The relationships between cellular characteristics of cortical tissue and changes in texture during storage under controlled atmosphere (CA, 3% O2 + 3% CO2) or air at 0C were studied. The cultivars used were `Delicious', `Cortland', `Honeycrisp' and its parents, `Honeygold' and `Macoun'. The force needed to break a 7-mm cylinder of apple flesh (breaking force) was greatest for `Delicious' and `Honeycrisp'. Scanning electron microscopy demonstrated that tissues of firm-fleshed cultivars (`Honeycrisp' and `Delicious') fractured through cells, while that of soft-fleshed cultivars (`Cortland', `Honeygold', and `Macoun') fractured between cells. `Honeycrisp' had fewer cells/100 cm2 than the other cultivars. After 9 months of storage, breaking force, cell size, and K+/Ca2+ decreased, while cell number/100 cm2, Ca2+ content, and K+ content increased for all cultivars. Cell number/100 cm2 was significantly less and breaking force was significantly greater for tissue from CA than air-stored fruit.
148 POSTER SESSION 17 (Abstr. 120–133) Postharvest Physiology/Storage/Food Science Wednesday, 26 July, 1:00–2:00 p.m.
Rhizomes of Oxalis adenophylla Gillies and bulbs of Ipheion uniflorum Raf. were planted and wet- or dry-stored at 5 °C for 0, 6, 10, 14, or 18 weeks, before being placed in a greenhouse. Regardless of moisture regime, foliage emergence and time to flower decreased for both species with increasing duration of cooling. Wet-stored bulbs/rhizomes within a cooling treatment required less time to foliage and flower emergence when compared with the corresponding dry-storage period. About 10 weeks of 5 °C was optimum for both species.
The development of ethylene preconditioning treatments for kiwifruit have made it possible to deliver ripe kiwifruit to consumers early in the season. We report on how maturity and length of storage time affect the ripening responses of kiwifruit [Actinidia deliciosa (A Chev) Liang et Ferguson cv Hayward] preconditioned with 100 ppm ethylene at 0°C for 24 hours and ripened for 10 days at 20°C. Kiwifruit freshly harvested at weekly intervals continued to soften faster in response to ethylene preconditioning compared to air controls for at least 5 weeks following commercial harvest. In contrast, kiwifruit commercially harvested and stored at 0°C for more than 2 weeks no longer responded to low-temperature ethylene preconditioning. However, kiwifruit stored more that 5 weeks were still responsive to exogenous ethylene and softened faster when exposed to continuous ethylene at either 0 or 20°C. Kiwifruit had relatively high respiration rates 1 days after transferring from 0 to 20°C, which quickly dropped to base levels within 1 day. Fruit stored >1 week at 0°C always had higher initial respiration than freshly harvested fruit on transfer to 20°C, and ethylene preconditioning increased initial respiration of freshly harvested fruit but had less of an effect on initial respiration of stored fruit. Plotting firmness against individual fruit's respiration and ethylene production revealed a distinct rise in respiration and ethylene production only after fruit softened to <6.5 N. Preconditioning fruit at 0°C did not significantly alter the timing of the climacteric respiration or ethylene peaks.
Tubers of Begonia × tuberhybrida Voss cvs. Ruffled Pink and Roseform Salmon, stored for 8 weeks at 2.5°C, respired more rapidly during a subsequent 24 hr at 20° to 21° than did tubers stored at 5° or 7.5°. Exposure of tubers to 1 μ·liter1 ethylene during a 48-hr period prior to planting had no effect on sex expression or other quality parameters of the plants at flowering. Storage of tubers in a 2-3% O2 atmosphere for up to 20 weeks at 5° increased the percentage of tubers sprouted compared to those stored in air. No differences in sex expression, flower size or doubleness, days to flower, or plant height at flowering were observed between low-O2 and air storage at any duration.
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.
Strawberry plants (Fragaria ×ananassa Duch. ‘Dover’ and ‘Florida Belle’) produced increased December fruit yields during 2 seasons when stored at 2°C for 1 week prior to transplanting rather than transplanting directly from the nursery. The total fruit yield of ‘Dover’ decreased with storage the 2nd season, whereas the total fruit yield of ‘Florida Belle’ was unaffected by storage. Lowering the soil fertility in the nursery prior to plant harvest increased ‘Dover’ December fruit yield the 2nd season, and increased ‘Florida Belle’ December yield both seasons. Total fruit yields of both cultivars as related to nursery fertility were inconsistent. Total fruit yields of ‘Dover’ in both seasons were greater with a fertilizer application in the fruit production field of 224N-50P-224K kg·ha-1 than with double this application. Total fruit yield of ‘Florida Belle’ was not affected by fertilization in a fruiting field. During the first season, both cultivars produced more misshapen fruit with the 448N-100P-448K kg·ha-1 application than with the 224N-50P-224K kg·ha-1 application.
Root regeneration and time to first budbreak of two-year white ash (Fraxinus americana L.) seedlings were strongly correlated with the number of hours of chilling. Physiological dormancy of the buds was removed after approx 2500 hours of storage at 5°C and this coincided with the beginning of increased root regeneration potential. Increased periods of chilling enhanced the rate at which growth was resumed after transfer of seedlings to environmental conditions adequate for growth. The present study indicates that fall-harvested white ash seedlings can be stored at 5° at least until May without any apparent detrimental effects on root regeneration potential or seedling condition.
`D'Anjou' pears (Pyrus communis, L.) growing in 3 locations with the elevation at 150 meters, 380 meters, and 610 meters respectively in Hood River valley, Oregon were harvested at the commercial maturity with the flesh firmness of 62.3 Newton (±2.2 N) and stored in air at -1°C. Regardless of different growing elevations, the incidence of superficial scald became noticeable after 2.5 months of storage and became substantial after 3 months. The rate of scald development was higher on the fruit from 150 meters elevation than those from higher elevations. Alpha-farnesene and conjugated trienes in the peel tissue accumulated at faster and higher rates in the fruit from 380 meters and 610 meters elevations than those from 150 meter elevation. The threshold level of conjugated trienes which causes superficial scald disorder was different from the fruit grown at different elevations.
Seeking non-chemical alternatives to use of DPA for scald control on apples, we interrupted storage with a brief warming period. This often reduces chilling injuries of fruit. Warming `Granny Smith apples for 5 days at 20 C after 2 weeks at 0 C reduced scald as effectively as a 1000 ppm DPA treatment at that time. To better characterize this response, we tested other timings of the warming period, and also lower warming temperature. Warming at 10 C, or for shorter times at 20 C, or after longer periods at 0 C all were less effective. Maintaining a warm period before storage was not effective. During warming of `Cortland' and `Delicious' apples softening and loss of green color occurred, the extent of which increased with warming time and usually was greater if the fruit had initiated the ethylene climacteric before warming.