Comparing mass transfer and reaction rate kinetics in starch hydrolysis during food digestion

Abstract

This study demonstrates evidence that the mass transfer process of an enzyme (a biocatalyst) is the rate-limiting step in the starch hydrolysis reaction during food digestion. The significance of this work has been to compare the reaction rate of starch hydrolysis by salivary enzymes with the mass transfer rate of rate-limiting enzymes. This research has applied mass transfer and reaction engineering theory in a quantitative study of starch hydrolysis, and a dimensionless group, the Damköhler number (Da), has been calculated based on glucose measurements from a beaker and stirrer system. The values of the Da number in this study (0.3–19) indicate that both the time constant for mass transfer and the time constant for reaction are significant parameters. Scanning electron microscopy images emphasize that compression (simulated mastication) helps to break the plant cell wall of starch. Mass-transfer resistance needs to be considered during food digestion studies. The Da numbers are significantly affected by both compression forces (internal mass-transfer coefficients) and stirrer speeds (external mass-transfer coefficients) in this beaker and stirrer system.