Desired soy sauce characteristics and autolysis of Aspergillus oryzae induced by low temperature conditions during initial moromi fermentation

Abstract

This is the first report on the effect of low temperature stress applied during initial moromi fermentation on the quality and taste of soy sauce. Koji was prepared to yield initial moromi under three comparative fermentation conditions over 9 days: (1) 4°C and 0% brine (i.e., water) (LTSF); (2) 4°C and 16% w/w brine (LTSH); (3) 25°C and 16% w/w brine (the control, CRTH). Greater extent of autolysis in samples was found under low temperature stress conditions (i.e., at 4°C, a temperature much lower than the normal temperature range like 25°C for natural microbial growth and performance). Compared to CRTH, LTSF had a twofold increase of glutaminase activity in dregs and 65.17% increase in supernatant, and after 60 days of moromi fermentation, a 5.73% and 3.47% increase, respectively, in the contents of glutamic acid (Glu) and aspartic acid (Asp). LTSF had the highest total free amino acid content due to both the low temperature stress and absence of salt. The intensity ranking of umaminess and kokumi sensation (LTSF [ LTSH [ CRTH) revealed by sensory analysis followed the changing trends of their umami and sweet amino acid contents with a trend reversal in the bitter amino acid content. Low temperature (4°C) without brine for initial moromi fermentation seemed beneficial, leading to a soy sauce product with desired taste and amino acid contents.

Enhancing Activities of Salt-Tolerant Proteases Secreted by Aspergillus oryzae Using Atmospheric and Room-Temperature Plasma Mutagenesis

“…Similar activity change trends of acidic proteases and neutral proteases in A. oryzae moromis were previously observed. , …”

“…The spore concentration in the resulting mixture was 1 × 10 6 spores/g dry mixture. Koji fermentation was conducted in an incubator at 28 °C, and then samples were periodically collected at 0, 4,8,12,16,20,24,28,32,36,40,44, and 48 h to analyze their protease activities. The activities of acidic proteases (pH 3.0), neutral proteases (pH 7.2), and alkaline proteases (pH 9.0) were determined using Folin−Ciocalteu phenol according to a previous method.…”

High Altitude Adaptability and Meat Quality in Tibetan Pigs: A Reference for Local Pork Processing and Genetic Improvement

“…The muscle amino acid composition of the three pig breeds varied significantly. In the context of the flavors they impart, amino acids are classified into umami amino acids, sweet amino acids, and bitter amino acids [41,42]. Among the breeds examined here, TP had the highest umami amino acid content, and QYP had the highest sweet amino acid content.…”

Development of a low‐salt soy sauce with enhanced flavor and functionality with soy residue andTenebrio molitorlarvae powder

“…The level of the free amino acid content followed the same trend as that of the protease activity (Figure 3), indicating that an LS or LSO could not result in a savory product. In general, the amino acids in soy sauce exhibit different taste characteristics: umami taste (glutamic and aspartic acids), sweet taste (glycine, serine, threonine, alanine, lysine, and proline), and bitter taste (valine, methionine, isoleucine, leucine, tyrosine, phenylalanine, histidine, tryptophan, and arginine) (Zhou et al, 2019). Overall, the most abundant amino acids in these soy sauces were glutamic acid (593–5600 mg/L), which is known to affect the taste of soy sauce and aspartic acid (102–4084 mg/L).…”