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To explore the underlying mechanisms by which superchilling (SC, -3 °C within 5 h of slaughter) improves beef tenderness, an untargeted metabolomics strategy was employed. M. Longissimus lumborum (LL) muscles from twelve beef carcasses were assigned to either SC or very fast chilling (VFC, 0 °C within 5 h of slaughter) treatments, with conventional chilling (CC, 0 ∼ 4 °C until 24 h post-mortem) serving as the control (6 per group). Biochemical properties and metabolites were investigated during the early post-mortem period. The results showed that the degradation of μ-calpain and caspase 3 occurred earlier in SC treated sample, which might be attributed to the accelerated accumulation of free Ca 2+ . The metabolomic profiles of samples from the SC and CC treatments were clearly distinguished based on partial least squares-discriminant analysis (PLS-DA) at each time point. It is noteworthy that more IMP and 4-hydroxyproline were found in the comparison between SC and CC treatments. According to the results of metabolic pathways analysis and the correlation analysis between traits related to tenderness and metabolites with significant differences (SC vs. CC), it can be suggested that the tenderization effect of the SC treatment may be related to the alteration of arginine and proline metabolism, and purine metabolism in the early post-mortem phase., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

This study investigated the relationship between tenderness and protein phosphorylation levels of normal ultimate pH (pH u , 5.4-5.8, NpH u ), intermediate pH u (5.8-6.2, IpH u ) and high pH u (≥6.2, HpH u ) Longissimus lumborum from beef. During 21 d of ageing, the HpH u group had the lowest Warner-Bratzler shear force (WBSF) values, while the IpH u group showed the highest and even after 21 days of ageing still had high levels. In the late stage of the 24 h post-mortem period the faster degradation rate of troponin T and earlier activation of caspase 9 in the HpH u group were the key reasons for the lower WBSF compared with the NpH u and IpH u groups. The activity of caspase 3 cannot explain the tenderness differences between IpH u and HpH u groups, since their activities did not show any difference. At 24 h post-mortem, 17 common differential phosphorylated peptides were detected among pH u groups, of which nine were associated with pH u and WBSF. The higher phosphorylation level of glycogen synthase may have caused the delay of meat tenderization in the IpH u group., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier Ltd.)

The objective of this study was to establish the effect of CO 2 on the bacterial community in beef steaks held under both high-oxygen modified atmosphere packaging (HiOx-MAP) types (CO 2 treated MAP: 50% O 2 /40% CO 2 /10% N 2 ; control MAP: 50% O 2 /50% N 2 ). Steaks were stored at 2 °C for 20 days. Gas composition, meat color, pH values, total volatile basic nitrogen values, total viable counts (TVC) and microbial community dynamics were monitored. Compared to the control MAP, the high level of CO 2 in the contrast MAP significantly delayed bacterial growth, resulting in a bright red color as well as extending the shelf-life to over 20 days. The microbial diversity decreased with prolonged storage in both MAP types, but it was more complex in high-CO 2 treated MAP steaks. When TVC values approached the shelf-life threshold for the control MAP, Pseudomonas and Brochothrix were the predominant bacteria, while Pseudomonas and Serratia under the CO 2 containing MAP were at a lower abundance than under the control MAP. The dominant Pseudomonas species causing spoilage in the control MAP steaks was P. fragi, and this species was inhibited significantly by CO 2 , followed by P. weihenstephanensis. Inversely, P. versuta instead of P. fragi became the dominant Pseudomonas species under the CO 2 treated MAP. Overall, the application of CO 2 in HiOx-MAP influenced microbiota succession, which played an important role in retaining beef quality., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

A long shelf life for fresh meat products is very important both to processors, retailers and consumers. In this work, the effect of repeat acid spraying on the shelf life of vacuum skin-packaged (VSP) chilled beef, as well as the quality and microbial community dynamics was evaluated. Carcasses were sprayed with 300 ppm peroxyacetic acid (PA) or 3% lactic acid (LA) three times during the chilling process, or one more time of LA spray before packaging (LLA). Quality, sensory attributes and microbial load of VSP beef during 32 days of storage at 4 °C were evaluated. The results showed that quality and sensory scores decreased over time for all treatments, but LLA treated samples were still above the rejection threshold at the end of the storage period. Moreover, the total volatile basic nitrogen value and the total viable counts were 15.0 mg/100 g and 7.2 log CFU/g for the control group, while acid treated groups remained below these two values until the end of the storage period. In particular LLA treated beef steaks exhibited the best preservation potential even at the end of storage. This is attributed to the reduction of Proteobacteria in LLA beef steaks shown by the bacterial diversity analysis via high-throughput sequencing, as well as the lower counts of B. thermosphacta and Enterobacteriaceae during storage. This indicates that LLA treatment has the potential to achieve a shelf life extension of VSP steaks without impacting on quality., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

The purpose of this work was to assess the effect of different packaging methods on the shelf life and bacterial communities of roast duck meat. Samples were packaged under the following five conditions: overwrapped packaging (OWP), 100% N 2 (100% N 2 -MAP), 30% CO 2 /70% N 2 (30% CO 2 -MAP), 50% CO 2 /50% N 2 (50% CO 2 -MAP), and 0.4% CO/30% CO 2 /69.6% N 2 (CO-MAP). Physicochemical and microbiological parameters were monitored during 14 days of chilled storage (0-4 °C). Results showed that MAP samples obtained higher and more stable redness, better sensory scores, and lower lipid oxidation, compared with OWP, in which CO-MAP samples had the lowest TBARS values (0.13-0.22 MDA/kg) during storage. Moreover, 30% CO 2 -MAP, 50% CO 2 -MAP, and CO-MAP effectively retarded the onset of bacterial spoilage and extended shelf life by 7 days compared with 100% N 2 -MAP and OWP treatments. Additionally, bacterial succession was significantly affected by the gas composition used in the packages, especially the dominant biota at the end of storage, which played an important role in the spoilage of roast duck meat under specific packaging. On day 14, Pseudoalteromonas spp., Lactobacillus spp., and Pseudomonas spp. became the most predominate genera in OWP, 100% N 2 -MAP, and 50% CO 2 -MAP, respectively. Notably, Vibrio spp. was dominant in both 30% CO 2 -MAP and CO-MAP, indicating 0.4% CO did not exert a further inhibitory effect on this genus. Additionally, the growth inhibition of Pseudoalteromonas spp., Lactobacillus spp., and Leuconostoc spp. by high CO 2 concentration might be the reason for MAP (CO 2 /N 2 ) samples having lower levels of TVC. Globally, these results indicate that 30% CO 2 -MAP, 50% CO 2 -MAP, and CO-MAP are promising packaging methods to improve roast duck meat quality and achieve shelf life extension., (Copyright © 2020. Published by Elsevier Ltd.)

The microbiota influence on meat color stability of chilled beef steaks under two modified atmosphere packaging (MAP) systems was studied: HiOx-MAP (80% O 2 /20% CO 2 ) and CO-MAP (0.4% CO/30% CO 2 /69.6% N 2 ). Steaks were stored for up to 20 days at 2 °C. Headspace gas composition and color stability were evaluated. High-throughput sequencing analyses were performed to characterize bacterial community dynamics. For HiOx-MAP steaks, Pseudomonas spp. became the dominant species, and an increased oxygen consumption caused by these bacteria contributed to metmyoglobin (MetMb) formation from day 10. Functional analysis based on 16S rDNA sequencing predicted higher abundance of genes related to amino acid and lipid metabolism in HiOx-MAP bacterial communities compared to CO-MAP bacterial communities, which probably accelerated meat discoloration. Lactic acid bacteria dominated in CO-MAP steaks, in which Lactobacillus spp. and Lactococcus spp. contributed to improve redness and chroma, and reduce MetMb%, respectively. These findings help our understanding of color stability in CO-MAP steaks in comparison to HiOx-MAP steaks as influenced by the microbial community., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

This study explored the shelf-life and bacterial community dynamics of beef cuts stored at super-chilled conditions (-1 ± 0.5 °C) for 20 weeks when sourced from two Chinese abattoirs, in order to determine whether domestic beef has equivalent quality as that imported from Australia. The initial total viable counts (TVC) were 4.15 and 4.87 log CFU/cm 2 in beef from abattoirs A and B, respectively at the commencement of the storage period. The TVC of beef from abattoir A was above 6.0 log CFU/cm 2 at 6 weeks and kept below 7.0 log CFU/cm 2 at 20 weeks; while the counts were above 6.0 log CFU/cm 2 at 3 weeks and reached at 7.3~7.6 log CFU/cm 2 in beef from abattoir B. The beef shelf-life was deemed less than 12 and 9 weeks in abattoirs A and B, respectively, based on the total volatile basic nitrogen (TVBN) threshold, although all samples were acceptable organoleptically. High-throughput sequencing showed that the initial bacteria community and bacterial succession during storage were different between the two abattoirs. Carnobacterium spp. and Lactobacillus spp. dominated in both abattoirs throughout 3-9 weeks while Serratia spp. co-dominated in abattoir B, and Lactobacillus spp. and Carnobacterium spp. were dominant for the rest of storage in abattoir A and B, respectively. Overall, the high initial TVC is a concern compared to imported beef from Australia. To achieve comparable shelf-life, domestic super-chilled stored beef would need to be sourced from abattoirs employing effective decontamination technologies or where strict hygiene procedures are adopted., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

The aim of this study was to investigate the shelf-life and microbial community dynamics of super-chilled vacuum-packaged beef striploins imported from Australia to China after approximately five weeks of shipping time and an additional 15 weeks of storage at -1 °C ± 0.5 °C. Data analysis using a mixed model (REML) with time as the fixed effect and portion as a random effect, showed that the only beef quality trait that changed during storage was total volatile basic nitrogen (TVBN; P < .05), which reached the threshold of 15 mg/100 g between 15 and 20 weeks (including 5 weeks of transport). The total viable count (TVC) accounted for 78% of the variance in TVBN, when storage time was included in the model. Sensory scores decreased as storage time extended (P < .05), but were still acceptable at 20 weeks. After 9 weeks, Carnobacterium spp. and Lactobacillus spp. dominated alternately and then Lactobacillus became the most prevalent bacteria. An operational taxominc unit based hierarchical cluster analysis using the unweighted pair-group method with arithmetic means was performed and it was shown that the bacterial communities tended to be consistent as storage time extended. Overall indications are that beef which is safe can be imported into China from Australia and aged for extended periods., (Copyright © 2018 Elsevier Ltd. All rights reserved.)