Particle size and fat content in coconut milk impact bioactive compounds and inhibition of Staphylococcus aureus in Thai red curry products

This research studied the impact of homogenization and concentration of coconut milk on antioxidant and antimicrobial activity in Thai red curry products. Total phenolic compounds, 2,2-diphenyl-1-picrylhdrazyl (DPPH) activity and inhibition of Staphylococcus aureus in Thai red curry products heated at 121 °C for 15 min were evaluated. Three homogenizing conditions included a mixer homogenizer (11,000, 16,000, 21,000 rpm), a 2-stage homogenizer (40/40, 70/40, 110/40 Bar) and an ultrasonic homogenizer (132, 232, 332 kJ). The fat concentration was calculated as the ratio of coconut milk to water at 100:0, 70:30, 50:50, and 0:100 (Control sample). Red curry paste solute with water (Control sample) showed the highest total phenolic compounds followed by the ratios of coconut milk to water at 50:50, 70:30 and 100:0 (30.14±0.04, 19.02±0.04, 17.40±0.04, and 13.49±0.02 mg GAE/10 g), respectively. High concentrations of coconut milk obstructed the extraction efficiency of phenolic compounds. The 2-stage homogenizer at 110/40 Bar was the most effective in reducing fat particle size with good distribution, while the smallest fat particle size gave high antioxidant activity. Increasing fat concentration in coconut milk protected Staphylococcus aureus . The highest antioxidant and antimicrobial activities of Thai red curry products were found at the lowest concentration of coconut milk as the appropriate proportion of polar and nonpolar solutions for the extraction of bioactive compounds. A concentration of 50% coconut milk showed the highest total phenolic compounds and antibacterial activity against S. aureus with the largest inhibition zone area.