The purpose of this study is to compare the quality characteristics and antioxidant activities of the tagatose yogurt with different contents (6, 8, 10%) of cold brew liquid coffee. Tagatose is a low-calorie food ingredient with putative health-promoting benefits. The tagatose yogurt was fermented with Lactobacillus delbrueckii subsp. bulgaricus at 37±1oC for 20 h. The changes in acid production (pH and titratable acidity), viscosity, and lactic acid bacteria were determined every 5 h during fermentation. Color value was determined before and after fermentation, and antioxidant activities were performed after fermentation in triplicate. The yogurts containing cold brew liquid coffee had lower pH, higher acidity, and viscosity than the control, regardless of the liquid coffee contents. All samples had increasing levels of lactic acid bacteria over the fermentation period, but lactic acid bacteria of yogurts with the addition of cold brew liquid coffee increased further than the control. The total polyphenol/flavonoid content, DPPH/ ABTS/H2O2 radical scavenging activities, and reducing power increased when the liquid coffee content of the yogurt rose. Consequently, the optimal quality of tagatose yogurt was found when 6-8% of cold brew liquid coffee was added according to the overall results of quality properties and antioxidant activity.

This study was conducted to evaluate the influence of Lactobacillus bulgaricus and/or Sterptococcus thermophilus on the fermentation of yoghurt containing 5% (w/v) buckwheat sprouts. The results revealed that after 12 hours of fermentation the appropriate pH, titratable acidity and number of viable cells were attained. At that time, the rutin content of the buckwheat sprout-added yoghurt prepared by the mixed culture method was not changed, but the quercetin content increased greatly. Conversely, the rutin content of yoghurt that only contained Streptococcus thermophilus was decreased while the quercetin content was increased. The total phenol contents as well as the DPPH radical scavenging activities of both the mixed culture and Streptococcus thermophilus yoghurt did not differ significantly. Taken together, the results revealed that the use of a mixed culture of Lactobacillus bulgaricus and Streptococcus thermophilus during the preparation of buchwheat sprout-added yoghurt was desirable due to the decrease in pH and increase in titratable acidity and viable cells that occurred after 12 hr of fermentation. Moreover, phytochemicals in buckwheat sprouts such as rutin, quercetin and phenol compounds were comparatively increased during fermentation and influenced the antioxidant activity in buckwheat sprout-added yoghurt.

The principal objective of this study was to investigate the influence of buckwheat sprouts on the acid production and growth of lactic acid bacteria in to which 5 and 10%(w/v) buckwheat sprouts was added, followed by fermentation with Lactobacillus bulgaricus. In yogurt to which 5 and 10% buckwheat sprouts was added, pH was lower and titratable acidity was higher than those of the control. It was also noted significant changes in the number of viable cell counts with differing amounts of added buckwheat sprouts until 12 hours. When the yogurt samples were stored for 12 days at 4℃, the pH and titratable acidity of the yogurt to which 5 and 10% buckwheat sprouts was added were maintained at lower and higher than control levels, respectively. The highest number of viable cell counts was found in the yogurt to which 5% buckwheat sprouts was added. Rutin content was reduced via lactic acid fermentation, but quercetin content increased significantly in the yogurt with added buckwheat sprouts. It may be that the glycosidic bonds connected to rutin were hydrolyzed during fermentation by lactic acid bacteria. The total phenol compound content of the yogurt samples also increased after fermentation. The antioxidative activity of yogurt to which 10% buckwheat sprouts was added was shown to have a 60.95% free radical scavenging effect, which was the highest among all yogurt samples evaluated.

본(本) 실험(實驗)은 Lactobacillus bulgaricus의 우유 배지(培地)에서 항균물질(抗菌物質)을 추출(抽出) 및 정제(精製)하여 항균효과(抗菌效果)를 조사(調査)하였으며 그 결과(結果)를 요약(要約)하면 다음과 같다. 칼처의 항균물질(抗菌物質)을 methanol-acetone으로 추출(抽出)하고 Sephadex G-50 gel filteration 그리고 thin layer chromatography로 정제(精製)하였다. 칼처의 산중화려액(酸中和濾液)이 탁도법(濁度法)에 의하여 Bacillus subitilis의 발육(發育)을 억제(抑制)하였으므로 산(酸)외에서 항균물질(抗菌物質)이 있음을 확인할 수 있었다. 정제(精製)된 항균물질(抗菌物質)은 Bacillus subtilis, Escherichia coli, Pseudomonas fluorescens, Staphylococcus aureus, Proteus vulgaris 및 Shigella dysenteriae의 발육(發育)을 억제(抑制)하였다. Thin layer chromatography로 정제(精製)한 항균물질(抗菌物質)은 항균작용(抗菌作用)을 나타내는 나 유산(乳酸)을 함유하지 않는 것이다.

This study was carried out to get basic resources for the industrial use of Lactobacillus bulgaricus SP5. The antibacterial activity of the supernatant obtained from Lactobacillus bulgaricus SP5 was tested against the pathogenic bacteria such as Escherichia coli KCCM 11234, Salmonella enteritidis KCCM 3313, Salmonella enteritidis KCCM 12021, and Salmonella typhimurium KCCM 40253. The supernatant of L. bulgaricus SP5 showed antibacterial activity against tested pathogenic bacteria. The antibacterial activity was examined after adjusting pH and heat treatment of supernatant. Heat treatment of supernatant had antibacterial activity against pathogenic bacteria at all temperature. However, pH changes showed no antibacterial activity. Antibacterial activity of the supernatant was confirmed to be due to organic acids (lactic, acetic, phosphoric, succinic, pyroglutamic, citric, malic, and formic acid).