Influence of Calcium on Fruit Firmness and Cell Wall Degrading Enzyme Activity in 'Elstar' Apples during Storage

Softening processes in apples during storage and shelf-life are related to cell wall degrading enzymes involved in the hydrolysis of cell wall components. Calcium also has a role in cell wall stability as calcium treatments can extend storage life, decrease fruit softening rate, and reduce both respiration and ethylene production. Our experiment investigates the influence of calcium infiltration in combination with different storage treatments, including the use of 1-MCP, on the softening behaviour of 'Elstar' apples. We measured the activity of the cell wall degrading enzymes (endo-(1-4)-beta-D-glucanase; polygalacturonase; pectate lyase; pectin methylesterase) to explain differences in fruit softening rates. Calcium treatments decreased respiration, ethylene production and fruit softening, but increased cell wall degrading enzyme activity. In general, the effect of calcium infiltration treatments on the measured parameters was comparable to the effect of 1-MCP.