Retention of bilberry anthocyanins in wood hemicelluloses coated microcapsules under the impact of humidity and packaging conditions

Abstract

Anthocyanins are attractive natural colorants with recognized health-promoting properties, but their susceptibility to moisture and oxygen limits their shelf-life in powdered formulations. This study investigated the storage stability of spray-dried bilberry anthocyanins microencapsulated with galactoglucomannans (GGM) and glucuronoxylans (GX), two emerging wood hemicelluloses, compared with gum Arabic (GA). The effects of relative humidity (RH; 8 and 33%) and packaging atmosphere (vacuum and sealed conditions) on anthocyanin degradation, color stability, antioxidant retention, and powder physicochemical properties were evaluated over 24 weeks of storage at ambient temperature. Anthocyanin degradation followed first-order kinetics under all storage conditions. Storage at 8% RH provided the highest stability, limiting anthocyanin loss to 17–22% and extending half-life (t 1/2 ) values to 62–69 weeks, whereas 33% RH storage resulted in anthocyanin loss of 48–57% and t1/2 of 23–30 weeks. Despite slight differences in degradation kinetics, GGM, GX, and GA provided comparable protection against anthocyanin degradation during storage. Vacuum packaging increased t1/2 values by 5–10 weeks compared with sealed packaging. Anthocyanin degradation was strongly correlated with polymeric color formation and non-enzymatic browning (R² > 0.905), indicating progressive pigment transformation during storage. Chromatographic analyses showed that cyanidin-based anthocyanins were more susceptible to degradation under high RH conditions than malvidin derivatives. Increased RH also promoted particle agglomeration, structural collapse, and surface cracking, facilitating oxygen diffusion and accelerating anthocyanin loss. These findings identify moisture control as the primary determinant of anthocyanin stability and highlight wood hemicelluloses as sustainable protective matrices for the development of shelf-stable natural functional powders.