Thermal and calcium pretreatment affects texture, pectinesterase and pectic substances of frozen sweet cherries

Abstract

Freezing causes loss of turgidity and firmness in sweet cherries. Thermal pretreatment at 50°C for 10 min followed by immersion in 100 mM CaCl2 and thermal pretreatment at 70°C/2 min with or without immersion in 100 mM CaCl2 prevented freezing-induced loss of firmness. Thermal pretreatments increased the pectin fraction soluble in EDTA, reduced the degree of pectin esterification, and increased both the concentration of divalent cations in the cell wall and the pectinesterase activity bounded to the cell wall. Immersion in CaCl2 increased the concentration of Ca2+ cations in the cell wall and enhanced the effect of thermal pretreatments on pectinesterase activity.