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Theaflavin 3,3′‐digallate (TF3), a major polyphenolic component of black tea, exhibits antibacterial effects against many foodborne pathogens. However, the antibacterial mechanisms of TF3 against Listeria monocytogenes remain unclear. In this study, we investigated the effects of TF3 on viability, biofilm, and membrane function of L. monocytogenes by the conventional plating method, crystal violet staining, and microscopy using fluorescent dyes JC‐1 and Laurdan, respectively. It was found that TF3 showed excellent antibacterial activity against L. monocytogenes with the minimum inhibitory concentration of 62.5 mg/L. The viable count determined on TSA decreased by 3 log after the treatment for 2 h with TF3 at 62.5 mg/L. The viable count determined on TSA containing 4% NaCl decreased by more than 4 log after the treatment for 30 min with TF3 at the same concentration, suggesting that TF3 gave damage on the cells, enhancing the antibacterial action of 4% NaCl, but the damage was recoverable in the absence of 4% NaCl. To explore the antibacterial mechanisms of TF3, the effects of TF3 on membrane potential and membrane fluidity were investigated. TF3 reduced both membrane potential and fluidity of L. monocytogenes at 62.5 mg/L, suggesting that TF3 damaged the structural integrity of the cell membrane. TF3 reduced biofilm mass of mature biofilm of L. monocytogenes. Moreover, THEAFLAVIN TF40, a commercially available Camellia sinensis leaf extract containing TF3, reduced viable count of L. monocytogenes by 2 log on apple skin. These results suggest the potential of theaflavins as a natural anti‐Listeria disinfectant. [ABSTRACT FROM AUTHOR]

Objective: This study aimed to investigate the impact of different ultrasonic power and time pretreatments on the structures and gel properties of the flaxseed gum and soybean protein isolate composite gel induced by TG enzyme. Methods: The structural characteristics, molecular conformation, and micro-network structures of the composite gel under varying ultrasonic conditions were analyzed using a texture analyzer, laser particle size meter, circular dichroism (CD), fluorescence spectrum, and scanning electron microscope (SEM). Results: The 50% power ultrasound pretreatment for 10 min could significantly improve the hardness, adhesiveness, chewiness, cohesiveness and water-holding property of the composite gel, and reduce its adhesiveness. After 50% power ultrasound pretreatment for 10 min, the α-helix and β-turn content of composite gel proteins decreased, and the content of β-folding and irregular curls increased, and the fluorescence intensity increased, which was conducive to the improvement of the functional properties of the gel. The microstructure of the composite gel became ordered from disorder, the network density increased, the pore diameter became smaller, and the pore wall was thickened. While after increasing the ultrasound power to 80%, the gel properties fluctuated only slightly and the microstructure was destroyed. Conclusion: 50% power ultrasound pretreatment for 10 min can significantly improve the gel properties and network structure of TG enzyme cross-linked flaxseed gum-soybean protein isolate composite. [ABSTRACT FROM AUTHOR]

A novel processing method of potato flour with a low starch gelatinization degree was realized by flash drying technique. Starch gelatinization degree, pasting properties, thermal characteristics, and morphological features between commercial potato flours (commercial potato flake and commercial potato granule) and flash-dried potato flour were analyzed and compared. Results showed that the gelatinization degree of flash-dried potato flour (14.52%) was reduced by nearly 80% than the commercial potato flours (about 95%). Typical viscosity profile, enthalpy value, and morphology features of flash-dried potato flour were retained maximally through an optimized processing of flash drying. The gelatinization temperature and pasting viscosity of flash-dried potato flour were increased significantly than the commercial potato flour. Besides, the intact morphological structure of flash-dried potato flour granules were kept due to the processing of flash drying. By utilizing the low gelatinization degree of flash-dried potato flour, desirable potato noodles were prepared with the ratio of potato flour up to 50%. Textural characteristics and cooking performance such as broken rate and cooking loss of flash-dried potato noodles were superior to these of the commercial potato flours (in the same amount) added noodles. [ABSTRACT FROM AUTHOR]

Clostridium perfringens is a major cause of foodborne disease in developed countries. The aim of this study was to isolate and characterize phages specific to C. perfringens to evaluate the most efficient phage cocktail for the biocontrol of C. perfringens , both in vitro and in curry roux. In this study, four phages were isolated from chicken meat and were morphologically and genetically characterized along with two phages previously isolated in our laboratory that display different host lysis spectra. Phage cocktail CP11, consisting of phages CPQ3, 7, 8, and 10, showed the broadest host range. Electron micrograph images suggested that all four phages belong to the Podoviridae family, and none of them carry any antibiotic resistance or toxin genes. Notably, the phages were stable at various pH values and in curry roux. Cocktails consisting of six, five, and four phages at the same concentrations were examined to determine the most effective phage cocktail. Phage cocktail PC11 significantly decreased the viable count of C. perfringens to a value less than the lower detection limit up to 48 h at both 8 and 37 °C in broth and at 24 °C in the curry roux. These results suggest that phage cocktail PC11 is a promising natural biocontrol agent against C. perfringens in vitro and in curry roux. • Phage cocktail PC11, including CPQ 3, 7, 8, and 10, displayed the broadest lytic spectrum. • Some phage cocktails suppressed the regrowth of resistant bacterial cells. • Phage cocktail PC11 displayed strong lytic activity in broth and curry roux. [ABSTRACT FROM AUTHOR]

Salmonella enterica subsp. enterica serotype Typhimurium (S. Typhimurium) is one of the most prevalent foodborne pathogens responsible for food poisoning and is spread through the consumption of contaminated poultry products. In this study, four antimicrobial peptides (AMPs) with varying hydrophobicity and helical structure-forming tendencies were designed and synthesized based on the amino acid sequences of peptides from egg white hydrolysate. Two of these AMPs, P1R3 (KSWKKHVVSGFFLR) and P1C (KSWKKHVVSGFFLRLWVHKK), exhibited inhibitory activity against S. Typhimurium and compromised its biofilm-forming ability. Investigation of their modes of action revealed that P1R3 and P1C interact with and permeabilize the cytoplasmic membrane of bacteria, leading to membrane potential dissipation, damage to membrane integrity, and consequent bacterial death. P1R3 also bound to S. Typhimurium DNA, resulting in DNA aggregation or precipitation. Moreover, both peptides showed negligible cytotoxicity to Vero cells, and P1C displayed significant antimicrobial activity in chicken meat. Peptides P1R3 and P1C, therefore, have the potential to be developed as promising food preservatives, especially against pathogenic S. Typhimurium. • P1R3 and P1C with higher helicity and hydrophobicity exhibited improved antimicrobial activities. • P1R3 and P1C damaged membrane functions. • P1R3 and P1C exhibited low cytotoxicity to mammalian cells. • P1C reduced viability of S. Typhimurium in chicken meat at 4 °C. [ABSTRACT FROM AUTHOR]