Nutritional, functional and rheological properties of processed sorghum and ragi grains

Abstract

This study was undertaken to determine the effect of different treatments such as roasting, puffing and germination of white sorghum, red sorghum and ragi grains on physicochemical, antioxidant, protein, amylose, bulk density, colour index and rheological properties of respective flour. In case of ragi, after roasting treatment, total phenolic content (TPC) content for flour was increased from 0.331 ± 0.001 to 0.373 ± 0.004 mg of gallic acid equivalents per gram of dry sample. However, total flavonoids content was also increased slightly after different processing treatments. The rheological properties of respective flour were studied using Chopin Mixolab, where wheat flour dough profile acts as a reference to study the effect of different treatments. Dough elasticity which is expressed by the values of amplitude (Nm) was found to be low in case of untreated flour as compared to wheat flour dough. Elasticity values of untreated flour such as white sorghum, red sorghum and ragi were 0.02, 0.00 and 0.06 Nm, respectively. Whereas, after processing treatments, values of elasticity for roasted flour dough of white sorghum, puffed flour dough of red sorghum and roasted flour dough of ragi increased to 0.36, 0.11 and 0.15 Nm, respectively, as compared to wheat flour dough of 0.10 Nm. The results found that roasted ragi flour had higher rate of starch gelatinization, lower starch retrogradation, high antioxidant and amylose contents which were found to be prospective ingredients in whole wheat flour in various baked and fermented food applications.

Keywords

• wheat
• sorghum
• ragi
• nutrition
• antioxidant
• rheology