IMPACT OF INGREDIENTS AND PROCESSING TECHNOLOGIES ON STRUCTURAL AND NUTRITIONAL PROPERTIES OF REDUCED-FAT FOODS

In the last decades, the demand for nutritionally-improved food has raised, drawing the attention of researchers on new solutions for product development. The design of foods able to satisfy specific sensory and nutritional functionalities requires a better understanding of the relationships between the composition of food materials, the effects of processing on their quality characteristics and structure, and their behavior during digestion. This PhD thesis aimed at evaluating how ingredients and technology affect structural properties of different reduced-fat matrices. Biscuits and whipping cream were used as case studies with different specific aims concerning the effects of ingredients and/or production technology. In particular, resistant starch, raw and extruded bean flour were evaluated as structuring ingredients in reduced fat biscuits, in combination with polydextrose or double emulsion as fat replacers. The effect on structural, nutritional and sensory properties of final biscuits were investigated. For whipping cream, gelatin addition and homogenization condition effects on structure and stability were evaluated, both immediately after production and after three weeks of storage. Design of Experiments techniques coupled with Response Surface Methodology were used for the multivariate investigation of both formulation and processing effect. Results from the biscuit case study demonstrated that combination of polydextrose and resistant starch allowed to obtain a reduced-fat biscuit (- 44 % fat) with structural characteristics similar to those of a standard full-fat biscuit prepared with shortening or butter. The use of extruded bean flour allowed to obtain biscuits nearly comparable to a traditional reduced-fat product, but with improved nutritional profile. The presented data suggest a hypoglycaemic potential of bean-enriched biscuits, to be confirmed by a dedicated in vivo study. Desirable nutritional value of bean powders, including high protein content and slow starch digestibility, may be successfully exploited in biscuits. On the other hand, the study of double emulsions by D-optimal design allowed to improve the knowledge about the effect of internal water gelling and the proportion of water and oil in the emulsion on yield, rheological behaviour and stability. However, the use of double emulsion in reduced-fat biscuits requires further investigations, in order to understand how to improve emulsion structuring and its effect on dough properties. Results from the whipping cream case-study demonstrated that the combination of gelatin addition and high homogenization pressure may be successfully exploited for the development of reduced-fat whipping cream (25 g/100g fat), with good quality characteristics and stability. D-optimal design and Response Surface Methodology resulted to be effective tools for the study of cream processing at a pilot level, allowing the collection of high quality information on the effect of the studied factors and their interactions, with a limited experimental effort. In particular, gelatin addition at a concentration of 0.25 g/100g, in combination with k-carrageenan, increased initial consistency of cream samples, leading to final overrun values even improved with respect to those obtained for commercial samples, without affecting texture properties and stability. Depending on gelatin concentration, homogenization pressure revealed a great potential to modulate whipping properties. The multidisciplinary approach adopted, comprehensive of all the functionality aspects related to a food product, may represent a starting point for the design of foods with targeted quality features and behavior during consumption. In such a complex investigation field, Experimental Design techniques coupled with multivariate analyses of the experimental data have confirmed to be effective tools for the characterization and optimization of both food formulation and processing. The developed mathematical models can be applied for reverse engineering and quality-by-design approaches, thus benefit both researchers and companies.