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- Author or Editor: Robert K. Prange x
Effects of ozone and storage temperature on carrots and two postharvest pathogens—Botrytis cinerea Pers. and Sclerotinia sclerotiorum de Bary—were investigated. Pathogen-inoculated and uninoculated whole carrots were exposed to an ozone concentration of 0 (control), 7.5, 15, 30, or 60 μl·liter-1. Treatment chambers were flushed with a total flow rate of 0.5 liters·min-1 (air and ozone) for 8 h daily for 28 days. The experiment was repeated twice at storage temperatures of 2, 8, and 16C. The residual ozone concentration (ozone supplied-exhausted and reacted ozone) increased with ozone supply concentration but was less at higher storage temperatures. A 50% reduction of daily growth rates of both fungi at the highest ozone concentration indicated that ozone was fungistatic. Carrot respiration rate, electrolyte leakage, and total color differences increased with ozone concentration. Ozone-treated carrots were lighter (higher L* values) and less intense (lower chroma values) in color than control carrots.
Berry crops can include a wide variety of plant species, with the most important temperate North American species in the genera Fragaria, Rubus, and Vaccinium. The preharvest factors affecting the postharvest quality of berry crops can be divided into abiotic and biotic factors. Amongst the abiotic factors, mineral nutrition, especially calcium and nitrogen, water, temperature, and light play important roles in postharvest quality attributes such as size, color, firmness, acidity, and sweetness. Amongst the biotic factors, several postharvest pathogens, which are also present as preharvest pathogens, can cause very significant reductions in postharvest quality. Grey mold (Botrytis cinera) is considered to be the most important pre- and postharvest pathogen in berry crops, but other preharvest pathogens (e.g., Alternaria, Colletotrichum, and Rhizopus) can become major problems, depending on other preharvest factors. In some growing areas, the presence of fruit fly larvae in the fresh fruit reduces the postharvest quality. Other biotic factors can be more subtle in their effects on postharvest quality, such as cultivar, pruning, and pollination.
Postharvest quality and sensory attributes of organically and conventionally grown `McIntosh' and `Cortland' apples (Malus domestica Borkh.) stored at 3C in ambient air or in controlled atmospheres were evaluated. Organically grown apples had higher soluble solids concentration than conventionally grown apples, while there were no significant differences in firmness or titratable acids content. Organically grown `McIntosh' were perceived by sensory panelists as firmer than conventionally grown `McIntosh' at harvest but not after storage, which may have been due to maturity differences. No significant differences were perceived in juiciness, sweetness, tartness, and off-flavor of apples at harvest or after storage.
Larvae of the blueberry maggot (Rhagoletis mendax Curran) were raised on apples (Malus domestics Borkh. cv. Idared), and exposed larvae were treated 48 hours with CO concentrations ranging from 0% to 100% at O concentrations of 2%, 5%, or 20% (0% for the 100% CO) at 5 or 21C. Blueberry maggot survival was reduced to 10% when the larvae were subjected to CO concentrations > 45% at 21C. Fumigation was more effective at 21C than at 5C. Oxygen at 2% or 5% did not reduce larval survival when compared with treatments containing 20% O. In a separate experiment, six commercial shipments, each consisting of four hundred eighty 0.5-liter containers of infested lowbush blueberries (Vaccinium angustlfolium Ait.), were placed in a large fiberglass tank and fumigated with 54% CO at 21C. The blueberries were sampled for quality and larval survival after 24 and 48 hours of CO treatment. Atter 48 hours, 9% of the blueberry maggots in infested blueberries survived fumigation with 54% CO, while 68% of maggots survived in air. The quality of fumigated lowbush blueberries was not adversely affected by fumigation with 54% CO for up to 48 hours, as indicated by marketable berries, berry weight, split berries, shriveled berries, epicuticular wax (bloom), firmness, soluble solids and titratable acid concentrations, offflavors, and skin browning.
This paper reports preliminary results on the postharvest quality and storage characteristics of several scab-resistant apple cultivars. `Novaspy', `Moira', `Priscilla', `Novamac', `Nova Easygro', `Prima', and `Macfree' were stored for 3 months at 3C in air or standard controlled atmosphere (CA; 4.5% CO2 and 2.5% O2) in 1990 and for 4 months at 0C in air, standard CA, or low-O, CA (LO; 1.5% CO2 and 1.5% O2) in 1991. `Moira', `Prima', and `Priscilla' had very limited storage life. `Moira' was susceptible to bitterpit, scald, core browning, vascular breakdown, and storage rots. `Prima' was susceptible to core browning and vascular breakdown and had a high incidence of storage rots in air storage. `Priscilla' had several defects as a result of insect damage and was susceptible to bitterpit and scald. `Novaspy' stored very well and had virtually no physiological disorders or storage rots. `Novamac, `Nova Easygro', and `Macfree' developed few storage rots and were essentially at the end of their storage life after 4 months, regardless of storage conditions. Firmness in `Novamac' decreased substantially in all storage atmospheres, while `Nova Easygro' and `Macfree' were susceptible to core browning and scald.
Previous studies have shown that the fry color of stored potatoes (Solanum tuberosum L.) can be negatively affected by an interaction between elevated CO2 (2 kPa) and ethylene gas (0.5 μL·L− 1) from various sources. Two consecutive trials were conducted during each of two storage seasons (2006 and 2007) to study the effects of varying concentrations of these two gases. In each year, CO2 at 0, 0.5, 1.0, or 2.0 kPa plus 0, 0.25, or 0.5 μL·L− 1 ethylene was applied in a factorial design to ‘Russet Burbank’ tubers for 9 weeks. Trials that began in Jan. 2006 and Jan. 2007 comprised the dormant-tuber experiment; trials that began in Apr. 2006 and Apr. 2007 comprised the nondormant-tuber experiment. Fry color of the tubers was evaluated at the start of each trial and thereafter at intervals of 3 weeks. In all trials, when tubers were exposed to different concentrations of CO2 but without ethylene, fry color was the same as in untreated controls. When only ethylene was applied, the fry color was 7 to 22 Agtron percent reflectance units darker than the controls. In the nondormant-tuber experiment, the darkening resulting from ethylene was dose-related, in agreement with previous research. When the tubers were exposed to both CO2 and ethylene, dose-related responses to both gases were observed in the nondormant-tuber experiment, i.e., fry color was darker with an increase in either CO2 or ethylene when both gases were present. Neither the dose–response to ethylene nor the interaction between ethylene and CO2 was statistically significant in the dormant-tuber experiment. In both experiments, the darkest color was observed when both gases were present at the highest concentrations. A dose–response of potato fry color to CO2 in the presence of ethylene has not been reported previously.
Potato (Solanum tuberosum L. `Russet Burbank' and `Shepody') tubers were exposed to continuous 4 μL·L-1 (166 μmol·m-3) ethylene in air. Treatment started after 8 weeks in storage and continued up to 33 weeks of storage at 9 °C over one (`Russet Burbank') or two (`Shepody') storage seasons. Tubers were sampled at 3 week (`Shepody') or 5 week (`Russet Burbank') intervals for polyamine content [putrescine, (PUT); spermidine, (SPD); and spermine, (SPM)] and sprout number and fresh weight per tuber. During the storage period, `Shepody' had higher concentrations of all three polyamines and a higher PUT/(SPD + SPM) ratio, compared with `Russet Burbank'. All three polyamines in both cultivars increased during storage, and the increase was more rapid in `Shepody' than in `Russet Burbank'. Regardless of cultivar and year, exposure to ethylene induced higher spermidine (SPD) content and a lower PUT/(SPD + SPM) ratio, compared with the air treatment. Sprouts appeared later and were smaller on ethylene-treated tubers and were more numerous in `Russet Burbank'. These long-term ethylene effects may be due, in part, to enhanced transformation of PUT to SPD.
`Kent' strawberries were harvested at red, pink, and white stages of development, and stored at 15C in the light. Fruit were sampled over a 10-day period and evaluated for volatile production and surface color. Volatile production by red and pink fruit peaked after 4 days of storage. Maximum volatile production by red fruit was 8- and 25-fold greater than maximum production by pink and white fruit, respectively. Aroma volatiles were not detected in the headspace over white berries until 4 days following harvest after which volatile production increased through the tenth day of storage. Changes in the surface color of white berries during postharvest ripening coincided with the production of volatiles. In another experiment, red, pink, and white `Kent' strawberries were stored for 3 days at 10 or 20C in the dark or light. Fruit were then evaluated for volatile production, weight loss, anthocyanin content, and surface color changes. White berries produced volatile esters after 3 days of storage at 20C in the light. Both light and temperature influenced the relative production of the volatiles produced by pink fruit. Fresh weight loss, color change, and anthocyanin content were temperature and light dependent.
Chlorophyll fluorescence was evaluated as a rapid and nondestructive technique to detect low-O2 or high-CO2 stress in apples (Malus domestica Borkh.) during storage. `Marshall' McIntosh apples were held for 5, 10, 15, 20, or 25 days at 3C in 1) standard O2 (2.5% to 3%) and low CO2 (<1%), 2) low O2 (1% to 1.5%) and low CO2 (<1%), 3) standard O2 (2.5% to 3%) and standard CO2 (4% to 4.5%), or 4) standard O2 (2.5% to 3%) and high CO2 (11% to 12%). Only 10% of the apples had skin discoloration after 5 days in 1% to 1.5% O2; 80% developed skin discoloration after 20 days in low O2. Small desiccated cavities in the cortex, associated with CO2 injury, developed in 10% of the apples after 20 days in 11% to 12% CO2. Five days in 1% to 1.5% O2 or 11% to 12% CO2 caused variable fluorescence (Fv) of apple fruit to decrease compared to those held in standard atmospheres. Additional exposure did not significantly affect Fv in either the low-O2 (1% to 1.5%) or high-CO2 (11% to 12%) treatment. Our results suggest that chlorophyll fluorescence techniques can detect low-O2 and high-CO2 stress in apples before the development of associated disorders.