Fortification of yogurt with mulberry leaf extract: Effects on physicochemical, antioxidant, microbiological and sensory properties during 21-days of storage

Abstract

Mulberry leaves are medicinal and edible, with many physiological functions. To improve the potential function of yogurt, the effects of mulberry leaf extract (MLE) incorporation on the fermentation kinetics, physicochemical, antioxidant properties, and sensory parameters of yogurt were evaluated. The results showed that 0.1-0.3 % MLE improved the acidification rate and shortened the fermentation process. The addition of MLE significantly increased the values of total titratable acids, water holding capacity (WHC), total phenolic content and antioxidant capacities of the yogurt (p＜0.05). Specifically, the WHC values of 0.1 % MLE added yogurt were 1.33-1.41 times that of the control over 21 days of storage. In addition, MLE changed the texture and sensory quality of yogurt, resulting in light green, more stable products. Compared to the control, the yogurt with an appropriate concentration of MLE (0.1 % and 0.2 %) showed stable microbiological properties, and the survival of lactic acid bacteria in the yogurt was able to maintain a stable probiotic count of 10⁸ CFU/g over 21 days of shelf life. The yogurt containing 0.1 % MLE achieved a good balance between the physicochemical and sensory qualities of the yogurt, and the use of MLE as an ingredient in yogurt production was a step towards the development of healthier dairy products.

Keywords: Antioxidant activity; Lactic acid bacteria; Mulberry leaf; Yogurt.

Graphical abstract

Fig. 1

Effects of MLE on yogurt pH during fermentation.

Fig. 2

Effects of MLE on the pH (a) and acidity (b) of yogurt during storage. Different letters within the same column represent statistically significant differences (p < 0.05).

Fig. 3

Effects of MLE on the water-holding capacity of yogurt during storage. Different letters within the same column represent statistically significant differences (p < 0.05).

Fig. 4

Effects of MLE on total phenolic contents (a), total reducing power (b), superoxide anion (c) and DPPH (d) radical scavenging capacity of yogurt. Different letters within the same column represent statistically significant differences (p < 0.05).

Fig. 5

Effect of MLE on the growth of L.bulgaricus (a) and S. thermophiles (b) in yogurt. Different letters within the same column represent statistically significant differences (p < 0.05).

Fig. 6

Effects of MLE on sensory evaluation of yogurt.