This study evaluated the effects of two Korean traditional plant extracts (Diospyros kaki THUNB. leaf; DK, and Nelumbo nucifera leaf; NN) on the fermentation, functional and sensory properties of herbal yogurts. Compared to control fermentation, all plant extracts increased acidification rate and reduced the time to complete fermentation (pH 4.5). Supplementation of plant extracts and storage time were found to influence the characteristics of the yogurts, contributing to increased viability of starter culture and phenolic compounds. In particular, the increase in the counts of Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus was highest (2.95 and 1.14 Log CFU/mL respectively) in DK yogurt. Furthermore, supplementation of the plant extracts significantly influenced to increase the antioxidant activity and water holding capacity and to produce volatile compounds. The higher antioxidant activity and water holding capacity were observed in NN yogurt than DK yogurt. Moreover, all of the sensory characteristics were altered by the addition of plant extracts. Addition of plant extracts increased the scores related to flavor, taste, and texture from plain yogurt without a plant extract, as a result of volatile compounds analysis. Thus, the overall preference was increased by plant extracts. Consequently, supplementation of DK and NN extracts in yogurt enhanced the antioxidant activity and physical property, moreover increased the acceptability of yogurt. These findings demonstrate the possibility of using plant extracts as a functional ingredient in the manufacture of herbal yogurt.

The aim of this study was to examine the levels of flavonols in mulberry leaf fermented by Lactobacillus plantarum isolated from a traditional Korean soybeanfermented food. Flavonol kaempferol and quercetin contents were markedly higher in fermentates of mulberry leave (FML) extracts than in unfermented mulberry leave (UFML) extracts (kaempferol and quercetin: 30.43 ± 1.83 mg/100 g and 49.96 ± 2.74 mg/100 g equivalent weight of dry in FML versus 0.54 ± 0.11 mg/ 100 g and 0.58 ± 0.15 mg/100 g equivalent weight of dry in UFML). In addition, total phenolic and flavonoid contents in FML extract were 1,183.28 ± 2.99 mg/ 100 g equivalent weight of dry and 425.61 ± 9.73 mg/100 g equivalent weight of dry, respectively, which were considerably higher than those of the control UFML extract. PRACTICAL APPLICATIONSFlavonols kaempferol and quercetin with antioxidant and anti-inflammatory properties have been implicated in the prevention and development of therapies for cancers, cardiovascular disease, neurological and metabolic disorders, and bone diseases and so on. These results suggest that Lactobacillus plantarum isolated from a traditional Korean soybean-fermented food could be used as a starter strain for improvement of biologically beneficial flavonol compounds in plantderived food materials.

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