Search Results

You are looking at 1 - 6 of 6 items for

  • Author or Editor: J.F. Nock x
  • Refine by Access: All x
Clear All Modify Search
Free access

C.B. Watkins and J.F. Nock

The inhibitor of ethylene binding, 1-methylcyclopropene (1-MCP) has been applied to `Gala', `Cortland', `McIntosh', `Empire', `Delicious', `Jonagold', and `Law Rome' apples under air and/or controlled atmosphere (CA) storage conditions. 1-MCP gas concentrations ranged from 0 to 2 mL·L–1. Effects of 1-MCP were greater in CA than air storage. A dose response of internal ethylene concentrations and flesh firmness to 1-MCP was found in cultivars such as `McIntosh' and `Law Rome', whereas in others, such as `Delicious' and `Empire', ripening was generally prevented by all 1-MCP concentrations. We have further investigated the effects of 1-MCP on `McIntosh' by increasing rates of the chemical to 50 mL·L–1, and confirming that fruit of this cultivar respond poorly if fruit have entered the climacteric prior to 1-MCP application. Efficacy of 1-MCP is affected by cultivar and storage conditions, and that successful commercial utilization of the chemical will require understanding of these relationships.

Free access

A.M. Salama, J.R. Hicks, and J.F. Nock

Maleic hydrazide (MH)-treated and untreated (control) onion (Allium cepa L.) bulbs were stored for up to 20 weeks at 0, 15, or 30C with relative humidities (RH) of 40% or 60%. MH and RH had minimal effect on sugars and organic acids in inner or outer scale leaves that were analyzed at S-week intervals. Concentrations of fructose, glucose, and total sugars were higher in inner than outer leaves of the bulb, while the reverse was true for sucrose. Total sugars, glucose, and fructose decreased and sucrose increased with higher storage temperature. Total sugars and glucose decreased with increased storage duration. Malic acid concentration was greater in the outer leaves while citric acid levels were higher in inner leaves. Malic acid increased in onion bulbs during storage while citric acid levels were not influenced by storage duration. Total acids showed little difference across temperatures, due to the concurrent increase in citric acid and decrease in malic acid at 30C.

Free access

J.P. Fernandez-Trujillo, J.F. Nock, and C.B. Watkins

Several strawberry fruit cultivars were exposed to air or CO2 at 2 °C for up to 9 days. Concentrations of fermentation products and organic acids, and activities of pyruvate decarboxylase (PDC) and alcohol dehydrogenase (ADH), were measured. Acetaldehyde, ethanol, and ethyl acetate concentrations accumulated in CO2-treated fruit of `Honeoye' and `Kent', but not in `Cavendish' or `Annapolis'. We classified the former group of cultivars as intolerant to high CO2 and the latter group as tolerant to high CO2. Activities of PDC and ADH were higher in CO2-treated than air-treated fruit of the tolerant cultivars but not in the intolerant cultivars. Succinate accumulated in fruit of all cultivars, but concentrations were highest in the tolerant than in the intolerant cultivars. These results will be discussed in relation to mechanisms of CO2 action on fruit metabolism.

Free access

J. Pablo Fernández-Trujillo, Jacqueline F. Nock, and Christopher B. Watkins

`Cortland' and `Law Rome' apples [Malus sylvestris (L.) Mill var. domestica (Borkh.) Mansf.] were either nontreated or treated with the inhibitor of superficial scald development, DPA, and exposed to air or CO2 (40 or 45 kPa) in air at 2 °C for up to 12 days. Fruit exposed to air or 45 kPa CO2 were sampled during treatment, and peel and flesh samples taken for fermentation product and organic acid analyses. After treatment, fruit were air stored for up to 6 months at 0.5 °C for evaluation of disorder incidence. `Cortland' apples were most susceptible to external CO2 injury and `Law Rome' to internal CO2 injury. DPA treatment markedly reduced incidence of both external and internal injury. Fermentation products increased in peel and flesh of both cultivars with increasing exposure to CO2, but the extent of the increase was cultivar dependant. Acetaldehyde concentrations were about 10 times higher in peel and flesh of `Law Rome' than that of `Cortland' apples. Ethanol concentrations in the flesh were similar in both cultivars, but were about twice as high in `Cortland' than in `Law Rome' peels. Neither acetaldehyde nor ethanol concentrations were affected consistently by DPA treatment. Succinate concentrations, often regarded as the compound responsible for CO2 injury, increased with CO2 treatment, but were not affected by DPA application. Citramalate concentrations were reduced by CO2 treatment in `Law Rome' peel, but other acids were not consistently affected by CO2. Results indicate that acetaldehyde, ethanol or succinic acid accumulation are not directly responsible for CO2 injury in apples. Chemical name used: diphenylamine (DPA).

Free access

J. Pablo Fernández-Trujillo, Jacqueline F. Nock, and Christopher B. Watkins

Effects of 20 kPa CO2 treatments on concentrations of fermentation products, organic acids, and activities of pyruvate decarboxylase (PDC) and alcohol dehydrogenase (ADH), were measured in fruit of selected strawberry cultivars (Fragaria ×ananassa Duch. `Annapolis', `Cavendish', `Honeoye', `Kent', `Jewell', `Lateglow', and `NorthEast'). Acetaldehyde, ethanol, and ethyl acetate concentrations accumulated in CO2-treated fruit of `Honeoye' and `Kent', but not in `Cavendish' or `Annapolis'. The former two cultivars were classified as intolerant to high CO2 and the latter two as tolerant to high CO2. Activities of PDC and ADH were higher in CO2-treated than in air-treated fruit of the tolerant cultivars but not in the intolerant cultivars. Succinate accumulated in fruit of all cultivars, but concentrations were higher in the tolerant than in the intolerant cultivars. Results are discussed in relation to tolerance of fruit to CO2.

Free access

C.B. Watkins, J.E. Manzano-Mendez, J.F. Nock, J. Zhang, and K.E. Maloney

The tolerances of strawberry fruit to postharvest CO2 treatments is an important factor in assessing their potential for extended storage and marketing, but little information on variation among cultivars is available. We have assessed differences in responses of seven strawberry cultivars (`Annapolis', `Earliglow', `Kent', `Honeoye', `Cavendish', `Jewel', and `Governor Simcoe') to high-CO2 atmospheres. Fruit were harvested at the orange or white tip stage of ripeness, kept in air, or 20% CO2 (in air), and sampled after 1, 2, or 7 days for analysis of firmness, color, and volatile concentrations. Berries from each cultivar were collected on three separate harvest dates. Flesh firmness measurements of all cultivars tested were higher when treated with high CO2, but the degree of firming was affected by cultivar and assessment time. For example, firmness of `Annapolis', `Earliglow', `Honeoye', and `Jewel' was consistently enhanced by CO2, compared with air, during storage. In contrast, firmness of `Kent' was not affected by treatment after 1 day of storage and benefits were relatively slight at each subsequent removal. Red color development of the fruits was affected by cultivar and treatment period, but not by CO2 treatment. Volatile accumulation varied greatly among cultivars. `Annapolis' for example, appears very tolerant of high-CO2 treatment levels as indicated by low accumulations of ethanol, acetaldehyde, and ethyl acetate in the fruit. In contrast, `Kent' and `Governor Simcoe' accumulated large amounts of these compounds. This study indicates that differences in cultivar responses to CO2 should be considered by growers planning to store fruit under these conditions to extend marketing options. Research supported in part by the North American Strawberry Growers Association.