Superficial scald, a functional disorder of stored apples VI.—Evaporation of α‐farnesene from the fruit

Abstract

During storage Granny Smith apples were ventilated with air at two flow rates differing by a factor of 10. The a-farnesene evaporated, a-farnesene retained by the fruit, and the severity of scald were determined. Increasing the ventilation increased the evaporation of a-farnesene. In two cases the amount evaporated was approximately equal to that retained. In some cases increased ventilation gave less retention of a-farnesene by the fruit and less scald, but in others the difference was negligible because increased evaporation stimulated production. The factors controlling evaporation and the concentration of a-farnesene remaining in the fruit during storage are discussed. IntroductionThe evidence already presented1v2 for a r61e of a-famesene in superficial scald includes the effects of variety and maturity, the transfer of a-farnesene to the oiled wrap, and the inhibition of its oxidation by diphenylamine. It remains to be considered whether the r81e of a-farnesene is the same as that of the volatile or gaseous substances postulated by Brooks et a1.3 as the cause of scald. Their theory was based primarily on observations that increased air movement over the fruit reduced scald. If a-farnesene is involved, air movement should increase its loss by evaporation and reduce its concentration in the fruit.In experiments over three seasons samples of 20-25 apples were stored in drums ventilated with air at 2 or 20 l/h. The a-famesene evaporated, a-farnesene remaining in the fruit, and the severity of scald were determined. Comparisons were made in 1965 between untreated and diphenylamine-treated apples, in 1966 between apples from two districts, and in 1967 between two storage temperatures.

A Poststorage Burst of 6-Methyl-5-hepten-2-one (MHO) May Be Related to Superficial Scald Development in `Cortland' Apples

“…The oxidation products of α-farnesene have been associated with the development of superficial scald (Anet, 1969(Anet, , 1972Huelin and Coggiola, 1970a, 1970b, 1970c. However, the pathway(s) resulting in the generation of scald-causing metabolites that originate from oxidation of α-farnesene are not fully understood.…”

“…Lipophilic volatile compounds continuously produced during low-temperature storage partition into the cuticle and would potentially accumulate to high levels (Huelin and Coggiola, 1970b). Huelin and Coggiola (1968) have suggested, in fact, that αfarnesene oxidation is prevented while it is in the living cell and that it is only after α-farnesene is excreted into the waxy portion of the cuticle that oxidation occurs.…”

“…α-Farnesene, a sesquiterpene hydrocarbon, accumulates and then declines in the peel of apple during low temperature storage and is present primarily in the trans-trans configuration (Murray, 1969). This compound has been implicated in the induction of scald in these fruit (Anet, 1969;1972;Huelin and Coggiola, 1970a, 1970b, 1970cHuelin and Murray, 1966;Ingle and D'Souza, 1989;Murray et al, 1964). Fruit cultivars that produce less αfarnesene are less likely to develop superficial scald during storage (Huelin and Coggiola, 1968;Whitaker et al, 1997) although treatments that reduce α-farnesene accumulation do not always reduce scald severity .…”

Superficial scald, a functional disorder of stored apples VII.—effect of applied α‐farnesene, temperature and diphenylamine on scald and the concentration and oxidation of α‐farnesene in the fruit

“…Measurements of changes in the concentration of afarnesene during storage of apples at 5 and 15"c in 1967 were included in the experiments on evaporation already reported. 3 Comparable samples from the same source in 1967 were stored at 0"c in cartons and analysed at intervals. Comparison of results obtained at the 3 temperatures indicated that the highest concentration of a-farnesene was reached at 5"c, and this result was of sufficient interest to suggest repetition of the effect of temperature in 1968.…”

Effect of Phorone on Accumulation and Fatty Acid Composition of Surface Lipid of Apple During Storage

“…The reduced levels of respiration and ethylene production induced by phorone at 0°C and enhanced levels at 5"-20°C reported by Wills et al (1989) may also be attributed to retarded gas exchange. The preferred storage temperature for many apple cultivars is around 0°C but a reduced transfer of water and organic volatiles at this temperature would be expected to increase the incidence of some disorders, for example, superficial scald (Huelin and Coggiola 1970b) and low temperature breakdown (Scott and Roberts 1968;Wills 1968) and hence act contrary to the action of phorone in reducing the incidence of these disorders. Enhanced gas exchange may, however, have a role in reducing the incidence of bitter pit and core flush which commonly occur at temperatures above 5°C.…”