تاثير شرايط مختلف عمليات خشك كردن و تمپرينگ بر كيفيت تبديل برنج

چكيده انگليسي :

Effect of Different Drying and Tempering Operations on Rice Milling Quality Ehsan Nasrnia e nasr esf@gmail com 14 march 2010 Department of Agricultural Machinery Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language Farsi Supervisors M Sadeghi sadeghimor@cc iut ac ir and A A Masoumi masoumi@cc iut ac ir Abstract Rice is one of the main food staple after wheat in the world According to population growth and production limitations one of the approaches is decrease in the processing losses at milling plants Hence the main purpose in rice industry is the processing with high quality To achieve such a goal it is necessary to dry fresh harvested rough rice immediately after harvest to prevent microbial and spoilage losses Nowadays multi pass procedure is used to remove moisture from rough rice kernels Between drying passes tempering operation is applied to prevent kernel fissure and crack at subsequent milling stages In this regard determining the best drying conditions the number of drying passes and tempering duration for quick drying operation low energy utilization and high quality of rice production is vitally important In this study two different rice varieties namely Shafagh long grain and Sazandegi medium grain were dried at high air temperature and relative humidity of 60 C and 17 and low air temperature and relative humidity of 40 C and 12 drying conditions at four drying durations to remove 1 5 3 4 5 and 6 moisture content from freshly harvested rough rice It is predicted that drying of rough rice samples at high and low drying conditions will happen at rubbery and glassy states respectively Each drying batch was split into seven sub samples which were tempered in sealed bags for 0 to 240 min in 40 min increments Finally all samples were dried to 12 5 w b moisture content which is suitable for milling process After whitening the quality parameters including head rice yield HRY optical degree of milling determined by a milling meter DOMmm mass degree of milling DOMm optical compound index C Imm and mass compound index C Im were obtained for each sample and statistically compared Factors included drying condition drying duration temrering duration and variety were splitted as drying condition as main factor the others as secondary factors and they were arranged according to completely randomized design Results showed that variety drying condition and drying and tempering duration had a significant effect on all quality parameters P 0 01 For both varieties and both conditions the HRY value decreased as drying duration increased Also the high temperature drying condition resulted in higher loss in HRY as compared to the low drying condition Results for both varieties revealed that at low drying condition applying tempering operation did not have a significant effect on measured quality parameters But at high drying condition and 6 point percent moisture removal PPMR it was possible to achieve high quality white rice by using adequate tempering duration So that for Sazandegi and Shafagh varieties after 6 PPMR in each drying pass for the highest HRY and CImm 120 min tempering is proposed Also for Sazandegi and Shafagh varieties after 6 PPMR in each drying pass considering DOMmm 160 and 240 min tempering DOMm 240 and 200 min tempering and C Im 200 and 120 min tempering were resulted in the best values respectively Therefore for both varieties it is concluded that using high air temperature to remove 6 moisture content is possible at each drying pass without damaging the rice kernel as long as sufficient tempering is allowed Keywords Degree of milling drying glass transition head rice yield tempering

نصرنيا، احسان

تاثير شرايط مختلف عمليات خشك كردن و تمپرينگ بر كيفيت تبديل برنج

عملكرد برنج سالم , درجه سفيدي