Qingxin Zhou

The quality modification of chilled, raw conditioned mutton (RCM) after storage significantly impacts consumer preferences, making shelf-life extension and quality preservation crucial. This study evaluated the effects of sodium diacetate (SDA), sodium dehydroacetate (DHA-S), ε-polylysine hydrochloride (PLH), and nisin on RCM quality and bacterial community at concentrations of 3.0, 0.50, 0.30, and 0.50 g/kg, respectively. Major spoilage bacteria were isolated, and the inhibitory effects of these preservatives were studied, leading to the development of compound preservatives. TVC increased significantly during RCM preparation, with continuous increases in TVC and TVB-N levels throughout storage, reaching spoilage thresholds by day 5. Bacterial diversity decreased markedly, with Brochothrix and Pseudomonas dominating. SDA effectively inhibited TVC proliferation and TVB-N formation, maintaining bacterial diversity and reducing Brochothrix and Pseudomonas abundance while promoting the growth of lactic acid bacteria. Five spoilage bacteria strains were isolated, including Serratia liquefaciens B2107-1, a potent meat spoilage bacterium under refrigeration. PLH and SDA demonstrated significant inhibitory activity against this bacterium, with minimum inhibitory concentrations (MICs) of 0.175 and 0.400 mg/mL, respectively. Combining PLH and SDA at 1MIC + 3MIC exhibited a synergistic antimicrobial effect, maintaining RCM quality with reduced SDA usage. These findings demonstrate the significant potential of these preservatives in chilled, raw meat products.

Cronobacter sakazakii (C. sakazakii) widely exists in the environment and is a common foodborne pathogenic microorganism. It can cause meningitis, bacteremia, and necrotizing enterocolitis in infants and elderly people with low immunity. Therefore, the development of the rapid detection method for foodborne pathogen C. sakazakii is very important for food safety control. This study has developed a kind of genomic nucleic acid reference material as a positive reference for the rapid detection of C. sakazakii in the edible fungus Flammulina velutipes. First, the genomic nucleic acids were extracted from the standard strain of C. sakazakii, and the nucleic acids were lyophilized. The uniformity test result of the lyophilized powder showed that there were no significant differences between samples. In short-term stability tests at 4°C and 37°C for 14 days, the properties of the nucleic acid reference material were good, and in long-term stability tests at 4°C and 20°C for 8 months, the samples are still stable. To verify the application of this nucleic acid reference material, it was used as a positive control template for PCR detection and applied to the rapid detection of C. sakazakii in F. velutipes. It was found that 13 of the 15 F. velutipes samples were positive for C. sakazakii. As far as we know, this is the first attempt to detect C. sakazakii in F. velutipes using the PCR method with nucleic acid reference material as the positive reference. This study is helpful in promoting the extensive and in-depth application of nucleic acid reference materials in foodborne pathogens detection.

We investigated the effects and possible mechanisms of Bacillus amyloliquefaciens NCPSJ7 against the gray mold caused by Botrytis cinerea in the postharvest Red Globe grapes. The disease incidence, lesion diameter, decay index, and some resistance‐related enzymes were evaluated. The antioxidant capacity of grape treated with 1 × 10⁴ CFU/ml B. cinerea alone and combined with 1 × 10⁷ CFU/ml NCPSJ7 was also determined. The results showed that NCPSJ7 + B. cinerea reduced the disease incidence, lesion diameter, and decay index of postharvest grapes and enhanced the activities of polyphenol oxidase, peroxidase, chitinase, and β‐1,3‐glucanase during different storage periods. Furthermore, the oxidative resistance, demonstrated by an escalating trend in the total phenolic content, DPPH free radical clearance rate, reducing power, and superoxide anion clearance rate after lesion presence, was improved. However, NCPSJ7 showed an inhibitory effect on gray mold, but resulted in the reduced antioxidant capacity in the grapes.

Pullulan, with its excellent characteristics of film-forming, water solubility, and biodegradability, is attracting more and more attention in agricultural products preservation. However, high pullulan production cost largely restricts its widely application due to its low production. In order to improve pullulan production by Aureobasidium pullulans NCPS2016, the medium was optimized using single factor experiment and response surface methodology. Based on the single factor experiments, the contents of soybean meal hydrolysates (SMHs), (NH₄)₂SO₄, and K₂HPO₄·3H₂O were considered to be main factors influencing the extracellular polysaccharide (EPS) production, and were further optimized by Box–Behnken design. The optimal content of SMHs of 7.71 g/L, (NH₄)₂SO₄ of 0.35 g/L, and K₂HPO₄·3H₂O of 8.83 g/L were defined. Finally, EPS production of 59.8 g/L was obtained, 39% higher in comparison with the production in the basal medium. The purified EPS produced by NCPS2016 was confirmed to be pullulan. This is the first time fructose is reported to be the optimal carbon source for pullulan production by Aureobasidium pullulans, which is of great significance for the further study of the mechanism of the synthesis of pullulan by NCPS2016. Also, the results here have laid a foundation for reducing the industrial production cost of pullulan.