The effect of different inoculum levels of Lactobacillus plantarum (10⁵, 10⁶ and 10⁷ CFU/g) on the quality characteristics and flavor profile of low-sodium dry sausage were explored in this study. The uninoculated sausage with 1.75% NaCl was regarded as a control. The pH, moisture content, water activity, shear force, lactic acid bacteria (LAB) count and Enterobacteria count of the four samples were measured on days 0, 3, 6 and 9 of fermentation and the flavor profiles were analyzed on the 9^th day by electronic nose (EN) and gas chromatography-mass spectrometry (GC-MS). The results showed that the moisture content and water activity of all treatments decreased gradually as the fermentation progressed; at the end of fermentation (day 9), the moisture contents and water activity of the LP6 and LP7 treatments were higher than those of the other treatments and the Enterobacteriaceae count of the LP7 treatment was the lowest among all treatments, while there was no significant difference in shear force among all treatments (P > 0.05). The pH of all treatments decreased gradually (except for day 0 of fermentation) with an increase in the inoculum level, and the LAB count increased gradually (except for day 6 of fermentation). Inoculation with L. plantarum increased the contents of acids and esters. The volatile compound contents of low-sodium dry sausages with different inoculum levels of L. plantarum were significantly different. Finally, sensory evaluation indicated that the overall acceptability of low-sodium dry sausage with an inoculum level of 10⁶ CFU/g was the highest, and its saltiness and sourness were moderate.

The effect of different salt contents (2.50%, 2.00%, 1.75% and 1.50%) on the flavor characteristics of air-dried sausages was explored by intelligent sensory technologies (electronic tongue and electronic nose) and gas chromatography-mass spectrometry (GC-MS). The results showed that the moisture content, water activity and lactic acid bacterial count increased gradually, while pH significantly decreased with the decrease in NaCl level (P < 0.05). The results of electronic tongue and electronic nose showed that the taste and odor characteristics of sausages with 1.75% and 2.00% NaCl were the closest to each other. Additionally, the contents of volatile compounds were significantly affected by NaCl level (P < 0.05). On the whole, salt reduction improved the formation of volatile compounds from carbohydrate metabolism and reduced the formation of volatile compounds from esterification. Finally, sensory evaluation indicated that the overall acceptability of sausages with 2.00% and 1.75% NaCl was the highest, but the saltiness of the sausage with 1.75% NaCl was not enough.

Quorum sensing (QS) is a communication mechanism between bacterial cells that can realize the expression of specific genes through the continuous accumulation of signal molecules. Quorum quenching can hinder the quorum sensing process by inhibiting or interfering with signal molecules, thereby slowing down the spoilage of specific foods and prolonging their shelf life. Therefore, quorum quenching plays a particularly important in food preservation. This article introduces the reader to different quorum sensing systems and the mechanism of quorum quenching. It reveals the great potential of quorum quenching in food preservation, which will provide a theoretical reference for food preservation.

In order to improve the hard texture, poor chewiness and unstable quality of traditional beef jerky, the effect of of ultrasonic power on the quality and myofibrillar protein structure of beef jerky, prepared by ultrasonic-assisted marination at different ultrasonic powers (0, 150, 300, 450 and 600 W) and 30 kHz frequency for 30 min followed by natural fermentation for six days, was explored. The quality characteristics of marinated beef strips and beef jerky such as moisture content, water activity, pH, color, salt content and shear force were evaluated. Meanwhile, changes in the myofibrillar fragmentation index (MFI), surface hydrophobicity, carbonyl group content, and total sulfhydryl and active sulfhydryl group contents of myofibrillar proteins in fresh beef strips after ultrasonic treatment were investigated and sensory evaluation of beef jerky were carried out. Results showed that the pH, moisture content, water activity, salt content, L^* value and b^* value of beef jerky increased with the increase in ultrasonic power, while the shear force decreased. Ultrasonic treatment increase the a^* value, whereas the opposite effect was observed at excessively high ultrasonic power. With the increase in ultrasonic power, the MFI, surface hydrophobicity, active sulfhydryl group content and carbonyl group content of myofibrillar proteins increased, while the total sulfhydryl group content decreased (P < 0.05). Sensory evaluation showed that beef jerky with ultrasonic treatment at 300 W had the best overall acceptability. In summary, to maintain color stability and avoid excessive oxidation of protein and energy waste, an ultrasonic power of 300 W was determined as the optimal treatment condition, which could significantly improve the overall quality of beef jerky.

A hydroxyl radical generating system consisting of 0.1 mmol/L FeCl₃, 0.1 mmol/L ascorbic acid, and various H₂O₂ concentrations (0, 0.25, 0.5, 1.0, 2.5, 5, 10 and 25 mmol/L) was established and used to investigate the interaction mechanism of differently oxidized myofibrillar proteins (MPs) with 3-methyl butanal, pentanal, hexanal and heptanal. First, the binding capacity of oxidized MPs to the four aldehydes were determined by gas chromatography-mass spectrometry (GC-MS). Then, ultraviolet (UV) absorption spectroscopy, fluorescence spectroscopy (quenching mechanism and thermodynamic analysis) and circular dichroism (CD) spectroscopy were used to reveal the interaction mechanism between oxidized MPs and aldehydes. The results showed that heptanal had the strongest binding capacity with MPs, and the binding capacity of oxidized MPs with a H₂O₂ concentration of 1.0 mmol/L to all four aldehydes was the highest (P < 0.05). UV absorption spectra and fluorescence spectra demonstrated that oxidized MPs interacted with the four aldehydes via static and dynamic quenching. The maximum absorption peaks of both tyrosine and tryptophan residues were red-shifted with an increase in heptanal concentration, indicating that the tyrosine and tryptophan residues of MPs were exposed to a more hydrophilic environment. Thermodynamic analysis showed that the interaction between MPs and heptanal was mainly driven by hydrophobic interaction. The CD spectra showed that the α-helix content decreased from 19.24% to 16.88% (P < 0.05) and the β-sheet content increased from 24.59% to 26.47% (P < 0.05) with increasing heptanal concentration, and the structure of MPs changed from the ordered to the disordered state. This study provides a theoretical basis for flavor regulation of meat products.

The level of cholesterol in the body is closely related to human health. Although cholesterol has many irreplaceable physiological functions, high cholesterol is one of the causes of many cardiovascular and cerebrovascular diseases. With more extensive and in-depth research on probiotics, many strains have been proved to have a good cholesterol-lowering effect, and their cholesterol-lowering effect has aroused more and more attention. Thus, the development and application of cholesterol-lowering probiotics have a bright future. In this paper, the mechanism of cholesterol synthesis and metabolism in the human body is briefly introduced in terms of its intake, synthesis, conversion and transport. The in vitro cholesterol-lowering mechanism of probiotics by absorbing and binding cholesterol as well as producing cholesterol-lowering metabolites, and the in vivo cholesterol-lowering mechanism of probiotics by inhibiting the intake and synthesis of cholesterol, promoting its transformation and regulating its transport are reviewed. Finally, the evaluation strategies for cholesterol-lowering probiotics are summarized including in vitro tests, animal experiments and clinical studies. This review is expected to provide a reference for the development of probiotic strains with a potent cholesterol-lowering effect.

Microorganisms are often affected by various environmental stresses (such as acid, heat, salt and oxidation) in the production and processing of fermented foods. Cross-protection refers to the phenomenon in which microorganisms are induced to increase stress tolerance after subjected to certain stresses. Improving microbial environmental tolerance with cross-protection is of great significance for improving the functional characteristics of microorganisms and promoting the development of the fermented food industry. In this paper, the cross-protection of microorganisms in fermented foods is reviewed. Furthermore, the response mechanisms of microbial cells under cross-protection are summarizes from the aspects of the cell wall and membrane barrier system, the intracellular pH regulation system, and the protein and amino acid regulation system, and possible strategies are suggested to improve the stability of microorganisms under stress conditions.

Gas chromatography-ion mobility spectrometry (GC-IMS) is a sensitive analytical technology for the detection, identification and monitoring of trace substances in different matrices, which enables secondary rapid separation and high-precision qualitative analysis of analytical substances through GC and IMS. With the advantages of environmental friendliness, ease of use, simple operation, and suitability for continuous large-scale industrial detection, GC-IMS has gradually become a popular analytical technology in the field of food authentication in recent years. In an effort to provide a theoretical reference for food authentication, this review introduces the types, structures, working principles, and analytical methods of GC-IMS, and focuses on its application in food authentication.

Chinese traditional fermented vegetables are made from fresh vegetables through microbial metabolism and a series of chemical reactions. During the fermentation process, the microbial community structure is complex, and the dominant microorganisms at different stages play different roles, which has a great impact on the quality, flavor and safety of fermented vegetables. Based on this, this article reviews the effect of the microbial diversity on the quality, flavor, and safety of Chinese traditional fermented vegetables as well as the abiotic factors affecting the microbial diversity, aiming to provide a theoretical basis for improving the quality and safety of fermented vegetables.

During the freezing, storage, and thawing process, physicochemical changes occur in raw meat, which will inevitably lead to quality deterioration mainly including decreased water-holding capacity and the deterioration of color and texture. The quality deterioration can be effectively reduced by novel freezing and its assistive technologies. This article summarizes the quality deterioration mechanism of raw meat during freezing and frozen storage, and reviews the approaches for improving frozen meat quality, such as novel freezing techniques, cryoprotectants, novel packaging techniques and novel thawing techniques, which will provide a theoretical basis and technical guidance for improving the quality of frozen meat.