Chemical studies on Phytase activity and phytate in the seeds and protein isolates of two soybean cultivars

Abstract EN

The seeds of two new soybean cultivars (Giza 22, Giza 35) were studied; phytate concentration in cotyledons, hull and protein isolates, effect of pH on the solubility of phytate and protein, effect of germination on phytase activity and phytate, preparation of partially purified phytase from seeds germinated for 7 days, removal of phytate from protein isolates by partially purified phytase, and the functional properties of soybean defatted meals and their proteins isolates.

Preparation of low phytate - protein isolates (1.5-1.8% phytate) using the differences in solubilities of phytate and protein at acidic pH (5-5.5) was studied.

The yield was lower compared with high phytate - protein isolates (2.7-3.1% phytate) precipitated at pH 4.5 with maximum yield.

No phytase activity could be detected in the dry seeds but appeared during germination to reach its maximum levels after 7 days of germination with concomitant decrease in phytate content.

Partially purified phytases showed pH optimum at 5 and 5.5 for enzymes of Giza 22 and Giza 35, respectively.

Incubation of partially purified phytase with high phytate-protein isolates at optimum pH and temperature 50°C resulted in complete removal of phytate from protein isolates of Giza 22 and Giza 35 after 60 and 80 min, respectively.

The functional properties determinations revealed that removed phytate soyprotein isolate (RP-SPI) exhibited functional properties similar to or superior to those of other protein isolates or defatted meals.