Chemical and Rheological Modifications of White Sorghum Flour by Physical Treatments with Possible Implications for...

This paper aimed to investigate the impact of dry heat treatment and fractionation on white sorghum grain's chemical and rheological properties. For this, dry heat treatment was applied to sorghum grains of different granulations, integral (I), large (L > 300 μm), medium (200 μm < M < 250 μm), and small (S < 200 μm), at corresponding temperatures of 144 °C, 132 °C (M), and 121 °C (S). The content of amino acids, fatty acids, minerals, and volatile compounds was determined in sorghum flours, along with the dynamic rheological behavior of sorghum dough. The results indicated that dry heat treatment increased mono and polyunsaturated fatty acid content, and decreased lysine, isoleucine, and glutamic acid contents. Significant differences (p < 0.05) in amino acid and fatty acid profiles were observed between fractions. Generally, Ca and Na increased after dry heat treatment of sorghum grains, while Fe, Zn, and Cu decreased, except in the M particle size sample. The optimal fraction M is distinguished by an increase in Fe, Zn and Cu content compared to the control. Volatile compounds were affected by both fractionation and dry heat treatment, with samples with S particle size possessing a distinct volatile profile. Dry heat treatment produced a stiffer, less deformable dough, maintaining elastic dominance and slightly reducing the peak gelatinization temperature. Particle size reduction led to dough strengthening and an increase in elastic and viscous moduli. The combined use of fractionation and dry heat treatment permits precise control of sorghum's nutritional and rheological properties.