Antioxidant, Antimicrobial and Anticancer Activities of Citrus Peels to Improve the Shelf Life of Yoghurt Drink

The present work aimed to evaluate the antioxidant, antimicrobial and anticancer effects of citrus peels. The quality and storage characteristics of probiotic yoghurt drink samples were investigated which were made with 1, 2 and 3% of citrus peels powder (Orange- Mandarin- Lemon). Sensory analysis, acidity, pH, and bacteria counts, of the yoghurt drink samples, were determined on days 0, 7, 14, and 21 during storage at 4°C. The results indicated the presence of antioxidant activity of citrus peels due to their high phenolic compounds content, the highest phenolic concentration was found in orange peel (1108mg/100 g). The flavonoid content of orange peel powder was 518 mg/100 g. The corresponding values for Mandarin and lemon peels were 420 mg/100 g and 860 mg/100 g respectively. The antioxidant activity determined by DPPH in orange, mandarin, and lemon peel powders, were 45.99, 36.10, and 43.60 % respectively. Polyphenols were identified in orange, mandarin, and lemon peels. The results revealed that orange, mandarin, and lemon peel powders exhibited an efficient cytotoxicity against human tumor cell lines representing colon carcinoma (HCT116) relative to the positive doxorubicin. The results also showed that lemon (Citrus limon), mandarin (Citrus reticulata) orange (Citrus sinensis) peels had antibacterial activity against all pathogenic bacteria and fungi and the ethanolic extract was higher than the aqueous with all microbes for citrus peels used, and the ethanolic extract of orange peels gave the highest inhibition of pathogenic microbes. The results of the sensory evaluation showed that yoghurt drinks containing 1% and 2% of orange, mandarin, and lemon peel powders concentrations compared with control had no significant differences. It can be concluded that citrus peel may be useful to be applied to the development yoghurt drink with excellent antifungal and antibacterial activities without affecting sensory characteristics of fermented milk.