Impact of α-amylase during breadmaking on in vitro kinetics of starch hydrolysis and glycaemic index of enriched bread with bran.

Nowadays, the use of enzymes has become a common practice in the bakery industry, as they can improve dough quality and texture of final product. However, the use of α-amylases could have a negative effect in the glycaemic load of product, due to the released sugars from the starch hydrolysis that are not used by yeasts during the fermentation process. This study evaluated the effect of the addition of α-amylase in bakery products with bran on in vitro kinetics of starch hydrolysis. The use of flour with a high degree of extraction or high bran amount could decrease the GI even with the inclusion of α-amylase in the formulation. It should be taken into account the amount of bran and α-amylase when formulating breads in order to obtain products with lower GI than white bread. However, the fact that kinetics of starch hydrolysis remained unaltered indicates that the use of α-amylase in bread-making processes could provide technological advantages improving quality of breads without markedly changes in their glycaemic index.

Application of bifidobacterial phytases in infant cereals: effect on phytate contents and mineral dialyzability.

Phytase activity was recently described in probiotic bifidobacterial strains, opening the possibilities for their use in foods, due to the generally regarded as safe/qualified presumption of safety status of these bacteria. Two raw materials for infant cereals (multicereal and gluten-free) were examined by measuring the myo-inositol phosphates content and the in vitro Ca, Fe, and Zn availability after a dephytinization process with purified phytases from Bifidobacterium longum spp. infantis and Bifidobacterium pseudocatenulatum. Treatment with both enzymes reduced the contents of phytate as compared to control samples (untreated or treated with fungal phytase) and led to increased levels of myo-inositol triphosphate. Dephytinization followed by an in vitro model of intestinal digestion increased the solubility of Zn. However, phytase treatment did not increase significantly the mineral dialyzability as compared to untreated samples. This is the first example of the application of purified bifidobacterial phytases in food processing and shows the potential of these enzymes to be used in products for human consumption.

Novel phytases from Bifidobacterium pseudocatenulatum ATCC 27919 and Bifidobacterium longum subsp. infantis ATCC 15697.

Two novel phytases have been characterized from Bifidobacterium pseudocatenulatum and Bifidobacterium longum subsp. infantis. The enzymes belong to a new subclass within the histidine acid phytases, are highly specific for the hydrolysis of phytate, and render myo-inositol triphosphate as the final hydrolysis product. They represent the first phytases characterized from this group of probiotic microorganisms, opening the possibilities for their use in the processing of high-phytate-content foods.

Assessment of iron bioavailability in whole wheat bread by addition of phytase-producing bifidobacteria.

In this study, the influence of phytase-producing Bifidobacterium strains during the breadmaking process (direct or indirect) on final bread Fe dialyzability and ferritin formation in Caco-2 cell as a measure of cell Fe uptake was assessed. The addition of bifidobacteria significantly reduced the InsP(6) + InsP(5) concentrations compared to control samples. Fe-dialyzable contents for samples with bifidobacteria were increased 2.3-5.6-fold, and dialyzability was improved by 2.6-8.6% compared to controls. However, this was not reflected in an increase of Fe uptake by Caco-2 cells as was predicted by the phytate/Fe molar ratios. The results demonstrated the usefulness of phytase-producing bifidobacteria to reduce phytate during the breadmaking process and to increase Fe accessibility, although the effects appeared to be still insufficient to improve Fe bioavailability in Caco-2 cells. Further refinement of the use of phytase-producing bifidobacterial strains and/or breadmaking technological processes is deserved for improving Fe uptake.

Phytate reduction in bran-enriched bread by phytase-producing bifidobacteria.

Bread fermented with the selected Bifidobacterium strains had similar technological and sensorial quality as the controls, resulting in breads with significantly lower (p < 0.05) levels of InsP(6) with residual amounts of myo-inositol triphosphates (InsP(3)). The fact that the phytate-degrading enzymes are produced by strains of bifidobacteria, which are GRAS/QPS (generally regarded as safe/qualified presumption of safety) microorganisms makes this strategy particularly suitable to reduce the content of InsP(6) in rich fiber products for human consumption.