Nutrient Levels, Bioactive Metabolite Contents, and Antioxidant Capacities of Faba Beans as Affected by Dehulling

Abstract

Legume dehulling often removes anti-nutrients while improving nutritional quality. However, the process may reduce the levels of other health-promoting metabolites. This study investigated the effect of dehulling on major nutrients, bioactive metabolites, and antioxidant activities using 22 faba bean cultivars typically grown in different parts of the world. The faba bean cultivars differed significantly in all the parameters assessed. Crude fiber (CFC), dietary fiber (DFC), crude protein, and crude fat contents were in the ranges of 5.24–10.56, 16.17–25.15, 19.83–30.90, and 0.79–1.94% in the whole seeds and 0.96–1.59, 4.14–9.50, 22.47–36.61, and 1.13–2.07% in the dehulled seeds, respectively. Moreover, fatty acids including palmitic acid, stearic acid, oleic acid, linoleic acid, and linolenic acid, bioactive metabolites including total phenol (TPC), total saponin (TSC), and total tannin (TTC) contents, and antioxidant activities including ABTS•+-scavenging activity, ferric antioxidant power (FRAP), and DPPH•-scavenging activity also showed significant variations. Dehulling significantly reduced DFC (55.09–79.30%), CFC (69.61–87.52%), and TTC (1.70–66.99%) in all the faba bean cultivars while increasing total protein content (9.31–17.69%). Dehulling also increased the total fat content (3.02–48.13%) in all the cultivars except Giant Three Seeded, a Japanese cultivar, which showed a 12.62% decrease. In contrast, dehulling exhibited varying results on fatty acids, TPC, TSC, and antioxidant activities among the faba bean cultivars. Accordingly, three cultivars: Primus from Hungary, Levens Marschbohne from Germany, and Ascott from France, exhibited simultaneous increases in nutritional levels after dehulling. Domasna-2 from Macedonia, Abawi# 1 from Peru, Seville from the United Kingdom, and Large Mazandran from Iran, on the other hand, exhibited marked reductions in nutritional levels, functional metabolites, and antioxidant activities. In general, our findings indicated that dehulling reduces crude fiber, dietary fiber, and tannin levels while increasing protein and fat contents in faba beans. However, fatty acids, phenolic content, and antioxidant activity may not be equally affected by dehulling and, therefore, specific genotypes should be inspected.