Chapter 16 - Effect of Addition of Thermally Modified Cowpea Protein on Sensory Acceptability and Textural Properties of Wheat Bread

Abstract

This chapter gives an overview of the use of plant proteins to fortify breads. It furthermore investigates the sensory acceptability and textural properties of leavened wheat bread fortified with cow protein isolates that had been denatured and glycated by thermal treatment. Defatted cowpea flour was prepared from cowpea beans, and the protein isolate was prepared as cowpea protein isolate (CPI) and thermally denatured cowpea protein isolate (DCPI). To prepare glycated cowpea protein isolate (GCPI), the cowpea flour slurry was heat-treated before the protein was isolated. CPI was more susceptible to thermal denaturation than GCPI, as determined by turbidity and sulfydryl groups, resulting in greater loss of solubility. This is attributed to the higher glycation degree and higher carbohydrate content of GCPI, as demonstrated by glycoprotein staining of sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) gel. Water absorption of bread dough was significantly enhanced by DCPI, and to a larger extent by GCPI compared to the control, resulting in softer texture. CPI resulted in significantly increased crumb hardness in baked bread than the control, whereas DCPI or GCPI resulted in significantly softer crumbs. Bread fortified with 4% DCPI or GCPI was similar to the control with regard to sensory and textural properties, whereas 4% CPI was significantly different, limiting its inclusion level to 2%. There was a trend for higher sensory acceptability scores for GCPI-containing bread compared to DCPI. Whole egg was replaced by 20% by GCPI (3.5%) in sponge cake without affecting the sensory acceptability, whereas CPI- and DCPI-supplemented cakes were significantly different from the control.