Molecule structural factors influencing the loading of flavoring compounds in a natural-preformed capsule: Yeast cells.

Yeast cells are efficient microcapsules for the encapsulation of flavoring compounds. However, as they are preformed capsules, they have to be loaded with the active. Encapsulation efficiency is to a certain level correlated with LogP. In this study, the effect of structural factors on the encapsulation of amphiphilic flavors was investigated. Homological series of carboxylic acids, ethyl esters, lactones, alcohols and ketones were encapsulated into the yeast Yarrowia lipolytica. Although, in a single homological series, the length of the molecule and thus the LogP were correlated with encapsulation efficiency (EY%), big differences were observable between series. For instance, carboxylic acids and lactones exhibited EY% around 45%-55%, respectively, for compounds bigger than C8 and C6, respectively, whereas ethyl esters reached only about 15-20% for C10 compounds. For a group of various C6-compounds, EY% varied from 4% for hexanal to 45% for hexanoic acid although the LogP of the two compounds was almost similar at 1.9. In total our results point out the importance of the level of polarity and localization of the polar part of the compound in addition to the global hydrophobicity of the molecule. They will be of importance to optimize the encapsulation of mixtures of compounds.