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.

The present study monitored bacterial succession, physicochemical properties, and volatile organic compounds (VOCs) changes in smoked chicken legs with modified atmosphere packaging (MAP, 60% CO₂ and 40% N₂) during a 25-day storage period at 4 ℃. After 15 days of storage, Serratia proteamaculans and Pseudomonas fragi became the predominant bacteria. Furthermore, physicochemical properties changed significantly, as evidenced by an increase in thiobarbituric acid reactive substances and b^* (yellowness) value, and a decrease in hardness. A total of 65 VOCs were identified during storage. Correlation between bacterial succession and quality indicators (including VOCs and physicochemical properties) allowed the identification of 26 core dominant bacteria, including S. proteamaculans, Psychrobacter alimentarius, Pseudomonas putida, and Pseudomonas poae, which were positively related to spoilage VOCs (e.g., 1-octen-3-ol, 1-pentanol, and 3-methyl-1-butanol) and could be defined as specific spoilage organisms (SSOs). The results of this study provide a systematic approach to predict SSOs in smoked chicken legs during storage, which can also provide a basis for product safety.

The effects of the co-inoculation of Debaryomyces hansenii separately with 3 lactic acid bacteria (LAB), Lactobacillus sakei, Lactobacillus plantarum and Lactobacillus curvatus, on the taste and odour profiles of dry sausages were investigated. The co-inoculated sausages showed higher free amino acid and organic acid contents than the non-inoculated control and sausages inoculated with D. hansenii alone. Meanwhile, the sausages inoculated with D. hansenii + L. plantarum, D. hansenii + L. sakei and D. hansenii + L. curvatus had the highest contents of aldehydes, esters and alcohols, respectively. The results of electronic tongue, electronic nose and sensory evaluation demonstrated that compared with the sausage inoculated with D. hansenii, the sour taste and floral odour increased and the fatty odour decreased in the sausage inoculated with D. hansenii + L. sakei; this was more favourable for the development of a desirable flavour in sausages. Moreover, the partial least squares regression analysis indicated that 10 taste and 33 odour compounds were mainly responsible for the differences in the flavour profiles among the sausages. Overall, these findings contributed to a more comprehensive understanding of the formation of sensory characteristics in dry sausages co-inoculated with yeast and LAB.