Study on coarse Rice Processing in a commercial Rice Mill

Abstract

This study was conducted in the Minar auto rice mill located at Chapai Nawabgonj district of Bangladesh during November 2003. The variety Parija was processed as parboiled and non-parboiled rice. Parboiled paddy was dried in the sun and milled in engelburg huller whereas, non-parboiled paddy was dried in Lousiana State University (LSU) drier and milled in rubber roll huller. The initial moisture content of rough rice was 15.2%. After soaking for 36-hrs the moisture content of paddy was increased to 29.8% (wb). Steaming was done twice before and after soaking for complete gelatinization of the rice kernels. The paddy was sun dried for 3 days followed by 18 hours tempering every day to reduce moisture content of the paddy from 29.8% to 9.3% (wb). Non-parboiled paddy was dried in LSU drier for 6 hours and moisture content was reduced from 15.2% to 9.0% (wb). The range of hot air temperature was 60 to 90 °C. The crushing strength of parboiled paddy was 6.2 kgf after three days of sun drying. The crushing strength of non-parboiled paddy was 4.8 kgf after 6 hours of drying in LSU dryer. The milling yield and head rice recovery of parboiled rice were 64.25% and 62.25%, respectively, whereas those of non-parboiled rice were 65.50% and 64.25%, respectively. Head rice yield was 2% higher in non-parboiled rice due to milling in rubber roll huller. The non-parboiled rice was finer than the parboiled rice due to polishing after dehusking. The production of non-parboiled rice was more profitable than the parboiled rice.