REDUCTION OF RAFFINOSE OLIGOSACCHARIDES IN CHICKPEA (CICER-ARIETINUM)FLOUR BY CRUDE EXTRACELLULAR FUNGAL ALPHA-GALACTOSIDASE

The efficiency of crude extracelluar alpha-galactosidases from Cladosp orium cladosporides, Aspergillus oryzae and A niger in reducing the ra ffinose and stachyose content in chickpea flours was studied and compa red with other traditional treatments. The optimum pH for alpha-galact osidase activity was found to be 4.5 for A oryzae and 5.0 for Cl clado sporides and A niger, while the optimum temperature of enzyme activity was 40 degrees C for Cl cladosporides and 50 degrees C for A oryzae a nd A niger. The specific activities of alpha-galactosidase from Cl cla dosporides, A oryzae and A niger were 3.35, 3.94 and 5.94 units mu g(- 1) protein, respectively. The enzyme activity was stable between pH 4. 0 and 7.0 for A oryzae and A niger and between pH 5.0 and 7.0 for Cl c ladosporides. The enzymes were thermostable when incubated at temperat ure ranges of 40-60''C for C1 cladosporides and 40-50 degrees C for A oryzae and A niger. The optimum conditions for removing the raffinose and stachyose were obtained by incubating chickpea flours with 30 mi o f crude fungal alpha-galactosidase extract (290, 210 and 130 units ml( -1) for C1 cladosporides, A oryzae and A niger, respectively) for 3 h at the optimum conditions of each strain. Crude fungal alpha-galactosi dases reduced the raffinose oligosaccharides content in chickpea flour s by 100%, while germination reduced the raffinose content by 69% and stachyose content by 75%. Other traditional techniques reduced the raf finose content by 13-49% and stachyose content by 10-32%. (C) 1998 Soc iety of Chemical Industry.