Enrichment of enzyme resi̇stant starch content of flour and researching of opportunity to use this flour in biscuit production as a dietary fiber source

In this research, the possibilities of enrichment of enzyme resistant starch (ERS) content of wheat flour by using different methods, and using ERS containing flour in biscuit production as an alternative source of dietary fiber was studied. High intake of dietary fibers, also known as indigestible food components, in diet is essential for a healthy lifestyle. In the study, it was evaluated that the ERS content of obtained flour has health promoting effects due to its dietary fiber-like behavior and low glycemic index. In literature review it was seen that, giving enzyme resisting properties to some starch types, obtained from different sources, are widely studied but studies, objecting wheat flour, are limited. In the first step of the study, the slurries with four different flour/water ratios (1:5, 1:10, 1:15, and 1:20) were prepared and each slurry was also adjusted to three different pH degrees (6.1, 5.5 and 4.5) and then all samples treated with or without sonication prior to heating at three different temperatures (80, 100 and 121°C) for gelatinization, then the samples were left at 25°C for retrogradation to enrich the ERS content. Each produced sample was degraded to flour and then analyzed for color values, water holding capacity, morphological properties, dry-matter and ERS content. As the second step, the flour sample with highest ERS content among the produced samples was determined and subjected to further analyses to evaluate thermal properties and prebiotic effects. The chosen sample was produced in mass amount and used in different ratios (0%-control, 25%, 50% and 75%) at biscuit production as a flour replacer. ERS containing flour and produced biscuits were stored at room temperature in zipped plastic bags for 60 days. Each sample were analyzed every 30th day to determine color values, glycemic index, dry-matter and ERS content. In addition, the biscuits were also analyzed for textural hardness and fracturability, and sensorial properties. It was determined that, the treatments applied to flour increased darkness, water holding capacity and, ERS content of samples increased to 3.29% from 0.11% (about 30 fold) while moisture content decreased. The treatments also induced formation of vitreous structure. The sample with highest ERS content was obtained from sonicated slurry prepared with 1:15 flour/water ratio at pH value of 6.1 at 121°C. The sample had higher melting point compared to control sample and have prebiotic effects on growth of L. acidophilus. It also had lower glycemic index value. The properties such as color values, moisture content, ERS content and glycemic index of the flour sample did not change significantly during storage. Increasing addition of ERS containing flour to biscuit formula did not affect the weight loss of biscuits significantly but resulted with obtaining wider and thinner biscuits due increasing interference to gluten network. It also increased the darkness, moisture and ERS content of biscuits while decrease the glycemic index, hardness and fracturability values. The lightness and moisture content of biscuit samples increased while glycemic index, hardness and fracturability values decreased during storage. Also, biscuits with medium glycemic index value were produced. There was no significant change in ERS content of samples. It was evaluated by result of sensorial analysis that the produced biscuits were acceptable for consumers.