Effect of an argon-containing packaging atmosphere on the quality of fresh pork sausages during refrigerated storage

The effects of modified atmosphere packaging (MAP) with commercial gas mixtures made up of either CO₂ and argon or CO₂ and nitrogen on the microbiological and physico-chemical characteristics of fresh pork sausages during refrigerated storage were studied and the results compared with vacuum and over-wrap packaging. The presence of argon in the mixture of gases barely affected the growth of enterobacteria, which were at their lowest levels (P < 0.05) at the end of the preservation period. MAP with argon did not affect (P > 0.05) lactic acid bacteria or total viable counts in samples with N₂. The biogenic amine levels in all the samples remained low during storage with the exception of spermidine and spermine. There were no significant differences between the two lots in MAP respecting color parameters. MAP with argon and CO₂ had a beneficial effect on sensorial evaluation during the 28 days storage period, when compared with that of the control, which was rejected after 11 days of storage.     

Effects of gamma irradiation on trans fatty acid composition in ground beef

The present study was conducted to evaluate the combined effects of irradiation (0, 1, 3, 5 and 7 kGy) of ground beef on fatty and trans fatty acids. Irradiation of ground beef was performed by gamma rays from a ⁶⁰Co source. Irradiated ground beef samples had higher concentrations of total trans fatty acids than the control samples. Irradiated ground beef samples with 7 kGy had the highest total trans fatty acids, total monounsaturated and total unsaturated fatty acids than the other samples. In this study results showed an increase in trans fatty acids related to the increase on irradiation dose in ground beef and irradiation dose changed fatty acids composition especially trans fatty acids in ground beef.     

Effect of washing with citric acid and packaging in modified atmosphere on the sensory and microbiological quality of sliced mushrooms (Agaricus bisporus L.)

The effect of washing with citric acid before slicing and the effect of modified atmosphere packaging on the sensorial and microbiological quality of sliced mushrooms when stored at 5 °C for up to 17 days was evaluated.The atmosphere generated with the perforated PVC film was similar to that of air atmosphere. The non-perforated PVC film generated CO₂ concentrations inside the packages ranging from 6.9% to 3.1% and O₂ concentrations ranging from 2% to 6% depending on the storage time. Washing with citric acid reduced microbial counts by 2.5 log units on day 0. The anti-microbial effect of citric acid decreased during storage but remained significant on each sampling day. Modified atmospheres reduced the microbial counts by 0.8 log units throughout storage. The effect of washing with citric acid combined with packaging in modified atmosphere resulted additive. The reduction of microbial counts avoided bacterial blotch in washed mushrooms during 17 days of storage at 5 °C.     

Effects of gamma radiation,individually and in combination with bioactive agents,on microbiological and physicochemical properties of ground beef

Effects of gamma irradiation (2 kGy) on microbiological and physicochemical properties of ground beef were investigated individually or in combination with bioactive compounds consisting of cinnamaldehyde, ascorbic acid, and sodium pyrophosphate decahydrate. Meat samples were mixed with cinnamaldehyde (1.47%, w/w), cinnamaldehyde plus ascorbic acid (0.5%, w/w), or cinnamaldehyde plus sodium pyrophosphate decahydrate (0.1%, w/w), followed by irradiation at a dose of 2 kGy. Microbiological and physicochemical properties of samples were analyzed. The results demonstrated that combined treatments using irradiation and bioactive compounds could significantly decrease the microbial load of meat samples compared with that of the untreated control samples. Moreover, the combined treatments did not cause any significant changes in physical or chemical properties of meat samples. Irradiation, both with and without cinnamaldehyde treatment, caused significant increases in concentrations of thiobarbituric reactive substances and peroxide in treated samples, compared with the concentrations of these substances in the control samples; however, in the presence of ascorbic acid, the pro-oxidative effect of irradiation treatment on ground beef was overcome.     

The effect of packaging conditions on the quality of minimally processed celeriac flakes

The aim of the study was to select packaging conditions of minimally processed celeriac to preserve their quality during storage for 12 days at 4 and 15 °C. The quality of the product was determined on the basis of colour measured in the CIE L¹a¹b¹ system, sensory quality and total counts of mesophilic and psychrophilic bacteria, counts of moulds and yeasts, coliform counts, counts of Pseudomonas bacteria and the presence of bacteria from the genus Clostridium perfringens. Moreover, changes were determined in oxygen and carbon dioxide contents in the atmosphere within the packs, in which the product was stored. Celeriac flakes were packaged in the atmosphere with varying CO₂ contents (0%, 5%, 10%, 20%, 30%, 50% plus 2% O₂ and with balance N₂). After 12 days at 4 °C, it was found that celeriac flakes packaged in atmosphere containing 5% or 10% CO₂, 2% O₂ and balance N₂ were characterized by better quality than samples packaged in air atmosphere or in the atmosphere with CO₂ contents of 0% or higher than 10%. Modified atmosphere with the content of 5% or 10% CO₂, 2% O₂ and balance N₂, applied in the packaging of celeriac flakes, resulted in the inhibition of growth of mesophilic, psychrophilic and coliform bacteria in the tested minimally processed product.     

Hurdle effect of vinegar and sake on Korean seasoned beef preserved by sous vide packaging

A Korean beef product seasoned in concentrated soy sauce was vacuum packaged in a gas barrier plastic pouch and pasteurised. Adding vinegar and/or sake to the product was examined as preservation hurdles to improve microbial stability, and sensory quality affected by the additions was evaluated. A combination of vinegar and sake improved the microbial stability of the product at 8 and 20 °C, while added vinegar and/or sake did not improve the sensory quality of the product. The vinegar and sake combination produced significantly inferior initial quality in taste and overall acceptability. The sensory quality of the products with or without single use of vinegar or sake degraded significantly during 10 days of storage at 8 °C, which made the treatment effect less pronounced. Thus, the combined addition of vinegar and sake may be an alternative means of extending shelf life, because sensory quality with this treatment became close to that of the control after extended storage.     

Influence of vacuum and modified atmosphere packaging in combination with UV-C radiation on the shelf life of rainbow trout (Oncorhynchus mykiss) fillets

The effects of UV-C radiation, modified atmosphere packaging (MAP) and their combination on rainbow trout (Oncorhynchus mykiss) fillets quality were examined during a period of 22 days. The samples were submitted to five packaging conditions: (AP) aerobic packaging; (VP) vacuum packaging; (VP + UV-C) vacuum packaging + UV-C radiation; (MAP) modified atmosphere packaging (80% CO₂/20% N₂) and (MAP + UV-C) modified atmosphere packaging + UV-C radiation (80% CO₂/20% N_2; 106.32 mJ/cm²) and storaged at 4 °C. The samples were analyzed daily for microbiological (mesophilic, psychrotrophic and Enterobacteriaceae counts) and chemical (pH, TMA-N, TBV-N, lipid oxidation, ammonia and biogenic amines) parameters. Overall, UV-C radiation promoted lag phase formation in mesophilic and psychrotrophic groups. Mesophilic and psychrotrophic groups presented significant lower (P < 0.05) growth rate and colony forming units in the stationary phase in the samples submitted to MAP. MAP significantly reduced (P < 0.05) total mesophilic count and MAP + UV-C total mesophilic and psychrotrophic counts. Values of pH decreased at all packaging conditions except in the case of aerobic packaging. TBARS value increased faster in samples subject to MAP and MAP + UV-C whereas TMA-N, TVB-N and ammonia values increased slowly. Lower production of putrescine and cadaverine was observed in MAP and VP samples. MAP reduced total production of ammonia, TVB-N and putrescine, whereas MAP + UV-C reduced total production of TVB-N and cadaverine during entire the storage time. Results of the current study suggest that MAP retarded microbial growth and delayed chemical changes enhancing the shelf life of rainbow trout fillets at least twice.     

Influence of modified atmosphere packaging and storage temperature on the sensory and microbiological quality of fresh peeled white asparagus

The sensory and microbiological quality of fresh peeled white asparagus packaged in two different types of P-Plus films and stored at two different temperatures (5 °C and 10 °C) for up to 14 days, was studied. The shelf life limiting alterations at each temperature were evaluated. The best modified atmosphere was determined.At 10 °C, the shelf life was 6 days, the loss of freshness was the main cause of quality loss, as indicated by colour darkening and presence of blotches. Moreover the sensorial acceptance of cooked asparagus was affected, being on the limit.Fresh appearance was maintained better at 5 °C than at 10 °C, being microbial spoilage the main limiting factor. The atmosphere generated with film A (around 7% CO₂ and 15% O₂) inhibited spoilage and maintained the acidity of asparagus better than the atmosphere generated by film B (around 2% CO₂ and 20% O₂). The shelf life of asparagus packaged in film A and stored at 5 °C was 14 days.Mesophiles and enterobacteriaceae counts in asparagus stored at 5 °C were acceptable during 14 days being around 7 log cfu/g. Mesophiles counts were slightly higher in asparagus stored at 10 °C than at 5 °C, while the increase in enterobacteriaceae was clearly higher in asparagus stored at 10 °C.     

Effects of chlorine treatment and packaging on the quality and shelf-life of modified atmosphere (MA) packaged coleslaw mix

The effects of an anti-microbial washing treatment combined with modified atmosphere packaging (MAP) on the quality and storage life of dry coleslaw were determined. The anti-microbial treatment consisted of washing for 5 min with agitation in a chlorine solution (100 ppm available chlorine). The coleslaw mix was packaged within two micro-perforated OPP films, PA-160, and PA-210 and stored at 4 and 8 °C for nine days. Chlorine treatment had large beneficial effects on quality, particularly at 4 °C. It significantly reduced respiration rate, resulting in significantly lower CO₂ and higher O₂ concentrations at both 4 and 8 °C compared with water washed coleslaw. Washing with chlorine was found to significantly improve sensory scores, particularly at 4 °C with better acceptability of appearance, colour and aroma. Microbial loads were significantly reduced by the use of chlorine and these reductions were substantially greater at 4 °C. Chlorine had no effect on tissue pH. Overall, chlorine washing had significant effects on the quality and storage life of MA packaged dry coleslaw mix of the treatments studied, the most effective was chlorine washing combined with storage in PA-160 film at 4 °C.     

Control of bacteria growth on ready-to-eat beef loaves by antimicrobial plastic packaging incorporated with garlic oil

This study was designated to ascertain the effectiveness of low density polyethylene (LDPE) based film incorporated with garlic oil for inhibition of food pathogen on ready-to-eat beef loaves. The blown film extrusion method was employed to produce film samples added with garlic oil in 2, 4, 6 and 8% w/w as well as sample with 0% w/w which served as control throughout the study. Besides, several analyses were also conducted to determine the water vapour barrier properties, thermal stability and bonding interaction of the plastic packaging as influenced by the incorporation of garlic oil. The outcomes of challenge test showed that regardless of the garlic oil amount (2–8% w/w), the antimicrobial plastic packaging was able to reduce the number of Listeria monocytogenes on beef loaves after 3, 6, 9 and 15 days of storage at 4 °C. However, there were insignificant effects on both Escherichia coli and Brochothrix thermosphacta. For water vapour barrier properties, films with higher amount of garlic oil proved to have weaker barrier properties. There was lack of significant difference in the thermal stability for all samples when tested with thermogravimetry analyser. Also, the infrared analysis indicated garlic oil does not change the polymer structure.     

废胎胶粉改性沥青改性机理研究

借助荧光显微镜、红外光谱等微观结构试验的分析方法，研究废胎胶粉在沥青中的改性机理。高温条件下，胶粉在沥青中吸收轻组分，并溶胀、脱硫和降解，同时胶粉中的活性物质进入沥青胶体体系中，达到改善沥青温度敏感性、老化性能的效果；常温及低温条件下，废胶粉改性沥青中未溶解的胶粉颗粒起到增强沥青的弹性性能和提高其抗裂性能的作用。弄清废胎胶粉改性沥青的改性机理，为合理应用废胶粉改性沥青提供理论支持和技术保障。     

Comparing the effectiveness of chitosan and nanochitosan coatings on the quality of refrigerated silver carp fillets

The coating effects of chitosan and chitosan nanoparticles on the quality of silver carp (Hypophthalmicthys molitrix) fillets during refrigerated storage at 4 °C were compared. Solutions of Chitosan (2%, w/v) and nanochitosan (2%, w/v) were used for the coating. The control and the coated fish samples were analyzed periodically for microbiological (total mesophilic and psychrotrophic count), physicochemical (pH, TVB-N, TBARS), and sensory attributes. The results indicated that both chitosan and nanochitosan coating were effective for the preservation of silver carp fillets during refrigerated storage. However, nanochitosan exhibited higher antimicrobial activity than chitosan during the storage period. Furthermore, nanochitosan showed a stronger ability to inhibit the TVB-N content than chitosan. Therefore, to extend the shelf life and delay the deterioration of fresh silver carp fillets during refrigerated storage, nanochitosan coating is more effective.     

Effect of catechin and ferulic acid on melanosis and quality of Pacific white shrimp subjected to prior freeze–thawing during refrigerated storage

Melanosis of Pacific white shrimp (Litopenaeus vannamei) subjected to freeze–thawing with different thawing methods and various cycles were monitored during subsequent refrigerated storage (4 °C) up to 4 days. Melanosis score was lower in Pacific white shrimp thawed at 4 °C, compared with that found in samples thawed at room temperature or using tap water. Polyphenol oxidase (PPO) activity increased as freeze–thaw cycles increased (P < 0.05). Enhanced PPO activity was most likely associated with increased melanosis. Pacific white shrimp treated with catechin (0.05%, 0.1% and 0.2% (w/v)) or ferulic acid (1%, 2% and 3% (w/v)) and subjected to freeze–thawing with various cycles showed the retarded melanosis during the subsequent refrigerated storage of 4 days, compared with the control (P < 0.05). Treatment of shrimp with both phenolic compounds could impede the growth of psychrophilic bacteria and the spoilage as evidenced by the lowered psychrophilic bacteria count and total volatile base content (TVB). Sample treated with 0.2% catechin or 3% ferulic acid also exhibited the retarded lipid oxidation during the subsequent refrigerated storage, compared with the control (P < 0.05). Thus, either catechin or ferulic acid could be used as the potential additive to lower melanosis of shrimp with prior freeze–thawing.     

The optimization and effect of back panel structure on the performance of refrigerated display cabinet

In this paper, the effect of the back panel structure on the performance of fluid flow and heat transfer of vertical open refrigerated display cabinets (VORDC) is presented by experiments and numerical simulation. Experimental tests are performed to validate the accuracy of numerical predictions. The characteristics of heat transfer and fluid flow of VORDC are investigated at the different locations of the perforations of back panel at the same porosity and the different flow ratios between back panel and air curtain at different porosities. By comparing numerical results with experimental results, the predictive abilities of the computational model have been revealed. Further computational results have also shown that less than 3% porosities can provide a better performance in the VORDC; the location of perforations has a minor influence on the temperature distribution of products. Furthermore, the suitable porosities in the back panel among the shelves are more likely to improve the uniformity of products temperature in the VORDC. As a result, the overall uniformity of product temperature inside the refrigerated display cabinet and the maximum deviation values of product temperature have been improve to 41% and 49%, respectively. The present study can provide the theoretical guide for the design of the narrow VORDC.     

The effect of temperature and citric acid,alone, and in combination with nisin,on the growth of Arcobacter butzleri in culture

Elevated temperature and citric acid have been shown to enhance the susceptibility of gram-negative bacteria to nisin both in culture and in those foods routinely contaminated with Arcobacter butzleri. This study investigated the sensitivity of A. butzleri cells to elevated temperature and varying concentrations of citric acid, alone and in the presence of nisin. The effect of a combination of short-term exposure to citric acid and low-temperature (modeling a chill-wash procedure) followed by continuous exposure to nisin, was also carried out in order to assess the effects to A. butzleri from a multiple hurdle approach to control. When incubated at sub-optimal temperatures (i.e. for aerobic growth, lower than 30 °C) A. butzleri cells show less sensitivity to 500 IU ml⁻¹ nisin than at 30 °C. Elevating the temperature to 60 °C for 10 min, followed by 24 h incubation at 30 °C resulted in no viable cells being detected. However, elevating the temperature to 50 °C resulted in some viable cells with the presence of nisin during the heat treatment significantly reducing number of survivors. A 30-min treatment with 1, 20, 50 or 100 mM citric acid, in the absence and presence of 500 IU ml⁻¹ nisin, reduced survival of A. butzleri cells. Stationary phase cells appear significantly more resistant to both citric acid alone, and citric acid in combination with nisin, than log phase cells. 10-min treatment with 20 mM or 100 mM citric acid, at 30 or 4 °C followed by incubation in the presence of 500 IU ml⁻¹ nisin, completely inhibited growth of A. buzleri cells over five hours. Over 24 h the most effective treatment was with 100 mM citric acid at 4 °C followed by incubation in the presence of 500 IU ml⁻¹ nisin suggesting that nisin prevents the recovery of sublethally damaged cells.     

Preservative effectiveness of essential oils in vapor phase combined with modified atmosphere packaging against spoilage bacteria on fresh cabbage

This study was conducted to investigate the antibacterial effects of various essential oils (EOs) against pathogens using the disc volatilization method. Also, combined effects of EOs in vapor phase and MAP were evaluated for reducing levels of total mesophilic microorganisms on fresh cabbage. The vapor phase activities of EOs (thyme-1, oregano-1, lemongrass-1, and lemongrass-2 oils) observed strong inhibitory effects. The MAP results showed that 100% CO₂ gas packaging reduced significantly levels of total mesophilic microorganisms on cabbage and radish sprouts, and their reduction level was 1.55 and 2.26 log₁₀ CFU/g compared to control after 21 days of storage (p ≤ 0.05). Based on previous results, combined effects of EOs in vapor phase and MAP (100% CO₂) showed that lemongrass-2 oil with 20 discs showed complete inactivation by <1.0 log₁₀ CFU/g after 14 days of storage. These results could provide useful information for developing alternative preservation method to improve the freshness and shelf-life of fresh produce using natural antimicrobials.     

Development of a controlling method for Escherichia coli O157:H7 and Salmonella spp. in fresh market beef by using polylysine and modified atmosphere packaging

Escherichia coli O157:H7 and Salmonella spp. often contaminate fresh beef. In Japan, an E coli outbreak caused by raw beef made 181 people ill and 5 individuals dead in 2011. Responding to this outbreak, an effective sterilization method for fresh beef is expected to be developed. In this study, ε-polylysine combined with CO₂-packaging method was examined for controlling these pathogens in fresh beef. At an incubation temperature of 4 °C, approximately 4.3 log and 2.4 log reduction in bacterial numbers were observed after 7-day incubation for E. coli O157:H7 and Salmonella, respectively, in ε-polylysine-added beef. When effectiveness of CO₂-packaging combined with ε-polylysine was investigated, CO₂ did not have additional inhibiting effect on bacterial growth compared to only-ε-polylysine-treated samples when incubated at 4 °C. However, effectiveness of CO₂ was observed when incubated at 10 °C where approximately 2.9 log and 4.4 log reduction in E. coli cell numbers were observed in only-ε-polylysine-treated samples and polylysine- and CO₂-treated group, respectively, and approximately 1.7 log and 3.5 log reduction in Salmonella cell numbers were observed in only-ε-polylysine-treated samples and polylysine and CO₂-treated group, respectively. This study confirmed that ε-polylysine or ε-polylysine combined with CO₂ packaging are effective in preventing foodborne diseases caused by raw beef.     

A risk assessment model for Escherichia coli O157:H7 in ground beef and beef cuts in Canada: Evaluating the effects of interventions

A stochastic, quantitative risk assessment model was developed to evaluate the public health risks associated with consumption of ground beef and beef cuts contaminated with Escherichia coli O157:H7 in Canada. The objectives of this work were to evaluate the relative effects of pre-harvest and processing interventions on public health risks using a novel approach, and compare the baseline risks from consumption of ground beef, non-intact beef cuts, and intact beef cuts. Rather than considering efficacy of all interventions at primary production and processing as default values, the model incorporated findings from critical systematic review and meta-analysis of published literature. Public health risks, expressed as average probability of illness per serving, were reduced by 30.9%–72.1%, 44.0%–96.5%, and 95.1%–99.9%, for single pre-harvest interventions, single processing interventions excluding water spray chilling, and combinations of interventions, respectively, relative to a worst-case scenario where no pre-harvest or processing interventions were applied. Combinations of interventions applied at pre-harvest and throughout processing resulted in the greatest relative risk reductions through their effects on both prevalence and concentration of the pathogen in cattle faeces and on cattle carcasses. The use of systematic review methodology to critically assess the results of scientific studies before use of the data in risk modelling enhances the confidence in risk predictions and provides a more evidenced-based model for public health analyses. Analysis of conditions reflective of current practices in Canada indicated that risks from consumption of ground beef were approximately two to three orders of magnitude greater than those for beef cuts, suggesting that risk management measures should focus on the former product to maximize benefits to public health. Risks from consumption of non-intact beef cuts, that is, steaks or roasts that are tenderized, were an order of magnitude greater than those for intact beef cuts. The model provides a useful tool to compare relative efficacies of different intervention strategies to determine their potential impact on public health risks. This tool can be used to evaluate an essentially limitless combination of intervention scenarios and can be adapted to include interventions applied at different points along the farm-to-fork continuum as critically-reviewed data become available.