Comparison of quality indexes and volatile flavor components of natural and yeast-fortified fermented soy sauce before and after sterilization

To explore the effect of sterilization on the quality and flavor of soy sauce, using natural fermented soy sauce samples and yeast-fortified soy sauce fermented by Zygosaccharomyces and Candida versatilis (1:1) as the research objects, the physicochemical indexes, organic acid, free amino acid contents and volatile flavor components of the naturally fermented soy sauce samples (N₀, N₁) and yeast-fortified fermented soy sauce samples (F₀, F₁) before and after sterilization (90 ℃、20 min) were analyzed by conventional detection methods, high performance liquid chromatography (HPLC), and headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS), and partial least squares-discriminant analysis (PLS-DA) was carried out based detection results. The results showed that the total acid, amino acid nitrogen, and reducing sugar contents of natural fermented and yeast-fortified fermented soy sauce samples (N₁、F₁) after sterilization increased, while ethanol content decreased. The contents of organic acid and free amino acid of samples F₀ and F₁ were 3553.25 mg/100 ml, 3486.67 mg/100 ml; 6753.35 mg/100 ml, 6306.76 mg/100 ml respectively, which were both higher than the contents of organic acid and free amino acid contents of samples N₀ and N₁ (2804.97 mg/100 mL, 2832.39 mg/100 mL; 4913.20 mg/100 ml, 4802.95 mg/100 ml). A total of 63 volatile flavor components were detected in samples N₀, N₁, F₀ and F₁ . Among them, the volatile flavor components of sample F₁ was the most abundant (50), and the characteristic aroma substances such as ethyl oleate and 5-ethyl-4-hydroxy-2-methyl-3(2H)-furanone increased, the sterilization treatment of yeast-fortified fermented soy sauce could to a certain extent enhance the characteristic flavor of soy sauce.