Functional Effects of Pomegranate Peel Extracts on Milk: Antibacterial Measurements, Antioxidant Activities, and Photochemical Characterizations

Abstract

Consumers are interested in antimicrobial by-products from natural sources. The present study aims to estimate the antibacterial effects of different concentrations and solvent extracts such as methanol, ethanol, and water extract of pomegranate peels with the milk quality application in-vitro. Listeria monocytogens, E. coli, Salmonella, and Staphylococcus aureus were used as bacteria growth indicators in two pomegranate varieties (i.e., Wonderful and Francis). Besides, evaluating somephysical characterization, antibacterial and antioxidant activities. Results showed that the highest inhibition zone of 18.88 mm was observed with 90% ethanol extract of Wonderful variety against Listeria monocytogens, at 0, 12.5, 25, and 50 mg/mL concentrations, while the lowest inhibition zone of 11.29 mm was observed with 90% methanol extract of Francis variety, at 12.5 mg/mL concentration. The milk treated with WPE of Wonderful variety maintained the bacterial growth from 1.19 ±0.29 x 109 to 1.43 x 1011 CFU/mL at 4 °C. Punicalagin was the most abundant polyphenolic compound (165.05–190.43 µg/mL) followed by gallic acid (153.08–177.65 µg/mL), and p-Hydroxybenzoic acid (91.29–92.5 mg/mL). Acetaldehyde (23.09–27.15 PPM), followed by acetoin (9.65–15.33 PPM) were the most predominant volatile compounds. The WPE treated milk maintained the sensory evaluations such as taste, color, texture, and overall acceptance longer time longer time (i.e., 144 h) than FPE treated milk (i.e., 168 h) at 4°C. DPPH and ABTS radical scavenging of capacity (IC50 values) of FPE treated milk were found to be lower than WPE treated milk (i.e., 159.65 µg/mL and 131.87 µg/mL), respectively. While, FPE treated milk reported a higher viscosity content than WPE treated milk (13.11 cP). In conclusion, pomegranate peel extracts especially Wonderful variety may be used to prolong the shelf-life of milk in dairy products manufacturers.