A method to simulate in vitro the physiological conditions in the stomach and small intestine has been developed as a modification of a method already described by Miller et al. [11]. This method enables the study of phenolic compound release from the food matrix and their trans formation during digestion, and has been applied to orange juice. strawberries. and strawberry jam. The dialysis rates obtained for the different phenolics in the new method are much better than those found in the original one. Some food constituents, as is the case of sugars in jams, can affect the dialysis rates in vitro, showing that the results obtained for dialysis should be taken with caution in these products. These assays have shown that strawberry anthocyanins are largely degraded (transformed) during the digestion and that free ellagic acid is released from ellagitannins leading to a ten-fold increase of this compound during digestion.