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Charles F. Forney*, Jun Song, and Michael A. Jordan

Apple fruit are treatmented with diphenylamine (DPA) in the form of a postharvest dip to prevent the development of storage scald. However, DPA residues have been detected on apples not treated with DPA, which is problematic in markets where DPA residues are not acceptable. The objective of this study was to identify sources of DPA contamination and evaluate the effectiveness of ozone to reduce contamination. Concentrations of DPA in the atmosphere of commercial storage rooms was monitored during the storage season and the adsorption of DPA onto wood and plastic bin material, plastic bin liners, foam insulation, and apple fruit was assessed. DPA was sampled from headspace with solid phase micro extraction using 65 μm polyacrylate micro fibers and analyzed using GC-MS. The effectiveness of gaseous treatments of 300 and 800 ppb ozone to reduce DPA contamination on apple fruit and bin material was also determined. DPA was found to volatilize from treated apples and bins into the storage room air, where it was adsorbed onto storage room walls, bins, bin liners and other fruit. DPA was found in the atmosphere of storage rooms containing apples that were not treated with DPA. Wood and plastic bin material, bin liners, and foam insulation all had a high affinity for DPA and were determined to be potential sources of contamination. Ozone reacted with DPA and following gaseous ozone treatments, off-gassing of DPA from wood and plastic bin material and bin liners was reduced. However, ozone was not effective in removing all DPA in contaminated materials and was ineffective in removing DPA from contaminated apples. Due to the pervasive and persistent nature of DPA, fruit should be handled and stored in facilities where DPA is not used to prevent contamination of fruit.

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Charles F. Forney, Stephanie Bishop, Michele Elliot, and Vivian Agar

Extending the storage life of fresh cranberries (Vaccinium macrocarpon Ait.) requires an optimum storage environment to minimize decay and physiological breakdown (PB). To assess the effects of relative humidity (RH) and temperature on storage life, cranberry fruit from four bogs were stored over calcium nitrate, sodium chloride, or potassium nitrate salts, which maintained RH at 75%, 88%, and 98%, respectively. Containers at each RH were held at 0, 3, 5, 7, or 10 °C and fruit quality was evaluated monthly for 6 months. Both decay and PB increased with increasing RH in storage. After 6 months, 32%, 38%, and 54% of fruit were decayed and 28%, 31%, and 36% developed PB when stored in 75%, 88%, and 98% RH, respectively. The effects of RH continued to be apparent after fruit were removed from storage, graded, and held for 7 days at 20 °C. The decay of graded fruit after 4 months of storage in 75%, 88%, or 98% RH was 10%, 13%, and 31%, respectively, while PB was 12%, 12%, and 17%, respectively. Fresh weight loss decreased as RH increased averaging 1.9%, 1.4%, and 0.7% per month for storage in 75%, 88%, and 98% RH, respectively. Fruit firmness was not affected by RH. Storage temperature had little effect on decay. However, PB was greatest in fruit stored at 10 °C, encompassing 55% of fruit after 5 months of storage. When graded fruit were held an additional 7 days at 20 °C, decay and PB were greater in fruit previously stored at 0 or 3 °C than at 5, 7, or 10 °C. Fresh weight loss increased as storage temperature increased, averaging 0.8%, 1.0%, 1.3%, 1.7%, and 1.9% per month at 0, 3, 5, 7, and 10 °C, respectively. Fruit firmness decreased during storage, but was not affected by storage temperature. To maximize storage and shelf life, cranberry fruit should be stored in a RH of about 75% at 5 °C.

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Jun Song, Lihua Fan, Paul D. Hildebrand, and Charles F. Forney

The biological effect of corona discharge on onions (Allium cepa L.) in a commercial storage was investigated. Surface discoloration and mold were modestly but significantly reduced by the corona discharge when onions were stored for 2 or 4 weeks with or without an additional 2 weeks of shelf life under high humidity. Corona discharge treatment also reduced airborne mold spores in the storage room. No significant changes in internal decay, firmness, sprouting, or rooting, in treated onions were found.

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Lihua Fan, Jun Song, Charles F. Forney, and Michael A. Jordan

Ethanol concentration and chlorophyll fluorescence (CF) were measured as signs of heat stress in apple fruit [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.]. `McIntosh', `Cortland', `Jonagold', and `Northern Spy' apples were placed in trays and exposed to 46 °C for 0, 4, 8, or 12 hours. Following treatments, fruit were stored in air at 0 °C and evaluated after 0, 1, 2, or 3 months. Ethanol and ethylene production, CF, peel and flesh browning, firmness, skin color, soluble solids, and titratable acidity were measured. Increases in ethanol were apparent immediately following 12-hour heat treatments as well as after 3 months. After 3 months, ethanol concentrations were 16-, 52-, 6-, and 60-fold higher in `McIntosh', `Cortland', `Jonagold', and `Northern Spy' apples than in controls, respectively. The concentrations of ethanol accumulated reflected the degree of heat-induced fruit injury. Heat treatments reduced ethylene production relative to control values. After 3 months of storage ethylene production of fruit exposed to 46 °C for 12 h was <0.48 μmol·kg-1·h-1 compared to >4.3 μmol·kg-1·h-1 for controls. Heat treatments also reduced CF which was expressed as Fv/Fm, where Fv is the difference between the maximal and the minimal fluorescence (Fm - Fo), and Fm is the maximal fluorescence. After 3 months storage at 0 °C, Fv/Fm was ≈0.2 in fruit held at 46 °C for 12 hours compared with 0.5-0.6 for control fruit. Exposure to 46 °C for 12 hours caused severe peel and flesh browning in all cultivars. Severity of peel and flesh browning increased with increasing duration of heat treatment and subsequent storage at 0 °C. `Northern Spy' apple fruit were most susceptible to heat stress based on the degree of flesh browning. Heat treatments of 8 and 12 hours reduced firmness of `McIntosh', `Cortland', and `Northern Spy', but not `Jonagold' apples. Hue angle of the green side of fruit was also reduced in `Cortland', Jonagold' and `Northern Spy' apples receiving the 8- and 12-hour treatments. Heat treatments caused a decrease in fruit tiratable acidity, but had no effect on soluble solids content. The increase in ethanol production and decrease in CF correlated with heat-induced injury, and were apparent before browning was visually apparent. Ethanol and CF have the potential to be used to nondestructively predict the severity of injury that develops during storage.

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Charles F. Forney, Sharon J. Peterson, and Preston Hartsell

Callus tissue grown from `Marsh' grapefruit (Citrus paradisi Macf.) albedo tissue was grown at 30C for ≈ 40 days. Calli were preconditioned in normal air for 5 days at 10 or 30C before being fumigated for 2 hr with 0, 32, or 48 g of methyl bromide (MB)/m 3. Calli were then held at 10C and K+ leakage was measured after 1, 10, 20, and 30 days. The amount of K+ leaked from MB-fumigated calli was greater than that for nonfumigated calli and increased with higher MB dose. Leakage also increased with time following fumigation. Leakage of calli preconditioned at 30C and fumigated with 48 g MB/m3 was 140%, 196%, and 260% greater than leakage from nonfumigated calli 10, 20, and 30 days after fumigation, respectively. Leakage from calli preconditioned at 10C for 5 days before MB fumigation was less than that from calli held at 30C. MB doses of 32 and 48 g·m-3 increased leakage of calli preconditioned at 10C by 6% and 43% and for those preconditioned at 30C by 99% and 140%, respectively, 10 days after fumigation. In addition to K+ leakage, MB induced the development of a tan to orangish-brown discoloration.

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Charles F. Forney, James P. Mattheis, and Rodney K. Austin

Broccoli (Brassica oleracea L., ltalica Group) produces severe off-odors when it is stored under anaerobic conditions which can develop in modified atmosphere packages. The compounds responsible for these off-odors, which render the broccoli unmarketable, were produced after sealing 50 g of fresh broccoli florets in glass pint jars held at 15C. Twenty-four hours after sealing oxygen concentration dropped to around 0.5% and remained at this concentration for 6 days. Volatile compounds found in the head space of the jars were identified using gas chromatography with flame photometric and mass spectroscopic detection. Volatile compounds produced were identified as methanethiol, hydrogen sulfide, dimethyl disulfide, acetaldehyde, acetone, ethanol, and ethyl acetate. Methanethiol was detected 48 hours after sealing and appears through olfactory evaluation to be the primary compound responsible for the objectionable odor.

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Charles F. Forney, Leonard J. Eaton, and Leigh Gao

Increasing the size of containers used to transport wild lowbush blueberry (Vaccinium angustifolium) fruit from the field to the processing facility has the potential to increase handling efficiency. Currently the wild blueberry industry uses a standard 18-inch-long × 15-inch-wide × 5-inch-deep plastic container that holds about 20 lb of fruit. This study examined the development of a new, pallet-sized high-capacity blueberry container and determined its effects on fruit quality following harvesting, transport, and processing. Laboratory studies on the effects of packing depth of berries on fruit quality demonstrated that container depths of 14.2 inches were damaging to fruit 24 hours following harvest, transport, and holding under ambient conditions, while depths of 7.1 inches were not. In commercial trials with larger pallet-sized prototype containers, fruit depths of up to 10 inches were not damaging to fruit under otherwise typical commercial handling conditions. Dumping fruit from the 10-inch-deep pallet-sized containers onto conveyer belts at the processing facility caused minimal damage to the fruit. In addition, fruit crushing that occurred in the large pallet-sized containers was similar to that occurring in the standard 20-lb plastic containers currently used by the industry. Results of these studies indicate that large pallet-size blueberry containers with a depth of 10 inches could be used without causing significant damage to fresh fruit during harvest, transport, and processing. Thus as a whole, the adoption of this type of container would improve handling efficiency and potentially the quality of the fruit.

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Wilhelmina Kalt, Agnes M. Rimando, Michele Elliot, and Charles F. Forney

Recent interest in the human health-promoting properties of fruit phenolics, and especially fruit flavonoids, has stimulated research on how these secondary metabolites may be affected by pre- and postharvest horticultural factors. Resveratrol, although a minor phenolic in many fruit, possesses potent bioactivities, and is therefore of particular interest. To study the effects of postharvest storage and UV-C irradiation on selected phenolic components and antioxidant capacity of cranberry (Vaccinium macrocarpon), fruit of cv. Pilgrim, Stevens, and Bergman, were irradiated with UV-C at levels between 0 and 2.0 KJ·m-2, followed by storage at 9 °C for 7 and 17 d. Total phenolic content did not change during storage. However, resveratrol content was higher and antioxidant capacity (ORAC) was lower at 7 days of storage compared to 17 days. There was no main effect of UV-C on total phenolics, anthocyanins, resveratrol, or ORAC. However, there was an interaction between storage time and UV-C irradiation. Anthocyanin content was lower at 7 days, and higher at 17 days, at UV dosages of 1.0 or 2.0 KJ·m-2. Resveratrol content was higher in UV-C irradiated fruit at 7 days, while at 17 days there was no difference between UV-treated and untreated fruit.

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ZhaoSen Xie, Charles F. Forney, WenPing Xu, and ShiPing Wang

In this study, the ultrastructure of phloem and its surrounding parenchyma cells in the developing grape berry produced under root restriction or without (control) was for the first time systematically investigated through transmission electron microscopy during the entire developmental process of the berry. The results showed that root restriction increased the number of plasmodesmata between sieve elements (SE) and companion cells (CC) and between the SE/CC complex and phloem parenchyma cells. Sieve elements in fruit produced under root restriction were smaller in size than those from the control treatment, but CC were bigger than in the control treatment. During the first rapid growth phase of the grape berry, there was denser cytoplasm in the CC produced under root restriction having more abundant mitochondria, endoplasmic reticulum, multivesicular bodies, vesicles, and plastids than in control fruit. During the second rapid growth phase of the grape berry, CC under root restriction showed more serious plasmolysis. Cytoplasmic contents such as vesicles were fused into the vacuole of which the tonoplast nearly disappeared in the phloem parenchyma cells, and cytoplasmic contents in fruit cells produced under root restriction became denser than the control treatment. These results demonstrated that grape berry adapted to the root restriction stress through ultrastructure variation of the phloem, and this variation explained the increase of photosynthate accumulation in the grape berry observed under root restriction.

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Jun Song, Lihua Fan, Charles F. Forney, and Michael A. Jordan

Ethanol production and chlorophyll fluorescence were measured as signals of freezing and heat stress in apple fruit. `Cortland' and `Jonagold' apples were held at –8.5 °C for 0, 6, 12 or 24 h (freezing treatments), or at 46 °C for 0, 4, 8 or 12 h (heat treatments). Following treatments, fruit were stored at 0 °C and evaluated after 0, 1, 2, or 3 months. Following storage, fruit samples were kept for 12 h at 20 °C and then analyzed for ethanol production, chlorophyll fluorescence, and visible injury. Severity of flesh browning increased with increasing treatment time for both freezing and heat treatments. Freezing for 24 h and heating for 12 h caused severe flesh browning in both cultivars. Severity of heat-induced browning increased during storage. Increases in ethanol production were apparent 12 h following treatments and reflected the degree of stress-induced fruit injury. After 2 months of storage, ethanol concentrations peaked and were as much as 400-fold greater than that of controls. These stress treatments also reduced ethylene production and chlorophyll fluorescence. The degree of increase in stress-induced ethanol production and decrease in chlorophyll fluorescence correlated with stress-induced injury and could be used to predict the severity of injury that develops during storage. Other volatile production and their relationship to fruit stress will also be discussed.