Development and functional characterization of new antioxidant dietary fibers from pomegranate, olive and artichoke by-products

A novel ingredient acting as a slow digestible dietary fiber (DF) was developed by including native corn starch in calcium alginate microspheres (MS). In this study three types of antioxidant DF-rich ingredients were designed and developed by including in the MS, polyphenol-rich vegetable by-product extracts (obtained from pomegranate peels, olive leaves and artichoke leaves) and their potential functionality was assessed in vitro. Specifically, the physico-chemical properties of the new MS were compared with those of six commercially available DF concentrates and with wheat and oat brans. To evaluate the potential efficacy to release PPs along the gastrointestinal tract (GiT), pomegranate peels-microspheres (PPe-MS) were subjected to in vitro simulated gastrointestinal digestion. Results showed that the newly developed MS had higher free antioxidant capacity (free-TAC) than commercial DF rich products, and the bound antioxidant capacity (bound-TAC) of PPe-MS was comparable to that of wheat bran and 4.4 folds higher than that of oat-bran. Furthermore, it was shown that the release of ellagitannins from cooked PPe-MS along in vitro simulated gastro-intestinal digestion decreased from the salivary to the small intestine phase whereas gallic acid, ellagic acid and its derivatives had an opposite trend. A certain amount of PPs was found in the spent pellet obtained from the in vitro digestion, which was mimicking the residue reaching the colon in vivo. In conclusion data showed that the new antioxidant MS have physical-chemical properties like those of wheat and oat brans, mainly including the bound antioxidant capacity. This open to new possibilities of functional utilization of vegetable by-products for obtaining valuable and healthy food ingredients.