Pomegranate Peel Extract Fortified Yogurt: Effect on Physicochemical, Microbiological and Sensory Quality of Functional Dairy Product

Background: The study aimed to evaluate the effect of incorporating Punica granatum (pomegranate) hydroethanolic extract as a functional ingredient in yogurt on the physicochemical, sensory quality and microbiological count of freshly prepared and refrigerated stored (4°C) yogurts. Methods: Pomegranate peels were dried, ground and extracted with 70% ethanol, then concentrated using a rotary evaporator and finally lyophilized to obtain pomegranate peel powder (PPP). Yogurts were prepared using pasteurized semi-skimmed cow’s milk, with phenolic extracts of pomegranate peels added at 10.0 mg, 20.0 mg and 30.0 mg per 100 mL of milk; a control product was simultaneously prepared without such pomegranate peel extract. The physicochemical analysis included pH, acidity, syneresis and viscosity measurements. Microbiological analysis was performed to determine the viability of Streptococcus thermophilus and Lactobacillus delbrueckii ssp. bulgaricus. Sensory scoring of the yogurt was carried out by 25 panelists using a 5-point scale. Result: Initial pH values of freshly prepared yogurt ranged between 4.48 and 4.64, decreasing to pH values of 4.3 and 4.15 at 21st day of refrigerated (4°C) storage. The titratable acidity of yogurt increased from initial value of 75°D for freshly prepared control product to 99°D as noted on 21st day of storage. Syneresis at the 21st of storage were 35.98%, 37.88%, 39.34%, 39.22% for yogurt samples control, experimental yogurt containing PPE of 10.0 mg, 20.0 mg and 30.0 mg respectively. The viscosity of yogurt utilizing 10.0 mg PPE peaked to value of 769.63 cP on 21st day of storage. Streptococcus thermophilus count peaked to 8.39 log CFU/g for experimental sample containing 10.0 mg of PPE as noted on 7th day of storage. Yogurt samples containing 20.0 mg and 30.0 mg of PPE received the superior overall acceptability scores over others. The extract improved yogurt’s physicochemical and sensory properties, enhancing its nutritional value and consumer acceptance.