Release, partitioning and stability of isoflavones from enriched custards during mouth, stomach and intestine in vitro simulations

Custard desserts were enriched with a soy germ extract as source of isoflavones and the influence of the thickening agent (starch or carboxymethylcellulose (CMC)) and the presence of fat on the release, partitioning and stability of the isoflavones after mouth, stomach and small intestine in vitro incubations were studied. A suspension in water of the soy germ extract was first analyzed. Mouth incubation did not affect the amount and partitioning of isoflavones. A lower recovery and different partitioning were found after the stomach incubation, which was associated to the low pH. After the intestine incubation, a higher recovery and an effect in the partitioning were found. Regarding the effect of the custard matrix, the starch custards were able to release a significantly higher amount of isoflavones than the CMC ones, due to the higher general enzymatic resistance of the latter one's. The presence of fat significantly increased the bioaccessibility of the aglycone forms, especially of genistein.