Development and Quality Assessment of Extruded Snack Products from Brewers’ Spent Grain, wheat Flour, and Soy Protein Isolate Blends

Abstract

Extruded snacks were produced from blends of Brewers’ Spent Grain (BSG), wheat flour, and soy isolate in order to provide nutritionally balanced products for both adults and children. Graded levels (0 - 35%) of dried and milled BSG were added to extruded snack formulation consisting of wheat flour, soy isolate, milk, flavour, salt and sugar. They were extruded and baked to obtain crispy products that were subjected to chemical, microbial, physical, functional, and sensory analysis using standard methods. The results showed that the incorporation of BSG and soy isolate increased the protein content of the extrudates. The following ranges of the proximate, macro and micronutrient contents were obtained: moisture 3.64 - 5.63%, fat 5.73 - 6.31%, protein 14.09 - 19.28%, ash 1.25 - 2.77%, vitamin B1 0.0 - 0.20 mg/g, vitamin B2 0.43 - 0.55 mg/g, vitamin B3 0.29 - 0.40 mg/g, vitamin C 0.00 - 0.05 mg/g, calcium 3.69 - 4.77 mg/g, sodium 0.30 - 0.37 mg/g, zinc 6.47 - 6.92 mg/g, magnesium 10.60 - 10.95 mg/g, and iron 0.42 - 0.49 mg/g. The addition of BSG significantly (p<0.05) affected the colour, increased bulk density, and decreased the sectional expansion index, water absorption index, and water solubility index. The extruded snacks were acceptable to the assessors up to 15% BSG inclusion. These results have proven that acceptable shelf-stable, ready-to-eat snack products could be produced from blends of BSG, wheat flour, and soy isolate, which will address the problems of protein and energy malnutrition in developing countries.