Microstructural, physicochemical, and starch digestion properties of cotyledon cell flours prepared by colloid milling of New Zealand pea varieties

This study compared the microstructural, physicochemical, and in vitro starch digestion properties of novel cotyledon cell flours (CCF) prepared via colloid milling with traditionally milled flour (TMF) from four NZ-grown pea varieties, namely White/Yellow (W-Y), Marrowfat (MFP), Blue (BP) and Maple pea (MP), respectively. The yield of CCF from each pea variety varied from 68.8% (W-Y) to 80.12% (BP). The Scanning electron microscopy (SEM) characterisation of both types of flours showed a distinct difference in their microstructural organisation. CCF's protein and fibre contents were 10 % and 3 % higher than their TMF counterparts. The peak temperature for the CF flour differed significantly (p < 0.05) from the TMF for three varieties except W-Y. The CCFs showed lower relative crystallinity (%) than TMFs, with W-Y showing the lowest (13.6 %). The starch hydrolysis and glycaemic response of CCFs were almost 10 % lower than the TMFs. The significant difference observed in the pasting, thermal and starch hydrolysis properties of the CCF and TMF could be attributed to the cell wall of cotyledon cells acting as a primary barrier. This study presents a novel use of colloid milling to create higher-yield functional cotyledon flours with reduced glycaemic impact.