Influence of Tempering Methods on Waxy White Sorghum Kernel, Milling, and Flour Properties

Abstract

Highlights Tempering moisture content and condition had a significant impact on waxy white sorghum kernel and flour properties. Physical sorghum kernel properties after tempering varies with efficiency of moisture penetration into kernels. Steam tempering for 15 s led to better physical kernel properties for handling, transportation, and processing. Room temperature water tempering (18%, 24 h) yielded better flour yield and protein content. Abstract. To optimize the yield and quality of waxy white sorghum flour, the effects of various tempering treatments on sorghum kernel physical properties, milling performance, and flour properties were evaluated. Waxy white sorghum kernels were tempered at different moisture levels and for different times using either room temperature water, hot water, or steam. Tempered sorghum kernels were milled into flour using a milling flowsheet developed for a laboratory-scale tabletop roller mill that consists of four break rolls and eight reduction rolls. The effects of these tempering methods on waxy white sorghum kernel properties, roller milling, and flour properties were investigated. Tempering moisture content and condition had a significant impact on the waxy white sorghum kernel’s physical and flour properties. Steam tempering for 15s led to desirable physical kernel properties that would positively impact handling, transportation, and processing: lower bulk (732.53 kg/m3), tapped (769.39 kg/m3), and true densities (1313.37 kg/m3); lower hardness index (65.01); higher abrasive hardness index (AHI) (23.73); higher angle of repose (23.60); and higher coefficients of static (0.35) and rolling friction (0.29). In terms of milling, room temperature water tempering at 18% w.b. moisture level for 24 h resulted in better bran-endosperm separation without compensating for important flour quality characteristics. It exhibited higher protein content (9.72%), low ash content (0.94%), high bran extraction (6.42%), and high brightness (80.67). Room temperature water tempering at 18% w.b. for 24 h is a more suitable pretreatment prior to the milling of waxy white sorghum kernels in terms of flour yield and quality. Keywords: Flour properties, Kernel properties, Roller milling, Tempering, Waxy white sorghum.