VALORIZATION OF RICE STRAW VIA PRODUCTION OF MODIFIED XYLANS AND XYLOOLIGOSACCHARIDES FOR THEIR POTENTIAL APPLICATION IN FOOD INDUSTRY

Abstract

The present study attempted to valorise rice straw, one of the most abundant, renewable and economic agricultural wastes, via production of modified xylans and xylooligosaccharides (XOS), which were evaluated for their total antioxidant capacity. The percent contents of extractives, cellulose, hemicelluloses, lignin and ash (silica) in rice straw were found to be 20, 41, 24, 9 and 6, respectively. Hemicellulosic xylan was extracted from straw by reaction with 11% (w/v) sodium hydroxide for about 3 h at 80 °C, so that a yield of about 19.4% was obtained, followed by spectral and thermal analyses. Xylan was then subjected to chemical modifications using acetic anhydride, benzyl chloride and sodium monochloroacetate, and the modifications of functional groups were confirmed by FT-IR and NMR spectral techniques. Controlled acid hydrolysis of xylan was carried out using dilute sulphuric acid (0.1, 0.25, 0.5 and 1.0M) at 121 °C, 15 psi for 10 min to produce XOS-rich hydrolysate. Xylan, modified xylans and XOS exhibited significant concentration dependent AAE values, XOS exhibiting the highest AAE value, followed by xylan, benzylated xylan, carboxymethylated xylan and acetylated xylan. Therefore, rice straw based modified xylans and XOS with potential antioxidant properties may serve as potential candidates for use in food industries as packaging films and functional food ingredients.