Vacuum-packaged Meat Research Articles

The importance of including metmyoglobin levels in reflectance-based oxygen consumption measurements

Reflectance-based oxygen consumption measurement utilizes changes in oxymyoglobin levels between bloomed and vacuum-packaged meat, assuming that oxymyoglobin is converted to deoxymyoglobin. However, the interconversion of oxymyoglobin to deoxymyoglobin depends on the age of the meat and the length of display; hence, oxygen consumption calculations might yield inaccurate interpretations if deoxymyoglobin is not the final form. The objective was to evaluate the effectiveness of determining metmyoglobin levels during oxygen consumption analysis and its relationship to beef color stability. Seven psoas major (color labile) and longissimus (color stable) were displayed in retail for 6 d and evaluated for oxygen consumption on the retail (oxygen exposed) and interior (non‑oxygen exposed) surfaces. The retail surface had greater (P < 0.05) metmyoglobin formed during oxygen consumption than the interior surface on d 6 of the display. Furthermore, the psoas major muscle exhibited greater (P < 0.05) metmyoglobin content during oxygen consumption than the longissimus on the retail surface paralleling with the decline in color stability. Therefore, the study indicates that sampling location and including metmyoglobin content in oxygen consumption calculations, along with changes in oxymyoglobin, will better explain meat color stability.

Comparative assessment of beef characteristics from young bulls of different breeds and the influence of storage conditions on meat quality indicators

Comparative assessment results for quality indicators of meat samples obtained from Black Pied, Simmental and Aberdeen Angus young bulls and the influence of different temperature conditions on the quality of vacuum-packed beef during refrigerated storage are presented. The general chemical composition, physicochemical properties, and biological value of the samples based on the content of nonessential and essential amino acids were determined, as well as the protein quality index (PQI) and amino acid score. Analysis of the general chemical composition revealed higher moisture and protein content and the lowest fat content in Black Pied beef compared to other breeds. The amino acid composition of the protein showed a higher content of essential amino acids and the highest PQI value in Simmental beef. According to the calculation results, higher amino acid scores for lysine (149.1% and 129.1%) and tryptophane (200.0% and 240.0%) were noted in meat from Simmental and Aberdeen Angus young bulls, respectively. For the process of storing vacuum-packed meat in a cooled (at a temperature of 2.0 ± 0.5 °C) and superchilled state (minus 2.0 ± 0.5 °C) at a relative air humidity of 85%, a comparative analysis of changes in free amino acids and dynamics of hydrolytic and oxidative spoil- age of meat samples from various breeds was conducted. After 21 days of storage in a superchilled state, the content of free amino acids in Black Pied, Simmental and Aberdeen Angus beef was lower by 13.1% (P &gt; 0.05), 24.1% (P ≤ 0.05) and 17.0% (P ≤ 0.01) compared to storage in a cooled state, respectively. For all studied samples stored in a cooled state, the acid number values were 40% to 41% (P ≤ 0.01) higher than in a superchilled state and peroxide number values were 20% to 23% (P ≤ 0.05) higher than in a superchilled state. It has been established that lowering the storage temperature of vacuum-packed beef helps to better preserve quality and ensure safety for meat from all breeds studied.

Sex Does Not Affect the Colour, Shear Stress, and Lipid Oxidation of Pork Meat, but Feed-Added Plant-Derived Extracts, Storage Time and Packaging Type Do.

Essential plant oils added to products, packaging or animal feed are used as a method of preserving food quality because they extend the shelf-life of meat due their antioxidant and/or antimicrobial capacity. This action can be achieved with the correct packaging that preserves the meat's quality and safety. This study investigates the effects of plant-derived extracts (PDE) on the meat quality and shelf-life of pork packaged in vacuum or modified atmosphere packaging (MAP). Thirty-six barrows and thirty-six gilts were allocated into three experimental groups: the control, garlic extract (1 kg/ton of feed) and oregano-rosemary oil (2 kg/ton of feed) with the same base-diet. Two packaging were used: vacuum and a commercial MAP (70% O2, 30% CO2). The meat fat content, pH, colour, TBARS values and Warner-Bratzler shear stress were investigated. The sex of the animals did not affect any of the studied variables, whereas PDE affected some of the colour variables and the shear stress; both the packaging type and the storage time affected the colour variables, lipid oxidation and shear stress. Vacuum-packed meat was more stable in terms of colour, lipid oxidation and shear stress than MAP-packed meat.

Isolation and characterization of the new isolated bacteriophage YZU-L1 against Citrobacter freundii from a package-swelling of meat product

Citrobacter freundii is an important foodborne pathogen that can cause urethritis, bacteremia, necrotizing abscess, and meningitis in infants. In this study, a gas-producing isolate from vacuum-packed meat products was identified as C. freundii by 16S rDNA. In addition, a new virulent phage YZU-L1, which could specifically lyse C. freundii, was isolated from sewage samples in Yangzhou. Transmission electron microscopy showed that phage YZU-L1 had a polyhedral head of 73.51 nm in diameter and a long tail of 161.15 nm in length. According to phylogenetic analysis employing the terminase large subunit, phage YZU-L1 belonged to the Demerecviridae family and the Markadamsvirinae subfamily. The burst size was 96 PFU/cell after 30 min of latent period and 90 min of rising period. Phage YZU-L1 could maintain high activity at pH of 4–13, and resist 50 °C for up to 60 min. The complete genome of YZU-L1 was 115,014 bp double-stranded DNA with 39.94% G + C content, encoding 164 open reading frames (ORFs), without genes encoding for virulence, antibiotic resistance, or lysogenicity. Phage YZU-L1 treatment significantly reduced the viable bacterial count of C. freundii in a sterile fish juice model, which is expected to be a natural agent for the biocontrol of C. freundii in foods.

Microbiological Changes during Long-Storage of Beef Meat under Different Temperature and Vacuum-Packaging Conditions

We evaluated a combination of two temperatures and two packaging materials for long-term storage of vacuum-packaged (VP) beef striploins. Microbial populations and microbiome composition were monitored during refrigerated storage (120 days between 0-1.5 °C) and refrigerated-then-frozen storage (28 days between 0-1.5 °C then 92 days at -20 °C) under low-O2 permeability VP and high-O2 permeability VP with an antimicrobial (VPAM). Pseudomonas (PSE) and Enterobacteriaceae (EB) counts in VPAM samples were significantly higher (p < 0.05) than in VP samples at 28, 45, 90, and 120 days of storage. Microbiome data showed that bacteria of the genera Serratia and Brochothrix were more abundant in VPAM samples at 120 days, while lactic acid bacteria (LAB) dominated in VP samples. Frozen temperatures inhibited microbial growth and maintained a relatively stable microbiome. Refrigerated and frozen VPAM samples showed the greatest difference in the predicted metabolic functions at the end of storage driven by the microbiome composition, dominated by PSE and LAB, respectively. Although no signs of visible meat deterioration were observed in any sample, this study suggests that VP meat refrigerated and then frozen achieved better microbiological indicators at the end of the storage period.

Microbiological quality and safety of vacuum-packaged white-tailed deer meat stored at 4 °C

Vacuum packaging is widely used for extending the shelf life of commercial fresh meat products. It also ensures product hygiene during distribution and storage. However, very little information exists concerning the effects of vacuum packaging on the shelf life of deer meat. One of our aims was to evaluate how storage under vacuum at 4 °C affects the microbial quality and safety of white-tailed deer (Odocoileus virginianus) meat cuts. This was assessed in a longitudinal study based on sensory analyses and measurements of (1) mesophilic aerobic bacteria (MAB), (2) lactic acid bacteria (LAB), (3) enterobacteria (EB), (4) and Escherichia coli (EC) counts, and the presence of foodborne pathogens (Campylobacter, Salmonella, stx-harbouring E. coli (STEC), Yersinia and Listeria). Microbiomes were additionally investigated by 16S rRNA gene amplicon sequencing at the time of spoilage. In total, 50 vacuum-packaged meat cuts from the carcasses of 10 wild white-tailed deer harvested in southern Finland in December 2018 were analysed. A significant (p < 0.001) drop in the odour and appearance scores and a significant increase in MAB (p < 0.001) and LAB (p = 0.001) counts of the vacuum-packaged meat cuts were observed after 3 weeks of storage at 4 °C. A very strong correlation (rs = 0.9444, p < 0.001) between the MAB and LAB counts were found during the 5-week sampling period. Clear spoilage changes, manifested as sour off-odours (odour scores ≤2) and pale colour, were detected in the meat cuts spoilt after 3-week storage. High (≥8 log10 cfu/g) MAB and LAB counts were also detected. According to the 16S rRNA gene amplicon analyses, Lactobacillus was the dominant bacterial genus in these samples, demonstrating that LAB can cause rapid spoilage of vacuum-packaged deer meat cuts stored at 4 °C. The rest of the samples were spoilt after four or five weeks of storage, and a vast number of bacterial genera were identified in them. Listeria and STEC were detected by PCR in 50 % and 18 % of the meat cut samples, respectively, which may indicate a public health problem. Our results demonstrate that it is very challenging to ensure the quality and safety of vacuum-packaged deer meat stored at 4 °C, and freezing is therefore recommended to prolong the shelf life.

Diagnostic capabilities of modern methods of determination pathogenic listeria in meat products

Annual reports on the morbidity of the adult population report outbreaks of listeriosis caused by Listeria monocytogenes with clinically pronounced febrile gastroenteritis. The main transmission route to humans is believed to be through consumption of contaminated food, especially ready-to-eat meat products. Rapid and specific detection of L. monocytogenes in food is critical for ensuring the safety of consumers. The aim of this work was to study the occurrence of L. monocytogenes in vacuum-packed meat products using modern diagnostic methods. In total, 60 vacuum-packed meat products were studied using real-time PCR (iQ-Check™ realtime PCR kit), immunoassay (VIDAS LMO2 test) and culturing. Thirty-two of 60 (53%) vacuum-packed meat products were L. monocytogenes positive by real-time PCR. The occurrence was especially high in heat-treated sausages (80%). Only two products (two bacons) were VIDAS and culture positive. Additionally, L. monocytogenes was isolated from one heat-treated sausage, which was VIDAS negative. All VIDAS and culture-positive samples were also PCR positive. In two (12%) out of 17 vacuum-packed ready-to-eat products, the number of L. monocytogenes was over 100 cfu/g demonstrating that the shelf life assigned to some vacuum-packed products is not appropriate. Real-time PCR based on iQ-Check™ realtime PCR kit was shown to be very sensitive to detect L. monocytogenes in foods and thus a useful tool for screening.

Inhibitory effect of licorice extract on the germination and outgrowth of Paraclostridium bifermentans spores.

Paraclostridium bifermentans is responsible for spoilage properties in vacuum-packaged meat. Ordinary heat treatment techniques are ineffective to control the extremely heat-resistant spores of P. bifermentans. Therefore, finding a new strategy to prevent the contamination of P. bifermentans spores in vacuum-packaged meat is challenging. In this study, P. bifermentans was isolated from the vacuum-packaged chicken, and the inhibitory effects of licorice extract on the germination and outgrowth of P. bifermentans spores, as well as the key bioactive components in the licorice extract involved in inhibiting spore activity, were investigated. The spores induced by combination-nutrient-germinant (150 mmol/L L-alanine and 20 mmol/L inosine, co-AI) did not germinate when the concentration of licorice extract was ≥ 3.13 mg/ml. The germination of P. bifermentans spores induced by non-nutrient-germinant (8 mmol/L dipicolinic acid, DPA) was completely prevented by licorice extract at least 1.56 mg/ml. While the outgrowth of P. bifermentans spores was inhibited at a concentration of 0.39 mg/ml. Licorice extract did not seem to damage the non-germinated spores but blocked the germinant sensing. Licorice extract prevented the outgrowing spores from becoming vegetable cells by disrupting the inner membrane. Furthermore, the results obtained from LC-MS data analysis exhibited 15 key bioactive compounds in licorice extract, such as glycyrrhizic acid, liquiritin, etc. Among them, glycyrrhizic acid and liquiritin apioside exerted efficient inhibitory properties on the germination and outgrowth of P. bifermentans spores. This present study demonstrated that licorice extract can be used as a promising inhibitor of spores and provides a new method to control the residual P. bifermentans spores in meat products. Meanwhile, this study exhibits a baseline for the better understanding of the potential application of licorice extracts to control the P. bifermentans spores in meat products.

Genome collection of Shewanella spp. isolated from spoiled lamb.

The diversity of the genus Shewanella and their roles across a variety of ecological niches is largely unknown highlighting the phylogenetic diversity of these bacteria. From a food safety perspective, Shewanella species have been recognized as causative spoilage agents of vacuum-packed meat products. However, the genetic basis and metabolic pathways for the spoilage mechanism are yet to be explored due to the unavailability of relevant Shewanella strains and genomic resources. In this study, whole-genome sequencing of 32 Shewanella strains isolated from vacuum-packaged refrigerated spoiled lamb was performed to examine their roles in meat spoilage. Phylogenomic reconstruction revealed their genomic diversity with 28 Shewanella spp. strains belonging to the same putative novel species, two Shewanella glacialipiscicola strains (SM77 and SM91), Shewanella xiamenensis NZRM825, and Shewanella putrefaciens DSM 50426 (ATCC 8072) isolated from butter. Genome-wide clustering of orthologous gene families revealed functional groupings within the major Shewanella cluster but also considerable plasticity across the different species. Pan-genome analysis revealed conserved occurrence of spoilage genes associated with sulfur and putrescine metabolism, while the complete set of trimethylamine metabolism genes was observed in only Shewanella sp. SM74, S. glacialipiscicola SM77 and SM91 strains. Through comparative genomics, some variations were also identified pertaining to genes associated with adaptation to environmental cues such as temperature, osmotic, salt, oxidative, antimicrobial peptide, and drug resistance stresses. Here we provide a reference collection of draft Shewanella genomes for subsequent species descriptions and future investigations into the molecular spoilage mechanisms for further applications in the meat industry.

Unraveling the Genotypic and Phenotypic Diversity of the Psychrophilic Clostridium estertheticum Complex, a Meat Spoilage Agent.

The spoilage of vacuum-packed meat by Clostridium estertheticum complex (CEC), which is accompanied by or without production of copious amounts of gas, has been linked to the acetone–butyrate–ethanol fermentation, but the mechanism behind the variable gas production has not been fully elucidated. The reconstruction and comparison of intra- and interspecies metabolic pathways linked to meat spoilage at the genomic level can unravel the genetic basis for the variable phenotype. However, this is hindered by unavailability of CEC genomes, which in addition, has hampered the determination of genetic diversity and its drivers within CEC. Therefore, the current study aimed at determining the diversity of CEC through comprehensive comparative genomics. Fifty CEC genomes from 11 CEC species were compared. Recombination and gene gain/loss events were identified as important sources of natural variation within CEC, with the latter being pronounced in genomospecies2 that has lost genes related to flagellar assembly and signaling. Pan-genome analysis revealed variations in carbohydrate metabolic and hydrogenases genes within the complex. Variable inter- and intraspecies gas production in meat by C. estertheticum and Clostridium tagluense were associated with the distribution of the [NiFe]-hydrogenase hyp gene cluster whose absence or presence was associated with occurrence or lack of pack distention, respectively. Through comparative genomics, we have shown CEC species exhibit high genetic diversity that can be partly attributed to recombination and gene gain/loss events. We have also shown genetic basis for variable gas production in meat can be attributed to the presence/absence of the hyp gene cluster.

Occurrence of genes encoding spore germination in Clostridium species that cause meat spoilage.

Members of the genus Clostridium are frequently associated with meat spoilage. The ability for low numbers of spores of certain Clostridium species to germinate in cold-stored vacuum-packed meat can result in blown pack spoilage. However, little is known about the germination process of these clostridia, despite this characteristic being important for their ability to cause spoilage. This study sought to determine the genomic conditions for germination of 37 representative Clostridium strains from seven species ( C. estertheticum , C. tagluense , C. frigoris , C. gasigenes , C. putrefaciens , C. aligidicarnis and C. frigdicarnis) by comparison with previously characterized germination genes from C. perfringens , C. sporogenes and C. botulinum . All the genomes analysed contained at least one gerX operon. Seven different gerX operon configuration types were identified across genomes from C. estertheticum , C. tagluense and C. gasigenes . Differences arose between the C. gasigenes genomes and those belonging to C. tagluense / C. estertheticum in the number and type of genes coding for cortex lytic enzymes, suggesting the germination pathway of C. gasigenes is different. However, the core components of the germination pathway were conserved in all the Clostridium genomes analysed, suggesting that these species undergo the same major steps as Bacillus subtilis for germination to occur.

Consumers' Attitudes toward the Use of an Edible Coating for Lamb Meat According to Label Information.

The use of edible coatings in meat is currently being investigated in several studies. However, consumers’ attitudes toward this technology are not clear. This study evaluated consumers’ intention to purchase vacuum-packaged meat with a chitosan coating based on the label information. Three factors combined with different levels were considered: type of cut (“loin”, “French rack”, or “leg steak”), coating/information (no information, chitosan without information explained, and chitosan with information explained), and price (low or high). Consumers’ purchase intentions were evaluated using a 7-point structured scale (1 = certainly would not buy; 7 = certainly would buy). The data were analyzed by conjoint analysis and cluster analysis. The average purchase intention value was 4.3 ± 0.5. The “French rack” cut showed the highest value for purchase intention and a high price was also a relevant factor. The packaging with the label stating the presence of a “chitosan” coating without giving any further information obtained higher purchase intentions than the one with the more detailed information label. In the cluster analysis, the factor “type of cut” showed the highest relative importance in two groups, while “price” had a higher impact in another. The type of cut was the main factor affecting consumers’ purchase intentions. However, different attitudes were observed depending on the group.

Surface Color Variations of Ground Beef Packaged Using Enhanced, Recycle Ready, or Standard Barrier Vacuum Films.

With current meat industry efforts focused on improving environmental influencers, adopting sustainable packaging materials may be an easier transition to addressing the sustainability demands of the meat consumer. With the growing popularity of vacuum-packaged meat products, the current study evaluated instrumental surface color on fresh ground beef using vacuum packaging films, recycle-ready film (RRF), standard barrier (STB) and enhanced barrier (ENB). Ground beef packaged using ENB barrier film was lighter (L*), redder (a*) and more vivid (chroma) than all other packaging treatments during the simulated display period (p < 0.05). By day 12 of the simulated retail display, the ground beef surface color became lighter (L*), more yellow (b*), less red (a*), less vivid (chroma) and contained greater forms of calculated metmyoglobin, oxymyoglobin (p < 0.05). The current results suggest that barrier properties of vacuum packaging film for ground beef are pivotal for extending the surface color during fresh shelf-life conditions.

Effect of modified atmosphere packaging and vacuum packaging on quality characteristics of lamb meat.

The aim of the study was to evaluate the effect of vacuum packaging and modified atmosphere packaging (80 % N 20 % CO) on the microbial and physicochemical parameters of lamb meat and the sensory properties of cooked meat. Musculus longissimus thoracis et lumborum samples were examined at 10 d intervals (0, 10, 20 and 30 d) during storage at 4 C. There was no significant effect of the packaging method and storage time used on cooking loss, natural drip loss, lightness, yellowness, and intensity of taste and aroma. An interaction between storage time, packaging method, and mesophilic aerobic bacteria and coliform counts was observed. Storage time significantly affected the number of aerobic psychrotrophic bacteria, redness, pH (), shear force value (), and the desirability of aroma () and taste (). During the storage time, an increase in red saturation from 11.92 to 13.33 and pH value from 5.69 to 5.80 was recorded. Moreover, the storage method affected sensory properties. Vacuum-packed meat was characterized by higher scores in juiciness, tenderness and taste desirability in comparison to MAP. The obtained results suggest that both packaging methods allow for maintaining high-quality lamb meat during a long period of storage under refrigeration conditions.

Feeding, Muscle and Packaging Effects on Lipid Oxidation and Color of Avileña Negra-Ibérica Beef.

Simple SummaryIn recent years, interest has grown in improving the productivity of pure local breeds in Spain using corn silage as an alternative to concentrates. The aim of this investigation was to evaluate the lipid oxidation, color and visual color acceptability of meat from the Avileña-Negra Ibérica breed fed with corn silage in total mixed ration. The inclusion of corn silage led to lower lipid oxidation and higher visual color acceptability when the samples were packaged in a modified atmosphere. The use of corn silage could serve as a feeding option for this type of animal without affecting the quality of the derived meat.In order to increase the economic profitability of Avileña-Negra Ibérica beef production, the inclusion of corn silage in total mixed rations was proposed during the fattening period. Twenty-four Avileña-Negra Ibérica breed entire young bulls were used to evaluate the effects of two feeding systems—concentrate (CON) and corn silage (SIL)—and two packaging systems—vacuum (VAC) and modified atmosphere (MAP)—on the lipid oxidation, color evolution and visual color acceptability of meat throughout display with either oxygen-permeable film (FILM) or modified atmosphere (MAP). Two muscles were assessed: Longissimus thoracis (LT) and Semitendinosus (ST). Meat from SIL-fed animals had higher TBA values than CON-fed animals after 7 days in MAP packaging. Lipid oxidation was prevented more effectively by VAC packaging than MAP. Display time highly influenced lipid oxidation, since oxidation rates were lower with VAC than MAP packaging. After 14 days of display in MAP, the LT from CON was lighter than the ST. Meat discoloration after 7 days of display was significantly different between packaging systems. Vacuum-packaged meat kept the same color throughout the storage time. Visual color acceptability for the LT was higher throughout display than for the ST. Samples from the MAP were well accepted by consumers, especially the meat from the SIL group. Alternatively, feeding with corn silage could be used for this type of animals without affecting important aspects of meat quality.

A Simple Sensor System for Onsite Monitoring of O2 in Vacuum-Packed Meats during the Shelf Life.

Vacuum packaging (VP) is used to reduce exposure of retail meat samples to ambient oxygen (O2) and preserve their quality. A simple sensor system produced from commercial components is described, which allows for non-destructive monitoring of the O2 concentration in VP raw meat samples. Disposable O2 sensor inserts were produced by spotting small aliquots of the cocktail of the Pt–benzoporphyrin dye and polystyrene in ethyl acetate onto pieces of a PVDF membrane and allowing them to air-dry. These sensor dots were placed on top of the beef cuts and vacuum-packed. A handheld reader, FirestinGO2, was used to read nondestructively the sensor phase shift signals (dphi°) and relate them to the O2 levels in packs (kPa or %). The system was validated under industrial settings at a meat processing plant to monitor O2 in VP meat over nine weeks of shelf life storage. The dphi° readings from individual batch-calibrated sensors were converted into the O2 concentration by applying the following calibration equation: O2 (%) = 0.034 * dphi°2 − 3.413 * dphi° + 85.02. In the VP meat samples, the O2 levels were seen to range between 0.12% and 0.27%, with the sensor dphi signals ranging from 44.03° to 56.02°. The DIY sensor system demonstrated ease of use on-site, fast measurement time, high sample throughput, low cost and flexibility.

Effect of UV-C Irradiation and Lactic Acid Application on the Inactivation of Listeria monocytogenes and Lactic Acid Bacteria in Vacuum-Packaged Beef.

The objective of this study was to test the effect of the combined application of lactic acid (0–5%) (LA) and UV-C light (0–330 mJ/cm2) to reduce Listeria monocytogenes and lactic acid bacteria (LAB) on beef without major meat color (L *, a *, b *) change and its impact over time. A two-factor central composite design with five central points and response surface methodology (RSM) were used to optimize LA concentration and UV-C dose using 21 meat pieces (10 g) inoculated with L. monocytogenes (LM100A1). The optimal conditions were analyzed over 8 weeks. A quadratic model was obtained that predicted the L. monocytogenes log reduction in vacuum-packed beef treated with LA and UV-C. The maximum log reduction for L. monocytogenes (1.55 ± 0.41 log CFU/g) and LAB (1.55 ± 1.15 log CFU/g) with minimal impact on meat color was achieved with 2.6% LA and 330 mJ/cm2 UV-C. These conditions impaired L. monocytogenes growth and delayed LAB growth by 2 weeks in vacuum-packed meat samples throughout 8 weeks at 4 °C. This strategy might contribute to improving the safety and shelf life of vacuum-packed beef with a low impact on meat color.

Inhibition of a spoilage exopolysaccharide producer by bioprotective extracts from Lactobacillus acidophilus CRL641 and Latilactobacillus curvatus CRL705 in vacuum-packaged refrigerated meat discs

The effect of bioprotective extracts (BEs) from Lactobacillus acidophilus CRL641 (BE-1) and Latilactobacillus curvatus CRL705 (BE-2) against the exopolysaccharide producer Latilactobacillus sakei CRL1407 in vacuum-packaged meat discs at 4 °C was evaluated. Lat. sakei CRL1407 was able to grow in control samples from 2.80 to 7.77 log CFU/g after 38 days. BE-1 and BE-2 reduced bacterial growth by 2.11 and 1.35 log CFU/g, respectively, but their combination led to a greater growth reduction (3.31 log CFU/g). The antimicrobial activity was detected in treated samples with BE-1 and BE-1 + BE-2 until day 16, while with BE-2 only at the initial time. The pH values remained constant in the discs treated with the BEs combination, whereas the greatest drop in pH was observed in control samples. The minor lipid oxidation without perceptible color changes was detected in the presence of BE-1 and BE-1 + BE-2. The combination of BEs as biocontrol agent plus conventional preservation barriers could extend the fresh meat shelf-life without quality loss.

Recovery of high pressure processing (HPP) induced injured Escherichia coli O157:H7 inhibited by Lactobacillus sakei on vacuum-packed ground beef

High pressure processing (HPP) has been demonstrated as an effective technique in reducing E. coli O157:H7 levels on beef. However, an “injure and recover” action of E. coli O157:H7 was found to raise their beef contamination after HPP disinfection. Furthermore, the recovered cell could be miscalculated owing to the complex bacterial community of meat. Therefore, the current work was aimed to evaluate the recovery of HPP treated pressure resistant E. coli O157:H7 with the existence of background bacteria on beef. In brief, inactivation, injury and pressure resistance of four E. coli O157:H7 strains, CICC 21530, NCTC 12900, and two strains isolated from beef (B1, and B2), were firstly evaluated using selective media. The lethal and injured ratio of E. coli CICC21530 was 62.21% and 64.29% after pressure processing at 400 MPa, while the other three strains were all under the detection limit. Thus, the most pressure-resistant strain CICC21530 was selected and inoculated into ground beef with and without Lactobacillus sakei, one of the predominant spoilage bacteria in vacuum-packed meat, respectively, to study their injured cell recovery after HPP treatment. The results indicated good pressure resistance and recovery ability of L. sakei 1018, that after treatment at 400 MPa for 10 min, the lethal rate was only 31.23%, and the enumeration of HPP treated L. sakei 1018 cells reached their initial level in 3 days. Besides, for the mixed L. sakei 1018 and E. coli CICC21530 inoculation, the spoilage bacterium L. sakei 1018 in vacuum packaging beef inhibited the recovery of E. coli tremendously during all the storage period after HPP process.

The study of amino acid composition and oxidation processes in meat of Aberdeen-Angus bull-calves in chilled and supercooled state

Improving the safety and quality of meat raw materials from animals of special-purpose beef cattle helps to meet the demand for foods at high nutritional value. In the Russian Federation, the Aberdeen-Angus breed is one of the leading beef cattle, from which high quality marbled beef is obtained. Investigations have been carried out to study the qualitative indices of beef from this breed at storage under temperature conditions of cooling medium of 1 ± 0.5 ° C and minus 2.5 ± 0.5 ° C in cold chambers during 12 and 24 days. A decrease in the content of free amino acids in meat during storage was noted. It was found that after 24 days of storage, the biological value of the product (ratio of essential amino acids to nonessential ones) at minus 2.5±0.5 ° C was 1.14 times higher as compared with storage at 1.0±0.5 ° C temperature. After 12 days of storage at 1.0±0.5 ° C temperature, the values of acid and peroxide numbers increased about 3 times in comparison with the initial values, while at minus 2.5±0.5 ° C two times only. After 24 days of storage, the increase of acid number in chilled meat was 42% higher than in super-cooled meat; the values of the peroxide number in meat at 1.0±0.5 ° C was 1.3 times higher than in meat at minus 2.5±0.5 ° C. The researches resulted in recommendations of the temperature conditions providing the storage of super-cooled vacuum-packed meat without phase transition of water into ice as well as ensuring better preservation of biologically relevant components and nutritional value of meat.