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To inhibit the development of adaptive acid tolerance response (ATR) and concurrent multiple stress resistance in Salmonella induced by the residual acid environment from carcass decontamination by organic acid spraying, the inhibitory effect of the addition of oregano essential oil and calcium chloride at different subinhibitory concentrations during acid adaptation on the ATR of Salmonella was investigated by determining the survival ability of Salmonella in acidic, thermal, hyperosmotic and oxidative environments before and after adaptation, and the possible mechanism was explored by determining the relative expression of stress resistance genes before and after treatments. The results indicated that the residual acid (pH 5.4) generated during carcass processing might induce ATR and heat-resistant cross-protection in Salmonella, suggesting a potential food safety risk. After 2 h treatment with hydrochloric acid at pH 3, the loss of the adapted strain in the 1/2 MIC oregano essential oil and 10 mmol/L CaCl2 treatment group increased by 1.32 (lg(CFU/mL)) compared with the control group, and oregano essential oil combined with CaCl2 had a synergistic inhibitory effect on ATR. The addition of oregano essential oil and calcium chloride during acid adaptation down-regulated the expression of the phoP and rpoS genes, which in turn intervened in the two-component system and global transcription factors, thereby suppressing ATR development. Sub-inhibitory concentrations of oregano essential oil inhibited the formation of the acid and heat resistance of acid-adapted Salmonella, but increased the resistance to hyperosmosis, whereas CaCl2 at a concentration of 10 mmol/L combined with sub-inhibitory concentrations of oregano essential oil reduced the osmotic resistance. The results of the current study help to understand the effects of essential oil and CaCl2 on the acid adaptation process of Salmonella and provide a theoretical basis for risk control for the use of organic acids in the beef industry.

Abstracts: In this study, the changes in autophagy and its relationship with beef quality during 14 days of postmortem aging were investigated. In terms of meat color, the L* value increased with aging time, and the a* and b* values increased first and then decreased; the tenderness increased, while the shear force and the expression of desmin decreased (P < 0.05). The water-holding capacity decreased during postmortem aging, while the purge loss and cooking loss increased (P < 0.05). Further studies on autophagy-related proteins showed that the expression of Beclin-1 and microtubule associated protein 1 light chain 3 (LC3), as the markers of autophagy, increased first and then decreased, reaching the maximum at 12 h. AMP-activated protein kinase (AMPK)-mammalian target of rapamycin (mTOR)-yeast Atg1 homolog unc-51 like kinase 1 (ULK1), as an important energy metabolic pathway, activated autophagy in an ischemia and hypoxia environment. During postmortem aging, the protein expressions of AMPK, p-AMPKThr172, and ULK1 all initially increased and subsequently decreased, reaching the maximum at 12 h. The expression of mTOR continuously decreased (P < 0.05), suggesting that autophagy was up-regulated from 0 to 12 h postmortem aging. Pearson correlation analysis showed that the expression levels of autophagy-related proteins were negatively correlated with meat color, but positively correlated with water-holding capacity and shear force during postmortem aging process (P < 0.05). In summary, autophagy could be activated through the AMPK-mTOR-ULK1 signaling pathway during the 336 h postmortem aging process, thereby regulating beef quality.

In order to explore the pork spoilage potential of Pseudomonas fragi and the antibacterial mechanism of garlic essential oil, P. fragi was isolated from chilled pork under aerobic storage conditions and tested its spoilage capacity. The isolates with strong spoilage capacity were selected for further investigation. The antibacterial activity of garlic essential oil against the selected strains was evaluated by determining the minimum inhibitory concentration (MIC) and plotting the bacterial growth curve. Furthermore, the antibacterial mechanism was investigated by scanning electron microscopic (SEM) observation as well as measuring cell membrane permeability, bacterial motility and metabolic activity. The results showed that P. fragi could cause pork spoilage. Garlic essential oil exhibited a strong inhibitory effect against P. fragi derived from pork, with a MIC of 0.125 μL/mL. Garlic essential oil could disrupt the normal structural morphology of P. fragi, enhance the permeability of the cell membrane, and inhibit bacterial metabolic activity and mobility. The results from this study can provide a theoretical foundation for the application of garlic essential oil as a natural food preservative.

This study investigated the effect of resveratrol on muscle fiber type transformation in bovine myotubes. Cell viability and related metabolic enzyme activities were measured by methyl thiazolyl tetrazolium (MTT) and colorimetric assays, and myogenic regulatory factors (MRFs), myosin heavy chains (MyHCs), and gene and protein expression related to mitochondrial biogenesis were determined. The results showed that resveratrol treatment significantly increased the gene expression of Myf5, Myf6, MyoG, and MyoD (P < 0.05) and promoted the differentiation of bovine myotubes. Resveratrol significantly increased slow MyHC expression and decreased fast MyHC expression, while upregulating the mRNA expression levels of MyHC I and MyHC IIa and downregulating the mRNA expression levels of MyHC IIx and MyHC IIb (P < 0.05). Resveratrol also significantly increased succinate dehydrogenase (SDH) and malate dehydrogenase (MDH) activity and decreased lactic dehydrogenase (LDH) activity (P < 0.05). In addition, resveratrol increased the gene and protein expression levels of silent information regulator 1 (SIRT1), peroxisome proliferator-activated receptor-gamma coactivator-1α (PGC-1α), nucleus respiratory factors-1 (NRF-1), mitochondrial transcription factor A (TFAM) (P < 0.05). Addition of the SIRT1 inhibitor 6-chloro-2,3,4,9-tetrahydro-1H-carbazole-1-carboxamide (EX527) significantly attenuated resveratrol-induced muscle fiber type transformation (P < 0.05), and the promoting effect of resveratrol on the gene and protein expression of SIRT1, PGC-1α, NRF-1, and TFAM (P < 0.05). Taken together, resveratrol can promote mitochondrial biogenesis and consequently muscle fiber type transformation by activating the SIRT1/PGC-1α signaling pathway.

As a key indicator to measure meat quality, meat color has always been the focus of attention in the meat industry. A large number of reactive oxygen species (ROS) are produced in the freshly slaughtered cattle carcass due to hypoxia and ischemia. The accumulation of ROS resultes in oxidative stress of the carcass, which further promotes the oxidation of myoglobin and adversely affectes the flesh color. However, currently there are few systematic reviews examining the effect of oxidative stress on meat color and its stability. In this article, the effects of oxidative stress on meat color and meat color stability are reviewed by regulating lipid oxidation, protein oxidation and degradation, and affecting the function of mitochondria to provide a theoretical rationale for maintaining good meat color by controlling post-mortem oxidative stress in the future.

With the increasing consumer demand for chilled meat, food safety issues related to chilled meat such as the prevalence and change of pathogenic bacteria during the processing, storage and consumption of chilled meat and their effects on public health have aroused great public concern. Quantitative microbial risk assessment (QMRA) is the core of chill meat safety risk analysis, which provides a theoretical basis for hazard analysis, determination of the critical control points and formulation of food safety goals and regulations. Since the promulgation of the Food Safety Law and the establishment of the Food Safety Risk Assessment Center in China, significant progress has been made in quantitative microbial risk assessment. In this paper, recent research on the quantitative risk assessment of common food-borne pathogens in livestock and poultry meat products is summarized, and recent progress in the application of process risk model, modular process risk model and omics technology in QMRA is reviewed. The current status of the application of quantitative microbial risk assessment in food safety management is summarized to provide reference for the development and application of quantitative microbial risk assessment in chilled meat.

China is a large agricultural country with a large annual output of straw resources. Compared with other straw treatment technologies, pyrolysis technology has the advantages of simple operation and high utilization value of products, but the traditional pyrolysis technology takes the combustion of fossil fuels as heat source, which has the problem of high energy consumption. Solar pyrolysis has attracted much attention because of its cleanliness and sustainability. To explore the feasibility of solar pyrolysis of straw. In this paper, the corncob biochar prepared by solar pyrolysis device and traditional pyrolysis device (muffle furnace and tube furnace) were compared. The experimental results show that the solar pyrolysis device can reach the pyrolysis temperature range of biomass, and the yield and physicochemical properties of the biochar obtained by the solar pyrolysis device are similar to those obtained by the traditional pyrolysis device. Therefore, the preparation of biochar by solar pyrolysis is a feasible method.

The aim of this study was to investigate the biological inhibiting effect of a beef‐derived Latilactobacillus sakei (RS‐25) on the spoilage of beef steaks in overwrapped packaging during the 12 days of storage at 4°C. Beef quality as well as microbial indicators were determined at different intervals during the storage after the inoculation of RS‐25 at the 6 log CFU/g, and the high‐throughput sequencing was applied to investigate the changes of microbial community structure during the storage. The inoculation of RS‐25 on beef had no effect (p >.05) on pH, TBARS, and TVB‐N during storage indicating the weak effect of such strain on the eat quality. Furthermore, the rise of L* and the delayed decline of a* and b* reveal the protection effect of RS‐25 on the meat color. RS‐25 reduced the re‐contaminated Salmonella typhimurium by 1.16 log CFU/g (p <.01), and the growth of Brochothrix thermosphacta was also inhibited but no inhibition was found on the Pseudomonas spp. at the first 6 days of storage. The inhibiting effect of RS‐25 was covered by the rapid growth of other microorganism during the following 6 days of storage. Consistent with the microbial counts results, high‐throughput sequencing analysis confirmed that the inoculated L. sakei RS‐25 was dominant at first 6 days, and then replaced by Pseudomonas spp. The findings obtained from the current study may provide basic information for the further application of bioprotective bacteria in preservation of beef steaks in the overwrapped packaging. [ABSTRACT FROM AUTHOR]