Journal 0/ CerealScience 8 (1988) 47-53 Studies on Phytase Activity in Oats and Wheat using 31P-NMRspectroscopy W. FR0LICH*t,M. WAHLGREN:j: andT. DRAKENBERG§ * University of Oslo,Institute for Nutrition Research, P.O. Box 1046, BUndem 0316, Oslo3, Norway and:j: Department ofFood Technology and § Department of Physical Chemistry 2, Chemical Centre, P.O. Box 124, 8-22100 Lund, Sweden Received 3 September 1987 andin revised/arm 12 February 1988 31P-Nuclear magnetic resonance spectroscopy (3 1 P-NMR)was used to follow the breakdown of phytatein oats andwheat.This techniqueoffersconsiderable advantages over currently used methods for the measurement of relative amounts of the intermediate metabolites of the enzymatic degradation of the parent phytate. The degradation of phytate was used as an indicator of the activity of the phytase enzyme. In contrast to earlier studies, the31P_NMR studies showed thatthe degradation of phytate in both wheatand non-heat treated oats proceed at similar rates. In the commercial oat productsexamined, however,no degradation of phytatewas observed. This strongly indicates that phytase is present in natural oats, but thathe enzyme is rendered inactive by the heat treatment normally used in processing oats for food products. Introduction Phytase (myo-inositol hexaphosphate phosphorylase) has a wide distribution in plants andanimaltissues l - 3 . Phytase prepared from rice bran was one of the firstenzymes to be described thatliberated inorganic phosphate from organic phosphorous compounds 4 • The existence of two types of phytasehasbeen suggested, onebeing characteristic for micro-organisms and the other for seedsfrom higherplants 1 ,s.6. The most likely principal function of phytasein grains is to provide inorganic phosphate from phytate (myo-inositol hexaphosphate) during germination, sincephytate is the predominant phosphorous-containing component in cereals 7 - o and because phytase activity has been shown to increase duringgermination 1o - 12 • Phytasefrom various sourceshas beenstudied,most commonlythe one from wheat1,lo. It has been shown 13 thatwheat phytase has a broad substrate specificity with a pH optimum around 5·0 anda temperature optimum ranging from45-57°Cwithan average of 50°C 1 . The activityof phytase from rye seems to be higher than phytase from other cereals 12 . 14 • Studies on phytasein oatsaresparse and the results are conflicting, either indicating no activit y14 orlow to medium activit y 12,lS-17.Thelow phytase activity has been claimed to be the reason for the rachitic effect of a diet high in oats 18 . However, thebreakdown of phytate in oats has beenshownto increase during germination 1Ho , indicatingthe presence of phytase. t To whom correspondence should beaddressed. 0733-5210/88/040047+07 $03.00/0 © 1988 Academic Press Limited