The Antimicrobial and Antioxidant Effects of Citrus aurantium L. Flowers (Bahar Narang) Extract in Traditional Yoghurt Stew during Refrigerated Storage

The antimicrobial and antioxidant effects of Citrus aurantium L. flowers (Bahar narang) extract (BE; 500, 1,000 and 2,000ppm) were studied in traditional yoghurt stew during storage at 4C for 28 days. The contents of total phenolics and flavonoids in BE were 811.8 and 46 +/- 2.4mg/g, respectively. In vitro antibacterial activity of BE showed that BE had a strong antimicrobial activity against Escherichia coli O157:H7, Pseudomonas aeruginosa, Staphylococcus aureus and Bacillus cereus. Application of BE in traditional yoghurt stew decreased the growth rate of all tested pathogens and P.aeruginosa was the most resistant pathogen. The ferric reducing-antioxidant power and free radical 2,2-diphenyl-1-picrylhydrazyl indicated that BE had a good antioxidant activity. Peroxide value, anisidine value, conjugated diene value and protein carbonyls value indicated that BE decreased lipid and protein oxidation products in traditional yoghurt stew during storage. The antimicrobial and antioxidant effects of BE were concentration dependent and BE at 2,000ppm was the most active. Sensory evaluation showed the addition of BE in traditional yoghurt stew was organoleptically acceptable and it can therefore be used as a natural additive in food industries.