Raw pinto bean flour contained 0.38% raffinose and 3.34% stachyose on a dry weight basis. Bean flour was heated at 100C or 115C for 25 min, and then treated with crudeα‐galactosidase (60 Gal U/mL) produced by Aspergillus awamori NRRL 4869. Crude enzyme completely hydrolyzed raffinose oligosaccharides in pinto bean flour and bean paste after 2 h treatment. Lipoxygenase and trypsin inhibitor activity were greatly inhibited (P < 0.05). Descriptive analysis showed that color, raw beany off‐flavor, bitterness and astringency of pinto bean paste increased significantly (P < 0.05) after the enzymatic treatment. There were no significant changes in stickiness, cooked bean aroma, nutty flavor, and sweetness of control pinto bean paste and enzymatic‐treated bean paste.
PRACTICAL APPLICATIONS
The use of dry edible beans is limited partly because of the presence of flatulence factors, especially the raffinose oligosaccharides. Crude fungal α‐galactosidases were very effective for removing raffinose oligosaccharides. However, the crude enzymes also contained other types of enzymes, which catalyzed undesirable reactions to produce low sensory quality products. Hence, more specific enzymatic methods for producing good sensory characteristics of the bean paste need to be developed before commercialization.