Effect of the Nigella sativa Linn concentrate addition on the physical and quality characteristics of gluten-free toast bread during storage

Celiac disease is an autoimmune disorder in which the patient is permanently exposed to gluten intolerance during their life. The only effective method for celiac disease is strict adherence to a gluten-free diet. So, attention to the high quality food production without gluten is important. The aim of this study is to produce gluten-free bread toast using Nigella sativa Linnconcentrate as an alternative to gluten and potato fiber. The Response Surface Method was used with two variables of potato fiber (2 to 6 %) and Nigella sativa Linnconcentrate (5 to 15 %). With increasing potato fiber and Nigella sativa Linnconcentrate, bread density increased significantly (p˂0.05). Potato fiber resulted in a significant decrease in porosity, but Nigella sativa Linnconcentrate was ineffective (0.01%). Potato fiber and Nigella sativa Linnconcentrate showed a linear effect alone at the level of 0.05. Moisture content decreased with increasing fiber and Nigella sativa Linnconcentrate, but the effect of protein concentrate was not significant (p˃0.05). In addition, moisture content of bread decreased during storage. Potato fiber and protein concentrate had a significant effect on the hardness of bread texture and the texture increased during the four days storage period. The non-fit index for all models was not significant (0.05%). The optimization of bread formulation showed that the toast containing 7.5% of Nigella sativa Linnconcentrate and 2.5% potato fiber had the best quality and is recommended for production.