In this study defatted cowpea flour was prepared from cow pea
beans and analysed for proximate composition and for different
types of mono-, di- and oligosaccharides. Protein isolate was prepared
(CPI) and thermally denatured (DCPI). To prepared glycated
cowpea protein isolate (GCPI) a cowpea flour slurry was heat treated
before isolation of the protein. Protein functionality as regards
to texture and sensory properties were tested by supplementation
of flours in bread and sponge cake.
Analysis of physicochemical properties of proteins showed that
CPI is more susceptible to thermal denaturation than GCPI during
heat treatment as evidenced by higher denaturation degree and
higher loss of solubility. This is attributed to the protective effect
of higher glycation degree and higher carbohydrate content of GCPI
as demonstrated by sugar analysis and glycoprotein staining of SDS
PAGE gels, resulting in improved maintenance of solubility. Water
absorption of bread dough was significantly increased by DCPI and
to a larger GCPI compared to the control, resulting in softer texture.
Sensory testing and textural analysis of bread indicate that denaturation
and glycation of CPI can allow the inclusion level in bread
to be increased from 2% to 4% without affecting the sensory acceptability
or textural properties.
Addition of 4% DCPI or GCPI to bread, leads to an increase in
total fibre from 0.08% to 0.46% (results not shown) and in protein
content from 7.5% to 9.5% (result not shown), thereby enhancing
the bread nutritional quality.