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Rice individual kernel breaking force and hardness index distributions and the relationship to milling quality

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  2007 ASAE Annual Meeting  076185.(doi:10.13031/2013.23512)
Authors:   Rustico C Bautista, Terry J Siebenmorgen
Keywords:   Rice, head rice yield, kernel breaking force, kernel hardness index

The objective of this study was to investigate rice individual kernel breaking force and hardness index distributions and their correlations to milling quality. Specifically, the goal was to correlate the percentage of strong kernels (kernels with breaking force greater than 20 N) and kernel hardness index to head rice yield as a possible indicator of milling quality. To accomplish this goal, rice varieties/hybrids Bengal, Cheniere, Cocodrie, Francis, Wells, and XP723 were harvested at various harvest moisture contents from Arkansas, Mississippi, and Missouri in 2004 and 2005. Samples were cleaned and gently dried at 20 oC and 56% RH to approximately 12% MC, then analyzed for kernel breaking force, hardness index, and HRY. For breaking force measurements, 200 rough rice kernels were randomly selected from each sample lot and manually--dehulled to produce brown rice. Individual kernel breaking force of brown rice kernels was measured using a texture analyzer (TA.XT2i, Texture Technologies Corp., Scarsdale, NY) with a flat--faced loading head, having a thickness of 1.48 mm and a width of 9.9 mm, and a loading rate of 0.5 mm/s. For kernel hardness index, 300 rough rice kernels were randomly selected from each sample lot. Individual kernel hardness index of rough rice was measured using a single kernel classification system (SKCS 4100, Perten Instruments, Springfield, IL). Individual kernel breaking force and hardness index distribution trends among varieties/hybrid were discussed. Results indicated a good correlation (R=0.81) between HRY and percentage of strong kernels across varieties/hybrids tested. Average kernel breaking force and kernel hardness index showed weak correlations with HRY across varieties/hybrid; however, a linear trend existed between the average breaking force/hardness index and head rice yield.

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