As one of the five basic tastes, umami taste is an important sensory attribute of meat as well as an important index to evaluate the quality of meat. The umami taste of meat mainly comes from the umami substances in meat, such as amino acids, nucleotides and peptides. Umami substances have gradually become a research hotspot in the field of food umami science due to their characteristics of improving food flavor and enhancing people’s appetite. In order to provide a reference for theoretical research and practical application of meat umami substances, this article summarizes the classification, taste formation mechanism and influential factors of meat umami substances as well as the methods for the detection of the major umami substances in meat.

In this study, Staphylococcus, Candida and Penicillium that had been isolated and purified from commercial salmon, chicken breast and citrus in our laboratory were used as target microorganisms to explore the sterilization effect and mechanism of applying negative ions in the 4 ℃ cold storage room of a refrigerator. The results showed that negative ion treatment was effective in killing Staphylococcus, Candida and Penicillium in the cold storage room, and this effect increased with sterilization time (when the sterilization time was extended from 0.5 to 2 h, the sterilization efficiency of negative ions on Staphylococcus increased from 92.61% to 99.29%, and the sterilization efficiency on Candida from 61.45%to 98.26%; when the sterilization time was 1 h, the colony growth of Penicillium could be completely inhibited). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observation showed that negative ion treatment disrupted the structure of Staphylococcus, Candida and Penicillium cells, resulting in leakage of intracellular contents. After this treatment, the conductivity and absorbance values at 260 and 280 nm of the suspensions of Staphylococcus, Candida and Penicillium increased significantly, indicating that their cell integrity was damaged, resulting in leakage of intracellular nucleic acids and proteins. Fluorescein diacetate (FDA) staining showed that negative ion treatment significantly decreased the cell vitality of Candida and Penicillium. In addition, it completely inhibited the spore germination and germ tube formation of Penicillium. Therefore, negative ion treatment in the cold storage room of a refrigerator can destroy the cell integrity of Staphylococcus, Candida and Penicillium, reduce the cell vitality of Candida and Penicillium, and inhibit the spore germination and germ tube formation of Penicillium, thereby effectively killing these target microorganisms.