Gluten-free bread crusts are known for their crumbly texture, light colour, poor nutritional quality and weak aroma. The objective of this research was to improve crust quality of glutenfree breads by the addition of rice, pea, egg white and whey proteins to the bread formulation in two levels (5% and 10%). Moisture, water activity, thickness, microstructure, texture, colour and volatile compounds were measured. A 99% negative significant correlation between spatial frequency of structural ruptures and crust moisture content was found. Results from texture analysis indicated that animal and 10% pea protein crusts were less crispy than control. Moreover, crust microstructure of animal protein bread was very different from control and vegetal protein crusts. Animal and vegetal protein crusts showed darker colour than control and the darkest was obtained from whey protein inclusion. With respect to the volatile profiles, rice protein crusts had the highest content of 2-acetyl-1-pyrroline while whey protein crusts had high level of pyrazines, which was in concordance with their dark colour. However, whey protein and, above all, rice protein also increased the content of volatile compounds from lipids oxidation. Thus, the suitable proportion between rice and whey protein should be found to achieve the most pleasant aroma.
Physically modified extruded flours are suitable ingredients for cold preparation of products such as creams and sauces. The rheological and textural properties and stability of model sauces prepared with wheat and rice extruded flours with three different particle size fractions were assessed. All tested sauces showed non-Newtonian, shear-thinning and thixotropic fluid characteristics. Sauces made with rice extruded flours, with lower protein and amylose contents, presented lower shear-thinning behaviour, consistency index and yield stress than wheat based sauces. Rice sauces also displayed a less compact microstructure and lower viscoelastic character but a higher resistance to freeze-thaw process. Regarding particle size, the finest flours showed lower values of consistency index, yield stress, and G' and G'' moduli but led to higher syneresis. Overall, results proved that pregelatinised extruded flours can be used in sauces applications without heating, but their properties greatly depend on the cereal type and its particle size.
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