Browsing by discipline "Livsmedelsteknologi (mjölkteknologi)"

The aim of this thesis was to find a suitable substitute of non-animal origin for fat free stirred yoghurt in order to attract new consumers such as vegetarians and people of different religions. The substitutes for gelatin studied here were two food enzymes (transglutaminase and proteinglutaminase), modified potato starch and whey protein. Costs of replacing the gelatin with food enzymes were also examined. Composition of milk, manufacturing process and structure of stirred yoghurt, formation of yoghurt gel and the substitutes for gelatin were reviewed in the literature section. The yoghurts were prepared in the process laboratory of Valio’s R&D using skimmed organic milk and milk powder. During the thesis two trials with food enzymes were also carried out in the production line of Valio’s non-fat yoghurt. Viscosity, pH and graininess of the yoghurts were measured and sensory analyses were conducted during three weeks of storage and the results were compared to handmade control yoghurt and to yoghurt that has been made in the production line in Riihimäki. Enzyme-treated yoghurts were also analyzed with gel electrophoresis. According to this study the best substitutes for gelatin were TG and PG enzymes and whey protein concentrate. Yoghurts prepared with these substitutes had a structure and flavor comparable with that of the control yoghurt. Their viscosities were even greater than the viscosity of Riihimäki’s yoghurt. No graininess or syneresis was observed in these yoghurts. However, the yoghurts manufactured in the production line were found to be grainy and also some syneresis was observed. The graininess could be reduced by treating the yoghurts with Ytron-Z-mixer. The resulting yoghurts did not differ from the current non-fat yoghurt in viscosity or in sensory properties. We also found out that it was possible to reduce the amount of protein content in the yoghurts without affecting the structure of the yoghurt. The reduction of protein content and substitution of gelatin with food enzymes did not cause any extra costs.