SUMMARY

INFLUENCE OF THE ADITION OF A FUNCTIONAL INGREDIENT ON THE QUALITY OF A BAKERY PRODUCT. RHEOLOGICAL AND TEXTURAL ASPECTS AND ITS RELATION TO THE SENSORY ACCEPTABILITY

In this thesis work the addition of a functional fibre, resistant starch, was studied in a traditional bakery product (magdalena). The effect on both the properties rheological of the raw batter as well as the textural ones on the final bakery product, and its relation to the consumer acceptability was evaluated. Nowadays, fibre is one of the most discussed subjects on food and nutrition. In spite of the nutritionist’s efforts, western people diet is below the fibre recommended daily intake (25-30g/day). In part this situation is due to the lack of attractive of the food high in fibre, usually associated to a strong flavour, absence of palatability, coarse texture and a dryness oral sensation.
A traditional muffin formulation is composed of flour, sugar, eggs, milk and oil. All these ingredients have different contributions to the sensory quality that the consumer is accustomed to. It is crucial to know the interactions that a new ingredient could develop with the basic constituents to predict the changes that would take place on the final bakery product characteristics or to reconsider the elaboration and baking process.
It was investigated whether the way of dosing the dough had any effect on the final product. The results showed that although there were found microstructural and rheological differences, these changes did not affect the characteristics of the final baked product.
The dynamic rheological properties of the raw batter and how these properties changed with the addition of resistant starch were studied. This allowed observing that the batter viscosity decreased with the addition of resistant starch, which was not favourable to the development of the final baked product. The study of the rheological properties revealed that during the heating process, when the addition of resistant starch increased, the elastic properties of the batter diminished.
The texture of the muffins with the addition of resistant starch and its evolution during the storage were studied. When the concentration of resistant starch increase the hardness of muffins decreased, and at high concentrations of resistant starch the springiness, cohesiveness and resilience decreased. During the storage time muffins with resistant starch stayed softer than the control ones, this effect was evident at high concentrations. Survival analysis methodology to estimate sensory shelf-life of muffins confirmed these results.
A selection of descriptors was made to define the sensory properties of a bakery product when resistant starch was added. A sensory panel of ten assessors was trained in the evaluation of these descriptors. A descriptive analysis was performed, grittiness appear as a new feature. Sensory acceptability of the muffins was evaluated with a consumers study, there were not significant differences between muffins with different resistant starch concentrations.
Finally, it was studied whether the effect of knowing the nutritional information could affect the consumers opinion about the acceptability of the muffins, the addition of resistant starch did not have much influence, because it seemed that they acted as though they ‘cannot quite believe’ that it was a muffin with fibre, because its appearance was similar to a traditional one.