Studies on the Determination of Wheat Starch Phosphorus as Glycerol Phosphates

Abstract

1. The phosphorus of glycerol-phosphate derivatives (Pg) in wheat and other cereal starches was determined quantitatively by the following method. Starch (100_??_400mg) was suspended in 3.3ml of 0.726 N HCl and hydrolyzed at 100°C for 90min. Glycerol-phosphates thus formed were hydrolyzed further with alkaline phosphatase and the resulting glycerol, of which amount was equivalent to Pg, was assayed spectrophotometrically by using glycerokinase and glycerophosphate dehydrogenase. The amount of Pg, thus obtained, was corrected for the loss during the acid hydrolysis by a factor 1.013.
2. By the above procedure, the amounts (% of total phosphorus) of Pg of wheat I (commercial), wheat II (laboratory prepared), corn (commercial), rice I (commercial) and rice II (laboratory prepared) starches were determined as 90.8, 99.9, 69.8, 74.9 and 62.7. No Pg was detected in potato, sweet potato, kuzu (a kind of arrowroot), waxy corn, and waxy rice starches.
3. It was revealed that these cereal starches contained acid unstable unknown phosphate (s) which was hydrolyzed within 60min under the conditions described above ac a minor component.