The formidable biofilm-forming ability of Pseudomonas fluorescens enables its persistent contamination under distribution conditions (0 - 4℃) of chilled meat, yet the mechanisms governing its biofilm formation remain inadequately explored. In this study, with 25℃ serving as the control, P. fluorescens developed more substantial and architecturally coherent biofilms at 4℃ during 96 h-incubation, accompanied by increased extracellular polymeric substances synthesis. This response phenotype enhanced cell adhesion to facilitate persistence and increased the cross-contamination after multiple cell transfers. Transcriptomic analysis revealed that 514 differentially expressed genes (DEGs) were up-regulated and 327 DEGs were down-regulated, which were involved in fatty acid degradation, flagellar assembly, lysine degradation, pyruvate metabolism, etc. Notably, as primary regulatory pathways, flagellar assembly and fatty acid metabolism suggested they could facilitate microbial accumulation and the efficient conversion of fatty acids, respectively. Correspondingly, changes in flagellar assembly-related genes and fatty acid degradation-related genes were consistent with transcriptome results. In view of these, the apparent reduction in motility and the increase in unsaturated fatty acid content, along with the enhancement of cell surface hydrophobicity and auto-aggregation, further verified the above-mentioned pathways. This study provided insights into formation mechanism of P. fluorescens biofilm and the development of control strategies.

Mixed biofilms formed with the coexistence of spoilage bacteria and foodborne pathogens represent a significant cause for persistent microbial contamination in the food industry. Deciphering the interspecies interaction mechanisms is a critical prerequisite for developing effective control strategies. This study systematically investigated the interaction mechanisms within dual-species biofilms of Pseudomonas fluorescens and Listeria monocytogenes. Results found that the dual-species biofilms exhibited significantly enhanced tolerance to sodium hypochlorite, with a higher survival rate than mono-species biofilms after 20 min treatment (P < 0.05). Dual RNA-Seq analysis revealed that P. fluorescens activated pathways related to the two-component system, flagellar assembly, fatty acid metabolism, and quorum sensing (QS) in the co-culture system. In response, L. monocytogenes regulated numerous genes and pathways, such as chemotaxis, two-component system, flagellar assembly, phosphotransferase system, and amino acid biosynthesis. The cell-free supernatant (CFS) from the co-culture significantly promoted biomass accumulation, increased matrix thickness, and reduced roughness in mono-species biofilms (P < 0.05), suggesting that metabolites could act as positive signaling molecules in this process. The autoinducer-2 (AI-2) concentration in the co-cultured CFS was significantly higher than that in mono-cultured CFS (P < 0.05). In addition, exogenous addition of AI-2 enhanced the biofilm formation of P. fluorescens and dual-species in a concentration-dependent manner (P < 0.05), confirming the key regulatory role of QS in this process. This study provided new insights into the synergistic mechanisms of dual-species biofilms and the development of control strategies.

Freezing is one of the oldest and most widely used preservation methods for maintaining meat quality and safety. However, during the production, storage, sale and consumption processes, frozen meat will constantly undergo the freezing and thawing process due to the imperfect cold chain system and eating habits. The recrystallization of ice crystals during freeze-thaw cycles leads to cellular contraction and ultrastructural damage, induces and accelerates fat hydrolysis, lipid oxidation, protein oxidative denaturation, conformational changes, and spatial reorganization, seriously affects the stability of the meat system, and causes a series of problems such as the decline of meat quality and the loss of commercial value. Therefore, this review comprehensively examines the effects of freeze-thaw cycles on key quality attributes of raw meat, including color, tenderness, water-holding capacity, lipid oxidation, protein oxidation and degradation. Furthermore, it summarizes and compares the principles, effectiveness, and limitations of current techniques for identifying frozen-thawed meat including enzyme-based, DNA fragmentation-based, bioimaging-based, and spectroscopic techniques. Special emphasis is placed on the application of spectroscopic techniques-specifically Raman spectroscopy, infrared spectroscopy, and hyperspectral imaging-for identifying frozen-thawed meat. This review aims to provide theoretical foundations and research perspectives for enhancing the quality control of frozen meat and developing novel technologies for identifying frozen-thawed meat.

Low-temperature storage is currently the most widespread method for meat preservation, during which the temperature has a great impact on meat quality. Therefore, the effect of common low-temperature storage methods, including chilled, super-chilled, controlled freezing-point, and frozen, on meat quality preservation is discussed herein. The focus is on the differences in the color, water-holding capacity, tenderness, lipid oxidation, microbial growth and shelf life caused by different storage temperatures and the underlying mechanism. We anticipate that this review will theoretically guide the practical application of different low-temperature storage methods in the meat industry.

Meat quality characteristics such as color, tenderness and water-holding capacity are always important factors affecting consumer willingness to purchase meat. Muscle energy metabolism can affect the growth, development and aging process of meat, and ultimately meat quality. The phosphocreatine system, the glycolysis pathway and oxidative phosphorylation are the main sources of ATP in muscle and play a major role in different postmortem phases. The internal environment of muscles changes after animals are slaughtered for bloodletting, and different energy supply modes will affect the energy metabolism process, thus affecting the conversion of muscle to meat. This paper reviews the pathways of postmortem muscle energy metabolism and the effects of energy metabolism on the development of meat quality. It also highlights the effects of AMP-activated protein kinase (AMPK) and silent information regulators (SIRTs) on the metabolic process. The findings of this review can provide new ideas for regulating the development of meat quality through energy metabolism.

To investigate the effect of ultra-fast prerigor freezing on beef quality, beef was subjected to conventional chilling (CC, chilling at 4 ℃), ultra-fast chilling (UFC, chilling at -30 ℃ until the internal temperature dropped to 12 ℃) or ultra-fast freezing (UFF, freezing at -30 ℃ until the internal temperature dropped to -10 ℃) and then stored at (0 ± 2) ℃ until 24 h postmortem. Beef tenderness, water-holding capacity (WHC) and other quality characteristics were measured. The results showed that UFF was more effective in improving beef tenderness during storage when compared with CC and UFC. UFF maintained a higher pH environment by slowing down the decrease in pH, thereby promoting the early degradation of myofibrillar proteins (desmin, troponin-T, and μ-calpain), disrupting myofiber structure, and resulting in elevated myofibril fragmentation index (MFI). These changes had a positive effect in improving muscle tenderness. Meanwhile, UFF reduced the cooking loss but increased the storage loss of beef. Overall, prerigor UFF treatment can improve the tenderness of beef.

Meat quality is closely related to consumer experience and the benefits of deep processing enterprises, and it is influenced by diverse and complex factors. Recently, the impact of ubiquitination on meat quality has attracted increasing attention, and multiple studies have confirmed its crucial role in meat quality. This paper reviews the literature on the effect of ubiquitination on postmortem muscle energy metabolism, and discusses the potential mechanisms through which ubiquitination affects meat tenderness, color, water-holding capacity, and fat content. Furthermore, it highlights the regulatory mechanisms of protein ubiquitination on meat tenderness in terms of the ubiquitin-proteasome system and the apoptotic pathway. This review is anticipated to enhance the understanding the mechanism through which ubiquitination affects meat quality, thereby laying a theoretical foundation for regulating meat quality through ubiquitination.

Myofibrillar protein is a salt-soluble protein that determines the quality of muscle, and its heat-induced gel properties directly affect the quality of emulsified and minced meat products. Meat researchers worldwide have been interested in the factors affecting the gel properties of myofibrillar protein. Structural and functional modification of myofibrillar proteins can improve the functional properties of myofibrillar protein gels. Currently, the main strategies for modifying myofibrillar proteins include addition of exogenous substances and physical treatments. However, a comprehensive summary of the effects of different treatments on the structure and function of myofibrillar proteins is lacking. Therefore, this review focuses on the various factors that affect and improve the gel properties of myofibrillar proteins and their mechanisms of action in terms of the environment in which the proteins exist, physical modification techniques and exogenous additives, clarifying that different environments in which myofibrillar proteins exist and physical modification techniques affect their gel properties by altering their conformation and that exogenous additives affect their gel properties by binding to the proteins to form aggregates. This review provides a theoretical reference for enhancing the quality of gelled meat products.

Fresh meat and meat products are prone to microbial contamination due to the presence of plentiful water, proteins and other nutrients, causing huge economic loss to the meat industry. With increasing consumer demand for green and natural meat products, lactic acid bacteria (LAB) have become an excellent alternative to traditional antibacterial agents by virtue of their natural availability and sustainable protective effect. However, a systematic review of the antibacterial mechanism and application in the meat industry of LAB is still lacking today. Therefore, this article outlines the major antibacterial mechanism of LAB as biological antibacterial agents (such as by production of organic acids and bacteriocins as well as competitive inhibition), and it also summarizes the current status of research on the effect of LAB on ensuring the safety of fresh meat and meat products under different packaging methods, different application methods, various metabolic environments or processing conditions, fluctuating temperatures. Moreover, this article discusses the impact of LAB on the quality of meat products and the safety of LAB applied in meat products. Finally, it concludes with future prospects for LAB application in the meat industry.

The growth and metabolism of microorganisms is the main cause of meat spoilage. The rapid and nondestructive techniques for detecting microorganisms in meat have attracted more and more attentions. Spectroscopic techniques such as Raman spectroscopy, infrared spectroscopy and spectral imaging show great advantages in rapid and non-destructive detection, but their application in meat spoilage detection has not been timely summarized. Based on an overview of the dominant spoilage organisms and microbial metabolism in meat under different storage conditions, this paper briefly describes the material basis for spectroscopic prediction of meat spoilage. Then, the application of Raman spectroscopy, infrared spectroscopy and spectral imaging technology in predicting the shelf life of meat is summarized. The efficiency of predictive modeling of meat shelf life based on total bacterial count or total volatile basic nitrogen (TVB-N) content and problems existing in this field are highlighted. We anticipate that this review will provide new ideas and theoretical guidance for the development and application of rapid and nondestructive techniques for meat spoilage identification.