Anthocyanin colourants from elderberry (Sambucus nigra L.). 3. Storage stability of the freeze dried product

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Abstract
Summary.: Storage of freeze dried anthocyanin extract from elderberry was conducted under various conditions of water activity (a), temperature, atmosphere composition and presence or absence of light. It was found that at a, 2 0.31, water uptake has essentially no effect on the anthocyanin product. At a, p 0.5, a significant increase in anthocyanin degradation rate is observed. The BET monolayer value for water sorption (a, = approximately 0.4) coincide with the a, interval (0.315 a, 5 0.5) over which anthocyanin degradation shows a marked change in behaviour.Temperature during storage is of prime importance to anthocyanin stability with high temperature in combination with high water activity having the most pronounced effect on the stability of anthocyanins. At conditions of 50â°C, 0.5 a, the anthocyanin half life was found to be approximately 2 months.The two factors, light intensity and presence of oxygen, were found to have no significant effect on anthocyanin stability, indicating that anthocyanin products with limited access to water are quite inert systems. When the dry anthocyanin extract was stored at ambient temperature and low a, (5 O.3), the degradation rate was found to be so low (anthocyanin half life > 5 years) that the use of the powder in low moisture food products is evident.
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