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Eric A. Curry

in closed cardboard cartons at −1 °C for 5 months. About 24 h after being placed in storage at −1 °C, a second set of apples (cold fruit) was removed and treated similarly to those treated immediately after harvest. All fruit were examined for peel

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Lee Kalcsits, Gregory van der Heijden, Michelle Reid, and Katie Mullin

dry, samples were homogenized using a mortar and pestle and then ground to micron size using a tissue homogenizer (VWR, Radnor, PA). For nutrient analysis of fruitlets collected during the growing season and peel and inner fruit samples prepared at

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Chris B. Watkins, Juan-Pablo Fernández-Trujillo, and Jacqueline F. Nock

Susceptibility of apple fruit to CO2 can be affected by cultivar and postharvest treatment with diphenylamine (DPA). To study possible metabolic reasons for CO2 injury development, `Cortland' and `Law Rome' apple fruit were either untreated or treated with DPA at harvest, and then exposed to air or 45 kPa CO2 for up to 12 days. Fruit were sampled at 3-day intervals during treatment, and peel and flesh samples were taken for organic acid and fermentation product analysis. Additional fruit were removed to air and stored for 25 weeks for evaluation of injury. `Cortland' apple fruit had more external CO2 injury, but less internal CO2 injury than `Law Rome'. DPA treatment markedly reduced incidence of both external and internal injury. Fermentation products increased in peel and flesh of both cultivars with increasing exposure to CO2. However, acetaldehyde concentrations were ≈10 times higher in peel and flesh of `Law Rome' than `Cortland' apples. Ethanol concentrations in the flesh were similar in both cultivars, but were about twice as high in `Cortland' than `Law Rome' peel. Neither acetaldehyde nor ethanol concentrations were affected consistently by DPA treatment. Cultivar or DPA treatment did not affect accumulation of succinate, often regarded as the compound responsible for CO2 injury. These results do not indicate that acetaldehyde, ethanol, or succinate accumulation is responsible for CO2 injury in apple fruit.

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Ignazio Infantino and Riccardo Lo Bianco*

Peel color is a critical index of external fruit quality and consumer appreciation level. Traditional methods for determination of peel color are based on visual analysis or punctual measurements by colorimeter. In this study we present a method based on digital image analysis that integrates the accuracy of an interactive measurement and the efficacy of an image analysis that descibes entire sides of the fruit. A sample of apple, mandarin, grape, and peach fruit was photographed (each fruit on two opposite sides) with a digital camera for determination of peel color. Digital images were converted from RGB to CIE L*a*b* format, and color characteristics were indexed and quantified. The implemented method uses a reference color image cropped from the best fruit (interactively chosen) to calculate a color index for each fruit of the image set. The final index is the weighted sum of the number of pixels of the fruit, where pixels closer to the reference color (distance in the CIE L*a*b space) are considered more relevant. This color index gives integrated information on fruit color quantity (% of cover color) and quality (hue and saturation). The method represents a rapid and efficient way of determining color of the entire fruit surface and overcomes difficulties and approximation of traditional methods. A modification of the same method can be used to determine peel rugosity (mandarin) and average size and number of grape berries per bunch.

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Zohar Shaham, Amnon Lers, and Susan Lurie

`Granny Smith' apples [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.] were harvested in two seasons and stored at 0 °C air storage with no pretreatment (control), after heating for 4 d at 38 °C, or after treating for 16 hours at 20 °C with 1 μL·L-1 1-methylcyclopropene (1-MCP). The effects of the two treatments on superficial scald development were consistent over both seasons. Scald began to appear after 8 weeks in control fruit, after 16 weeks in heated fruit but not on 1-MCP treated fruit. α-Farnesene accumulation and oxidation were slower in the skin of heated than in control fruit, and almost entirely absent in 1-MCP treated fruit. The activities of five antioxidant enzymes, ascorbate peroxidase, catalase, glutathione reductase, peroxidase and superoxide dismutate, were measured at two-week intervals in the apple peel, quantitatively as total activity and qualitatively by isozyme analysis. Enzyme activities either increased or remained stable during 16 weeks of storage, except for superoxide dismutase activity, which decreased. Ascorbate oxidase activity was higher in heated than control apples and there was an additional peroxidase isozyme present in activity gels. The activities of antioxidant enzymes were lower in 1-MCP treated fruit except for catalase during the first month of storage. Lipid soluble antioxidant activity was higher in 1-MCP treated fruit than the fruit of the other treatments, and water soluble antioxidant activity was higher in both treatments than in control fruit during the time that scald was developing in control apples. Both free and total phenol contents in the peel fluctuated during storage but no consistent trend was detected. The differences in enzyme activity and antioxidant content of the peel of 1-MCP and heated apples may play a role in preventing or delaying the appearance of superficial scald.

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Mark A. Ritenour, Sunita Kochhar, Larry E. Schrader, Tsui-Ping Hsu, and Maurice S.B. Ku

Western immunoblot analyses showed that small heat shock proteins (smHSPs) are low or undetectable in the peel of `Fuji', `Jonagold', `Criterion', `Gala', and `Delicious' apples [(Malus sylvestris (L.) Mill var. domestica (Borkh.) Mansf.] growing shaded within the tree canopy (shade apples), but are high in apples growing exposed to direct sunlight (sun apples). `Fuji', `Jonagold', and `Gala' sun apples sampled biweekly between 1 July and 21 Oct. 1997 were highest in content of smHSPs on 31 July, 13 Aug., and 10 Sept., corresponding to some of the warmest periods of the sampling period. The smHSPs started to disappear first in `Gala', the earliest maturing cultivar, and last in `Fuji', the latest maturing cultivar indicating that maturity might play a role in regulating smHSP accumulation. In sun apple fruit left on trees for 60 to 120 days beyond commercial maturity and exposed to field temperatures as low as -4 °C, a 71.7 ku (u = unified atomic mass unit) polypeptide was detected with a polyclonal antiwheat (Triticum aestivum L.) HSP70 in the peel and cortex of all five cultivars. While no smHSPs were detected in these apples, three smHSPs, as detected by antibodies against pea (Pisum sativum L.) cytosolic HSP18.1, could be induced in the same fruit 24 hours after heating to 45 °C for 4 hours. In `Fuji' shade apples heated at 40 °C, smHSP accumulation was detected after the second hour of a 4-hour heat treatment and continued to increase over the next 48 hours at 22 °C. Levels of HSP70 did not change in `Fuji' shade apples heated at 45 °C for 2, 4, or 6 hours, but smHSPs became detectable immediately after each of these heat treatments and further increased over the next 24 hours at 22 °C. Accumulation of smHSPs was maximal in the 4-hour heat treatment. After a 4-hour heat treatment at 45 °C, smHSPs increased during the next 48 hours at 22 °C and then declined by 72 hours. Using two-dimensional electrophoretic analysis, as many as 17 proteins ranging from 15 to 29 ku were found to accumulate in the peel 48 hours after a 4-hour heat treatment. Thus, apples can respond rapidly to high temperature stress, even at advanced stages of maturity, by synthesizing smHSPs, which likely play an important role in protecting cellular biochemical processes during these periods of stress.

Open access

D. C. Ferree, R. L. Darnell, R. D. Fox, R. D. Brazee, and R. E. Wittmoyer


The microclimate surrounding ‘Rome Beauty’ apples (Malus × domestica Borkh.) was modified by enclosing clusters at petal fall (PF) in various types of bags, and the influence of these treatments on development of scarf skin, cuticular waxes, and peel nutrient status was determined. The cuticle and epidermis of fruit with scarf skin generally was unbroken, but cell separations several cell layers below the surface resulted in gaps or air spaces which caused the visual whitish-gray appearance (scarf skin). Energy dispersive x-ray analysis and tissue analysis of apple peel indicated an increase in concentration of Al, Ca, and Mn with severe scarf skin. All bag types reduced scarf skin compared with the unbagged control, with cheesecloth giving the smallest reduction (34% on green side) and the large polyethylene bag the largest reduction (75% reduction green side). The total amount or components of cuticular wax was not influenced by the bagging treatments or by the different levels of scarf skin. Light level, temperature, and absolute and relative humidity were modified by the various types of bags, but the role of the individual environmental parameters on the expression of scarf skin was not indicated.

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D.R. Rudell, J.P. Mattheis, X. Fan, and J.K. Fellman

1 Biological sciences technician. 3 Research food technologist. 4 Associate professor. We thank William Duplaga for UV light measurements and David Buchanan for technical assistance with peel analyses.

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N.A. Mir, J. Song, and R. Beaudry

Peel discs (0.2 mm in diameter) of refrigerated, air-stored apple that were immersed in a medium isotonic with that of fruit sap were allowed to photosynthesize either in a closed or flow-through system. The photosynthetic net evolution of O2 in the light or consumption in the dark was used to predict the duration of the experiment that would be within the critical limits of aerobiosis. Using GC-MS system, volatile emissions from these tissues were determined, in the head space and liquid medium. The volatile profile generated from head space analysis was essentially similar to that of whole fruit. Light, compared to the dark treatment, stimulated the synthesis of nearly all volatiles, especially α-farnesene. The synthesis of 6-methyl-5-hepten-2-one, an oxidative product of α-farnesene that causes scald like symptoms in whole fruit, was observed only under lighted conditions. While O2 content in the medium seemed to have no effect on the volatile build-up in the head space, a C15 sesquiterpene with a mass spectrum similar to hydroperoxide breakdown products of α-farnesene was synthesized only in presence of O2 in the reaction medium. Inhibition of light reactions of photosynthesis with DCMU, suppressed the synthesis of various volatiles in the head space suggesting the role of chloroplast activity in aroma development. We suggest that peel discs work well as a model system to study flavor chemistry in apple.

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Luiz C. Argenta, Xuetong Fan, and James P. Mattheis

each combination of treatment, storage temperature, and storage duration, except for determination of the peel discoloration disorder that followed a randomized complete block design with four replicates of 10 fruit. Data were analyzed by analysis of