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Lipid oxidation in frozen, mechanically deboned turkey meat as affected by packaging parameters and storage conditions.

Mechanically deboned turkey meat (MDTM) was stored in different packaging materials (film produced with natural antioxidant (alpha-tocopherol) or synthetic antioxidant) at -20 degrees C for 12 mo in a vacuum, modified atmosphere, or air. One-half of the samples were thawed at 4 degrees C for 24 h after 1 mo of storage and then refrozen. Oxidative rancidity was evaluated during storage by measuring the development of 2-thiobarbituric acid reactive substances (TBARS), and hexanal, a volatile oxidation product. Vacuum- and modified atmosphere-packaged samples had lower TBARS values and hexanal content than air-packaged samples with corresponding treatments. Hexanal content and TBARS values increased with storage time, and the highest levels were obtained after 6 mo of storage. The largest increase was obtained with presence of oxygen. Mechanically deboned turkey meat stored in packages where a natural antioxidant (alpha-tocopherol) was used in production of one of the PE layers, had, in almost every instance, the lowest TBARS values and hexanal content when stored in vacuum or modified atmosphere. However, this difference was not statistically significant. Neither TBARS values nor hexanal content showed dependency of the temperature profile (frozen or frozen/thawed/refrozen) during storage.

Aldehydes↗

[Influence of microbiological quality of lactic acid cheese on water phase in conditions of hermetic packing].

Aim of research was to assess the influence of lactic acid cheese micro-flora on water phase fluctuation between surface of products and the packaging. Results of research showed that changes of water content could be expressed with the help of polynomial cubic equation. From linear correlation equations describing level of micro-flora in lactic acid cheese and water content it resulted micro-organisms had a significant influence on the water phase fluctuation. Values of determined coefficients of determination suggested that yeast, enterococci and staphylococci had a significant influence on water fluctuation between product and the packaging.

Cheese↗

Combining pediocin (ALTA 2341) with postpackaging thermal pasteurization for control of Listeria monocytogenes on frankfurters.

Frankfurters packaged in 1-link, 5-link, or 10-link packages were surface-inoculated with a five-strain mixture of Listeria monocytogenes (3.40 or 5.20 log CFU/g) after treatments with 3,000 arbitrary units (AU) or 6,000 AU pediocin (in ALTA 2341) per link. The frankfurters were vacuum packaged, after which the packages were heated in hot water at 71, 81, or 96 degrees C for 30, 60, or 120 s. L. monocytogenes was enumerated following the treatments. Selected treatments were subsequently evaluated during storage at 4, 10, and 25 degrees C for up to 12 weeks. L. monocytogenes was reduced by all treatments, but 81 degrees C or more for at least 60 s in combination with pediocin (Pdn-6000) was necessary to achieve a 50% reduction of initial inoculations. Heat treatments were most effective for 1-link packages and least effective for 10-link packages. Little or no growth of L. monocytogenes occurred on frankfurters for 12 weeks at 4 or 10 degrees C, and for 12 days at 25 degrees C. Generally, the treatments mentioned above did not significantly (P > 0.05) affect the sensory qualities of frankfurters. Therefore, pediocin (in ALTA 2341) in combination with postpackaging thermal treatment offers an effective treatment combination for improved control of L. monocytogenes on frankfurters.

Animals↗

Characterisation of the dominant bacterial population in modified atmosphere packaged farmed halibut (Hippoglossus hippoglossus) based on 16S rDNA-DGGE.

It is not well understood why Atlantic halibut (Hippoglossus hippoglossus) has longer shelf-life than most other white fish species. Our approach was to examine the microbiological diversity of the spoilage microbiota during modified atmosphere (MA) packaging of farmed Atlantic halibut. Portions were packaged with gas mixtures of CO(2):N(2) and CO(2):O(2) (50%:50%) and with air as a reference. The packages were stored at 4 degrees C and samples were taken 6 times during the 23 days of storage. Analyses with molecular techniques (PCR-DGGE) determined profiles of the bacterial populations in the various samples and sequencing detected the bacterial species present. In addition, samples were analysed for microbial, chemical and sensory parameters. The shelf-life was 10-13 days when stored in air and between 13 and 20 days for MA packages, with oxygen-enriched packages suggested as the better gas mixture, based on microbial growth and sensory scores. From sequence analyses of the bacterial population Photobacterium phosphoreum and Pseudomonas spp. were found to dominate in the halibut. Brochothrix thermosphacta was found in most samples at the end of the storage period. Shewanella putrefaciens was found sporadically and in low concentrations based on microbial methods, but not detected by PCR-DGGE.

Animals↗

Conditions that regulate the growth of moulds inoculated into bottled mineral water.

The influence of different storage conditions (temperature, illumination, brand of mineral water and storage time) on growth of mould spores was studied. Alternaria alternata, Penicillium citrinum and Cladosporium cladosporioides spores were inoculated in bottles of mineral and mineralised water, packaged in polyethylene terephtalate (PET). The bottles were incubated under different storage conditions. The strains had been isolated from bottled mineral water in a previous study. Storage time was the parameter that had the most important influence in mould growth. The spores grew into visible colonies after 5 month of incubation in bottles just filled, and in a month in bottles that had been stored for 5 month. This could be due to the migration of compounds from PET packaging material into mineral water. This compounds could be used as nutrients (organic matter) for mould growth. The plasticizer additive di-n-butyl phthalate (DBP) concentration in recently bottled mineral water and in 5-month stored bottles was measured. An increase of 20% of DBP concentration was observed. A. alternata and P. citrinum strains were toxicological characterised. Both strains produced mycotoxins in vitro, and P. citrinum produced citrinin in mineral water, posing a potential health risk for consumers.

Alternaria↗

The interaction of the non-bacteriocinogenic Lactobacillus sakei 10A and lactocin S producing Lactobacillus sakei 148 towards Listeria monocytogenes on a model cooked ham.

Two lactic acid bacteria, Lactobacillus sakei subsp. carnosus (10A) and lactocin S producing Lactobacillus sakei 148 (LS5), were examined for their usefulness as protective culture in the biopreservation of cooked meat products. Co-culture experiments on a model cooked ham (MCH) between 10A or LS5 and a cocktail of three Listeria monocytogenes strains were performed to examine the influence of inoculum level (10(5) vs. 10(6)cfu/g), storage temperature (4 vs. 7 degrees C) and packaging type (vacuum-packaging vs. modified atmosphere-packaging). At 7 degrees C, applying Lactobacillus sakei 10A at 10(6) cfu/g limited the growth of Listeria monocytogenes to <1 log(10) cfu/g during 27 days, whilst an application level of 10(5) cfu/g failed to prevent growth to unacceptable levels. Lactobacillus sakei LS5 did not demonstrate an antagonistic effect towards Listeria monocytogenes. Lowering the temperature to 4 degrees C or switching from vacuum-packaging to modified atmosphere packaging (MAP) did not influence the ability of strain 10A to grow on the MCH, as its dominance did not change. A combination of strain 10A and 4 degrees C or a MAP containing 50% CO(2) completely inhibited the growth of Listeria monocytogenes. Sensory assessments and pH measurements confirmed that 10A, even when present at a high level for prolonged storage times, did not acidify the cooked ham to a point of sensory rejection.

Animals↗

Front-face fluorescence spectroscopy and chemometrics in analysis of yogurt: rapid analysis of riboflavin.

The present study demonstrates the use of front-face fluorescence spectroscopy and chemometrics for monitoring light-induced changes in plain yogurt during storage. Fluorescence analysis is suggested as a new rapid method for measuring riboflavin content in yogurt. Fluorescence landscapes with excitation wavelengths from 270 to 550 nm and emission wavelengths in the range 310 to 590 nm were obtained from front-face fluorescence measurements directly on yogurt samples during two storage experiments over a period of 5 wk at 4 degrees C. Yogurts were stored in two different packaging materials (polylactate and polystyrene) and under fluorescent light (3500 lux) or in darkness. Principal Component Analysis of unfolded fluorescence emission spectra revealed systematic changes in fluorescence signal throughout the storage period, strongly related to the storage conditions, i.e. storage time and differences in packaging materials. Correlation between fluorescence spectra and riboflavin content determined by the standard AOAC fluorometric method was evaluated using a Partial Least Square Regression model. The regression model showed a good ability to predict riboflavin in plain yogurt with a high correlation (R = 0.99) and a prediction error of 0.092 microgram riboflavin/g. Thus, it is concluded that nondestructive fluorescence spectroscopy can be used to monitor riboflavin content in yogurt, and that the suggested rapid method has the potential to substitute the standard method for analysis of riboflavin in yogurt.

Food Handling↗

Enterococcus species dominating in fresh modified-atmosphere-packaged, marinated broiler legs are overgrown by Carnobacterium and Lactobacillus species during storage at 6 degrees C.

In order to show which of the initial lactic acid bacteria (LAB) contaminants are also causing spoilage of a modified-atmosphere-packaged (MAP), marinated broiler leg product at 6 degrees C, LAB were enumerated and identified on the 2nd and 17th days following manufacture. A total of 8 fresh and 13 spoiled packages were studied for LAB levels. In addition, aerobic mesophilic bacteria and Enterobacteriaceae were determined. The average CFU/g values in the 8 fresh packages were 1.3 x 10(3), 9.8 x 10(3) and 2.6 x 10(2) on de Man Rogosa Sharpe agar (MRS), Plate Count Agar (PCA) and Violet Red Bile Glucose agar (VRBG), respectively. The commercial shelf life for the product had been set as 12 days, and all packages analyzed on the 17th day were deemed unfit for human consumption by sensory analysis. The corresponding CFU/g averages in the spoiled product were 1.4 x 10(9), 1.1 x 10(9) and 3.9 x 10(7) on MRS, PCA and VRBG agar, respectively. For characterization of LAB population, 104 colonies originating from the fresh packages and 144 colonies from the spoiled packages were randomly picked, cultured pure and identified to species level using a 16 and 23S rDNA HindIII RFLP (ribotyping) database. The results showed that enterococci (35.7% of the LAB population) were dominating in the fresh product, whereas carnobacteria (59.7%) dominated among the spoilage LAB. Enterococcus faecalis, Carnobacterium piscicola and Carnobacterium divergens were the main species detected. In general, when the initial LAB population is compared to the spoilage LAB, a shift from homofermentative cocci towards carnobacteria, Lactobacillus sakei/curvatus and heterofermentative rods is seen in this marinated product.

Animals↗

Effect of prestorage treatmlents and storage conditions on the survival of Salmonella enteritidis PT4 and Listeria monocytogenes on fresh marine and freshwater aquaaculture fish.

The effect of prestorage treatments, such as immersion in a sorbate solution (5%, wt/vol), heating (60 degrees C, 1 min), and a combination of the two treatments, and the subsequent storage in air or under modified atmosphere packaging (MAP; 40% CO2, 30% O2, and 30% N2) at chill temperatures (0 +/- 1 degrees C), on Listeria monocytogenes and Salmonella Enteritidis PT4 was studied. The prestorage treatments affected the pathogenic bacteria, and in all cases, there was a decrease in their population, with the sorbate and combination (hot water and sorbate) treatment being most effective. The beneficial effect of the prestorage treatments, which was more pronounced in storage under MAP conditions, suggests an interaction of the treatments with the CO2 of MAP against injured bacterial cells.

Animals↗

Identification of lactic acid bacteria from spoiled, vacuum-packaged 'gravad' rainbow trout using ribotyping.

A total of 296 lactic acid bacteria (LAB) isolated from spoiled, vacuum-packaged 'gravad' rainbow trout stored at 3 and 8 degrees C were characterised and identified using a molecular approach. The isolates were initially grouped according to their HindIII restriction endonuclease profiles and further identified to species level using an rRNA gene restriction pattern (ribotype) identification database. Lactobacillus sakei, L. curvatus and Carnobacterium piscicola were the three main species detected. Only one isolate was identified as C. divergens. Most of the carnobacteria were found in the samples stored at 3 degrees C. The relative proportion of L. sakei was higher in the samples stored at 8 degrees C.

Animals↗

Microbiological, biochemical and sensory assessment of mussels (Mytilus galloprovincialis) stored under modified atmosphere packaging.

AIMS: To determine the microbiological, biochemical and sensory changes of mussels during storage under aerobic, vacuum packaging (VP) and modified atmosphere packaging (MAP) conditions at 4 degrees C, and to determine shelf-life of mussels under the same packaging conditions using the above assessment parameters. METHODS AND RESULTS: Aqua-cultured mussels (Mytilus galloprovincialis) were obtained from a local culture farm, packaged aerobically under VP and MAP (50%/50% CO2/N2: M1, 80%/20% CO2/N2: M2, 40%/30%/30% CO2/N2/O2: M3), and stored at 4 degrees C. Quality evaluation was carried out using microbiological, chemical and sensory analyses. Microbiological results revealed that the M2 and VP delayed microbial growth compared with that of air-packaged samples. The effect was more pronounced for total viable count (TVC), Pseudomonas spp., lactic acid bacteria (LAB) and H2S-producing bacteria. TVC was reduced by 0.9-1.0, Pseudomonas spp. by 0.7-0.8, LAB by 1.0-2.2, H2S-producing bacteria by 0.7-1.2. Enterobacteriaceae were not significantly affected by MAP conditions. Of the chemical indices determined, the total volatile basic nitrogen and trimethylamine nitrogen values remained lower than the proposed acceptability limits of 35 mg N 100 g(-1) and 12 mg N 100 g(-1), respectively, after 15 days of storage. Both the VP and air-packaged mussel samples exceeded these limits. The thiobarbituric acid value of all MAP and VP mussels remained lower than the proposed acceptability limit of 1 mg malondialdehyde kg(-1). The air-packaged samples exceeded this limit. All samples retained desirable sensory characteristics during the first 8 days of storage. CONCLUSIONS: Based on odour and taste evaluation, the M1 and M3 samples remained acceptable until ca day 11-12, the M2 samples remained acceptable until ca day 14-15 days while the VP and air-packaged mussel samples remained acceptable until ca days 10-11 and 8-9 of storage respectively. Based primarily on sensory, but also on biochemical and microbiological parameters determined, M2 gas mixture was the most effective for mussel preservation achieving a shelf-life of ca 14-15 days. SIGNIFICANCE AND IMPACT OF THE STUDY: MAP (M2) can be used to increase the shelf-life of refrigerated mussels. A shelf-life extension of refrigerated mussels by ca 5-6 days under MAP may be obtained.

Animals↗

Observations on the succession dynamics of lactic acid bacteria populations in chill-stored vacuum-packaged beef.

Drip samples were collected at 4-week intervals from 10 vacuum-packaged beef striploins stored for 16 weeks at -1.5 degrees C and assayed for populations of lactic-acid bacteria (LAB), pH and spoilage-causing fermentation products. A total of 15 LAB species were identified using pulsed-field gel electrophoresis and biochemical analysis. A pattern of succession was observed during storage between strains of Carnobacterium, Lactobacillus, Leuconostoc and Pediococcus. Acetic acid production was associated with increasing LAB populations generally and butyric acid production was associated with the development of a particular strain of Leuconostoc. Changes in pH is postulated as a driver of succession.

Animals↗

Effect of high-barrier packaging films with different oxygen transmission rates on the growth of Lactobacillus sp. on meat fillets.

The goal of this study was to determine the combined effect of (i) the oxygen transmission rate (OTR) of packaging film, often called oxygen film permeability or film permeability and (ii) temperature on the growth rate of the main prevailing organism, Lactobacillus sp., in 100% CO2-packed sterile meat fillets. Multifactorial experiments were designed to study the effect of OTR and temperature (0, 5, 8, and 10 degrees C) on the growth rate of Lactobacillus sp. inoculated on sterile meat fillets under 100% CO2 and aerobic conditions. The packaging conditions (air or 100% CO2) and the film OTR significantly affected the growth rate of Lactobacillus sp. only at temperatures higher than 0 degrees C. Low-permeable films with different OTRs did not affect the final population of the bacterium, but the growth rate was significantly changed. The correlation of an ephemeral microbial association with a low spoilage potential (e.g., lactic acid bacteria) or their growth retardation cannot always be assumed unless other determinants (e.g., OTR) of equal importance are taken into account. The present study provides information that can be of benefit to industry and the consumer.

Animals↗

Numbers and types of microorganisms in vacuum-packed cold-smoked freshwater fish at the retail level.

Fifty-four packages (each one belonging to a different lot) of vacuum-packed cold-smoked salmon (30) and trout (24) produced by six Spanish smokehouses were obtained at retail level after 3 weeks storage at 2+/-1 degrees C. Sensorial, chemical, physicochemical and microbiological characteristics were examined. Overall, pH, a(w), salt content in water phase, aerobic plate counts at 30 and 25 degrees C. levels of Enterobacteriaceae, lactic acid bacteria (LAB), fungi and presumptive aeromonads and staphylococci are in agreement with available data on lightly preserved fish products. Psychrotrophic clostridia ranged between 1.71 and 2.21 log CFU/g. Levels of ethanol were highly variable and not significantly related (p > 0.05) to sensory scores or to microbial numbers. Salmonella, Escherichia coli and Listeria monocytogenes were not detected in any sample. Listeriae other than L. monocytogenes were isolated from three packages. Levels of Staphylococcus aureus lower than 4 log CFU/g were also found in three packages. Among 377 bacteria randomly isolated from aerobic 25 degrees C plate counts, LAB predominated, with Carnobacterium (C. piscicola) and Lactobacillus (eight species) being the genera most frequently found. The second and third major groups were Enterobacteriaceae and Micrococcaceae, respectively. Proteus vulgaris, P. mirabilis and Serratia liquefaciens were dominant among Enterobacteriaceae and coagulase-negative staphylococci among Micrococcaceae. Minor microbial groups such as aerobic gram-negative bacilli (Acinetobacter; Moraxella and Pseudomonas), Brochothrix, Aeromonas, Bacillus and Vibrio constituted less than 17% of the total flora.

Animals↗

Preservation of fresh meat with active and modified atmosphere packaging conditions.

The sensory, microbiological and physicochemical attributes of fresh meat stored at 5 and 15 degrees C were affected by the combined effect of volatile compounds of oregano essential oil and modified atmosphere packaging conditions (40% CO2/30% N2/30% O2, 100% CO2, 80% CO2/20% air, vacuum pack and air). It was found that the extension of shelf life of meat samples depended on the packaging conditions and augmented in the order: air < vacuum pack < 40% CO2/30% N2/30% O2 < 80% CO2/ 20% air < 100% CO2. Longer shelf life was observed in samples supplemented with the volatile compounds of oregano essential oil and stored under the same packaging conditions mentioned above. The extension of shelf life may be due to the synergistic effect of volatile compounds of oregano essential oil and the modified atmosphere packaging used on the microbiological and physicochemical characteristics of meat. Indeed, both these hurdles can prolong and delay microbial growth or suppress the final counts of the spoilage microorganisms in comparison with the 'control' samples. The effect of essential oil volatile compounds was even more pronounced on the physicochemical changes of meat samples caused by microbial association. Oregano essential oil delayed glucose and lactate consumption, both indicators of meat spoilage aerobically as well as under 40% CO2/30% N2/30% O2, and 100% CO2. Finally, changes in other metabolites such as formic acid were also observed.

Aerobiosis↗

Quality of fresh chicken breasts using a combination of modified atmosphere packaging and chlorine dioxide sachets.

The objective of this research was to observe the effect of chlorine dioxide (ClO2) combined with modified atmosphere packaging on the quality of fresh chicken breasts under refrigerated storage for 15 days. Each chicken breast was inoculated with a 4-log CFU/ml culture of Salmonella Typhimurium (nalidixic acid-resistant strain) and placed into a barrier foam tray. Fast- or slow-release ClO2 sachets were placed next to the chicken in each package. A control set of packages that did not contain a ClO2 sachet was also included in the study. Packages were flushed with either 100% N2 or 75% N2-25% CO2 and stored at 3 degrees C. Microbial analysis, CIE L.a.b. color, and sensory (appearance and aroma) were performed every 3 days for 15 days. Total plate counts for chicken increased steadily after 6 to 9 days of storage regardless of package atmosphere or ClO2 treatment. However, those treated with ClO2 sachets had 1 to 1.5 log CFU per chicken breast lower total plate counts compared with those without ClO2 sachets. After 15 days, samples treated with ClO2 (fast- and slow-release sachets) had significantly lower Salmonella Typhimurium (nalidixic acid-resistant strain) populations (approximately 1 log) compared with chicken that did not contain ClO2 sachets. The ClO2 adversely affected the color of the chicken in areas close to the sachet. No off-odor was detected by the sensory panelists.

Animals↗

Combined effect of modified atmosphere packaging and addition of rosemary (Rosmarinus officinalis), ascorbic acid, red beet root (Beta vulgaris), and sodium lactate and their mixtures on the stability of fresh pork sausages.

The effects of rosemary, in combination with ascorbic acid, red beet root, and sodium lactate, as well as their mixtures, on the inhibition of both lipid and pigment oxidation of fresh pork sausages packaged in a modified atmosphere were studied. Sausages (240) were packaged in a 80% O2 + 20% CO2 gas mixture and analyzed for CIE a, metmyoglobin, TBARS, psychrotrophic aerobes, and sensory discoloration and off-odor throughout 20 days of storage at 2 +/- 1 degrees C. The mixture of rosemary + ascorbic acid + sodium lactate + red beet root extract extended the shelf life of fresh pork sausages from 8 to 16 days. Results demonstrated that all of the components of the mixture contributed to obtaining the maximum delay in color and/or odor decay, due to a combined inhibitory action on both pigment and lipid oxidation, as well as on microbial growth.

Animals↗

Use of mustard flour to inactivate Escherichia coli O157:H7 in ground beef under nitrogen flushed packaging.

This study was undertaken to determine whether the glucosinolates naturally present in non-deheated mustard flour could serve as a source of allyl and other isothiocyanates in sufficient quantity to kill Escherichia coli O157:H7 inoculated in ground beef at three different levels, during refrigerated storage of the meat under nitrogen. Mustard flour was mixed at 5%, 10% or 20% (w/w) with freshly ground beef, then the beef was inoculated with a cocktail of five strains of E. coli O157:H7 at either 3, 6 or < or =1.6 log10 cfu/g. The ground beef was formed into 100 g patties and each was placed in a bag of Nylon/EVOH/PE, which was back-flushed with 100% N2, heat-sealed and stored at 4 degrees C for < or =21 days. During storage, the allyl isothiocyanate (AIT) levels in package headspaces were determined by gas liquid chromatography. By 21 days, the levels present in treatments were not significantly different. After 21 days storage, there were 0.5, 3 and 5.4 log10 decreases in numbers of E. coli O157:H7 from the initial levels of 6 log10 cfu/g in meat containing 5%, 10% and 20% mustard flour, respectively. When inoculated at 3 log10 cfu/g, E. coli O157:H7 was reduced to undetectable levels after 18, 12 and 3 days with 5%, 10% and 20% mustard flour, respectively. When immunomagnetic separation (IMS) was used for E. coli recovery following its inoculation at < or =1.6 log10 cfu/g, 5% mustard did not completely eliminate the pathogen from ground beef stored for 6 days. The natural microflora of the ground beef which developed in vacuum packages was unaffected by the addition of 5% mustard flour but some inhibition was found at higher concentrations. Sensory evaluation of the cooked ground beef showed that there were no significant differences in the acceptability of meat treated with 5 or 10% mustard flour. However, panelists could distinguish untreated controls from mustard treatments, but considered the mustard-treated meat to be acceptable. These results showed that it is possible to use mustard flour at levels of >5-10% to eliminate E. coli O157:H7 from fresh ground beef.

Animals↗