Protective performance of delivery systems in production, shelf life and digestion

Abstract

Protection is one of the major aims when designing delivery systems. Depending on the encapsulant, this may refer to minimisation of losses of volatile compounds, prevention of chemical deterioration or protection against an unintended release of the encapsulant. Specific examples are discussed in the present chapter. Important delivery systems are based on glassy carbohydrate-containing matrices prepared by spray drying, extrusion or spray granulation. These delivery systems provide excellent oxygen barrier properties. The impact of the molecular weight profile on molecular mobility and permeation of small molecules is discussed. The presence of low molecular weight carbohydrates generally improves the protective performance in the glassy state. A key characteristic in this context is the molecular free volume, which undergoes significant changes upon moisture sorption. Protective performance of hydrogel-based delivery systems, which are frequently used for immobilisation or in vivo delivery of an encapsulant, depends on diffusional phenomena and mechanical stability of the delivery systems. Since it becomes evident that protection is intrinsically tied to the structure of a delivery system, analytical methods to monitor the protective performance are reviewed.