Investigation and comparison of losses and energy consumption in conventional and modern rice milling systems (Mazandaran Province report)

In this research, operational process and energy consumption of paddy milling factories in three categories: conventional system (Engelberg Machine for hulling and whitening), semi modern system (Rubber roll dehusker and Engelberg whitener), modern system (Rubber roll husker and abrasive whitener) were investigated in Mazandaran province. Besides, milling efficiency, Degree of hulling, breakage percent of brown rice and white rice, degree of whitening, and quality factors gelation index, percentage of elongation and amylose of cooked rice were studied. Results showed that, more than 87 percent of paddy milling factories in Mazandaran province have conventional or semi modern systems. Using of semi modern system was more abundant than other systems. Average of rice milling capacity varies between 800–1300 ton/annually and more than 80 percent this capacity used for milling of traditional varieties. Degree of rice milling changed between 60–65 percent in conventional, semi modern and modern systems. In milling factories, 45-50 kg head rice, 10-15 kg half rice and 5 kg broken rice were obtained of each 100 kg paddy, averagely. There is no quality control unit observed in almost paddy milling factories and technical supervisor has responsibility about machinery, operation and quality of production. For drying and milling of paddy 486 MJ and 158.4 MJ energy consumed per ton respectively. Observation showed that paddy drying process were done in temperature range 30 to 55°C and 40 to 70 hours as one or multi steps. Moisture content of paddy was decreased to 7 to 9 percent at the end of drying process. Using of Engelberg whiteners causes to raising paddy temperature to 70°C. Increasing paddy temperature in whitening and high tolerance of storage temperature cause to more chance cracking of rice kernels. Abrasive whiteners have low pressure on rice and less paddy temperature increasing. It is concluded, correct field management and fast yield transportation is very important in order to decreasing losses and increasing degree of milling. Statistical analysis indicated that no significant difference exist in degree of milling among conventional, semi modern and modern systems. It was changed in 62.45 to 63.58 percent. The systems had significant difference in hulling operation and adding gravity separator to de hulling process increased de hulling to 96 percent. Engelberg de husker had significant effect on brown rice breakage than Rubber roll de husker. In overall, modern rice milling system had less harmful effects on rice than other systems. Rice milling systems did not have significant effect on amylose and gelation index of white rice. The parameters and gelation index varied in treatments from 21 to 22 percent and 3.97 to 3.99 respectively. Using of conventional milling system has more effect on elongation percent than other systems. Development of parboiling and new industrial methods in rice industry, recommended in order to suitable influence on energy saving and cost reduction.