Ripening behavior of `Bartlett' pears (Pyrus communis L.), with or without ethylene (C2H4) treatment, was assessed at harvest, and after 2, 4, 6 and 12 weeks of cold storage at –1 °C. Fruit exhibited increasing rates of C2H4 production and consequently faster ripening rates with increased length of cold storage. Ripening characteristics were influenced by storage duration, but to different degrees. The data indicate that the threshold C2H4 concentration for softening may be lower than that for color change from green to yellow. Ethylene treatment for 24 h at harvest resulted in a rate of ripening equivalent to that following cold storage for 2 to 4 weeks, depending on the orchard location. Storage for 12 weeks significantly increased C2H4 production upon transfer to ambient temperature, indicating that fruit were reaching the end of their storage life. `Bartlett' pears may ripen to a firmness of 14 N (ready to eat) at 20 °C within 2.5 to 7 days depending upon the duration of prior cold storage.
I. Tayfun Agar, William V. Biasi, and Elizabeth J. Mitcham
Elena de Castro, William V. Biasi, and Elizabeth J. Mitcham
Apple [Malus ×sylvestris (L.) Mill. var. domestica (Borkh.) Mansf. ‘Cripps Pink’] fruit were harvested yearly, at two or three maturity stages, from the same California orchard in 2002 through 2005. Fruit firmness, soluble solids, titratable acidity, background color, and percent blush were correlated with the starch pattern index at harvest. Fruit from each harvest were stored at 0.5 ºC in air or in a controlled atmosphere (CA) with 1.5 or 2 KPa O2 in combination with 1, 3, and 5 KPa CO2. Subsets of fruit were treated with 1 μL·L−1 1-methylcyclopropane for 24 hours at 0 ºC or 2200 μL·L−1 diphenylamine (DPA) for 5 minutes. Ethylene production was measured for 30 days after harvest. Ethylene concentration in the storage atmosphere was also monitored during storage. Fruit quality was evaluated after storage plus 5 days of ripening at 20 ºC. Fruit in a CA with 1 or 3 KPa CO2 maintained firmness and green background color, and produced less ethylene during ripening at 20 ºC than fruit stored in a CA with 5 KPa CO2; however, quality of all CA-stored fruit was better than air-stored fruit. Flesh browning developed only in CA storage, appearing by 2 months and not increasing in incidence with further storage periods. 1-Methylcyclopropane conserved fruit quality in air as well as CA during 4 months of storage, and DPA-treated fruit were firmer after CA storage, but similar after air storage, compared with untreated fruit. Diphenylamine did not control a stem-end scald disorder, which increased with time in storage and affected more than 80% of the fruit after 6 months of air storage.
Richard K. Volz, William V. Biasi, and Elizabeth J. Mitcham
Apple (Malux ×domestica Borkh., cv. Fuji) fruit were harvested from two California orchards 190 and 210 days after full bloom and from an additional three orchards at 190 days after full bloom. Fruit were immediately exposed to 20 or 50 kPa CO2 in air at 20 °C. Area of flesh browning and tissue ethanol, acetaldehyde, and ethyl acetate concentrations for individual fruit were determined immediately before exposure and after 3 and 7 days (20 kPa) or 1 and 3 days (50 kPa) exposure to CO2. Area of flesh browning and concentrations of all compounds increased with increasing duration of exposure to high CO2, were greater in response to 50 kPa than to 20 kPa CO2, and were greater for fruit harvested later in the season. For individual orchards and for individual fruit within most orchards, greater flesh browning was associated with higher acetaldehyde concentrations after 7 days exposure to 20 kPa CO2 or 3 days exposure to 50 kPa CO2. Similarly, flesh browning was positively correlated with ethanol concentrations after 7 days at 20 kPa CO2, but was not related to tissue ethyl acetate concentrations at either CO2 partial pressure. However, higher production of ethanol, acetaldehyde, or ethyl acetate relative to flesh browning occurred during exposure to 50 kPa than to 20 kPa CO2. This suggests that the relationship between accumulation of these compounds and CO2-induced flesh browning in `Fuji' is not simply causal.
Murray Clayton, William V. Biasi, and Elizabeth J. Mitcham
`Bartlett' pears (Pyrus communis L.) were harvested and ripened with and without ethylene in standard field bins at a commercial cannery. Mean firmness and firmness uniformity within a bin was evaluated for ethylene- and nonethylene-treated fruit. Uniformity of firmness among pears within a bin increased as ripening progressed. Applying 100 ppm (10 Pa) of ethylene gas during the first 24 hours of commercial ripening accelerated ripening of `Bartlett' pears held in standard field bins. Improved firmness uniformity would therefore be expected in ethylene-treated fruit commercially ripened to a lower firmness than untreated fruit otherwise ripened and processed at a higher firmness—the improved firmness uniformity was due to the lower firmness and not a specific effect of ethylene on ripening uniformity. When fruit were cold-stored for 20 days at 32 °F (0 °C) before ripening, the mean firmness and firmness uniformity of fruit exposed to ethylene during initial ripening was no different than nonethylene-treated fruit. Results from this study also indicate that fluctuations in ripening room air temperature, under some conditions, might increase firmness variability between fruit within a standard field bin.
Murray Clayton, William V. Biasi, I. Tayfun Agar, Stephen M. Southwick, and Elizabeth J. Mitcham
`Bing' sweet cherry (Prunus avium L.) trees were treated with hydrogen cyanamide (CH2N2) or calcium ammonium nitrate (CaNH4NO3) during dormancy, or gibberellic acid (GA3) 26 days before harvest during three consecutive years. Fruit were evaluated at harvest for sensory taste quality using twenty trained panelists sampling for firmness, sweetness, tartness, and cherry flavor. Nondestructive instrumental firmness preceded destructive sensory firmness on the same untreated and GA3-treated cherries in one year when used as a supplementary evaluation. Sensory firmness was consistently higher in GA3 fruit and to a lesser extent in CH2N2 fruit than in CaNH4NO3 and untreated fruit. Instrumental firmness of GA3 fruit did not increase significantly compared with untreated fruit yet instrumental firmness of each treatment correlated relatively well with perceived sensory firmness. Sensory sweetness and cherry flavor scored very similarly, yet both attributes simultaneously varied between treatments across the years. Perceived sensory tartness of treated fruit was variable among years; yet, on average, was rated among treated and untreated fruit as similar. Under the assumption that elevated sensory firmness, sweetness, and cherry flavor intensity reflects improved sweet cherry quality, GA3 fruit were rated of higher quality than untreated fruit given their increased firmness and similar or occasionally elevated sweetness and cherry flavor intensity. CH2N2 fruit maintained quality similar to that of untreated fruit, despite often having marginally higher firmness, due to similar or reduced ratings for sweetness and cherry flavor intensity. Notwithstanding similar firmness between CaNH4NO3 and untreated cherries, sensory quality of CaNH4NO3-treated cherries was reduced due to their often-diminished levels of perceived sweetness and cherry flavor.
Murray Clayton, William V. Biasi, I. Tayfun Agar, Stephen M. Southwick, and Elizabeth J. Mitcham
During three consecutive years, 'Bing' sweet cherry (Prunus avium L.) trees were treated during dormancy with the dormancy-manipulating compounds, CH2N2 or CaNH4NO3, or were treated with the plant growth regulator GA3 at straw color development. Fruit of a range of maturities, based on skin color, were evaluated for quality following harvest and simulated transit and market storage conditions. At comparable maturities, CH2N2 and GA3 fruit were of similar firmness and were consistently firmer than CaNH4NO3-treated and untreated fruit across years, storage regimes, and maturities. CaNH4NO3 and untreated fruit were of similar firmness. CH2N2-treated cherries were larger than fruit of other treatments, but only marginally with respect to variation in fruit size between years. Contraction of fruit diameter occurred after 3 days storage, but ceased thereafter up to 11 days storage. Soluble solids and titratable acidity varied between years, storage regimes, and maturities. Strong interactions of treatment and year concealed possible treatment effects on these indices. GA3 fruit contained fewer surface pits in one year while CH2N2 fruit suffered less shrivel in another. The earlier harvest date for CH2N2 fruit often avoided higher field temperatures and the resulting promotion of postharvest shrivel. Pitting and shrivel were more prevalent in stored fruit. Brown stem discoloration developed in storage, occurring most frequently in mature fruit, although methyl bromide-fumigated fruit were particularly susceptible. This disorder was more common in GA3 fruit during years of high incidence. Chemical names used: gibberellic acid (GA3); calcium ammonium nitrate (CaNH4NO3); hydrogen cyanamide (CH2N2).
Max G. Villalobos-Acuña, William V. Biasi, Sylvia Flores, Elizabeth J. Mitcham, Rachel B. Elkins, and Neil H. Willits
Preharvest applications of 1-methylcyclopropene (1-MCP) were tested on California ‘Bartlett’ pears at 80 N maturity and at rates of 0, 28, and 56 mg·L−1 in 2006 and 0, 50, and 100 mg·L−1 in 2007. In 2007, a parallel experiment was conducted to compare 50 mg·L−1 1-MCP with 96 g a.i./ha 1-naphthaleneacetic acid (NAA) used commercially to control or decrease premature fruit drop. Premature fruit drop, maturity, firmness at harvest, color, softening, and ethylene production during ripening and physiological disorders were studied in fruit harvested between 7 and 21 days after 1-MCP application and either ripened at 20 °C immediately after harvest or after 3.5 to 6 months storage at –1 °C. Overall, 50 mg·L−1 1-MCP reduced the incidence of premature fruit drop when compared with the untreated fruit and fruit drop was similar to adjuvant-treated fruit and NAA-treated fruit, especially 28 days or longer after the treatment. 1-MCP was more effective in retarding color, softening, and ethylene production during ripening than delaying fruit maturation on the tree (loss of firmness), and both rates of 1-MCP tested each season yielded similar fruit responses on most evaluation times. 1-MCP's effect on ripening was lost if fruit remained on the tree 21 days or after the fruit were stored for 3.5 months in cold storage regardless of treatment concentration. A reduction of internal breakdown incidence was observed in 1-MCP-treated fruit.
Rachel B. Elkins, Janet D. Turner, Steve Castagnoli, Clark F. Seavert, Elizabeth J. Mitcham, William V. Biasi, and Ann Colonna
Assessing consumer acceptance is an important aspect of cultivar evaluation. Since 2002, about 2700 consumers have participated in pear preference surveys. Surveys were conducted on multiple dates and at multiple venues from 2002 to 2005 in Oregon and northern California. Survey participants were asked to indicate their preference for pears based on size, appearance, taste, and overall preference. They were also asked to indicate what attributes they liked or disliked about their favorite and least favorite varieties and to indicate their level of purchase intent. Each survey consisted of four to six cultivars, including at least one standard commercial comparison; i.e., Bartlett, Bosc, or Anjou. Data was analyzed (RCBD; Friedman Analysis of Rank or ANOVA/Tukey's HSD) at the OSU Food Innovation Center Experiment Station using Compusense® five v.4.6 software (Guelph, Ont., Canada). Results indicated several alternative possibilities for both summer and winter sales. Among the most preferred cultivars (variable between states) were Anjou (commercial standard winter pear), Bartlett (commercial standard summer pear and most-consumed cultivar), Blake's Pride, Cinnamon, Concorde, and 71655-014. Other major findings were preference for large pears for adults and small for children, overall liking based on sweetness and flavor rather than skin color, and general lack of knowledge of many commercial pear cultivars. Sensory evaluation surveys will be continued in 2006 in California, with focus on differential harvest times for selected preferred cultivars. Consumer preference data is being combined with production and postharvest quality data in order to provide the pear industry a comprehensive data set on potential alternative cultivars.