ice cream. A radiation dose of 1 kGy was sufficient to eliminate the natural number of pathogens present in the ice cream. No statistically significant differences were observed in the sensory attributes of all the three flavours of ice cream either unirradiated or exposed to 1 kGy (P < 0.05).     

Influence of polymer matrix and adsorption onto silica materials on the migration of alpha-tocopherol into 95% ethanol from active packaging.

In this study, the effect of polymer materials with different polarity, namely low density polyethylene (LDPE) and ethylene vinyl acetate (EVA), on the migration behaviour of alpha-tocopherol from active packaging was investigated. The antioxidant was also adsorbed onto silica materials, namely SBA-15 (Santa Barbara-15) and Syloblock, in order to protect the antioxidant during extrusion and to ensure a controlled and sufficient release during the shelf-life of the food product. Migration experiments were performed at 7.0 +/- 0.5 degrees C and 95% ethanol was used as fatty food simulant. All films contained a high concentration of alpha-tocopherol, approximately 2000 mg kg(-1), to obtain an active packaging. Polymer matrix had a small influence on the migration profile. The migration of 80% of total migrated amount of antioxidant was retarded for 2.4 days by using LDPE instead of EVA. When alpha-tocopherol was adsorbed onto both silica materials, the migration of 80% of total migrated amount of antioxidant was retarded for 3.4 days in comparison to pure alpha-tocopherol. No difference was seen between the migration profiles of alpha-tocopherol adsorbed onto both silica materials. In the case of pure alpha-tocopherol, 82% of the initial amount of alpha-tocopherol in the film migrated into the food simulant at a rather fast migration rate. In the case of adsorption on silica materials, a total migration was observed. These antioxidative films can have positive food applications.     

Effect of ionizing radiation on structural and functional attributes of red kidney bean (Phaseolus vulgaris L.) lectin

Gamma radiation inactivation of phytohemagglutinin (PHA) of red kidney bean in purified form as well as in seeds in different moisture conditions was demonstrated at different doses viz. 1, 10, 30, 50, 100 and 200 kGy. Irradiation of PHA in dry state (99.5% dry) or in 50% moisture condition showed structural intactness as studied by SDS–PAGE, size exclusion chromatography (SEC), fluorescence measurement, CD spectroscopy below 30 kGy, while a 50% reduction in hemagglutinin and mitogenic activity was observed in the dose range of 30–50 kGy. Radiation inactivation of purified PHA was more pronounced when irradiated in aqueous solution form resulting in complete destruction of secondary and tertiary structure as well as function at a dose of 10 kGy. Radiation processing of dry and soaked seeds of kidney bean exhibited 50% loss in functional activity of PHA at the doses of 50 and 30 kGy, respectively. Practicality of implication of the radiation processing for inactivation of this antinutrient in legume seeds is discussed.     

Irradiation D-values for Escherichia coli O157:H7 and Salmonella sp. on inoculated broccoli seeds and effects of irradiation on broccoli sprout keeping quality and seed viability

Like alfalfa sprouts, broccoli sprouts can be a vehicle for bacterial pathogens, which can cause illness when they are consumed. The gamma irradiation process was used to reduce numbers of bacterial pathogens on broccoli sprouts and seeds, and the effect of this process on the seeds was studied. The irradiation destruct values for Salmonella sp. and for strains of Escherichia coli O157:H7 inoculated on broccoli seeds were determined. Results obtained in this study indicate that a dose of 2 kGy reduced total background counts for broccoli sprouts from 10(6) to 10(7) CFU/g to 10(4) to 10(5) CFU/g and increased the shelf life of the sprouts by 10 days. Yield ratio (wt/wt), germination percentage, sprout length, and thickness were measured to determine the effects of various irradiation doses on the broccoli seeds. Results show a decreased germination percentage at a dose level of 4 kGy, whereas the yield ratio (wt/wt), sprout length, and thickness decreased at the 2-kGy dose level. The radiation doses required to inactivate Salmonella sp. and strains of E. coli O157:H7 were higher than previously reported values. D-values, dose required for a 1-log reduction, for the nonvegetable and vegetable Salmonella sp. isolates were 0.74 and 1.10 kGy, respectively. The values for the nonvegetable and vegetable isolated strains of Escherichia coli O157:H7 were 1.43 and 1.11 kGy, respectively. With the irradiation process, a dose of up to 2 kGy can extend the shelf life of broccoli sprouts. A dose of > 2 kGy would have an adverse effect on the broccoli seed and decrease the yield of broccoli sprouts.     

Properties of soya milk and tofu prepared with γ-irradiated soya beans

Soya beans (Glycine max) ‘hwang keum’ were γ-irradiated at dose levels of 0, 2.5, 5, 10 and 20 kGy and the effects of the irradiated soya beans on soya milk and tofu properties were studied. An irradiation dose of 5 kGy caused an increase in yield of soya milk and tofu while having very little effect on their quality. The properties of tofu prepared with the soya beans irradiated at 2.5–5 kGy showed no significant difference from the non-irradiated control. However, at higher doses (10–20 kGy), decreases in yield, water holding capacity and sag value of tofu were observed. Compared with the non-irradiated control, hardness and fracturability in the texture of tofu were both significantly increased when the soya bean had been irradiated at 10–20 kGy, while cohesiveness and adhesiveness decreased. The changes in color values of soya milk and tofu were pronounced at 20 kGy.     

A comparative study on the effect of packaging material and storage environment on shelf life of fresh bell-pepper

The effect of packaging materials [low density polyethylene (LDPE), polypropylene (PP)] and storage environment [modified atmospheric packaging (MAP)] on shelf life enhancement of bell pepper in terms of quality attributes such as physiological weight loss, ascorbic acid, texture, surface colour and subjective quality analysis have been studied at ambient and refrigerated condition. Different packaging techniques used for the experiment were MAP with LDPE, MAP with PP, MAP in perforated LDPE films, MAP in perforated PP films, shrink packaging with bi-axially oriented PP (BOPP) film and vacuum packaging with PP film. The in-pack bell pepper created a suitable headspace environment with low O₂ and high CO₂ concentrations, which resulted in a better retention of freshness of the vegetables and its marketability. Shrink packaging with BOPP film could not yield better result under ambient storage because of high water vapor transmission rate of the film and consequently loss of turgidity of the vegetables. Among different packaging techniques and storage conditions, MAP with PP film in refrigerated condition was found to be the best followed by vacuum pack with PP film in refrigerated condition and could be used to store for 20 days for bell pepper with maintenance of texture, colour, ascorbic acid and marketability. It is also inferred that under ambient conditions, bell pepper could be stored for 4 days using ventilated LDPE and PP as MAP storage. Further studies are needed to evaluate the sensory aspects, as well as to microbiological evaluation to characterize the fresh bell pepper during storage.