Hye Sun Choi

Optimization for rice koji preparation using aspergillus oryzae CJCM-4 isolated from a korean traditional meju

To obtain a useful mold strain in rice-doenjang production, enzyme activities were investigated in rice and wheat koji prepared with 13 different strains isolated from traditional Korean meju. The CJCM-4 strain, which had been selected as a superior strain for the production of protease, was identified as Aspergillus oryzae by the gene sequence of the ITS-5.8S rDNA region as well as aflatoxin production capacity. The enzyme activities of koji prepared with CJCM-4 according to the polishing degree of rice bran were examined. The enzyme activities of koji prepared with 70% milling degree of rice bran were higher than those of other kojis. Protease activity showed its highest level on day 3 at 30°C. Glucoamylase activity showed its highest level on day 2 at 30°C. The optimum enzyme production of koji was determined at different conditions such as incubation time, temperature, moisture, and inorganic salt content. The optimum ratio of water added to the rice for the production of enzymes was 35% on the dry basis of the rice, and the optimum temperature was 25°C. When inorganic salts were added to increase enzyme activity, the combined addition of 0.15% CaCO3 and 0.05% NaH2PO4 resulted in the highest enzyme activities.

Quality Characteristics of Commercial Korean Types of Fermented Soybean Sauces in China

Sun Young Lee, Soo Hwa Baik, Yu Jin Ahn, Jin Song, Jae Hyun Kim, and Hye Sun Choi*Department of Agro-food Resources, National Academy of Agricultural Science, RDAAbstract Soybean-based fermented foods have been used as traditional condiments in Korea, Japan and China. ThirteenKorean types of soybean sauce that had been manufactured and sold in China were examined to evaluate their quality.The pH, salinity, and moisture content of the samples were pH 5.17-6.86, 8.0%-23.0%, and 46.446-70.40%, respectively.The amino-type nitrogen content was in the range of 199.18 to 736.46 mg%. The total aerobic bacterial counts were 4.83-7.89 Log CFU/g. The coliform count of gochujang (CNH-2) was 2.31 Log CFU/g, but none were detected in the othersamples. Moreover, Bacillus cereus counts from samples of doenjang and gochujang were in the range 2.00-4.09 LogCFU/g. The protease and amylase activity of samples were 379.02-781.36 unit/g and 5.29-63.27 unit/g, respectively.Keywords: China, fermented soybean paste, quality characteristics, fermentation

Quality Characteristics of Rice Cultivars Suitable for Rice Beer

본 연구에서는 쌀맥주 가공에 적합한 쌀 품종을 선정하기 위해 연질미 품종인 한가루, 설갱과 초다수성 품종인 다산1호 및 안다의 품질특성을 살펴보고 이를 이용하여 쌀맥주를 제조한 후 가공특성을 살펴보았다. 원료 쌀의 수분함량은 연질미인 한가루 및 설갱이 각각 14.48 및 14.62%로 다산1호 및 안다보다 높게 나타났...

Molecular and morphological identification of fungal species isolated from rice meju

The microflora of natural fermented Korean rice meju are assumed to be diverse, but has not yet been investigated. The fungi was isolated and identified from rice meju on the bases of morphology, culture characteristics, and molecular approaches of internal transcribed spacer and β-tubulin gene sequencing, and their enzyme activities were determined. Six species of fungi were primarily isolated from rice meju, specifically Aspergillus candidus, Aspergillus tritici, Cladosporium oxysporum, Penicillium commune, Penicillium griseofulvum, and Rhizomucor variabilis var. regularior. All isolates produced protease (5.17–15.78), and all strains except Mucor circinelloides PR06 expressed amylase activities (0.04–0.23). In comparison, lipase was produced by zygomycetous fungi isolates (1.70–0.25) and Aspergillus oryzae PR07 (0.68). The enzyme producing fungal strains might be involved in the rice meju fermentation. The identification of fungal diversity in meju is useful for understanding the fermentation processes and these strains might be used in the fermentation of foods.