Effect of Indigenous Black Glutinous Rice of Phatthalung Province on the Quality of Sweet Fermented Rice (Khaomak) During Fermentation

Abstract

Black glutinous rice is known as a healthy food because of its richness in bioactive phenolic compounds. The objective of this research was to study the effect of black glutinous rice on the quality of sweet fermented rice during fermentation. White glutinous rice (Oryza sativa var. Glutinosa) was substituted by polish black glutinous rice (Oryza sativa Linn.) in the ratio of 75:25 (PB₂₅), 50:50 (PB₅₀) and 0:100 (PB₁₀₀) or unpolished black glutinous rice in the ratio of 75:25 (UB25), 50:50 (UB50) and 0:100 (UB₁₀₀) in comparison with white rice (ratio 100:0, W₁₀₀). The qualities of all
sweet fermented rices during fermentation were monitored daily for 3 days. Total soluble solid and alcohol content were increased when fermentation time increased, while pH decreased. PB₂₅ exhibited the highest overall liking score from
sensory evaluation. UB₁₀₀ showed the highest antioxidant activity (DPPH Radical Scavenging Activity, Ferric Reducing Antioxidant Power, Metal Chelating Activity). Thus, qualities of sweet fermented rice were governed by type and amount
of black glutinous rice substituted.