Influence of fermentation followed by ultrasonication on functional properties of sorghum extrudates

Extrusion process deals with a compromise between better texture and less nutrition. In the present study, sorghum flour was subjected to fermentation followed by ultrasonication prior to extrusion to increase the antioxidant activity (AA) and total phenolic content (TPC) in the flour. AA and TPC of the sorghum flour were increased when fermented for 12 hr and further decreased significantly with an increase in the fermentation time. During the ultrasonication, a significant diminution in AA and TPC of the flour was reported with an increment in the ultrasonication intensity and fermented flour to water ratio. No significant impact of the ultrasonication time was found on AA and TPC of the sorghum flour. Optimum AA and TPC were obtained as 178.8 mu mol TE/100 g dry weight (DW) and 77.8 mg GAE/100 g DW, respectively. Extrudates obtained from the pretreated sorghum flour under optimum conditions had improved nutritional and textural qualities. Also, the pretreated sorghum flour showed low stability of starch crystallites and crystalline fraction. Practical Applications Millets and sorghum possess high amounts of phenolics, polyphenols, and other bioactive compounds. It was explicated from the results that the fermentation followed by the ultrasonication could improve the antioxidant activities and phenolics in the sorghum flour. Furthermore, sorghum extrudates with remarkable retention of antioxidant activity, phenolic content, functional, and textural properties were obtained. This technology may help the food industries to develop gluten-free and healthy snacks by incorporating sorghum (underutilized cereal) into human diet.