# Characterization of Sorghum Processed through Dry Heat Treatment and Milling
###### Abstract
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Anatomic Part** & \begin{tabular}{c} **Whole Kernel** \\ **(\%)** \\ \end{tabular} & \begin{tabular}{c} **Protein** \\ **(\%)** \\ \end{tabular} & \begin{tabular}{c} **Fat** \\ **(\%)** \\ \end{tabular} & \
\begin{tabular}{c} **Ash** \\ **(\%)** \\ \end{tabular} &
\begin{tabular}{c} **Starch** \\ **(\%)** \\ \end{tabular} \\ \hline Whole grain & 100 & 11.5–12.3 & 3.6 & 1.6–1.7 & 72.3-75.1 \\ Endosperm & 81.7–86.5 & 8.7–13.0 & 0.4–0.8 & 0.3–0.7 & 81.3-83.0 \\ Germ & 8.0–10.9 & 17.8–19.2 & 26.9–30.6 & 3.9–10.4 & - \\ Pericarp & 4.3–8.7 & 5.2–7.6 & 3.7–6.0 & 2.0–3.8 & - \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Sorghum grain fraction chemical composition, adapted from [PERSON] [12] with permission from Elsevier. Figure 1: Kafirin structure. Image adapted from [PERSON] et al. [8] with permission from Elsevier. The processing of sorghum grains by milling promotes lipase enzyme release, which results in triglyceride transformation, rise of free fatty acid content, and consequently diminishes the shelf life of the flour [14]. Heat-treatment processing of the grains may be considered a suitable practice for overcoming these disadvantages, causing at the same time changes in final product texture, proximate composition, tannin and antinutrient content, antioxidant properties, digestibility, etc. [15]. Dry heat treatment is a practice in snack manufacturing that has been proved to enhance product edibility, digestibility, and organoleptic characteristics [16]. [PERSON] et al. [17] demonstrated that dry heat treatment of oat up to 160 \({}^{\circ}\)C generated an improved sensory profile of the final product and enhanced nutritional value, with lipid, protein, starch, and \(\beta\)-glucan content not being influenced by the treatment, whereas the dietary fiber content was slightly affected. Dry heat treatment of little millet generated the increase of the total phenolic, flavonoid, and tannin content, and antioxidant activity [18]. Milling has a great influence on starch digestibility of cereal-based products, higher digestibility being obtained for lower particle dimensions [19]. On the other hand, obtaining fine particles implies higher energy costs and might not be recommended due to their ability to increase the erosion of the gastrointestinal wall [19]. Furthermore, fine particles may diminish enzyme flow to substrates caused by the release of viscosity, promoting such components as \(\beta\)-glucans, which may influence gastrointestinal residence time, distribution, and digestion [20]. Thus, while it may be preferable to decrease sorghum flour particle-size dimensions for enhanced digestibility, other factors must also be considered to achieve an effective size for a desired product quality. Fractions should be selected according to the purpose of the flour. [PERSON] et al. [21] stated that the fraction containing more sorghum bran resulted in lower expansion and stability when extruded than flour with smaller particles. The chemical and physical properties of sorghum flour fractionated by two milling methods were distinguished depending on the particle size, indicating that sorghum grains were separated into different anatomical parts [22]. The transformation of sorghum grain components into forms that can be readily used in food products without generating negative effects on food sensory characteristics are of interest and under continuous development. To our knowledge, no paper has been published to date regarding the combined effect of sorghum grain dry heat treatment and grain fractionation. The purpose of this paper was: (1) to study the effects of dry heat treatment, temperature, and fractionation on the functional properties and proximate composition of sorghum flour, (2) to optimize the processing conditions for each fraction and compare the characteristics of the optimal samples with untreated ones, and (3) to characterize optimal products regarding molecular, physical characteristics, and bioactive compounds.