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United States Department of Agriculture

Agricultural Research Service

Research Project: New Sustainable Processing Technologies to Produce Healthy, Value-Added Foods from Specialty Crops and their Co-Products

Location: Healthy Processed Foods Research

Title: Determination of sockage for accurate rough rice quality assessment

Authors
item Atungulu, Griffiths -
item Prakash, Bhagwati -
item Wang, Xiaoturo -
item Tianxin, Wang -
item Fu, Ruipeng -
item Khir, Ragab -
item Pan, Zhongli

Submitted to: Applied Engineering in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 13, 2013
Publication Date: April 1, 2013
Citation: Atungulu, G.G., Prakash, B., Wang, X., Tianxin, W., Fu, R., Khir, R., Pan, Z. 2013. Determination of sockage for accurate rough rice quality assessment. Applied Engineering in Agriculture. 29(2):253-261.

Interpretive Summary: A comprehensive study of factors influencing rice dockage is essential to provide guidelines to the rice industry on how to update shrink chart. The focus of this study was to identify the levels of rice dockage affected by various factors and provide suitable recommendations for updating rice shrink chart. The dockage of freshly harvested rice with moisture contents (MCs) ranging from 18 to 27% wet basis (w.b.) varied between 0.2% and 2.0%. Similarly, average value of dockage of dried rice with MC of 14±1% (w.b.) was 0.65% in 2011 and 0.78% in 2010 harvest seasons. There were no significant differences in dockage among studied rice varieties. It was also observed that dockage was not significantly affected by harvest moisture content and geographical location of field. However, wind and rainfall events significantly increased dockage. The results also revealed that type of harvester and header affected dockage with stripper header indicating least dockage (0.5%) compared to conventional header (up to 0.8%). Average value of dockage for freshly harvested rice was determined to be 0.9% which was significantly lower than the widely accepted value of 2% at present. Therefore, dockage value of 1% may be used to update rice shrink chart.

Technical Abstract: Determination of dockage of freshly harvested rice is crucial for precise development of a universal rice shrinking chart. The objectives of this research were to determine the effect of different factors, including rice variety, farm location, harvest moisture and time, drying, dropping, weather events such as wind and rainfall, and type of harvester, on dockage. The study was conducted during two consecutive rice harvesting seasons. The dockage of freshly harvested rice with moisture content (MC) ranging from 18 to 27% wet basis (w.b.) varied between 0.2% and 2.0% with averages of 0.92% and 0.79% in 2010 and 2011 harvest seasons, respectively. The corresponding averages of dockage of dried rice with MC of 14±1% (w.b.) were 0.78% and 0.65%, which were lower than those of freshly harvested rice. There were no significant differences in dockage among the studied rice varieties. It was also observed that dockage was not significantly affected by the harvest MC, geographical location and dropping from certain height. However, wind and rainfall events significantly increased the dockage. The results also revealed that the type of harvester affected the dockage. The obtained dockage results for all tested factors were significantly lower than 2% which is normal accepted value in rice industry at present.

Last Modified: 9/10/2014