Influence of ultrasound tempering on roller milling of white and sumac sorghum

Authors: PULIVARTHI, MANOJ - Kansas State University; Bean, Scott; Pordesimo, Lester; SILIVERU, KALIRAMESH - Kansas State University

Submitted to: Journal of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/19/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary: Sorghum plays an important role as a staple food in arid and semi-arid regions, providing sustenance to millions of people. In countries such as Australia and the United States, sorghum is primarily utilized for livestock feed and bioethanol production. However, there is a growing demand for and utilization of sorghum in the food markets in Western countries. This research investigated the use of ultrasonic tempering to improve milling of sorghum grain which was found to significantly improve sorghum flour quality. One obstacle in increasing the utilization of sorghum in food products is the lack of optimized milling techniques. This research provides a new avenue for milling sorghum and benefits the sorghum industry and food industries interested in incorporating sorghum flour into products.

Technical Abstract: Sorghum, a nutritious and gluten-free cereal crop, is currently underutilized with the absence of standardized milling technology one issue to increased utilization in food production. Most existing milling methods adopted from other crops yield inferior flour quality with excessive endosperm loss. However, implementing appropriate tempering techniques prior to roller milling can enhance flour characteristics and yields. In this study, a roller milling technology was developed using a laboratory-scale roller mill to produce high-quality sorghum flour suitable for gluten-free applications. Ultrasound treatments were conducted using a probe-type ultrasound device with a frequency of 20kHz and a power level of 600W. The kernels were soaked in water (1:1 w/v) and subjected to ultrasound treatment for 1, 1.5, and 2 min, set at 75% amplitude. After the treatment, the kernels were drained, surface dried, and tempered for 24 hours in sealed polythene bags to achieve a target moisture level of 17%. The effect of ultrasound tempering (UST) using a non-tannin white and a red tannin sorghum on milling and flour characteristics was investigated. The results were compared to sorghum milled using a standard tempering process (17% moisture). Ultrasound tempering (UST) significantly impacted milling and flour quality in terms of milling yield, particle size, damaged starch, and ash content. UST resulted in a significant reduction in the hardness index of both the white sorghum (72.57-73.61 from 79.02 (control)) and the red-tannin sumac sorghum (76.22-78.29 from 84.50 (control)). Notably, the milling yield of the white sorghum showed a significant increase with treatment times, from 73.31% (control) to 76.56-78.16%. The red-tannin sumac sorghum milled using the 1 min UST resulted in a higher bran yield (5.67%) compared to the standard tempering method (1.7%), indicating an improvement in milling efficiency. The 1 min UST resulted in efficient bran separation and improved ash contents for both the white (0.87%) and red-tannin sumac (0.69%) sorghum, as compared to their respective controls (1.05% and 1.4%). Principal component analysis clearly defined the inter-relationship among the treatment groups and analyzed parameters for both kernel and flour properties. Overall, the developed milling flowsheet was suitable for both the white and red-tannin sumac varieties, regardless of their differences in physical properties and the use of UST has significantly improved the flour quality of both samples.