Retrogradation of Sorghum Starch: An Investigation into the Effects of Alcohol and Water

Abstract

This study investigated the retrogradation behavior of sorghum starch (Sorghum bicolor) under the influence of alcohol and water, with emphasis on changes in physicochemical properties relevant to food, pharmaceutical, and industrial applications. Sorghum starch was extracted using a modified alkaline steeping method involving sodium hydroxide treatment, wet milling, filtration, centrifugation, and controlled drying. Preliminary qualitative tests confirmed the presence of starch carbohydrates, including amylose and amylopectin. Retrogradation was induced under controlled conditions using water and ethanol, and key physicochemical parameters such as bulk density, tapped density, water sorption capacity, true density, amylose and amylopectin fractions, hydration capacity, swelling capacity, porosity, Hausner ratio, and compressibility index were evaluated over time. The results showed that alcohol-treated starch exhibited increased structural compaction, reduced water sorption capacity, and delayed amylose recrystallization, indicating suppression of retrogradation. In contrast, water-treated starch demonstrated enhanced compressibility, higher amylopectin reorganization, and improved hydration behavior, reflecting increased molecular mobility and starch reassociation. These solvent-specific effects significantly influenced the functional and flow properties of sorghum starch. The findings highlight the potential of solvent manipulation as a practical strategy for controlling starch retrogradation and optimizing sorghum starch performance in product formulation. Understanding the differential effects of alcohol and water on sorghum starch retrogradation provides valuable insights for improving texture, stability, and shelf life in starch-based systems and supports the broader utilization of sorghum starch in diverse industrial applications.