HYDROLYSIS OF PHYTATE IN BROWN RICE-ADDED BREAD BY ADDITION OF CRUDE AND PURIFIEDASPERGILLUS NIGERPHYTASE PREPARATIONS DURING BREAD MAKING

Abstract

Brown rice‐added breads were prepared with and without crude and purified Aspergillus niger phytase preparations. By adding 30% (w/w) brown rice flour and no phytase preparation, the phytate (myo‐inositol hexaphosphate; IP6) content of the bread was increased and the loaf volume was reduced. The direct addition of a food‐additive grade phytase preparation (3,000 U) resulted in a significant decrease in the IP6 content. However, it collapsed the bread crust. The crude phytase preparation had significant protease and amylase activities. A simple chromatographic method for the separation of phytase activity from the protease and amylase activities was developed. By using purified phytase, the IP6 content was reduced without any adverse effects on the rising of the bread, which indicates that protease and amylase may be responsible for the collapse of the crust by the commercial phytase preparation. PRACTICAL APPLICATIONS Phytate in unrefined cereals and beans lowers bioavailability of minerals. On the other hand, these materials are rich in health‐promoting components. To reduce the phytate in them during processing, some commercially available phytase preparations are now used. However, we found that such preparation contains significant amylase and protease activities, which may cause adverse effect on the appearance and textural properties of final products. To solve these problems, a simple and inexpensive procedure for separation of phyatase from amylase and protease was developed in the present study. The purified phytase can reduce phytate in brown rice‐added bread without adverse effect on rising of bread. These results would encourage prepare the phytase preparation in high purity in an industrial scale to improve nutritional value of unrefined cereal‐ and bean‐based functional foods.

Control of amylase and protease activities in a phytase preparation by ampholyte-free preparative isoelectric focusing for unrefined cereal-containing bread

“…However, consumption of brown rice in its steamed form is not prevalent due to its poor swelling and textural properties. Alternatively, brown rice has been processed to flour and used for bread making (Matsuo, Sato, Nakamura, & Ohtsuki, 2005;Matsuo, Sato, Park, Nakamura, & Ohtsuki, 2010;Nakamura, Satoh, & Ohtsubo, 2010). The use of brown rice flour in bread is gradually gaining popularity in Japan.…”

“…Our earlier studies have shown that the IP 6 content of brown rice flour-added bread decreased by direct addition of a food additive-grade A. niger phytase preparation to the dough. However, the A. niger phytase preparation had significant protease and amylase activities (Matsuo et al, 2005;Matsuo et al, 2010). Addition of high doses of such phytase preparations to the dough induced bread crust collapse and deteriorated the appearance and textural properties of the final products.…”

Utilization of Aspergillus niger Phytase Preparation for Hydrolysis of Phytate in Foods

“…However, these microbial also produce protease, amylase and etc. As demonstrated in the following sections, a food additive-grade Asperigillus niger phytase preparation has significant protease and amylase activities (Matsuo et al, 2010). In some cases, occurrences of protease and amylase in the food additive-grade phytase preparation exerts adverse effects on texture and appearance of the final products.…”

“…However, addition of high dose of the phytase preparation (3000 U) induced collapse of whole bread crust and deteriorates texture and taste of the final product as shown in Figure 4 E (Matsuo et al, 2005). Figure 5 shows that the food additive-grade phytase preparation contains significant activities of protease and amylase, which can be separated from the phytase activity by anion-exchange column chromatography (Matsuo et al, 2010). Addition of the purified phytase fraction free from protease and amylase activities into the dough mix decreased IP 6 level without affecting bread volume ( Figure 6).…”

“…A; 30% brown rice bread, B; added with the crude phytase, C; added with the purified phytase. From Matsuo et al, 2010 www.intechopen.com…”