ABSTRACT
     
     More often it is increasingly common the demand of certain foods which do not cause undesirable effects related, for example with the consumption of sugar, such as the development of caries and diabetes. Alongside this, the fact that people may appreciate the continued progress on improving the organoleptic quality and nutritional content, food industry leads to the development of new products that satisfy all these consumer expectations. The existence in the market of new functional carbohydrates which might replace sucrose allows developing and/or reformulating products which accomplish these expectations.
      Traditional osmotic dehydration or wet method (WOD) is a widly extended technic in processinfg of fruits and vegetables due to the high quality of the obtained products. Nevertheless, there are some disadvanteges releated with the handle of big volumes of the generated solutions, which should be taken in account. Dry osmotic dehydration  (DOD) should be considered as an alternative, as the volum of generated solutions is considerably lower and moreover this solution is richer in aromatic and hydrosoluble (vitamins and minerals) compounds which come from the fruit itself.
      The work performed in the pressent docotral thesis consisted in the optimization of the formulation process of a strawberry fruit spread made by means of osmotic dehydration, in which sucrose has been partially or totally repleaced by other helathier suggars. Therefore, the influence of different variables of the process (kind of sugar, dehydration method, % of pectin, % of citric acid) on mass transfer kinetics and on diferent parameters releated with functional (antocianins and antioxidant activity content) and sensorial quality (colour, texture, reology and aromatic profile) in the obtained spread products was studied. 
     The obtained results showed that mass transfer kinetics is higher when the concentration of the surrounding medium is variable, being slightly superior in wet osmotic dehydration than in dry osmotic dehydration processes. Moreover the medium concentration, (constant or variable), and dehydration method (wet or dry), do not determine the maximum flux values, being those determined by the average concentration gradient between the fruit and the surrounding medium. 
     As for the formulation process of 30 and 50 Brix fruit spreads, either kind of sugar, the elaboration method and % of pectin had an influence on optical, mechanical and rheological properties of the obtained products. Dry osmotic dehydration without removing liquid phase (S1) can be selected as a dehydration method since the obtained products have adequate sensorial characteristics and moreover lower volumes of solution are generated being these solutions richer in characteristics compounds coming from the fresh fruit. 
     Finally, the optimization process showed that no matter the mix of sugars used (sucrose-isomaltulose or fructose-isomaltulose), the levels of variables: 50 % of isomaltulose, 1,5 % of pectin, 1 % of citric acid and without thermal treatment, allows obtaining products with adequate sensorial and functional  characteristics. Thus, the mix fructose-isomaltulose is appropriated for the total replacement of sucrose in this kind of products.