Properties of phosphatase from six varieties of apricot relevant to potential use in apricot air‐drying

Abstract

Apricot phosphatase measured with p‐nitrophenol phosphate as substrate, was present as soluble and membrane‐bound isoforms at levels per gram of tissue generally lower than those found in other fruits, vegetables and cereals. Properties such as substrate affinity, stability at acid pH, heat stability at 50 to 60°C (normal apricot drying temperatures), optimal reaction temperature of 58°C, and reactivity with ascorbic acid polyphosphate favor the use of phosphatase to catalyze the slow release of ascorbic acid over the 36 to 40 h required for air drying. A feasibility trial demonstrated that low levels of ascorbic acid polyphosphate present in the infusion solution (0.5 to 2 g/L) were insufficient to prevent browning, but levels greater than 5 g/L resulted in commercially acceptable dried fruit.