By the end of fermentation, the α-amylase activities in gruels fermented by single cultures were, in average, between 50.5 and 69.2 CU · 100 g− 1 in RS and between 47.1 and 73.7CU · 100 g− 1 in RSPF gruels (Fig. 2A and B). Even lowering the time to achieve pH 4.5, passion fruit fiber increased significantly the α-amylase activity of single cultures of L. plantarum and of L. acidophillus, but the mechanism of this positive effect remains unclear and requires further studies. The enzymatic activity was also higher in RSPF gruels fermented by L. fermentum but, regarding its curve of α-amylase activity ( Fig. 2B), this effect can be due rather to the increase in the fermentation time promoted by passion fruit fiber (Table 1) than to a direct effect of the fiber on the activity or production of the enzyme. However, the lower final α-amylase activity in RSPF fermented by L. casei can be associated to the shorter fermentation time induced by the passion fruit fiber ( Table 1, Fig. 2B).