• Korean journal of food and cookery science
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• v.29 no.3
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• pp.267-274
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• 2013

Demand for a rice cake, a popular traditional food in Korea, is rising, but its industrial-scale production is extremely difficult due to its short shelf-life caused by starch retrogradation and microbial spoilage. By means of the sourdough fermentation technique, we attempt to develop rice cakes with a longer shelf-life. Heterofermentative lactic acid bacteria (Weissella koreensis HO20, Weissella kimchii HO22) isolated from kimchi were used to ferment wet-milled rice flour for their abilities to produce exopolysaccharides and to inhibit the microbial spoilage of rice cakes. After 24 hr of fermentation at $25^{\circ}C$, viable cell counts in rice dough increased from $10^6$ CFU/g to $10^8$ CFU/g and total titratable acidity increased from 0.05% to 0.20%, whereas pH decreased from 6.5 to 5.1. Fermented rice flour showed significantly lower peak, trough, and final viscosities as well as breakdown and setback viscosities measured by rapid viscoanalyzer. Both lactic acid bacteria showed in vitro antifungal activity against Penicillium crustosum isolated from rice cakes. The antifungal activity remained constant after the treatments with heat, proteinase K and trypsin, but fell significantly by increase of pH. Rice cakes made of fermented rice flour were found to retard mycelial growth of P. crustosum. The degree of retrogradation as measured by the hardness of the rice cake was significantly reduced by the use of fermented rice flour. The results suggest that use of fermented rice flour has a beneficial role in retarding starch retrogradation and in preventing fungal growth, hence extending the shelf-life of rice cakes.

• Microbiology and Biotechnology Letters
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• v.44 no.1
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• pp.74-83
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• 2016

In order to improve the sour taste and foul odor of fermented soymilk, bacteria were isolated from kimchi and identified. Of the 89 bacterial strains isolated from kimchi, 3 isolates produced fermented soymilk with a sour taste and foul odor. The selected bacterial strains R53, R83, and R84 were identified by morphological, biochemical, and 16S rRNA analyses as Weissella koreensis. The strain R83, which produced fermented soymilk having the mildest sour taste and foul odor, was selected for further investigation and named W. koreensis KO3. The optimum culture condition for the fermentation of soymilk by W. koreensis KO3 was at $30^{\circ}C$ for 12 h. When soymilk was fermented under the optimum culture conditions, the viable cell count reached up to $8.71{\times}10^8CFU/ml$ and pH and acidity reached as low as 6.02 and as high as 0.33%, respectively. Twenty-seven amino acids and their derivatives were detected in fermented soymilk. The amounts of serine, glycine, threonine, alanine, and aspartic acid, which contribute to a sweeter taste, increased during fermentation. Orinithine, which was not detected before fermentation, increased during fermentation. Sensory evaluation showed that W. koreensis KO3-fermented soymilk has improved bean, roasted nut, and sour flavors as well as an enhanced mouthfeel, appearance, preferability, and overall acceptability compared with those of standard fermented soymilk. With further study and development, soymilk fermented by W. koreensis KO3 could serve as a health-promoting food with favorable sensory qualities.