Characterization of effector protein Hap determining meat spoilage process from meat-borne Aeromonas salmonicida.

The spoilage roles of effector proteins secreted by dominant spoilage bacteria during food spoilage remained unknown. In this investigation, a hemagglutinin protease (Hap) belonging to the M4 family metallopeptidase was identified from Aeromonas salmonicida 29 isolate. It, has a molecular weight of 33.5 kDa, a Vmax of 17.06 µg/mL/min, and a Km of 2.46 mg/mL, and is conserved in various dominant spoilage bacteria. The stability testing demonstrated that Hap could maintain specific activity in the common environments (pH, temperature, and metal ions) of chilled meat. It exhibited high spoilage ability on meat in situ, increasing TVB-N, pH values, and the production of volatile organic compounds (VOCs), which was consistent with proteolytic activity analysis, completely confirming the determinant role of Hap for meat spoilage. These observations will enrich the spoilage theory and provide new insights into the control of food quality and safety.

Stability of oil-in-water emulsions improved by ovalbumin-procyanidins mixture: A promising substrate with emulsifying and antioxidant activity.

The aim of this study is to develop a dual-functional ingredient with antioxidant activity and emulsification. The emulsion stability of ovalbumin (OVA) was improved by procyanidins (PC). The interactions between OVA and PC were investigated using multi-spectroscopy and molecular docking. Furthermore, the effect of the addition of the OVA-PC mixture on emulsion stability was evaluated as well. The fluorescence results showed that the quenching mechanism of PC to OVA's endogenous fluorescence was static quenching, and the binding ratio of OVA and PC was 1:1. Circular dichroism (CD) and Fourier Transform Infrared Spectrometer (FT-IR) showed that the addition of PC promoted the unfolding of OVA, and transformed the secondary structure of OVA from α-helix to ß-sheet. The main driving force of OVA and PC was hydrogen bonding, according to molecular docking analysis. Among all the samples, the stability of the emulsion of OVA-PC at a ratio of 1:30 exhibited extremely high stability and the smallest particle size. In comparison with individual OVA emulsions, the OVA-PC emulsions had excellent physical stabilities. Meanwhile, the oxidation degree of protein and oil for the OVA-PC emulsions was lower than that of the native OVA emulsion after 8-day storage. Our work provides important insights for understanding the interaction between OVA and expanding the application of OVA-PC.

Supplementation of egg white peptides on attenuating skin mechanical damage symptoms: a promising way to accelerate wound healing process.

Recent studies have indicated that active peptides can induce an improvement in wound repair. Herein, we evaluated egg white peptides (EWPs) as a nutritional supplement to improve mechanical skin damage in BALB/c mice. Two symmetrical circular full-thickness wounds were created with 5 mm biopsy punches in the skin of the mouse dorsal region, and EWPs (200, and 400 mg kg-1) were administrated by gavage for 14 days. We analyzed the EWPs for their in vivo and in vitro antioxidant capability, toxicity, and microscopy of skin wounds, and there was no cytotoxicity or in vivo toxicity. During the period of wound healing, EWPs could promote healthy cell migration, increase serum superoxide dismutase and catalase activities and accelerate the wound healing process in a time- and dose-dependent manner, whereas the levels of malondialdehyde and reactive oxygen species showed the opposite trend. After administration with 400 mg kg-1 EWPs for 10 days, the wound had almost healed. Meanwhile, EWPs significantly enhanced serum amino acids, particularly enhancing the content of Arg, Glu, Pro, Met, and Lys, which could provide sufficient nutrition in the wound healing process. The present study demonstrates that EWPs possess a positive potential to accelerate the wound healing process of mechanical skin damage at the cellular and animal level.