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

Abstract

The a-farnesene content of apples usually passed through a maximum during storage. Studies in the range 0 to 15"c indicated that the highest maximum was reached at approximately 5"c. The concentration of total lipid and fatty acids in the coating increased with temperature. Application of a-famesene to the surface before storage inhibited further production of a-farnesene and reduced the production of total lipid and fatty acids.Application of a-farnesene by dipping in ethanolic solution caused injury to the outer cortex which differed from typical scald. Application within marked circles induced typical scald only with previously oxidised famesene. In comparing experiments over five years, conjugated trienes gave a higher correlation with scald than a-famesene or the peroxide value.Superficial scald is discussed in relation to the concentration of a-famesene and its oxidation products and the concentration of natural antioxidants. Tests for artificial antioxidants are discussed. IntroductionMuch evidence for a r61e of a-farnesene in superficial scald was given in previous p a p e r~. l -~ This evidence includes the transfer of a-farnesene to the oiled wrap, the relation of scald to the oxidation of a-farnesene, and the effect of air movement on its evaporation. The oxidation of a-farnesene was studied by Anet,4 who identified two conjugated triene hydroperoxides with U.V. absorbance peaks similar t o those reported for extracts of the natural coating of long-stored apples2Measurements 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. Attempts to induce superficial scald by applying a-farnesene to the surface of the fruit were initiated in 1968, and peroxide values as a measure

Effect of DPA [Diphenylamine] and 1-MCP [1-methylcyclopropene] on chemical compounds related to superficial scald of Granny Smith apples

“…However, the two products control the disorder in different ways. Compared to the control, fruit treated with DPA reduced the accumulation of α-farnesene (Huelin and Coggiola, 1968;Du and Bramlage, 1994) and conjugated trienes (Huelin and Coggiola, 1970;, especially CT 269 and CT 281, and increased the total anti-oxidant concentration. DPA's effect on scald development is associated with the inhibition of α-farnesene oxidation and to some extent to a reduced synthesis of the compound Bramlage, 1993, 1994), as well as the fruit's higher resistance to cell damage incited by the conjugated trienes (Du and Bramlage, 1995).…”

“…the earlier the harvest, the more severe the damage (Ingle and D'Souza, 1989;Watkins et al, 1993). Scald is effectively controlled with the synthetic anti-oxidant diphenylamine (DPA) (Huelin and Coggiola, 1970;Meir and Bramlage, 1988). Due to the possible restriction of its use, since it is considered to be a pollutant and a health hazard (Drzyzga, 2003), there is great interest in finding new control methods.…”

Cloning and functional expression of an ( E , E )-a-farnesene synthase cDNA from peel tissue of apple fruit

“…Early experiments showing that DPA inhibited oxidation of (E,E)-afarnesene in vivo and in vitro and largely prevented scald development lent support to the a-farnesene oxidation-scald induction hypothesis (Huelin and Coggiola 1970;Anet and Coggiola 1974). The most compelling recent evidence supporting the hypothesis was the demonstration by Rowan et al (2001) that treatment of 'Granny Smith' apples with synthetic conjugated triene alcohol and hydroperoxide oxidation products of afarnesene induced symptoms indistinguishable from ''natural'' superficial scald.…”

“…Cloning of the AFS1 cDNA has provided a new tool for testing the validity of the (E,E)-a-farnesene oxidation-scald induction hypothesis, which has prevailed for more than 30 years (Huelin and Coggiola 1970) but remains unproven. Opponents of the hypothesis have raised the question of cause and effect, i.e., are (E,E)-afarnesene oxidation products truly the cause of scald development, or are they merely one manifestation of unbridled active oxygen species and free-radical reactions that lead to tissue injury and necrosis (Rupasinghe et al 2000b).…”

“…Oxidation products of (E,E)-a-farnesene are hypothesized to be the causal agents of superficial scald, a serious physiological disorder that occurs in fruit of susceptible apple cultivars after several months of cold storage and intensifies after warming to market temperature (Huelin and Coggiola 1970;Ingle and D'Souza 1989;Rowan et al 1995). Production of (E,E)-a-farnesene occurs in the epidermal and/or adjacent hypodermal cell layers (Rupasinghe et al 1998), and the sesquiterpene can accumulate to high levels in the natural epicuticular coating of scald-susceptible apples during the first several weeks of storage (Huelin and Coggiola 1968;Whitaker et al , 1998.…”