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A new method for the determination of lipolytic activity (LA) in milled products from cereals is described. This method is based on the use of the pHstat titration of free fatty acids (FFA) released by LA after incubating a mixture of defatted wholemeal or milling wheat fraction and olive oil during 72 hours at selected conditions of temperature and activity of water (A w ). The results given by this method have been compared systematically to those given by the time-consuming and classic one of the determination of the LA in low moisture media based upon the FFA determination by gas chromatography (GC) after separation by thin layer chromatography. The two methods have been used under various experimental conditions in order to study the effects of temperature, A w and addition of exogenous lipase in different wheat milled products. For the germ, bran, flour and whole meal fractions at 30°C and A w = 0.8, LA determined by the titration pHstat method was correlated to the values obtained by the GC method (r = 0.99). By pHstat, LA was found equal to 0.054, 0.75, 0.29 and 0.51 µmol.h -1 .g -1 (dm) vs 0.053, 0.79, 0.27 and 0.48 µmol.h -1 .g -1 (dm) by GC for the flour, bran, germ and wholemeal fraction respectively. When experimental conditions were modified, LA determined by pHstat was correlated with LA obtained by GC either when A w was varied for the bran fraction between 0.17 and 0.87 or temperature between 30 and 40°C (r = 0.95) or after addition of exogenous lipase to wheat flour (r = 0.97). This less time-consuming method for the determination of LA may be of a great interest to improve the storage conditions of cereal milled products as well as to estimate the efficiency of heat treatments on the denaturation of endogenous lipase in these products.

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