Antinutritional factors
Common beans contain several antinutritional compounds, notably enzyme inhibitors (trypsin, chymotrypsin, α-amylase), phytic acid, flatulence factors, saponins and lectins (Lyimo et al., 1992). The nature and activity of those compounds vary greatly among cultivars: for instance, raw navy beans were shown to contain twice the trypsin inhibitor activity than red kidney beans but half the lectin activity (Dhurandhar et al., 1990). Those antinutritional factors may hamper the performance of monogastric animals or even be toxic: for example lectins are known to have caused food poisining in humans who have eaten undercooked or raw beans. It is then highly recommended to process raw common beans before feeding them to pigs, poultry and other monogastric livestock. Treatments such as heating, autoclaving, cooking or extruding have been shown to remove heat-sensitive antinutritional factors (Bollini et al., 1999; Akande et al., 2010a; Carvalho et al., 1997; Dhurandhar et al., 1990; Kakade et al., 1965). Biological treatments such as germination, ensiling, treatment with pancreatin or with chemicals can also be effective in removing antinutritional factors in common beans (Schulze et al., 1997; Savelkoul et al., 1994). Lectin content may be reduced by cooking above 100°C, but cooking at a lower temperature (80°C) increased lectin content and toxicity (FDA, 2012).