The objective of this study was to determine the quality characteristics of Goji berry soy yogurt and milk yogurt fermented by lactic acid bacteria from Kimchi(Leuconostoc mesenterioides, Lactobacillus sakei SL1103 and Lactobacillus plantarum LS5). Changes in lactic acid bacteria numbers, pH, titrable acidity, Brix and Hunter color were monitored during 48hr fermentation.
24hr fermentation time was suitable for development of Goji berry soy yogurt because the lactic acid bacteria numbers was more than 108CFU/mL and pH was in 3.9 ~ 4.2. After 24hr of fermentation at 30℃, the lactic acid bacteria numbers of goji berry soy yogurt was 8.19 ~ 8.50 log CFU/mL, pH was 3.97 ~ 4.23, titratable acidity was 0.90 ~ 1.17%, Brix was 12.75 ~ 16.25°Bx, color L value was 70.93 ~ 83.57, color a value was -2.17 ~ 9.61, and color b value was 14.52 ~ 26.89.
24hr fermentation time was not enough for development of Goji berry milk yogurt, although the lactic acid bacteria numbers of goji berry milk yogurt was 8.21 ~ 8.41 log CFU/mL, but pH only was 4.97 ~ 5.95. The pH of yogurt have an important means about taste, storage period, and more, so I think Goji berry milk yogurt need 48hr or more to fermented. After 40hr fermentation, the lactic acid bacteria number of Goji berry milk yogurt was 7.90 ~ 8.63 log CFU/mL, pH was 4.20 ~ 4.73, titratable acidity was 0.90 ~ 1.27%, Brix was 16.10 ~ 17.85°Bx, color L value was 71.68 ~ 89.31, color a value was -2.69~ 9.80, and color b value was 7.82 ~ 27.54.
By sensory evaluation, 1% Goji berry soy yogurt was best rating in color, taste and overall acceptability. 3% Goji berry milk yogurt was best rating in color, taste, flavor, texture and overall acceptability.
Therefore, 1% Goji berry soy yogurt and 3% Goji berry milk yogurt fermented by lactic acid bacteria from Kimchi(Leuconostoc mesenterioides, Lactobacillus sakei SL1103 and Lactobacillus plantarum LS5) is possible to develop a case Goji berry yogurt that have sensible preference as well as excellent bioactivity functional foods.