Comparison of physicochemical properties and volatile flavor compounds of plant-based yoghurt and dairy yoghurt

The aim of this study was to investigate and compare the physicochemical characteristics and volatile flavor compounds of three kinds of yoghurt made from reconstituted milk, soy drink and oat drink. The results showed that with the same fermentation ending pH of 4.5, reconstituted yoghurt had the highest titratable acidity mainly due to the highest buffering capacity and microbial counts (LAB). The textural and water holding capacity (WHC) parameters revealed that soy-based yoghurt had the highest firmness, consistency and WHC, indicating more rigid gel was formed. Meanwhile, rheological analysis showed soy-based yoghurt owned higher G ' and G values and higher stability against external stress, demonstrating that more and stronger interactions between soy proteins were built during fermentation. The confocal laser scanning microscopy (CLSM) image witnessed that soy-based yoghurt had the densest and finest network, while oat-based yoghurt had much coarser and looser structure, which was consistent with the lowest firmness and G ' value for oat-based yoghurt. In terms of color, reconstituted yoghurt was the lightest and oat-based yoghurt showed more reddish and yellowish. The main volatile flavor compounds in all yoghurts were ketones, while aldehydes contributed more in soy and oat yoghurt. PCA plot showed that volatile flavor compounds of reconstituted yoghurt and oat-based yoghurt were relatively similar, while soy-based yoghurt was much more different with high OAVs of hexanal, 1-octen-3-one, 1-octen-3-ol and 2-octenal. This study supplied a theoretical basis and an improvement direction for the better development of healthier plant-based yoghurt similar to dairy yoghurt.

Automated summary

The aim of this study was to investigate and compare the physicochemical characteristics and volatile flavor compounds of yoghurts made from reconstituted milk, soy drink, and oat drink. The results showed that reconstituted yoghurt had the highest titratable acidity due to its highest buffering capacity and microbial counts. Soy-based yoghurt had the highest firmness, consistency, and water holding capacity, indicating the formation of a more rigid gel. Soy-based yoghurt also demonstrated higher stability and stronger protein interactions during fermentation. Confocal laser scanning microscopy images showed that soy-based yoghurt had the densest and finest network structure, while oat-based yoghurt had a coarser and looser structure. Reconstituted yoghurt had the lightest color, while oat-based yoghurt showed more reddish and yellowish hues. The volatile flavor compounds in all yoghurts were mainly ketones, with aldehydes contributing more in soy and oat yoghurts. This study provides a theoretical basis and direction for the development of healthier plant-based yoghurts similar to dairy yoghurts.