Rheological behaviour of ancient wheat flours

Abstract

The need to preserve genetic diversity, the request for high adaptability to low agronomic input, along with the increasing demand for traditional products with better nutritional composition are recognized as a major driving forces behind the renewed consumers', manufacturers' and farmers' attention toward ancient wheat grains. In order to convert ancient grains into food products with acceptable techno-functional properties, dough’s rheological behaviour has to be considered. In this study a comparative evaluation of the rheological properties of ancient wheat species (emmer, spelt and khorasan) was conducted. The wholegrain flours of these varieties were prepared and evaluated for chemical composition, wet gluten quantity and quality and rheological properties in terms of gluten aggregation and disruption kinetics (GlutoPeak), dough proofing (Rheofermentometer), as well as mixing and thermal behaviour (Mixolab). Although emmer and spelt flours had higher protein and wet gluten content, they were characterized with lower gluten indexes (GI) in comparison to khorasan flour (GI were 64, 50 and 11% for khorasan, spelt and emmer, respectively). This influenced significant differences in dough rheology of investigated ancient wheat flours. High wet gluten content of spelt flour led to formation of strong gluten network (high maximum torque as measured by GlutoPeak) with the highest Mixolab water absorption (62.6%) and maximum dough height (Hm at Rheofermentometer curve) in comparison to other varieties. On the contrary, khorasan flour, although having very low wet gluten content, exhibited the highest dough stability both during mixing (Mixolab test) and fermentation (Rheofermentometer dough development curve) due to high gluten index value. Despite being characterized with high wet gluten content, very low gluten index value of emmer flour affected dough development process, resulting in the lowest maximum dough height and pronounced loss in dough height during fermentation and the lowest percentage of gas retained in the dough relative to the total gas production compared to other wheat species. Emmer flour was also unable to form gluten aggregation peak under the conditions used during GlutoPeak test. The results obtained in this study can be used to better understand the techno-functionality and target application in cereal based products of different ancient wheat species.