Matrix and preservation technology dependent stability and bioaccessibility of strawberry anthocyanins during storage

Anthocyanins, often assocated with health benefits, readily degrade during processing and storage, and anthocyanin-matrix-interactions affect their stability and bioaccessibility.

Our study investigated how anthocyanins in strawberry puree were affected by preservation technologies and addition of relatively protein-rich kale juice. Strawberry-kale-mix (M) was compared to strawberry-water-mix (S), untreated and treated thermally, by pulsed electric fields (PEF) and high pressure (HPP). Anthocyanin stability and bioaccessibility after in-vitro digestion was evaluated during refrigerated storage.

The degradation of the strawberry anthocyanins during storage followed 1^st-order-kinetics (c = c₀∙e^-kt). The degradation rate constant k varied depending on juice system, preservation technology and anthocyanin structure. Generally, k was at least doubled for M compared to S. The untreated sample showed the highest k, followed by thermal, PEF and HPP. Both likely resulted from high enzyme activity measured in M and untreated samples.

Relative gastric bioaccessibility of anthocyanins was higher for M (1.27-1.29) compared to S (1.10-1.14 ), indicating interactions of anthocyanins with the kale matrix. Additionally, relative gastric bioaccessibility increased during storage, possibly resulting from anthocyanin polymerization during storage, followed by their decomposition during digestion. Intestinal bioaccessibility was overall low with 20-30 % compared to the initial bioaccessible fraction due to instability at neutral pH.

This research shows evidence that processing and formulation strongly affect stability and gastric bioaccessibility of anthocyanins during storage.