The Volatile Flavor Substances, Microbial Diversity, and Their Potential Correlations of Inner and Surface Areas within Chinese Qingcheng Mountain Traditional Bacon

Insights into the flavor contribution, mechanisms of action, and future trends of coagulase-negative staphylococci in fermented meat products: A review

During fermentation, meat is pre-treated and cured to cultivate a diverse microflora, resulting in fermented meat products with distinctive flavors. Coagulase-negative staphylococcus holds a crucial role in all fermented meat products, contributing to the breakdown of proteins, carbohydrates, and fats, and the creation of flavor compounds. Fermentation technology has important research value and significance in fermented meat products. The optimization and improvement of flavor by CNS can be achieved by regulating the fermentation environment, initial microflora and processing conditions. The review explores the ways in which coagulase-negative staphylococci contribute to the flavors in fermented meat products. The mechanism of flavor substance formation and means of regulation in coagulase-negative staphylococci were also investigated. The review concludes by summarizing future development trends and drawing conclusions.

Investigating Flavor Enhancement Methods in NaCl-Reduced Chinese Bacon (Larou) by Focusing on Physicochemical Characteristics, Bacterial Diversity, and Volatiles

The higher NaCl concentration of Chinese bacon, which features a unique flavor, is a major restriction to consumption. Investigating the role of NaCl in Chinese bacon (Larou) would be beneficial to optimize the dosage and enhance flavor. This study was conducted to categorize Larou by comparing the quality of Larou cured with different concentrations of NaCl and then to investigate the methods of flavor enhancement of NaCl-reduced Larou. The results showed that, based on the differences in quality, Larou were categorized into three types, including the low-NaCl type (<4%, LT), the medium-NaCl type (4-8%, MT), and the high-NaCl type (>8%, HT). The vital physicochemical characteristics (PCs), predominant bacteria, and key volatile compounds (VOCs) were different for each type of Larou. The PCs contributing to the regulation of VOCs were total volatile basic nitrogen (TVB-N) and pH in LT, thiobarbituric acid reactive substance assay (TBARS) in MT, NaNO2, and moisture content in HT. Lactococcus or Lactobacillus, Staphylococcus, and Kocuria were flavor-producing bacteria in LT, MT, and HT, respectively. Vital PCs and predominant bacteria were associated with several key aldehydes, alcohols, and esters in Larou. Increasing the TVB-N, TBARS, and moisture content, decreasing the pH and NaNO2 properly, and inoculating with Staphylococcus and Kocuria were effective methods to enhance the flavor of LT. Vital PCs and predominant bacteria are prioritized to meet most of the quality and the biosafety, although key VOCs may be sacrificed at this point.

Occurrence of ochratoxin A in Sichuan bacon from different geographical regions and characterization and biocontrol of ochratoxigenic Aspergillus westerdijkiae strain 21G2-1A

Sichuan bacon represents the most prevalent dry-cured meat product across Southwest China, but it is vulnerable to fungal spoilage. In the present study, a total of 47 Sichuan bacons were obtained from different regions of the Sichuan Province and analyzed for the presence of ochratoxin A (OTA), yielding a positive rate of 23.4 % (11/47). All the observed OTA concentrations exceeded the maximum admissible dose in meat products (1 μg/kg) established by some EU countries, with the highest OTA concentration being 250.75 μg/kg, which raises a food safety concern and reveals the need for a standardized scientific processing protocol. Then, an OTA-producing fungus named 21G2-1A was isolated from positive samples and found to be Aspergillus westerdijkiae. Further characterization suggested a positive correlation between fungal growth and OTA production. The optimal temperature for the former was 25 °C, while it was 20 °C for the latter. Although the A. westerdijkiae strain 21G2-1A demonstrated greater mycelium growth in the presence of NaCl, OTA production was significantly dismissed when the salinity was greater than 5 %. Four lactic acid bacteria (LAB) were screened out as antagonists against the ochratoxigenic fungus. In vitro evaluation of the antagonists revealed that live cells inhibited fungal growth, and adsorption also contributed to OTA removal at different levels. This study sheds some light on OTA control in Sichuan bacon through a biological approach.

Evaluation of Dynamic Changes of Volatile Organic Components for Fishmeal during Storage by HS-SPME-GC-MS with PLS-DA

Headspace solid-phase microextraction, combined with gas chromatography-mass spectrometry and partial least squares discriminant analysis, was adopted to study the rule of change in volatile organic compounds (VOCs) for domestic and imported fishmeal during storage with different freshness grades. The results showed that 318 kinds of VOCs were detected in domestic fishmeal, while 194 VOCs were detected in imported fishmeal. The total relative content of VOCs increased with storage time, among which acids and nitrogen-containing compounds increased significantly, esters and ketones increased slightly, and phenolic and ether compounds were detected only in domestic fishmeal. Regarding the volatile base nitrogen, acid value, pH value, and mold counts as freshness indexes, the freshness indexes were significantly correlated with nine kinds of VOCs (p < 0.05) through the correlation analysis. Among them, volatile base nitrogen had a significant correlation with VOCs containing nitrogen, acid value with VOCs containing carboxyl group and hydrocarbons, pH value with acids which could be used to adjust pH value, and mold counts with part of acids adjusting pH value and VOCs containing nitrogen. Due to the fact that the value of all freshness indexes increased with freshness degradation during storage, based on volatile base nitrogen and acid value, the fishmeal was divided into three freshness grades, superior freshness, corrupting, and completely corrupted. By using partial least squares discriminant analysis, this study revealed the differences in flavor of the domestic and imported fishmeal during storage with different freshness grades, and it identified four common characteristic VOCs, namely ethoxyquinoline, 6,7,8,9-tetrahydro-3H-benzo[e]indole-1,2-dione, hexadecanoic acid, and heptadecane, produced by the fishmeal samples during storage, as well as the characteristic VOCs of fishmeal at each freshness grade.