Molecular organization and dynamics of protein-maltodextrin blends: impact on the barrier properties of dry powders

Abstract

Microencapsulation by spray drying using a carbohydrate-protein matrix is often applied to protect active ingredients, such as natural colorants and oxidizable oils from volatilization and oxygen exposure. While the role of the carbohydrates in acting as an efficient oxygen barrier in the glassy state is by now established, the fundamental mechanisms governing protein functionality in such systems remain largely elusive. Surface-active components, including proteins, are mainly exploited for their role as emulsifiers that allow the formation of stable emulsions of the desired droplet size of the often hydrophobic active ingredients. This is specifically important in the retention of the active ingredients. However, they are also responsible for the development of three-dimensional architecture in the encapsulation matrix that impacts the porosity at both molecular and microscopic length scales and consequently the oxygen diffusion through the matrix. Recently, our group started investigations based on the hypothesis that proteins can close molecular pores (so-called free volume holes) in the encapsulating matrix conferring higher protection to sensitive encapsulated compounds during the processing and storage. Our preliminary results, obtained between 2018 and 2020 in collaboration with the University of Minnesota, indicate that there are fundamental differences in behavior of different types of proteins adopted. The goal of the current project is to deepen the understanding of the relation between the protein structure in the glassy matrices and the protection these matrices they confer. Specifically, a correlation with the amino acid composition and protein structure are required to resolve these important questions. Considering the pivotal importance of proteins for human nutrition and the crucial requirement for diversification of sources of protein, this study will enlarge the possibility to use other non-allergenic or alternative sources of proteins in the encapsulation purposes.