Phytate phosphorus determination in feedstuffs by enzyme analysis.
1995
Takemasa M. | Murakami H.
For the facile determination of the phytate phosphorus content in feedstuffs, a new method using enzyme "phytase" was developed. Results using sodium phytate as a substrate demonstrated that phytate phosphorus could be determined as follows. A finely ground sample containing 10-15mg phytate phosphorus is weighed in a test tube, followed by dissolving 10 ml of 0.25 unit/ml enzyme solution in the tube. After 16 hr incubation at 55 degrees C, 5ml 6% trichloro acetic acid are added. After 30 min, the contents of the tube are filtered through filter paper. One ml of the filtrate is transferred to a volumetric flask, and inorganic phosphorus content is determined colorimetorically. At the same time, the blank analysis is carried out using an inactivated enzyme solution, prepared by being held in boiling water for 5 min. Nine different feedstuffs used most frequently in Japan were quantitatively analyzed for phytate phosphorus content. This content in major feed ingredients except barley and wheat could be determined satisfactory by the present method than by the Fe precipitation method. Barely and wheat values were less than those by the latter method. The phytase action of barley and wheat may have been the reason for these lower values. To inactivate phytase, dry-heating at above 100 degrees C for 60 min in barley and at above 150 degrees C for 30 min in wheat, was sufficient. By dry-heating at 160 degrees C for 30 min at the start of blank analysis, phytate phosphorus in barley and wheat could be determined with sufficient accuracy by the present method. Phytate phosphorus in feedstuffs can be easily determined by the method proposed here, though with less accuracy than by the Fe-precipitation method.
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