OPTIMASI VARIASI FERMENTASI TERHADAP KUALITAS DAN POTENSI ANTIBAKTERI YOGHURT FORTIFIKASI DENGAN KULIT BUAH NAGA MERAH (Hylocereus polyrhizus)

Red dragon fruit peel, which has long been considered as waste, has great potential in the fields of microbiology and food science due to its bioactive compounds with antibacterial activity. The utilization of red dragon fruit peel can be carried out through fortification into yoghurt to produce yoghurt with improved quality and antibacterial potential. This study aimed to determine the optimal conditions for producing yoghurt fortified with red dragon fruit peel and to evaluate its effects on the quality and antibacterial potential of yoghurt. The treatments consisted of variations in red dragon fruit peel concentration (15%, 20%, and 25%) and fermentation time (8, 12, 24, and 48 hours). The results showed that yoghurt fortified with 20% and 25% red dragon fruit peel at fermentation times of 12–24 hours exhibited the best antibacterial activity against Escherichia coli strain ATCC 25922 and Staphylococcus aureus strain ATCC 25923 and possessed physicochemical properties that met the Indonesian National Standard (SNI) No. 2981:2009.