ABSTRACTThe effect of water activity (“dry”– 0.84) and moisture content on the stability of beet pigments (betanine and vulgaxanthine I) was investigated in beet powder stored at 35°C. Pigment deterioration followed a first order reaction. Water activity and moisture content had a pronounced exponential effect on pigment stability. A decrease of approximately one order of magnitude in pigment stability was observed when awwas increased from 0.32 to 0.75. Storing the powder at awof 0.12 or below resulted in practically no deterioration of the pigments over a period of several months. Profound differences in pigment stability were attributed to sorption hysteresis and system compo
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