Trials were conducted in California to evaluate techniques to extend storage life of netted muskmelons (Cucumis melo L.). The use of polyethylene bags, either as individual melon wraps or as liners for 18-kg commercial cartons, minimized water loss and associated deterioration of the fruit. Individual bags and carton liners were equally effective. A 3-minute dip in 60C water effectively checked surface mold development on wrapped fruits. Lower temperature and/or shorter exposure treatments were less effective. When applied in addition to hot water treatment, imazalil fungicide did not confer significant additional benefit. The combination of polyethylene bags and hot water treatment maintained high quality, marketable fruit for at least 28 days of storage at 3C,
K.S. Mayberry and T.K. Hartz
Ahmad Shirazi and Arthur C. Cameron
The feasibility of controlling relative humidity in modified atmosphere packages using compounds possessing Type III sorption isotherm behavior was studied. Ten grams each of dry sorbitol, xylitol, NaCl, KCl, or CaCl2 sealed with one maturegreen tomato (Lycopersicon esculentum L.) fruit at 20C in simulated packages for 48 days resulted in stable relative humidities of ≈75%, 80%, 75%, 85%, and 35%, respectively. Relative humidity was a function of the ratio of chemical to fruit mass. Relative humidities within control packages were in the range of 96% to 100% throughout the experiments. A simple system that uses spunbonded polyethylene pouches for the application of this humidity control method to packages is described. The storage life of packaged red-ripe tomato fruit at 20C was extended from 5 days using no pouch to 15 to 17 days with a pouch containing NaCl, mainly by retardation of surface mold development.
Chilling injury (CI) is an important postharvest physiological problem that limits the storage life of many warm-season fruits and vegetables. Variability exists among cultivars and CI appears to be related to moisture loss during low temperature storage. The relationship between moisture loss and CI was examined using fruit from 64 PI lines of field-grown Cucumis sativus. A wide variation existed among the lines in the sensitivity of their fruit to low temperatures. Fruit from 8 of the lines developed severe symptoms of CI after 5 days at 5°C and fruit from 21 lines developed no injury symptoms. CI symptoms developing during 2 and 4 days of storage at 15°C were highly significantly correlated with weight loss during the 5 days of storage at 5°C. Crosses were made between chilling-sensitive and chilling-resistant lines. CI symptoms of the F1 fruit were highly significantly correlated with weight loss during the 5 days of storage at 5°C.
Federica Galli, Douglas D. Archbold, and Kirk W. Pomper
Pawpaw[Asiminatriloba (L.) Dunal] is a highly perishable climacteric fruit. Generally, fruit may be stored at 4 °C for 4 weeks with minimal loss in quality or subsequent ripening capacity. However, comparisons among cultivars and advanced selections for ripening behavior and postharvest storage life have not been reported. Ideally, cultivars with superior ripening traits (higher firmness, or a slower rate of firmness loss) and longer storage life may be identified for the commercial market. To determine if differences among genotypes may exist, respiration, C2H4 production, and fruit firmness of six varieties, 8-20, 9-58, `Middletown', `PA Golden', `Taytwo', and `Taylor', were measured during ripening after harvest and after 1, 2, 3, 4, 5, and 6 weeks of 4 °C storage. No differences were observed among the cultivars regarding respiration and C2H4 production. Respiratory and ethylene peaks were detected within 48 hours after harvest or removal from cold storage. Rapid loss of firmness was measured during ripening at ambient temperature after harvest and after removal from cold storage (days 0–3), with some loss during cold storage itself (weeks 1–6). As expected, firmer fruits at harvest had a lower respiration rate. However, no obvious differences in ripening behavior or cold storage response were observed among the six genotypes. As a general guideline, only firmer fruits should be cold stored, since fruit softening did not stop at 4 °C. A broader analysis of all of the named cultivars and advanced selections of pawpaw will be needed to determine if the present results are generally representative of pawpaw.
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.
Gene E. Lester and Michael A. Grusak
Commercially grown honey dew fruit [Cucumis melo (Inodorus group)] typically are harvested before abscission because fruit cut unripe have a longer storage life than fully ripe fruit. However, because fully ripe fruit contain higher concentrations of soluble solids (predominantly as sugars), an attribute that increases their preference among consumers, methods are being explored to extend the storage life of fully ripe fruit. In this study, fully abscised honey dew fruit were evaluated for tissue attributes and consumer preference following postharvest dipping in either chelated or nonchelated calcium (Ca) solutions. Calcium sources were an amino acid-chelated Ca, ethylene-diamine tetraacetic acid (EDTA)-chelated Ca, or calcium chloride (CaCl2), with each provided at three different rates. Fruit were evaluated at harvest, and after 14 or 22 days commercial storage. Evaluations were peel surface changes (color and disorders), hypodermal-mesocarp tissue Ca concentration, flesh firmness, soluble solids concentration, and consumer preference of the edible flesh. Peel color became yellowed and lighter during storage for all fruit, with higher Ca rates resulting in more intensely yellowed fruit. Hypodermal-mesocarp tissue Ca concentration was 0.90 mg·g-1 of fresh weight (900 ppm) at harvest, and declined in all fruit by 22 days storage. Peel disorders (disease and spotting) were none to slight for all fruit by 14 days storage, but by 22 days storage disease incidence ranged from none to severe, depending on the Ca source and rate. Fruit firmness declined in all fruit throughout storage, with the smallest declines measured in fruit treated with the amino acid-chelated Ca. Soluble solids concentration of fully ripe fruit was 12.3% at harvest, and showed either no decline or slight declines with storage among the treatments. Consumer preference was highest for freshly harvested fruit, but fruit were desirable even after 22 days storage across all treatments. Postharvest application of Ca at ≤0.16 m Ca in an amino acid-chelated form, versus EDTA-chelated Ca or CaCl2, slowed honey dew melon senescence so that after 22 days of commercial and retail storage the fruit were of high marketable quality, and there was no detrimental effect on consumer preference for the edible flesh.
Gloria Lopez-Galvez, Mikal Saltveit, and Marita Cantwel
Phenylalanine ammonia-lyase (PAL) activity in iceberg lettuce (Lactuca sativa L.) is increased in response to several kinds of stress, including wounding, exposure to ethylene, and fungal infection. Ethylene-induced PAL activity is correlated with the discoloration and shelf-life of fresh cut lettuce (Couture et al. 1993. HortScience 28:723). The objective of this research was to further characterize the kinetics of wound-induced PAL in fresh cut lettuce. Leaves of different cvs were cut into salad pieces (1.5 × 3 cm), rinsed in chlorinated water, centrifuged manually, and placed into containers at 5 or 15C through which humidified air flowed. Samples were evaluated for overall visual quality and specific types of discoloration. Midrib tissue was also finely cut (1 × 0.5 cm) for enhanced wound-induction of PAL, which was assayed spectrophotometrically. The kinetics of PAL in midrib tissue of fine cut and salad cut lettuce were similar, with maximum activities obtained within 12-16 h at 15C and within 40-60 h at 5C. Maximum PAL levels in the fine cut lettuce were 1.5-2.0 times those observed in the salad cut pieces, and similar to those induced by ethylene. The usefulness of PAL as a predictor of the storage life of fresh cut lettuce depends on simplifying and expediting the PAL assay.
Bruce D. Whitaker
Plastids and microsomal membranes were isolated from pericarp tissue of mature green and red-ripe tell pepper fruit harvested from greenhouse and field grown plants. The lipid composition of these membrane fractions changed far more with ripening of field grown than greenhouse grown fruit. Also, the phospholipid (PL), free sterol (FS), steryl glycoside (SG) and acylated steryl glycoside (ASG) content of microsomes and plastids from both green and red fruit were very different under the two growing conditions. Total steryl lipids (TSL = FS + SG + ASG), and the TSL/PL ratio, increased in microsomes and decreased in plastids with ripening. These changes were much greater in field grown fruit. The ASG/SG ratio decreased with ripening in both membrane fractions, under both growing conditions. Ripening and growth conditions affected the phospholipid and sterol composition in plastids much more than in microsomes. Lipid changes associated with the chloroplast – chromoplast transformation were similar in field and greenhouse grown fruit, including an increase in the galactolipid/PL ratio. Future studies will assess how differences in membrane lipid composition affect postharvest storage life of the fruit.
Charles F. Forney and David G. Brandl
Humidity is an important component of the enviornment that influences the growth, development and storage life of most horticultural crops. A method to control relative humidity (RH) in experimental chambers using solutions of glycerol-water has been developed. A constant RH can be established and maintained by bubbling air through a glycerol-water solution of known water content. The air rapidly reaches equilibrium with the glycerol-water solution producing the desired RH. The relationship of the specific gravity (SG) of glycerol-water solutions and the corresponding equilibrium RH was determined. Any desired RH can be produced by using solutions of the appropriate SG ranging from 100% with pure water (SG 25/25 = 1.000) to 0% with pure glycerol (SG 25/25 = 1.261) This system can be used in flow through systems by bubbling the incoming air through the solution or in closed systems by circulating air through the solution and the chamber. Multiple jars of solution can be used for more precise RH control. The effects that temperature and atmospheric pressure in the jars have on the equilibrium RH will be discussed.
P. Perkins-Veazie, J.K. Collins, and J.R. Clark
Promising white peach and nectarine selections, many with nonmelting flesh, from the Univ. of Arkansas breeding program were evaluated for fruit quality and flavor. About 20 kg of fruit, consisting of mature ripe and ripe stages, were harvested from 4- to 7-year-old trees in Arkansas and transported to Lane, Okla. Fruit were divided into two boxes per selection. One box was held at 5 °C for 8 days, then transferred to 20 °C for 4 days to induce chilling injury and was evaluated for storage quality. The other box was held at 20 °C for 4 days and fruit used for taste panels. Of the 14 nectarine and 12 white peach selections evaluated, one nectarine and four white peach selections had slight chilling injury. Flesh firmness of selections after storage ranged from 6 to 50 N. Taste panelist scores indicated that sweetness was associated with peach flavor in both nectarines and white peaches and that overall acceptability was dependent on sweetness, peach flavor, and low tartness. Ten of the white peach selections were equal to or better in overall acceptability compared to `Summer Pearl' and `Carolina Belle' cultivars included in the study. Panelists did not consider firm texture to be detrimental to overall acceptability. Results indicate that many of the breeding lines used in this study had fruit equal to or better than currently available cultivars in storage life, firmness, and sweetness.