Dry milling of field pea (Pisum sativum L.) groats prior to wet fractionation influences the starch yield and purity

Field peas from two cultivars were dehulled and groats were processed by two protocols: (1) groats directly ground with water into a slurry and fractionated into fibre, protein and starch concentrates (groat wet fractionation, GWF), and (2) groats dry milled into flour and then wet fractionated using steps identical to that of protocol-1 (flour wet fractionation, FWF). The yield (%, w/w) and composition (%, w/w) of starch, protein and fibre concentrates from both protocols were determined. The data indicated that the FWF had significantly higher starch yield when compared to GWF. Scanning electron micrographs clearly suggested that better tissue fragmentation caused by dry milling may be responsible for better starch yield in FWF. The purity of starch isolate from FWF was lower than that of GWF. Brabender viscoamylographs showed differences in pasting properties of starches between protocols. Furthermore, the effect of sonication on starch yield and purity was studied between two wet fractionations. A combination of FWF with the sonication at 75% amplitude for 10 min showed better starch yield.