Method of creating starch-like ultra-fine rice flour and effect of spray drying on formation of free fatty acid

Abstract

Rice flour from long, medium, and waxy grain cultivars were processed by passing a 32% rice flour slurry through a microfluidizer at 10 × 104 kPa and spray dryer at three different outlet temperatures (50, 80, and 115°C). Spray-drying conditions were controlled by the flow rate of the slurry and inlet temperature. Spray-dried rice flours and unprocessed rice flour were examined for their lipolytic stability during storage for 210 days by measuring free fatty acid (FFA) formation. The percentage of lipid and FFA in rice flour was significantly reduced by spray drying. The resulting amount of lipid and percentage of FFA was rice-type dependent and related to the amylose content and the outlet temperature. Upon storage, the formation of FFA was lowest for rice flours processed at 115°C outlet temperature as compared to 80°C, 50°C, and control (untreated rice flour). Pin milling of the spray-dried flour resulted in the breakdown of loose re-agglomerated rice flour formed during spray drying with a particle size similar to rice starch but increased starch damage by about 1% per pass through pin mill. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.