Changes of Physiochemical and Enzymatic Activities of doenjang Prepared with Different Amount of Rice koji during 30 Days of Fermentation

Abstract

Koji is an intermediate fermentation agent, made by inoculating known microorganisms in grains, such as rice, beans, and barley, to hydrolyze starch or protein. The quality of koji can influence the final quality of doenjang. This study aimed to investigate changes in the physiochemical and enzymatic activities of doenjang prepared with different amounts of rice koji during a 30-day fermentation period. Three doenjang samples were prepared with varying levels of rice koji: K1 (11% reduced), K2 (control), K3 (11% increased). Physiochemical characteristics including pH, TA, acid value, moisture content, color, sugar and reducing sugar content, and enzymatic activities including α- and β-Amylase, acidic and neutral protease activities. Samples were taken every 5 days for 30 days of fermentation period. The doenjang with a high content of rice koji had higher levels of total sugars, reducing sugars, alcohol, and protein enzyme activity than the doenjang samples with a lower content of rice koji (p < 0.05). However, no differences in the physiochemical and enzymatic activities were found between the doenjang made with a lower amount of koji and the control doenjang during fermentation (p > 0.05).

Combination of Solid State and Submerged Fermentation Strategies to Produce a New Jellyfish-Based Food

“…During fermentations controlled by bacterial and yeast strains, reducing sugars decreased, with the exception of samples inoculated with the bacterial B. amyloliquefaciens MS3 strain and the yeast D. hansenii BC T3-23 strain. These effects can be seen when, during fermentation, reducing sugars are produced by the decomposition of the starch material, and the content can increase if the production speed is faster than that used for microbial growth [ 76 ]. At the same time, the protein content reduced in all fermented Jellyfish paste samples throughout fermentation due to the decomposition of initial value [ 77 ].…”

Comparison of volatile aroma and sensory characteristics of doenjang and Korean‐style doenjang

“…Koji is an intermediate fermentation agent used in the mass production of commercial doenjang , made by inoculating Aspergillus oryzae into starchy substances such as rice or soybeans. Typically, koji is added to soybean fermentation, to accelerate the ripening process, as it contains hydrolyzed starch and proteins via enzymatic degradation attributed to A. orizae (Jo et al, 2021). Koji is generally used in the manufacture of improved meju .…”

“…The aroma intensity of Korean-style doenjang was significantly higher than that found in doenjang ( p < .05). Typical process of making doenjang (both doenjang and Korean-style doenjang) involves the separation of liquid and solid upon completion of fermentation(Jang et al, 2021;Jo et al, 2021), and the separated liquid became soy sauce, and the remaining solid became doenjang. Due to the manufacturing process, the presence of soy sauce aromatics in the doenjang sample is as expected and wasT A B L E 2 Sensory lexicons of doenjang and Korean-style doenjang.…”

The influence of packaging materials on the physiochemical properties, antioxidant properties, microbial community, and sensory characteristics of doenjang

“…Modified doenjang is made by making koji using barley or rice and aging it by mixing boiled beans and salt (Hong & Kim, 2020 Koji is manufactured by inoculating aspergillus oryzae to starchy materials and it contains amylase and protease produced by fungi, and its main role is to convert starch and protein in raw materials into fermentable sugars and amino acids. (Jo, Bang, & Kim, 2021; Lee et al, 2016). The traditional method of manufacturing doenjang utilizes Korean earthenware called onggi , which is a pot with yellowish brown glaze, for the further aging process to develop versatile flavors.…”