Inhibition of the amylolytic hydrolysis of starch by ethanol

Gelatinized native corn starch dispersion (GSD, 5 g/100 mL water) was diluted with ethanol/water mixtures (EWM, 0.0, 1.0, 2.5, and 5.0 mL ethanol/100 mL) to a final concentration of 2.0 g GSD/100 mL EWM. The GSD were subjected to digestion by porcine pancreas α-amylase (0.33 and 0.66 IU/mL) at 37 °C for 90 min. The digested starch was reduced as an inverse function of ethanol concentration. The digested starch reduction can be as high as 15–30%, depending on the α-amylase concentration. 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.