Impact of dry (air classification) and wet fractionation on pea protein
molecular structure and gelling properties
Abstract
Dry fractionation is an environmentally friendly and cost-effective
method to separate protein fractions. While most research has focused on
the structure and functional properties of pea protein isolates (PPI),
the information on dry fractionated pea protein (DFPP) is limited. This
study compared DFPP (protein content (PC)-50.7%, insoluble fiber-17%),
to PPI (PC-80.1%, insoluble fiber-8.33%), in terms of the protein
structure, solubility, and heat-induced gelation. SDS-Page,
size-exclusive chromatographic, and Fourier-transform infrared
spectrophotometer analysis indicated that DFPP contained the major
protein components in pea, and their native structures were well
maintained. Whereas for PPI, some proteins were lost during wet
extraction, and partial protein unfolding and aggregation were observed.
At neutral pH, DFPP showed significantly higher solubility
(44.64±0.55%) than PPI (12.09±1.42%). Interestingly, DFPP showed good
gelling capacity as reflected by lower gelling concentration and higher
gel mechanical strength and elasticity compared to those made from PPI.
The DFPP gels were twice higher in mechanical strength (7.71±0.21kPa)
than that prepared from PPI at pH 7. Strong gels were also obtained for
DFPP at pH 5. The gel morphology revealed phase separation between
protein and polysaccharides by heating, with stick-shaped fiber
(10-25μm) dispersed in the continuous protein networks. Eventually, the
polysaccharides including fiber and starch helped strengthen the gel
network by acting as fillers. This knowledge will help to expand the
applications of DFPP as a gelling ingredient in food formulations, but
also allow industry to benefit from the dietary fiber co-exist in the
protein to develop healthier food products using a holistic approach.