Potential of sequential pearling to explore macronutrient distribution across faba beans (Vicia faba L.) for chemical-free hybrid fractionation

Abstract

Compositional analyses of sequentially pearled fractions of high-tannin (HT, Athena) and low-tannin (LT, Snowbird) faba bean (Vicia faba L.) cultivars demonstrated that the decreasing trend of protein, ash and total dietary fibre (TDF) contents from outer to inner layers was offset by starch contents. LT and HT proteins were positively correlated (r = 0.9, P < 0.0001) with ash and total dietary fibre contents while negatively correlated (r = −0.9, P < 0.0001) with starch contents with increasing degree of pearling. The 55–57 % single-step pearling flour had a higher (P < 0.05) protein content (LT:39.07 ± 0.06 % and HT:37.37 ± 0.03 %, N × 6.25) as compared to whole beans (LT:30.51 ± 0.39 and HT:29.63 ± 0.20 %). The starch contents of the pearled beans were significantly higher (P < 0.05) than whole beans. These single-step pearling flour fractions subjected to aqueous fractionation to isolate proteins (>94 % purity) resulted in starch isolates and dietary fibre concentrates as co-products. Hybrid fractionation had minimal impact on the native protein secondary structures where β-sheets were dominant. This study suggests that the inclusion of pearling as an upstream processing step prior to wet fractionation of both LT and HT faba beans has the potential to generate novel “clean label” ingredients for the food industry.