Influence of carrot fibre powder addition on rheological,microstructure and sensory characteristics of stirred-type yogurt

The incorporation of 1% (E1) and 2% (E2) of the carrot fibre powder obtained from carrot discards to yogurts was studied. The effect of the fibre addition on the physicochemical parameters, water-holding capacity (WHC), microbial counts, rheological, microstructure and sensory characteristics of yogurts was studied in comparison with control yogurt without fibre addition (C). Titratable acidity, global composition and microbial counts showed a similar trend among yogurts. Fibre particles seemed to change the organisation of protein aggregates of the gel network. An open structure with bigger aggregates was observed in E1 and E2 yogurts, while the microstructure appeared more homogenous and without granules in C. However, carrot fibre increased the WHC of yogurt. All the yogurt samples exhibited shear-thinning behaviour and no differences were found in the rheological parameters, excepting for E2 that presented a decrease in apparent viscosity at 200 s^-1 compared with C and E1 samples. Trained sensory panel (12 members) indicated an increase in brownish colour, strange flavour, grittiness and aftertaste and a decrease in overall appearance, odour, sweetness and creaminess in yogurts enriched in fibre. In order to mask these negative characteristics, E1 formulation was produced in the same way but strawberry flavour and colour were added. A consumer test (101 volunteers), purchase intention and a Check All That Apply (CATA) questionnaires were carried out. Flavoured and coloured E1 yogurt was pleasant for consumers, since 93% of the consumers selected positive degrees of acceptability and 68% of them manifested that they are willing to consume the product. Therefore, the addition of carrot fibre powder in yogurts could be an alternative to incorporate dietary fibres into dairy foods.