Comparison of the 3 PPIs revealed that although their basic
chemical compositions were similar their functional properties
correlated with the proteins’ thermal properties. These in turn affected
the viscosity of the protein mass during the initial heating
phase of the extrusion process, but became less relevant at temperatures
above the proteins’ denaturation temperature. In order to
screen unknown protein ingredients for their processing behavior
particularly during the critical heating phase, RVA viscosity tests
of protein slurries could be a simple and useful tool for simulation
of the extrusion process. Although all powders were suitable for
HMEC, larger particles (PPI 3) were easier to process than fine powders
(PPI 1). Fiber formation depended on cooking temperature
and was basically similar among the three PPIs, although considerably
different energy input was observed during their extrusion
texturization. In order to comprehensively explore the effect of
the protein ingredients on HMEC, further investigations of the proteins’
properties are necessary. Comparison of their molecular
weight distribution, amino acid composition, and protein–protein
interactions before and after extrusion could provide further insight
into the structure-process-texture-relationship.