2 Present address: DOLE Fresh Vegetables, P.O. Box 1759, Salinas, Calif. 93902. This material is based on work supported by the National Research Foundation under grant number GUN: 2046844 and the Deciduous Fruit Producers Trust of South Africa. We
W.J. Steyn, D.M. Holcroft, S.J.E. Wand, and G. Jacobs
Ahmed F. El-Shiekh and David H. Picha
Peaches stored in air for 40 days at OC developed severe internal breakdown and poor quality after transferring them to 20C to ripen. Comparable fruit stored under controlled atmosphere (1% O2 + 5% CO2) and then ripened at 20C had no breakdown and retained good quality. Fruit stored under CA had less reducing sugars but more sucrose than air stored fruit. Fruit pH increased and titratable acidity decreased over a 40 day storage period. Citric acid increased slightly while malic acid decreased during storage. Little or no differences in overall acidity and individual organic acids existed between CA and air storage. Little or no change in individual phenolic acid content occurred during storage or between CA and air storage. Internal color darkened and became redder with storage. CA stored fruit was significantly firmer than air stored fruit. Sensory evaluation indicated CA stored fruit was more acidic, sweeter, and had better overall flavor than air stored fruit.
The effects of grapefruit cultivar and coating type on chilling injury (CI) incidence were examined. The shellac coating widely used for exported citrus resulted in the lowest CI incidence in white `Marsh' grapefruit stored for 2 months at 4 °C and 92% ± 3% relative humidity compared with nonwaxed fruit or fruit waxed with either carnauba or polyethylene waxes. The order of coating performance for reducing CI was shellac > carnauba > polyethylene > nonwaxed fruit. For `Flame' little difference of coating type on CI was detected after 2 months of storage. Overall, CI incidence was high in fruit of the cultivars harvested from September to December, low in February, and high again after March but was generally higher in white `Marsh' seedless grapefruit than `Ruby Red', `Rio Red', or `Flame'. However, little difference of cultivar on CI incidence was found among the `Ruby Red', `Rio Red', and `Flame' grapefruit except the October harvest in which CI was higher in `Ruby Red' than in `Rio Red' and `Flame' grapefruit. These studies suggest that the coating and cultivar should be considered in the postharvest management of CI in commercial packing.
Joseph C. Goffreda
The stony hard gene in peach is a recessive gene which increases fruit firmness and shelf-life. Five progenies segregating for the stony hard trait were scored for several ripening-related characteristics. Fruit from stony hard segregants produced little or no ethylene, had lower respiration rates, and tended to ripen later than `normal' fruit. Stony hard fruit also had a lower percentage red overcolor in three of the five progenies. Stony hard fruit, harvested when firm-ripe, maintained their firmness after five days storage at 20°C. Firmness of stony hard fruit decreased significantly if the fruit were sprayed with ethephon (2-chloroethylphosphonic acid) at 250 ppm prior to storage. Fruit firmness of `normal' freestone or clingstone varieties was not significantly affected by the application of ethephon. The conversion of ethylene precursors to ethylene in stony hard fruit will also be discussed.
Kirk W. Pomper and Patrick J. Breen
Expansion of green-white and red fruit in control (watered) and water-stressed greenhouse-grown strawberry (Fragaria ×ananassa Duch. `Brighton') plants was monitored with pressure transducers. Expansion of green-white fruit in control plants was rapid, showing little diurnal variation; whereas in water-stressed plants, fruit expansion occurred only during dark periods and shrinkage during the day. Red fruit were mature and failed to show net expansion. The apoplastic water potential (ψaw), measured with in situ psychrometers in control plants was always higher in leaves than in green-white fruit. In stressed plants, ψaw of leaves was higher than that of green-white fruit only in the dark, corresponding to the period when these fruit expanded. To determine the ability of fruit to osmotically adjust, fruit were removed from control and water-stressed plants, and hydrated for 12 hours; then, solute potential at full turgor (ψs 100) was measured. Water-stressed green-white fruit showed osmotic adjustment with a ψs 100 that was 0.28 MPa lower than that of control fruit. Mature leaves of water-stressed plants showed a similar level of osmotic adjustment, whereas water stress did not have a significant effect on the ψs 100 of red fruit. Fruit also were severed to permit rapid dehydration, and fruit solute potential (ψs) was plotted against relative water content [RWC = (fresh mass - dry mass ÷ fully turgid mass - dry mass) × 100]. Water-stressed, green-white fruit had a lower ψs for a given RWC than control fruit, further confirming the occurrence of osmotic adjustment in the stressed fruit tissue. The lack of a linear relationship between turgor pressure and RWC prevented the calculation of cell elasticity or volumetric elastic modulus. Osmotic adjustment resulted in about a 2.5-fold increase in glucose and sucrose levels in water-stressed green-white fruit. Although green-white fruit on water-stressed plants showed osmotic adjustment, it was not sufficient to maintain fruit expansion during the day.
P. Perkins-Veazie, J.K. Collins, and J.R. Clark
104 POSTER SESSION (Abstr. 427–440) Postharvest Physiology–Temperate Fruit
Gerard Krewer, Tom Beckman, Jose Chaparro, and Wayne Sherman
`Gulfking' and `Gulfcrest' peaches are jointly released for grower trials by the U.S. Department of Agriculture, Agricultural Research Service, the Georgia Agricultural Experiment Station, and the Florida Agricultural Experiment Station. Trees of `Gulfking' and `Gulfcrest' produce an attractive, sweet-tasting, yellow and non-melting flesh fruit intended for the fresh fruit market. They are expected to produce fruit with tree-ripened aroma and taste while retaining firmness for longer shelf life than fruit from conventional melting-flesh cultivars. Trees of `Gulfking' reach full bloom most seasons in mid-February in lower southern Georgia and are estimated to require 350 chill units. We expect this new peach to be adapted in areas where `Flordaking' has been successfully grown. Fruit ripen 73 to 80 days from full bloom, typically in early May, usually with `Flordaking' in southern Georgia. The fruit are large, ranging from 105 to 130 grams. Commercially ripe fruit exhibit 80% to 90% red (with moderately fine darker red stripes) over a deep yellow to orange ground color. Fruit shape is round with a recessed tip. Pits are medium small and have little tendency to split even when crop loads are low. Trees of `Gulfcrest' are estimated to require 525 chill units. This is based on full bloom consistently occurring with `Sunfre' nectarine at Attapulgus, Ga. where full bloom occurs most seasons in early-March. Fruit ripen 62 to 75 days from full bloom, typically in early to mid-May, usually a few days after `Flordacrest' in southern Georgia. The fruit are medium-large, averaging about 105 g. Commercially ripe fruit exhibit 90% to 95% red over a deep yellow to orange ground color. Fruit shape is round with a recessed tip. Pits are medium small and have little tendency to split even when crop loads are low.
R.E. McDonald, T.G. McCollum, and E.A. Baldwin
The objective of this study was to determine the effects of prestorage heat treatments on chilling tolerance of tomatoes. Mature-green `Agriset' tomato fruit (Lycopersicon esculentum Mill.), either C2H4-treated or not, were immersed in 42C water for 60 min, held in 38C air for 48 hours, or not treated, and then stored at either 2C (chilled) or 13C (nonchilled) for 14 days before ripening at 20C. Heat-treated fruit stored at 2C and transferred to 20C ripened normally while nonheated fruit decayed before reaching red ripe. Color (a*/b* ratio), lycopene content, and internal quality characteristics of fruit were similar at the red-ripe stage irrespective of method of heat treatment. In red-ripe heat-treated fruit, free sterol levels were significantly higher in chilled fruit than in nonchilled fruit. Heating fruit in 38C air resulted in significantly higher levels of some free sterols compared with heating fruit in 42C water. Of the 15 flavor volatiles analyzed, six showed significantly decreased concentrations as a result of C2H4-treatment and seven showed decreased concentrations when stored at 2C before ripening. Some volatiles were decreased by the heat treatments. Prestorage short- and long-term heat treatments could allow for storage of mature-green tomatoes at lower temperatures with little loss of their ability to ripen normally.
P. Perkins-Veazie, J.K. Collins, and J.R. Clark
Fruit at three stages of ripeness were harvested from four erect blackberry (Rubus spp.) cultivars, `Navaho', `Choctaw', `Cheyenne', and `Shawnee', for 2 years to evaluate fresh-market shelf life during 7 days of storage at 2C, 95% relative humidity. Ethylene production was highest from dull black fruit and varied widely among cultivars, ranging from 7.3 to 51.1 pmol·kg–1·s–1 for `Navaho' and `Choctaw' fruit, respectively. Weight loss ranged from 0.8% (`Shawnee') to 3.3% (`Navaho') after storage. Mottled (50% black) fruit of all cultivars were higher in fruit firmness and titratable acidity and had lower soluble solids and anthocyanin concentrations than fruit at other stages of maturity. Cultivars did not differ in total anthocyanin concentration, but dull black fruit had a higher anthocyanin concentration than shiny black fruit. Dull black `Choctaw', `Shawnee', and `Cheyenne' fruit were softer and had more leakage and decay than shiny black fruit. Both shiny and dull black `Navaho' fruit had less leakage than fruit of other cultivars. All cultivars at the shiny black stage were considered marketable after 7 days at 2C because fruit were firm with little decay or leakage. However, red discoloration appeared more frequently on shiny black than on dull black fruit. Mottled fruit of erect cultivars should not be harvested, while shiny black fruit of `Cheyenne', `Shawnee', and `Choctaw' might be suited for regional markets. Either shiny black or dull black `Navaho' fruit could be shipped to distant markets.
James R. Cooksey, James E. Motes, and Brian A. Kahn
Ethephon has increased yields of red fruit, but its use as a pepper (Capsicum annuum L.) fruit ripening agent has been limited by premature fruit abscission and defoliation. We tested ethephon solutions of 0,1500,3000,4500, and 6000 μl·liter-1 with or without 0.1 m Ca(OH)2 as a onetime foliar application to field-grown paprika pepper in southwestern Oklahoma. There was a linear increase in fruit abscission with increasing ethephon rates in 2 of 3 years, with or without added Ca. Marketable fruit as a percentage of total harvested fruit weight was improved by ethephon at 6000 μl·liter-1 in 2 of 3 years, primarily due to a decrease in weight of harvested green fruit. However, ethephon never significantly increased the dry weight of harvested marketable fruit over that obtained from the control. There also was no effect of ethephon on the intensity of red pigment extracted from dehydrated marketable fruit. The only consistently significant effect of Ca(OH)2 was an undesirable increase in the retention of green fruit on the plants. Ethephon had little value as a fruit-ripening agent for paprika pepper under the conditions of our studies, and Ca(OH)2 was not useful as an additive to ethephon sprays. Chemical name used: (2-chloroethyl) phosphoric acid (ethephon).