Effect of pasteurization on in vitro α-glucosidase inhibitory activity of apple juice

The in vitro alpha-glucosidase inhibitory activity of raw, mildly (F-71.7(5) = 0.4 min, 5 Log reductions of Cryptosporidium parvum) and intensively (F-90(12) = 14.8 min, 2 Log reductions of Alicyclobacillus acidoterrestris) pasteurized apple juice was studied. Raw apple juice (23 mg(dw)/mL) caused 90% alpha-glucosidase inhibition. Analogous results were obtained for the mildly treated sample. The most intense treatment reduced by 35% the alpha-glucosidase inhibition. However, such a decrease was associated with an increase in the phenolic content, suggesting that alpha-glucosidase inhibition might not rely on these compounds, but depend on more complex mechanisms. Apple juice was combined with acarbose to investigate their interaction towards alpha-glucosidase inhibition. A synergistic behavior was observed for concentrations < 2 mg/mL. Increasing the concentration of the combined system (up to 9 mg/mL) produced an antagonistic effect, while a further increase (< 9 mg/mL) allowed approaching an addictive behavior.