Effect of paddy moisture, drying air temperature and type of whitener on the whole kernel percentage and quality characteristics of the common rice cultivarsin north of Iran

Different rice varieties, due to their inherent characteristics, show different reactions to changing the drying conditions and milling operations. Hence, determining the optimum drying conditions and selecting the appropriate milling system can play an important role in reducing the losses in the milling process. In this regard, in order to study the effects of the paddy drying parameters and type of whitener on whole kernel percentage and the quality characteristics of two local and two high yielding rice varieties in the north of Iran, the factorial experiment with four factors in a completely randomized design was used. The four factors were including the rice variety in 4 levels (Hashemi, Tarom, Gohar and Keshvari), type of whitener in 2 levels (abrasive and friction), paddy final moisture content in 2 levels (9-10 and 11-12%) and drying air temperature in 2 levels (40 and 50°C). Results revealed that water absorption of Gohar and Keshvari was lower than that of Hashemi and Tarom, however the effect of milling system was not significant on water absorption. Higher and lower solid loss related to Gohar and Taroom, respectively. In total, results of this research showed that drying of paddy with 40°C, final moisture content of 11-12% and applying the abrasive type whitener for milling of local and high yielding rice varieties achieved more whole kernel, butfor milling of paddy with friction type system, final moisture content of 9-10% lead to more whole kernel.