New techniques in the post‐harvest treatment of apple fruits with calcium salts

Publisher Website
Google Scholar
Abstract
Calcium penetrates apple (Malus domestica Borkh) fruits from externally applied solutions primarily through lenticels and other small discontinuities. Since the skin is the major barrier to absorption, control of storage disorders varies with skin porosity. Calcium uptake is greater at higher concentrations of solution but, in practice, risk of lenticel injury limits application rates. Incorporation of a surfactant may increase initial rates of uptake but not necessarily the total calcium absorbed. Addition of cornflour or xanthane gums improves retention and provides a continuous calcium supply during storage. The synergistic effect of lecithin in controlling bitter pit and breakdown appears limited to smooth‐skin varieties in which internal CO2 concentration is markedly increased after treatment. Controlled atmosphere storage delays or inhibits the development of certain disorders; therefore calcium treatments which also modify gaseous exchange through the skin are likely to provide this additive effect. Fruits which had been vacuum‐infiltrated with CaCl2 contained three times more calcium than the untreated, and were firmer, greener, and free of bitter pit. However 17% of treated fruits were damaged. The mode of action of these different post‐harvest treatments will be interpreted by reference to results obtained at East Mailing and elsewhere.