Multifilm Mass Transfer and Reaction Rate Kinetics in a Newly Developed In Vitro Digestion System for Carbohydrate Digestion

Multifilm mass transfer theory has been used in conjunction with developing a new in vitro starch digestion model and applied to assessing starch digestion kinetics. One significance of this research is that this in vitro model has similar dynamics, such as similar Reynolds numbers for both in vivo and in vitro systems. In the in vitro intestine model, when the flow rate changes from 5.9 × 10^-6 m³ s^-1 to 1.0 × 10^-5 m³ s^-1 inside the intestine wall (inside the sausage casing), the <i>Re</i> number changes from 362 to 615. An oral digestion model, a stomach model, and an intestine model have been built to quantitatively understand reaction rate kinetics and two-film (or multifilm) mass transfer for carbohydrate digestion. This in vitro digestion system represents the oral mastication process to reduce the length scale of the test food, amylase inhibition in the stomach, and glucose generation and transport through the intestine wall according to the various emptying rates from stomach. Another dimensionless group, the Damköhler number (<i>Da</i>), has been calculated based on glucose measurements from this in vitro model, which show similar glycemic responses of the hydrolysis for banana and carrot with in vivo results. Another significance of this research is to distinguish a low GI food from a high GI one in this in vitro system and the possibility to estimate the GI value based on the glucose measurements.