Investigation of the effect of sourdough starter and enzyme additives on the gluten content of tarhana throughout fermentation

Although tarhana is a traditional product which can be produced with different formulations depending on region, but surely includes wheat flour. Gluten degredation can be anticipated to occur throughout fermentation. The aim of this study is examination of gluten degredation throughout fermentation with natural microflora, as well as the addition of lyophilized sourdough yeast and/or proteolitic enzyme (derived from Aspergillus sp.). Basic tarhana formulation (TT) was prepared with a standard recipe containing wheat flour, instant chickpea flour, yoghurt, tomato paste, pepper paste and water. Addition of commercial dry sourdough culture, food-grade peptidase mixture and a combination of peptidase mix and sourdough culture (in order of EM, EN and EE) were the factors evaluated in the study plan and each fermentation mixture was subjected to fermentation at 22 °C for 30 days. Gluten degredation in the samples which were taken from day 0, 5, 10, 20 and 30 of fermentation were examined in terms of gluten content with the use of a sandwhich ELISA method based of the R5 antibody. The same samples were also analyzed for pH, moisture and ash content. Samples from the first and last day of fermentation were also analyzed to determine the protein content of the dough. After 30 days of fermentation tarhana samples which were cooked in a standard fashion to yield soup were analyzed to determine sensory properties of the final product. During fermentation, the decrease in gluten contents was different for different tarhana formulations. These decreases in the formulations of EN and EE were higher than formulations TT and EM. The lowest gluten content was detected in order of EE (3,05 ppm), EN (7,68 ppm), EM (30034,30 ppm) and TT (31824,75 ppm) at the final day of fermentation. According to Turkish Food Codex, to define a product as 'gluten free' it should contain less than 20 ppm gluten. Based on this, 30 day fermentation of the EN and EE formulations results in dough that can be labeled as gluten-free. According to sensory analysis, the products were acceptible for consunsumption and statistically there was no diffirence between tarhana formulations except for odor and sourness properties.