Characterization of apple dietary fibers influencing the in vitro starch digestibility of wheat flour gel

- Gel made by dietary fiber blends with various SDF/IDF ratios and replacement levels.
- Delayed starch digestion was dependent on SDF/IDF ratios as well as TDF levels.
- Less than the 20% of TDF, an equal blend of SDF and IDF is critical factor.

Two dietary fiber enriched-materials (FEMs) were prepared from apples and their effects on in vitro starch digestibility were investigated in a wheat flour gel model. Apple FEMs were highly effective at lowering starch hydrolysis. The predicted glycemic index (pGI) values were noticeably reduced when wheat flour was replaced with an equal blend of soluble (SDF) and insoluble dietary fibers (IDF) at 20% by weight. However, at the levels of above 30% replacement, the pGI changes were not dependent on the ratio of SDF and IDF. Pearson correlation analysis showed that the pGI values were negatively correlated to the contents of TDF and SDF. Consequently, TDF contents were more effective than SDF and IDF ratio in lowering pGI values.