Reference Number: 10
Whole-grain foods play an important role in human diet as they are relatively rich in minerals, however, the absorption of those minerals in human gut can be very low due to high content of the mineral binding phytate. Therefore, the object of this study was to identify phytase-active lactic acid bacteria (LAB) which could be used as a starter to increase mineral bioavailability in whole-meal bread. Hence, LAB isolates were isolated from Lithuanian sourdoughs, tested for phytase activity, and phytase active isolates were identified. Studies of phytase activity of the isolates were carried out at conditions optimal for leavening of bread dough (pH 5.5 and 30 C). The phytase active isolates belonged to the species Lactobacillus panis, Lactobacillus reuteri, Lactobacillus fermentum, and Pediococcus pentosaceus. Phytase activities of the tested LAB isolates were both extra- and intra-cellular. The highest extracellular phytase production was found in L. panis with a volumetric phytase activity of 140 U/mL. Phytate degradation in whole-wheat dough fermented with L. panis or L. fermentum was 90% and 70%, respectively.
Significance of the study to the baker
Whole-grain products, such as whole-grain bread, have been recommended because of their high content of dietary fibre, B-vitamins, vitamin E and several minerals of which P, Mg, Fe, Cu, and Zn. However, the main parts of these minerals in cereals are complexly bounded to phytic acid as phytate, thereby reducing their bioavailability (reduced absorption) when consumed. Phytase, an enzyme specifically known to degrade phytic acid can help improve mineral bioavailability of whole grains. The sourdough process has shown to activate the enzyme phytase and the current paper states that the reduction of phytate can be achieved by enzymatic degradation during bread making, either by increasing the activity of endogenous phytase (phytase present within wheat) or by the phytase-active lactic acid bacteria (LAB) or yeasts during the slow long fermentation process.