Evaluation of pasting and rheological properties of flours with different extraction rate and their impact on the production of fresh pasta

The use of whole grain flours in food preparation is becoming increasingly attractive thanks to their high fibre content which offers important nutritional benefits. Fibre, indeed, has been demonstrated to have a prebiotic effect and to prevent some of the most common diseases of the digestive and cardiovascular systems. Therefore, awareness of bran consumption is increasing. Bran accounts for about 25% of wheat grain weight and, as a by-product in the milling industry, is an inexpensive and abundant source of dietary fibre. To produce high quality food products with high fibre content, good knowledge of the effects of flour extraction rate (which is directly related to bran and thus dietary fibre content) on flour pasting and rheological properties is required. For this reason, the characteristics of commercial soft wheat flours with different extraction rates were investigated. The results showed that different extraction rates not only change the composition (especially the protein and, more importantly, the dietary fibre content), but also the overall technological properties of the flours. Specifically, flours with higher extraction rates exhibited higher water holding capacity and thus higher swelling capacity, higher fat absorption capacity, and higher solvent retention capacity related to pentosans and glutenins. As for the starch thermal properties, less refined flours showed lower consistency and breakdown values of the thermally formed gels, which exhibited a higher stability. In addition, the overall gelatinization process was negatively affected by bran content, which led to an increase in the transition temperature that delayed the swelling of the starch granules. Dough rheological properties were investigated through empirical and fundamental methods to achieve an in-depth microstructural investigation. The outcomes revealed that dough properties were dramatically affected by the bran content in flours. More in detail, empirical rheology indicated that the higher protein and fibre contents of less refined flours were associated with higher water absorption, dough development time and stability, in parallel with higher tenacity and lower elasticity and gluten strength of dough. On the other hand, fundamental rheology indicated that the predominant solid-like viscoelastic character of dough increased with the extraction rate, and that starch gelatinization temperature and process rate increased and decreased, respectively, with the bran content. Since empirical and fundamental methods provided complementary information, the combined approach allowed a complete study of the rheological characteristics of dough and, specifically, it was possible to overcome the limitations of the empirical methods as the integrated approach showed a good applicability in determining the alveograph indices of white refined wheat flours enriched with wheat bran, which can hardly be analyzed with the official standard protocol. Nonetheless, the final aim of food technologies is the production of high quality foods and, in light of this, the technological properties of fresh pasta made from soft wheat flours with different extraction rate were studied. First of all, fresh pasta was successfully produced without adding any ingredients other than water and flour. After cooking, a decrease in the water absorption index, volume mass gain and swelling ability was observed. Both fresh pasta hardness and firmness increased with the extraction rate, while the lower elasticity indicated that the higher is the bran amount in flours, the less elastic the end product was. Finally, the sensory analysis demonstrated that the use of flours with high extraction rates resulted in the production of fresh pasta which was not notified as different from the conventional ones made with white refined flours. Hence, the use of these flours having high fibre contents proved to be a good solution for the production of fresh pasta with naturally enhanced nutritional value and good consumers acceptance. In conclusion, this study investigated the impact of the degree of refinement of wheat flours on the functional and technological properties of the flours and the resulting dough. These aspects are important for the design of functional products rich in bran (therefore in fibre), which are acceptable to consumers from a health and sensory point of view.