Milling characteristics of rice grains as affected by paddy mixture ratio and moisture content.

The paper presents results of study on the effects of moisture content and paddy mixture ratio (defined as the mass percentage of paddy accompanied with brown rice when arriving into rice whitener machine on milling characteristics of rice grains. The experiments were conducted at four levels of moisture contents (MC), namely 8, 10, 12 and 14% (w.b.) and five levels of paddy mixture ratio (PMR), including 2, 3, 4, 5 and 6%. The milling characteristics were determined in terms of fissured kernels (FK), Head Rice Yield (HRY), whiteness percentage (WP) and whiteness index (WI). The results revealed that as PMR increased from 2 to 6%, the values of FK and WP decreased, whilst HRY decreased by increasing PMR from 2 to 6%. At all of the evaluated PMRs, the values of HRY, WP and WI decreased by decreasing MC from 14 to 8% (w.b.). It was observed that with decreasing MC from 14 to 10% (w.b.), the number percentage of FK decreased and then the further decrease in MC from 10 to 8% (w.b.) caused the FK to increase. It was concluded that in the whitening process, if rice grains arrived into the whitener with higher levels of PMRs, higher values of HRY could be obtained for the product. This is also accompanied with lower WPs.

[1]  Bienvenido O. Juliano,et al.  Rice : chemistry and technology , 1985 .

[2]  Yanjun Dong,et al.  Molecular genetic mapping of quantitative trait loci for milling quality in rice (Oryza sativa L.) , 2004 .

[3]  J. Frączek,et al.  Influence of moisture content and number of mechanical impacts, upon the energy and sprouting capacity of wheat grains , 1998 .

[4]  Y. B. Li,et al.  STUDY ON ROUGH RICE FISSURING DURING INTERMITTENT DRYING , 1998 .

[5]  Jason A. Bond,et al.  Effects of pre-harvest desiccants on rice yield and quality , 2007 .

[6]  W. Yang,et al.  Mechanical properties of sound and fissured rice kernels and their implications for rice breakage , 2005 .

[7]  S. Linscombe,et al.  Grain fissuring and milling yields of rice cultivars as influenced by environmental conditions , 1996 .

[8]  John R. Piggott,et al.  Changes in lipids and in sensory attributes on storage of rice milled to different degrees , 2007 .

[9]  Z. T. Nehus,et al.  Milled rice breakage due to environmental conditions , 1998 .

[10]  B. K. Yadav,et al.  Changes in head rice yield and whiteness during milling of rough rice (Oryza sativa L.) , 2008 .

[11]  W. Woźniak.  Mechanical properties of wheat grain in relation to internal cracks , 2001 .

[12]  Eiko Arai,et al.  Distribution of amylose, nitrogen, and minerals in rice kernels with various characters. , 2002, Journal of agricultural and food chemistry.

[13]  J. I. Wadsworth,et al.  Rice Science and Technology , 1993 .

[14]  T. Strouboulis,et al.  Transient Moisture Gradients in Rough Rice Mapped with Finite Element Model and Related to Fissures After Heated Air Drying , 1996 .

[15]  Hemad Zareiforoush,et al.  Rupture strength of brown rice varieties as affected by moisture content and loading rate , 2011 .

[16]  K. Gravois.  Optimizing selection for rough rice yield, head rice, and total milled rice , 1998, Euphytica.

[17]  C. W. Hall,et al.  Moisture Adsorption Characteristics of Brown Rice , 1967 .

[18]  Kwang Ok Kim,et al.  Effect of Milling Ratio on Sensory Properties of Cooked Rice and on Physicochemical Properties of Milled and Cooked Rice , 2001 .

[19]  R. Lu,et al.  ABSORPTION of WATER IN LONG‐GRAIN RICE ROUGH DURING SOAKING , 1994 .

[20]  B. D. Webb,et al.  Quality evaluation of U.S. medium-grain rice using a Japanese taste analyzer , 1996 .

[21]  M. H. Komarizadeh,et al.  Effects of crop-machine variables on paddy grain damage during handling with an inclined screw auger , 2010 .

[22]  R. Dilday,et al.  Influence of Thresher Cylinder Speed and Grain Moisture at Harvest on Milling Yield of Rice , 1987 .

[23]  C. W. Hall,et al.  Relative Humidity Changes That Cause Brown Rice To Crack , 1965 .

[24]  R. L. Roberts.  COMPOSITION AND TASTE EVALUATION OF RICE MILLED TO DIFFERENT DEGREES , 1979 .