UNREFINED WHEAT FLOURS IN BREAD-MAKING: TECHNIQUES AND TECHNOLOGIES TO IMPROVE DOUGH PROPERTIES AND BREAD QUALITY

In recent years the demand for healthy and high nutritional value foods has grown greatly, leading to a higher interest in the exploitation of unrefined wheat flours in the bread-making process. Indeed, many scientific evidences reported that the regular consumption of unrefined cereal products has positive effects on human health. However, the use of unrefined wheat flours in the bread-making process poses many technological issues since the germ and the bran negatively affect dough properties and bread quality. The different chemical composition of unrefined wheat flours may require changes in the processing conditions which should be specifically designed to improve the bread-making performance of these raw materials. Bread is the staple food in many diets, hence the possibility of increasing the nutritional value of the product while maintaining an acceptable technological quality could significantly impact human health. At first we performed an in depth analysis of the literature about the main techniques and technologies for the bread-making process with unrefined wheat flours. The most common strategies developed by the scientific literature are based on the addition of improvers in the bread formula, whereas processing strategies have been scarcely investigated. Hence, we performed a survey to bakers that use ancient wheat flours for bread production; the aim was to obtain an empirical state of the art about the main bread-making strategies developed by the experts in the field. Results showed that bakers do not add improvers to the bread formula, but they have developed some processing strategies to improve the bread-making performance of ancient and unrefined wheat flours. However, they emphasised the necessity to find innovative techniques and technologies for the bread-making process with unrefined wheat flours. The literature and empirical state of the art allowed us to direct the experimental research on specific issues related to the use of unrefined wheat flours in the bread-making process. We proposed a different approach for the bread-making with unrefined wheat flours compared to the standardisation approach used with refined flours; an adaptation of bread formula and processing conditions to the specific requirements of unrefined wheat flours is necessary to improve dough properties and bread quality. At first we investigated strategies related to bread formulation, testing the effect of a natural improver, i.e. gelatinised brown flour, on dough properties and bread quality and proposing a two-step optimisation approach to optimise the formula of unrefined wheat bread. Then, the thesis research focused on the optimisation of the bread-making process; for the first time we applied 1H nuclear magnetic resonance (NMR) technique during the kneading step of unrefined wheat dough to reveal the chemical-physical phenomena occurring to the flour constituents. Furthermore, two dough water levels were tested in order to investigate the critical role of the water amount during unrefined dough development. The thesis research performed an organised scientific study on the behaviour of unrefined wheat flours. The study showed that an adaptation of the bread formula and bread-making conditions is crucial to improve the bread-making performance of unrefined wheat flours, which are characterised by poor technological quality and high variability. The optimisation approach was able to significantly improved unrefined dough properties and bread quality. However, this approach can not be applied on an industrial-scale, hence the introduction of new standard tests or innovative methods for process control is required to promote the exploitation of unrefined wheat flours. NMR technique was able to reveal the main physical-chemical phenomena occurring during the kneading of unrefined wheat dough and the crucial role of kneading variables (water and time).