Effect of Pretreatments on the Physicochemical Properties of Rice Husk Fiber and the Antioxidation Properties of Rice Husk Extracts

Ong, Yen Ting (2018) Effect of Pretreatments on the Physicochemical Properties of Rice Husk Fiber and the Antioxidation Properties of Rice Husk Extracts. Final Year Project (Bachelor), Tunku Abdul Rahman University College.

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Abstract

Rice husk is the lignocellulosic agricultural residue generated from the rice milling industries. In general, rice husk consists of about 38% cellulose, 22% hemicellulose and 18% lignin. This study was carried out to investigate the effect of different pretreatments on the physicochemical properties of rice husk fiber and the antioxidation properties of the rice husk extracts. Initially, the rice husk was pretreated with 8 pretreatment methods, namely aqueous glycerol, acidified aqueous glycerol, alkaline aqueous glycerol, enzyme pretreatment and the combination of aqueous glycerol, acidified aqueous glycerol and alkaline aqueous glycerol with enzyme pretreatment. The pretreated rice husk was further extracted with 0.1N NaOH to obtain rice husk insoluble fiber and phenolic extract. The physicochemical properties of rice husk insoluble fiber were characterized based on its water holding and oil holding capacity. While, the antioxidation properties of rice husk extract were determined through DPPH test and FRAP assay. The results revealed that the alkaline aqueous glycerol-enzyme cellulase pretreatment had improved the water and oil holding capacity of rice husk insoluble fiber from 4.07 ± 0.18g/g and 5.80 ± 0.06g/g to 6.93 ± 0.34g/g and 7.79 ± 0.50g/g respectively. However, the phenolic extract of acidified aqueous glycerol-enzyme cellulase pretreated rice husk has been found possesses the highest scavenging activity (13.11 ± 0.05ppm at 10x dilution) and reducing power (267.62 ± 19.02μM FSE/g), compared to control (scavenging activity at 14.10±0.88ppm and reducing power at 130.95 ± 4.36μM FSE/g). Nevertheless, the quality of psyllium husk is still the best, compared to the insoluble fiber and phenolic extract of rice husk in this study.