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William J. Bramlage

`Cortland' and `Delicious' apples were stored at 0C for up to 25 weeks, and at 20C in either open boxes or non-sealed poly bags for up to 8 weeks. At 20C, lesions occurred mostly around lenticels, but with some calyx bronzing and scald-like symptoms on shaded areas. At 0C, typical scald symptoms occurred. At both temperatures, high concentrations of alpha-farnesene and conjugated trienes occurred in conjunction with symptom appearance, and both these concentrations and discolorations decreased with later harvest of fruit. Scald development appeared to be chilling-enhanced, but not chilling-dependent.

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William J. Bramlage and Sarah A. Weis

Preharvest environmental conditions apparently determine susceptibility of apples to postharvest scald development. Cool temperature, as hours below 10C, can greatly reduce susceptibility, but greater than 30C appears to enhance it. These effects appear to interact, because a high-temperature episode can cause loss of some low-temperature benefit. Shading of fruit increases their scald susceptibility and preharvest light conditions, along with preharvest rainfall, appear to be factors in scald susceptibility in New England. Fruit maturation reduces scald susceptibility. We are constructing models of contributions of these variables to scald susceptibility of fruit grown under different environmental conditions, and in this the relative importance of these variables is being evaluated.

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Zhenyong Wang and David R. Dilley

We are investigating alternative strategies to control scald on apples. Ethanol vapors were applied to `Law Rome' and `Red Delicious' apples in the storage chambers by ventilating air through aqueous solutions of ethanol at different concentrations, and in modified atmosphere packages by adding various initial concentrations of ethanol vapor. Fruits in storage chambers treated with ethanol vapor at 1600 ppm for about 2 months showed no scald when stored for an additional period in air storage whereas the scald index in control was up to 2.33 (the highest is 3). The similar results in the modified atmosphere experiments confirmed that ethanol vapor could prevent apple scald. Ethanol vapor treatment was also correlated with a reduction of α-farnesene production by the fruits. α-farnesene is an isoprenoid metabolite in the pathway to carotenoid synthesis that has been implicated indirectly as a factor in scald development. Evidence for this based on diphenylamine (DPA) reducing the level of a conjugated terpene product of α-farnesene oxidation. Our results suggested that the control of scald by ethanol vapor treatment may be related to the reduction of α-farnesene production and its subsequent oxidation. Ethanol vapor treatment resulted in accumulation of ethanol in the fruits in direct proportion to the ethanol concentration administered and reduced the rate of ethylene production, and the internal ethanol levels dropped rapidly when fruits were returned to air without ethanol vapor.

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John B. Golding, Vassilios Sarafis, Stuart Crozier, and Stephen E. Rose

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Morris Ingle, J.C. Morris, and M.C. D'Souza

Three types of soil were mixed with water containing DPA (2000 mg·liter-1) and benomyl (300 mg·liter-1) at 1% to 5% (w/w). `Rome' apples (Malus domestica Borkh.) were dipped in the mixtures over 8 days. The efficiency of DPA as a scald inhibitor was not consistently affected by soil type, soil concentration, or age of mixture. Chemical names used: methyl[1-[(butylamino)carbonyl]-1 H-benzimidazol-2-yl]carbamate (benomyl); diphenldyamine (DPA).

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Mervyn C. D'Souza, Morris Ingle, and Suman Singha

Chromaticity values (L*, a*, b*) of `Rome Beauty' apples (Malus domestics) were measured at weekly intervals during maturation periods in 1988 and 1989. Chromaticity was measured using a Minolta Chroma Meter CR-200b calorimeter on four quadrants of the fruit at locations midway between the stem and calyx ends. The apples continued to develop red color through the maturation period. After storage, the peel areas where chromaticity was measured were evaluated for scald intensity. The L* value at harvest was correlated positively with scald intensity, while the a* value was correlated negatively. An equation has been developed to describe the relationship between chromaticity values at harvest and scald intensity after storage.

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Zhiguo Ju, Chenglian Liu, Yongbing Yuan, and Yongzhan Wang

“Colormotor” is a new product formulated mainly from seaweed extracts for promoting anthocyanin synthesis and improving fruit coloration in apples. The product was applied (150 ppm) 3 weeks before harvest in 2 years of experiments with `Delicious' apples. Colormotor treatment promoted anthocyanin accumulation by 2.5-fold and increased color index of fruit by 50% over controls. Only 23.5% of control fruit had full red color when harvested 140 DAFB, whereas 80% of the fruit sprayed with Colormotor had full red color. UDPG-o-3-glucosyltransferaw activity also was significantly greater in treated fruit. Treatment did not affect ethylene synthesis, fruit firmness, soluble solids, total sugars, or titratable acid incidence either at harvest or during prolonged storage. However, scald incidence after 20 weeks at 0C was significantly decreased by Colormotor treatment. The scald scores were 1.59 in control fruit and 0.67 in treated fruit, respectively, on a scale of 1 to 4.

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D.P. Murr, K. Hustwit, R. Tschanz, M.V. Rao, and G. Paliyath

Heat treatment of apples (Malus domestica Borkh cvs. Red Delicious, Starkrimson) and its effect on scald development have been investigated. Several parameters indicative of scald, such as ethanol and acetaldehyde content, UV-absorbing components from skin, and fruit quality parameters, such as fruit firmness and soluble solids content, were monitored after exposing apples to heat therapy at 40C for 24 h, followed by storing them at room temperature in polyethylene bags. In general, heat-treated apples possessed higher ethanol and acetaldehyde levels. As well, heat-exposed apples appeared to possess a lower degree of scald. The content of soluble solids did not appear to be affected by heat treatment. The degree of firmness, however, was maintained in heat-treated apples. Effect of heat treatment on several other physiological and biochemical parameters will be presented.