Inhibition of the amylolytic hydrolysis of starch by ethanol

Abstract

Gelatinized native corn starch dispersion (GSD, 5g/100 mL water) was diluted with ethanol/water mixtures (EWM, 0.0, 5.0, 10.0 and 20.0 ml ethanol/ml water) to a final concentration of 2.0 g GSD/100 mL EWM. The different EWM are representative of the ethanol content of different typical alcoholic drinks. The GSD were subjected to digestion by porcine pancreas α-amylase at 37 oC for 90 min. The percentage of digested starch reduced as an inverse function of EWM concentration. For 20.0 ml ethanol/ml water mixture the digested starch percentage was reduced by about 50%. Log-of-slope (LOS) method was used for analyzing the digestion kinetics curve, showing the presence of two (fast and slow) time scales. The fast and slow digestion kinetics were linked to rapidly (RDS) and slowly (SDS) starch fractions. It was found that ethanol reduced the RDS fraction, while increasing the resistant starch (RS) fraction. FTIR analysis suggested that modification of the enzyme secondary structure is behind the inhibition of the α-amylase activity by ethanol solvation.