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A Laboratory-Scale Tempering and Milling Method for Grain Sorghum

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

Citation:  Transactions of the ASABE. 61(2): 713-721. (doi: 10.13031/trans.12343) @2018
Authors:   Yumeng Zhao, R. P. Kingsly Ambrose
Keywords:   Flour properties, Milling, Sorghum, Tempering.

Abstract. The current commercial milling process for pigmented sorghum leads to inconsistent milling quality and performance. Proper pretreatment of sorghum may improve the milling performance. The effects of cold water, hot water, and steam tempering of sorghum on the milling performance and flour quality were investigated in this study. A tabletop roller mill system that had five break rolls and two smooth rolls was used. The millstream output at different stages of roller milling was used to evaluate the effectiveness of the conditioning treatments. Steamed sorghum had high bran yield due to toughening of the bran, which allowed gradual scraping of the endosperm from the bran. Flour yield was not significantly different among the pretreatments. Flour crude fiber content of the 1 min steam treated sorghum was 1.28% ±0.09%, which was significantly higher than that of cold water treated sorghum (0.87% ±0.19%). The damaged starch content in the milled flour was highest in the cold water treated (5.96% ±0.24%) sorghum, and steam treatment resulted in lower damaged starch content (3.63% to 4.18%). Steam treatment resulted in flour with more convex and circular particles compared to the other treatments, indicating better separation of starch granules from the endosperm. Steam treatment of sorghum kernels at high temperature and pressure led to better separation of bran and endosperm without negatively impacting flour quality. Steam tempering could be a better pretreatment process for milling sorghum for food purposes.

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