SUMMARY

Effect of inulin addition on physical and sensory properties of milk beverages

The research developed in this thesis was focused on two topics: to develop the methodology to study the influence of consumer beliefs, attitudes and expectations on the acceptability of products with special nutritional characteristics and to develop and optimise the acceptability of new milk beverages formulations with low fat content and prebiotic characteristics. 

To analyse the influence of consumer characteristics, beliefs and attitudes and of the expectations created by nutritional information on the acceptability, two types of commercial vanilla beverages (milk and soymilk) with different nutritional and sensory characteristics were selected. The influence of consumer demographic characteristics, consumption habits and individual preferences on acceptability of both types of products was studied and the relationship between sensorially perceived differences and acceptability of products was analysed. Results showed that differences in acceptability between both types of beverages were more related with sensory attributes than with the other studied characteristics (demographics, consumption habits and individual preferences). In a second study, the influence of expectations created by the type of product and the nutritional information indicated on the packages and consumer beliefs and attitudes on acceptability and purchase intention was studied. Results indicated that the nutritional information influenced purchase intention more than product acceptability, and that some consumer attitudes, as that related with the interest in healthy eating, changed their responses before confirmation or not of expectations created by the nutritional information. 
For designing and optimising the formulation of new prebiotic milk beverages, an ingredient with proved healthy effects, inulin, was selected. The influence of the addition of inulin with different chain lengths on flow behaviour and on perceived thickness and creaminess in low-fat and full-fat milk beverage model systems was studied. Results showed that inulin concentration effect on flow behaviour and on thickness and creaminess of beverages was different depending on the chain length of inulin and on the type of milk used. The higher increases on instrumental viscosity, and sensory thickness and creaminess were obtained with long chain length inulin, followed by short chain length and native inulins. Parallelly, it was stated that the potential of the different types of inulin to act as fat substitutes depended on their chain length as well as on the concentration of added inulin. Depending on these results, the optimisation of new milk beverage formulations elaborated with skimmed milk and added inulin was planned using response surface methodology, according to a two-factor central composite rotatable design, varying inulin and sucrose concentration. The design was applied to two lots of samples, one with short chain length inulin and another one with long chain length inulin. The relationship between acceptability variation and the variations in ingredient concentrations was obtained, and formulations corresponding to the optimum acceptability for each inulin type were selected. Finally, acceptability of beverages elaborated according to the two optimum formulations were compared between them and then each one of the optimum formulations with a control sample prepared with whole milk and without inulin added. No significant differences in acceptability between the two new low-fat beverages were found and they showed no differences in acceptability when compared with the full fat control sample.



Introducción

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