Composition and in vitro digestibility of raw versus cooked white- and colour-flowered peas

Ten pea cultivars (four white-flowered, Pisum sativum ssp. hortense, and six colour-flowered, Pisum sativum ssp. arvense) grown in Latvia were analyzed and tested in in vitro experiments, as raw and cooked seeds. The colour-flowered (CF) had a greater proportion of hulls and a higher acid detergent fibre (ADF) content than white-flowered (WF) pea seeds (10.7 vs. 8.2% and 92.2 vs. 84.5 g/kg dry matter (DM), respectively). Three out of six CF varieties had a significantly greater amount of protein bound to neutral detergent fibre (NDF) than WF peas. The tannin content was higher in CF than in WF peas (8.46 vs. 0.37 g/kg DM). In vitro protein and amino acid digestibility was about 8% higher in WF than in CF varieties. Cooking decreased the tannin content in CF peas (8.46 vs. 5.51 g/kg DM) but had no effect on in vitro protein digestibility. Heat treatment reduced significantly trypsin inhibitor activity and amount of protein bound to NDF in CF and WF varieties (from 6.50 to 0.52 and from 6.54 to 0.46 trypsin inhibitor units (TIU)/mg DM; from 1.250 to 0.831 and 0.761 to 0.209 g N/100 g NDF, respectively). However, the protein bound to NDF content in pea DM increased in CF and decreased in WF varieties (from 1.525 to 2.145 and from 0.913 to 0.502 g N/kg DM, respectively). Cooking resulted in an increased NDF content over two times in both CF and WF pea seeds (from 122 to 259 and from 120 to 262 g/kg DM, respectively). The results suggest that colour-flowered pea may be considered as an interesting dietary alternative to white-flowered pea since cooking removes trypsin inhibitor activity (TIA), decreases tannins, and increases dietary fibre contents.