How do different ingredients affect the fermentation time and structure of plant-based yoghurt-like products?

Sammanfattning: The market of plant based dairy alternatives such as yoghurt alternatives continues to grow as more information on the environmental impact of traditional dairy products become available. The plant-based yoghurt alternatives come with a new set of problems, including longer fermentation times and poor gel structure formation. The aim of the project was to see if fermented yoghurt alternatives could be created based on pea, oat and chickpea protein powders at different weight percentages using two different bacterial strain mixtures of Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus. The addition of potato starch was also studied due to the poor gel structure formation in some recipes. The project included an investigation into the fermentation time, texture, microstructure, spontaneous syneresis and viability of the created yoghurt alternatives. Results showed satisfactory fermentation times regarding food safety for all protein sources and both bacterial strain mixtures, but not all fermentations reached a final pH of 4.6 within the desired timespan (600 min). The texture analysis results showed that an increased protein powder concentration resulted in an increase in the texture properties of firmness, consistency and cohesiveness. Only the recipes with chickpea powder resulted in proper gel structures for all tested protein concentrations, although syneresis occurred at 2.5 wt% protein content after 1 day of cold storage. For pea and oat, protein percentages of 5 wt% or below resulted in phase separation. The addition of potato starch to the recipes resulted in reduced spontaneous syneresis and reduced phase separation for all samples. The differences in texture properties and phase separations were to some extent explained by the microstructures. For pea yoghurt alternatives, the network was made from mainly protein interactions from both denatured and partially denatured proteins. For chickpea yoghurt alternatives, it was made from a mixture of protein and starch networks. Oat yoghurt alternatives on the other hand, had mostly undenatured proteins, with some starch but no clear network. Conclusively, fermented plant-based yoghurt alternatives with varying properties were able to be created. However, further investigation on the suitability on a pilot-scale as well as investigation of problems that occurred during the study is needed. These included the curdling phenomenon of the chickpea concentrate and pH differences within separated samples.