Pawpaw [Asimina triloba (L.) Dunal] is a highly perishable climacteric fruit, softening rapidly once ripening commences which may limit its marketability. In studies to determine the optimum cold storage temperature and maximum storage life of the fruit, pawpaw fruit were stored at -2, 2, and 6 °C for 1, 2, 4, 8, and 12 weeks, and then ripened upon removal to ambient temperature. Through 4 weeks, fruit exhibited adequate firmness upon removal from cold storage, but at 8 and 12 weeks fruit held at 2 and 6 °C were very soft. Irrespective of storage temperature, at 8 weeks fruit showed a delay in a climacteric-like respiratory increase, and by 12 weeks a respiratory climacteric was not apparent. An ethylene climacteric was evident after all temperature and storage periods except those held at 6 °C for 12 weeks. Significant symptoms of cold injury were found by 8 weeks of 2 °C cold storage. In addition to a delayed respiratory climacteric, pawpaw fruit stored for 8 and 12 weeks exhibited flesh browning within 48 h of moving to ambient temperature. A change in fruit aroma volatile profile suggested injury might have been developing by 4 weeks of cold storage even though other symptoms were not evident. Immediately after harvest, methyl octanoate was the dominant volatile ester followed by methyl hexanoate. By 4 weeks of postharvest cold storage, ethyl hexanoate was the dominant ester followed by ethyl octanoate, but methyl octanoate production was still substantial. At 8 weeks, volatile ester production was generally lower with ethyl hexanoate the major volatile followed by ethyl octanoate. These symptoms indicate that pawpaw fruit can suffer cold injury during extended periods of cold storage.
Federica Galli*, Douglas D. Archbold, Kirk W. Pomper, Thomas R. Hamilton-Kemp, and Randall W. Collins
Bob Ebel, Bobby Boozer, and Jim Pitts
This experiment was conducted to determine peach harvest delay, quality, and storage life by ReTain. ReTain was applied to `Loring' at 50 ppm at 17, 14, 12, 10, or 7 days before harvest (n = 4). Fruit were harvested based on conversion of ground color to yellow over five dates at 3- to 4-day intervals in July. Fruit were segregated into five size classes, counted, and weighed. Ten fruit were randomly selected from the 2.5-in. size class, and fruit quality was measured at harvest and after 5 days at 20 °C. Some fruit were stored for 5 days at 4 °C, removed from storage, and fruit quality measured 4 h after removal. Harvest date was not affected by ReTain. Firmness was higher for fruit held at 5 days in cold storage with earlier treatment application but not at harvest or after 5 days at room temperature, although the trend at harvest was similar to the 5-day storage data. Soluble solids were not affected at harvest, after storage or after 5 days at room temperature. Red blush was slightly less at harvest and after 5 days in cold storage with earlier application rates, but differences disappeared after 5 days at room temperature. Yellow color was higher with earlier application date after 5 days of cold storage but not at harvest or after 5 days at room temperature. These results indicate that ReTain may have some utility for improving peach firmness at harvest, but there was no benefit of harvest delay at the rates applied in this study.
Melkizedek O. Oluoch and Gregory E. Welbaum
Priming (controlled hydration followed by drying) has been shown to decrease seed storage life in some species The germinablity of primed (0.3 M KNO3, 6 d, 25°C) and unprimed muskmelon (Cucumis melo L., cv. PMR 45) seeds were compared after storage for 9 yrs at less than 20°C and 6% moisture content (MC) (dwt basis). Germination performance was compared at 30°C in water and polyethylene glycol solutions of -0.2, -0.4, -0.6, -0.8, and -1.0 MPa water potential or in water at 15, 20, and 25°C. Seeds were also germinated in field soils at 17, 19, and 21% (dwt. basis) MC in a greenhouse, Some seeds were subjected to controlled deterioration at 20% MC and 45°C for 72 hrs prior to testing. The germination percentage and rate of stored, primed seeds at 30°C and all water potentials was less than stored, unprimed seeds. At 30°C, stored, unprimed seeds germinated more rapidly and to higher percentages at -0.2 MPa than in water, while germination percentages and rates of stored, primed seeds were essentially the same. At 15, 24, and 25°C, stored, primed seeds outperformed unprimed seeds in all germination tests. In saturated soils at 21% MC, there was no germination of either stored, primed or unprimed seed. At 17% soil MC, stored, primed seeds germinated 73% compared to only 56% for unprimed seeds. The enhancement due to priming was retained after 9 yrs of storage at germination temperatures <30°C. At higher temperatures, the germination of unprimed seeds was superior to primed.
Melkizedek O. Oluoch and Gregory E. Welbaum
The viability and vigor of osmotically primed (0.3 m KNO3, 6 days, 25C) and nonprimed `PMR 45' muskmelon (Cucumis melo L.) seeds were compared after storage for 9 years at <20C and 6% moisture content (MC, dry weight basis). Viability was compared at 20, 25, and 30C at water potentials of 0, -0.2, -0.4, -0.6, and -0.8 MPa and in soil. Additionally, stored primed and nonprimed seeds were either primed, aged (15% MC and 45C) for up to 8 days, or aged for 72 hours and primed. The force required to puncture 5-mm-long, micropylar seed pieces was measured using an Instron universal testing machine. Less force was required to puncture primed seed pieces at 0, 5, 15, 20, and 25 hours of imbibition, demonstrating that osmotic priming weakens the perisperm envelope tissue that the radicle must penetrate for germination to occur. In an earlier report, germination rate and final germination percentages were higher for osmotically primed seeds both in laboratory tests and field emergence studies conducted immediately after priming. After 9 years in storage, nonprimed seeds germinated to higher percentages in water at 30C and reduced water potential at all temperatures, while primed seeds germinated to higher percentages in water at 20 and 25C and exhibited a higher percentage of seedling emergence at a soil MC of 17%. Priming durations of ≤5 days had no effect on the viability, while longer durations decreased the viability of stored primed and nonprimed seeds. Priming generally decreased the log mean time to germination of stored nonprimed seeds but increased values for stored primed seeds. Controlled deterioration increased the log mean time to germination and decreased the viability of primed seeds faster than nonprimed seeds. Priming following controlled deterioration had no effect on nonprimed seeds and reduced the percent viability of primed seeds by 20%. Osmotic priming has a deleterious effect on the seed storage life of muskmelon seeds.
Karen L.B. Gast
Fresh-cut peonies are one of few cut flowers that can be stored for weeks and still provide a marketable flower. Peonies are usually marketed by color: reds, pinks, whites, and corals. Several different cultivars may be included in each color depending on their country of origin and time during the harvest season. Previous work with peonies has shown that different cultivars of the same color may behave differently during postharvest handling, whether it is storage life, vase life, opening time, storage temperature, etc. One problem of long-term cold storage is diseases that may render flowers unmarketable. This study evaluated the effect of four storage disease prevention treatments on seven peony cultivars, two reds, two pinks, and three whites, stored at 1 °C. The four disease prevention treatments included a control, methyl jasmonate during storage, a pre-storage calcium chloride pulsing for 2 h at room temperature, and a pre-storage fungicide spray. Flowers were evaluated for disease incidence on leaves and flowers, and for flower bud openness after 4, 8, and 12 weeks of cold storage. Overall results support previous work that shows peony cultivars react differently to postharvest treatments. Two cultivars were greatly affected by the disease prevention treatments and three were moderately affected, while there were few treatment effects seen with the other two. The calcium chloride pulse produced the greatest disease incidence and resulted in the flowers being more opening, which is not desirable. There was often no difference in the control, methyl jasmonate, and fungicide treatments. It appears that pre-storage treatments may not be beneficial for some fresh-cut peony cultivars.
Nihal C. Rajapakse, William B. Miller, and John W. Kelly
Low-temperature storage potential of rooted cuttings of garden chrysanthemum [Dendranthema ×grandiflorum (Ramat.) Kitamura] cultivars and its relationship with carbohydrate reserves were evaluated. Storage of chrysanthemum cuttings at -1 and -3 °C resulted in freezing damage. Visual quality of rooted cuttings stored at 0 or 3 °C varied among cultivars. Quality of `Emily' and `Naomi' cuttings was reduced within a week by dark storage at 0 or 3 °C due to leaf necrosis, while `Anna' and `Debonair' cuttings could be held for 4 to 6 weeks without significant quality loss. In `Anna' and `Debonair', low-temperature storage reduced the number of days from planting to anthesis regardless of storage duration. However, flowers of plants grown from stored cuttings were smaller than those of nonstored cuttings. At the beginning of storage, `Emily' and `Naomi' had lower sucrose, glucose, and fructose (soluble sugars) content compared to `Anna' and `Debonair'. Regardless of temperature, leaf soluble sugar was significantly reduced by dark storage for 4 weeks. In stems, sucrose and glucose were reduced while fructose generally increased during low-temperature storage probably due to the breakdown of fructans. Depletion of soluble sugars and a fructan-containing substance during low-temperature dark storage was greater in `Emily' and `Naomi' than in `Anna' and `Debonair'. Low irradiance [about 10 μmol·m-2·s-1 photosynthetically active radiation (PAR) from cool-white fluorescent lamps] in storage greatly improved overall quality and delayed the development of leaf necrosis in `Naomi'. Cuttings stored under light were darker green and had a higher chlorophyll content. Leaf and stem dry weights increased in plants stored under medium and high (25 to 35 μmol·m-2·s-1 PAR) irradiance while no change in dry weight was observed under dark or low light. Results suggest that the low-temperature storage potential of chrysanthemum cultivars varies considerably, and provision of light is beneficial in delaying the development of leaf necrosis and maintaining quality of cultivars with short storage life at low temperatures.
Jinhe Bai, Elizabeth A. Baldwin, Kevin L. Goodner, James P. Mattheis, and Jeffrey K. Brecht
Apples [Malus sylvestris (L.) Mill var. domestica (Borkh.) Mansf. (`Gala', `Delicious', `Granny Smith' and `Fuji')], pretreated or nontreated with 1-methylcyclopropene (1-MCP, 0.6 to 1.0 μL·L–1 for 18 hours at 20 °C), were stored in controlled atmosphere (CA, 1 to 1.5 kPa O2; 1 to 2 kPa CO2) or in regular atmosphere (RA) for up to 8 months at 1 °C. Firmness, titratable acidity (TA), soluble solids content (SSC), and volatile abundance were analyzed every month directly or after transfer to air at 20 °C for 1 week to determine effect of 1-MCP, storage atmosphere and storage time on apple quality immediately after cold storage and after simulated marketing conditions at 20 °C. The 1-MCP ± CA treatments delayed ripening and prolonged storage life as indicated by delayed loss of firmness and TA in all four cultivars during storage. The 1-MCP ± CA also slightly delayed loss of SSC for `Gala' but had no effect on SSC levels for the other cultivars. There were differences among treatments for firmness and TA content [(1-MCP + RA) > CA] for `Gala', `Delicious', and `Granny Smith' apples, but not for `Fuji'. These differences were generally exacerbated after transfer of fruit to 20 °C for 1 week. A combination of 1-MCP + CA was generally best [(1-MCP + CA) > (1-MCP + RA) or CA] for maintaining `Delicious' firmness and TA. However, the treatments that were most effective at retaining TA and firmness also retained the least volatiles. The results indicate that the efficacy of 1-MCP and CA in maintaining apple quality factors is cultivar dependent and that 1-MCP + RA may be a viable alternative to CA for optimal eating quality for some cultivars.
Paul J.R. Cronje, Graham H. Barry, and Marius Huysamer
Because photosynthesis provides the required carbohydrates for fruit development and respiration releases the stored energy from these carbon compounds, interalia during postharvest storage, it is therefore important that fruit tissues have an adequate carbohydrate concentration at the start of the postharvest period to ensure optimal storage life. In addition to photosynthate supply from leaves, the chlorophyll-containing flavedo of citrus (Citrus sp.) fruit (outer, colored part of the rind) has the ability to fix CO2 through its own photosynthetic system. In this experiment, spanning three seasons, the three main sugars (sucrose, glucose, and fructose) were quantified in the flavedo of ‘Nules Clementine’ mandarin (Citrus reticulata) fruit during Stages II and III of fruit development. Flavedo was sampled from fruit borne on the inside (low light intensity) or outside (high light intensity) of the tree’s canopy. In one season, the photosynthetic and respiration rates of fruit borne in the two canopy positions were measured pre- and post-color break (March and April, respectively). Sucrose concentration increased constantly from initial sampling in February until harvest (May), whereas glucose and fructose concentrations increased significantly only during the last month of fruit development. The flavedo of inside fruit, developing under low-light conditions, was less well colored (higher hue angle) and had a lower sugar concentration compared with outside fruit developing under conditions of high light levels. This response could be attributed to the higher pigment concentration leading to a higher photosynthetic rate as well as greater sink strength of the outside fruit. The inside fruit had an increased susceptibility to the progressive postharvest physiological disorder, rind breakdown. The lower carbohydrate and pigment concentrations of the rind from fruit borne inside the canopy compared with those from the outside of the canopy could be indicative of a weaker rind condition at the time of harvest.
Chien Yi Wang
The outer leaf laminae of Chinese cabbage (Brassica campestris L Pekinensis group) contain higher amounts of ascorbic acid than the outer midribs, inner leaf laminae, or inner midribs. However, the outer leaf laminae lost ascorbic acid at a faster rate than other parts of the Chinese cabbage during storage at 0°C. Quantitative differences in sugars were also found in different parts of the Chinese cabbage. The outer leaf laminae were low in total sugars and had higher amounts of fructose than glucose, whereas outer midribs contained much higher amounts of glucose than fructose. The inner leaf laminae were high in both fructose and glucose and had a higher ratio of glucose to fructose. A similar ratio was also found in inner midribs, but their total sugar content was lower than inner leaf laminae. Relatively low levels of sucrose were found in all parts of Chinese cabbage. Total sugars decreased, but the relative composition of individual sugars did not change during storage. Exposure of Chinese cabbage to 30 or 40% CO2 for 5 or 10 days was detrimental to quality. Short-term exposure to high but noninjurious concentrations of CO2 (10–20%) showed no beneficial effect on quality retention during subsequent storage in air at 0°. However, low O2 (1%) atmosphere was very effective in extending the storage life of Chinese cabbage at 0°. It slowed down the decline of ascorbic acid and sugar contents, delayed the loss of chlorophyll and yellowing of the leaves, and reduced the incidence of decay. The Chinese cabbage was not salable without extensive trimming after 3 months of storage at 0° in air, whereas those in 1% O2 at 0° were still in salable condition after 5 months of storage with only slight trimming. No off-odor, off-flavor, or other symptoms of suboxidation were found at the end of 5 months of storage in 1% O2 at 0°.
Martha A. Mutschler
Storability, ripening, and fruit characteristics were studied in fruit of tomato (Lycopersicon esculentum Mill.) from plants heterozygous or homozygous for alc. Ripe fruit from heterozygotes showed a 78% increase in storability compared to ‘Rutgers’. Full ripe fruit of the homozygous recessive showed over 300% increase in storability, with a mean storage life of 40 days. Increased storability is not associated with initial fruit Firmness, but is accompanied by a decrease in the rate of fruit softening during storage of the fully ripe fruit. This trait does not affect pH, soluble solids, or the time required for development from flowering to mature-green fruit. The rate of further ripening is decreased. The degree of ripeness obtained by the mutant fruit is dependent on its ripeness when the fruit is picked. Mutant fruit will not fully ripen off the vine unless picked when the fruit is already at the late streak to light color stage. Ethylene production is reduced in detached, mature-green ‘Alcobaca’ fruit to 25% of that observed in ‘Rutgers’. A climacteric pattern of ethylene and CO2 production was not observed in single, detached fruit of ‘Alcobaca’ or other alc lines. The highest ethylene production detected externally was observed in the first (day one) reading of alc fruit, regardless of maturity of fruit when picked. Afterwards, ethylene production decreased to 2.5 to 3 μl·kg−1hr−1. The stage of ripeness at harvest affects the level of ethylene production of detached fruit. The maximum day-one ethylene readings were obtained from fruit harvested at the turning (40% color) stage. The rise in ethylene production during ripening also was detected in internal gas samples.