The development of new techniques to rapidly and accurately detect bacteria has drawn continuous attention due to the potential threats posed by bacteria to human health and safety. Recently, a novel strategy based on fluorescent probes has drawn considerable interest for the detection of bacteria due to its high selectivity, fast response, and simple operation. In this review, we summarize the recent progress on fluorescent probes for the specific recognition and discrimination of Gram-negative and Gram-positive bacteria. In particular, we outline current design strategies, such as targeting of the differences in surface components, cell wall components, endogenous enzymes, surface charge, and hydrophobicity of various kinds of bacteria to develop various fluorescent sensors (organic small-molecule fluorescent probes, nanoprobes, and metal ion probes). We also emphasize the application of organic molecules in probe recognition elements. We hope that this review can stimulate this research area in bacterial detection and imaging in the future.

Yanbian cattle have a unique meat flavor, and high-grade meat is in short supply. Therefore, in this study, we aimed to improve the added value of Yanbian cattle low-fat meat and provide a theoretical reference for the subsequent development of an excellent starter. Rump meat from Yanbian cattle was dry-aged and then screened for protease-producing fungi. Three protease-producing fungi (Yarrowia hollandica (D4 and D11), Penicillium oxalicum (D5), and Meesziomyces ophidis (D20)) were isolated from 40 d dry-aged beef samples, and their ability to hydrolyze proteins was determined using bovine sarcoplasmic protein extract. SDS-PAGE showed that the ability of Penicillium oxalicum (D5) to degrade proteins was stronger than the other two fungi. In addition, the volatile component content of sarcoplasmic proteins in the D5 group was the highest (45.47%) and comprised the most species (26 types). Metabolic pathway analysis of the fermentation broth showed that phenylalanine, tyrosine, and tryptophan biosynthesis was the most closely related metabolic pathway in sarcoplasmic protein fermentation by Penicillium oxalicum (D5). Dry-aged beef-isolated Penicillium oxalicum serves as a potential starter culture for the fermentation of meat products.

Dry-aging is a postmortem process that can substantially enhance the texture and flavour of beef. This study entailed suspending Yanbian cattle M. gluteus medius in the aging cabinet, maintained at a temperature of 2–4 °C and a relative humidity of 85 ± 5% for 35 days. Throughout this period, samples were systematically collected every 7 days. The widely targeted metabolomic analysis has been used in this investigation to analyse the dynamic changes in Yanbian cattle metabolites during dry-aging. A total of 883 metabolites were identified, with amino acids and their metabolites representing the largest proportion. Multivariate statistical analysis showed that 373 metabolites were identified as differential metabolites that changed significantly during the dry-aging process, including metabolites of amino acids, glycerophospholipids, and nucleotides and their metabolites. Additionally, 308 metabolites exhibited various increasing trends with time in dry-aging. The analysis of KEGG pathway analysis showed that ABC transporters, glycerophospholipid, and arachidonic acid metabolism are the most important metabolic pathways during dry-aging. These findings can guide technological developments in the meat processing sector and provide valuable insights into the metabolic traits and pathways of Yanbian cattle during the dry-aging process.

This study investigated the effects of different concentrations (0.0005, 0.005, 0.05, 0.25, and 0.5%) of onion extract (OE) and onion peel extract (OPE) on the formation of four polycyclic aromatic hydrocarbons (PAHs) in charcoal-grilled pork patties. Both OE and OPE inhibited the formation of four PAHs in charcoal-grilled pork patties, with the highest inhibition rate reaching 88.33% on 0.50% OE addition and 98.79% on 0.05 and 0.25% OPE addition. OPE has greater inhibitory effect on the formation of four PAHs than OE does; this may be related to OPE's higher concentrations of flavonoids and higher free-radical scavenging activities. Both OE and OPE worked to lower thiobarbituric acid reactive substance values of charcoal-grilled pork patties. The inhibitory effect of OE and OPE on four PAHs showed the same trend as their antilipid oxidation effects, but the correlation was not strong. In addition to antilipid oxidation, other pathways are also involved in the inhibition of PAH formation.HIGHLIGHTSOPE exhibited stronger inhibitory effect on PAH4 than did OE.Inhibitory effects grew as the concentration of extracts increased, within limits.Inhibitory effect of extracts on PAH4 showed the same trend as antilipid oxidation effect.Antilipid oxidation was not the only pathway of inhibition of PAH4 formation.