Rheological properties of ancient wheat varities and sourdough processing used as a tool for improving antioxidative properties of bread

Abstract

Wheat (Triticum aestivum) is one of the most grown cereal crop in the world, beside rice and corn. Modern wheat varieties have been created to fulfill various requirements such as high yield and different quality parameters. During recent years consumers are getting more interested in consumption of bakery product based on ancient wheat varieties. The reason for such growing interest is related to the fact that ancient cereals such as spelt, emmer, khorasan, etc. are considered as “healthier” among general population. According to some findings ancient wheats are characterized by higher protein, soluble fiber, vitamins, minerals, lipids and different bioactive compound content. Among bioactive substances, polyphenols are mostly in the focus of nutritionists since these compounds have numerous health beneficial effects such as anti-inflammatory, antioxidant, anticarcinogenic and antimutagenic, as well as preserving properties against food deterioration, etc. Although considered nutritionally improved, ancient cereals are generally characterized by low yield, the necessity of dehulling technology application and lower technological quality compared to modern wheat varieties. Recently, sourdough fermentation was proposed as a tool for increasing phenolic compound content as well as for overcoming the shortcomings related to ancient wheat flours dough processing. In order to determine technological quality of three different ancient wheat varieties (emmer, spelt, khorasan) various rheological test were performed. Common wheat served as a control sample. Mixolab measurements (Chopin France) using Chopin+ protocol were conducted to reveal mechanical changes in tested dough samples upon mixing and heating. Moreover, wet gluten content and gluten index parameter which is also related to dough mechanical properties were determined. Spontaneous sourdough fermentation was performed in order to evaluate the impact of the sourdough fermentation on total phenolic content (TPC) bioaccessibility as well as DPPH antioxidant capacity during breadmaking. Bread samples prepared with common wheat flour using yeast as well as spontaneous sourdough fermentation served as control samples. The obtained results revealed that spelt flour exhibited high wet gluten content and consequently formed strong gluten network which was characterized by the highest water absorption among all tested samples. However, khorasan flour showed the lowest wet gluten content but the highest dough stability during mixing which could be related to high gluten index values. Moreover, although all samples were characterized by similar starch content, khorasan flour showed the highest starch gelatinization and retrogradation rate during thermal treatment. The results of sourdough fermentation revealed that, after fermentation, antioxidant activity and TPC increased which was followed by minor decrease or it stayed unchanged upon baking. The obtained results also showed that emmer and spelt sourdough were characterized by higher bound phenolics release rate due to the higher acidity of these sourdoughs. According to obtained results, it can be concluded that rheological properties were dependent on wet gluten content and gluten index values, i.e. gluten quantity and quality. Moreover, it was also determined that sourdough fermentation favored the release of bound phenolics which can be potentially utilized to increase the bread shelf life while avoiding antioxidant addition as food additives in different bakery products.