The ethylene antagonist 1-methylcyclopropene (1-MCP) was investigated for its potential impact on the transcription of key flavonoid biosynthetic (PAL and CHS) and ethylene perception (ERS1) genes during the postharvest storage of pear (Pyrus × communis L.). Optimally harvested red and green `d'Anjou' fruit were treated with 1 μL·L-1 1-MCP for 24 h at 0 °C to 1 °C, and subsequently placed in cold storage (0–1 °C, 90–95% RH). Fruit were removed every 21 days for 126 days, and evaluated for firmness, TSS, and ethylene and volatile production for up to 10 days (≈21 °C). Tissue samples were collected for Northern blot analysis and determination of flavonoid and chlorogenic acid content. PAL content increased during the 1-week simulated marketing period irrespective of storage duration, which coincided with an increase in respiration and ethylene content. Although it was still detectable, total PAL content was dramatically reduced by the 1-MCP treatment. CHS was abundant immediately after harvest and after removal from storage, but declined rapidly thereafter, and was not detectable after 1 week at room temperature. The 1-MCP treatment further exacerbated this decreasing trend in CHS content. ERS1 content appears to be stable throughout storage and the simulated marketing period, with levels lower in 1-MCP-treated fruit. These results suggest that 1-MCP significantly inhibits the transcription of key flavonoid and ethylene regulatory enzymes, possibly compromising the nutraceutical content of pear fruit. The increase in PAL with the concomitant decrease of CHS after removal from storage suggests a diversion of carbon from flavonoid compounds into simple phenols, such as chlorogenic acid.
Dan D. MacLean, Dennis P. Murr, Jennifer R. DeEll, and Eugene Kupferman
John M. DeLong, Robert K. Prange, Peter A. Harrison, R. Andrew Schofield, and Jennifer R. DeEll
A final harvest window (FHW), expressed as Streif Index coefficients [firmness/(percentage soluble solids concentration × starch index)], was developed for identifying maximum fruit quality for strains of `McIntosh', `Cortland', and `Jonagold' apples (Malus ×domestica Borkh.) following 8 months of controlled-atmosphere (CA) storage. The Streif Index was calculated during nine preharvest (twice per week) intervals and four weekly harvests over three seasons. The relationship between Streif Index (dependent variable) and day of year (independent variable) of the preharvest and harvest samples was then derived by negative first-order linear regression equations that had parameter estimate (b1) probability values ≤0.0001 for all of the strains. Apples from the four harvest periods were stored in standard CA storage for 8 months and then subjected to a 7-day shelf-life test at 0 °C followed by 5 days at 20 °C. Poststorage quality data were categorized and combined to produce an overall fruit quality rating scale. For each strain, the final harvest (i.e., day of year) was identified as that which directly preceded at least a 10% drop in the poststorage fruit quality rating compared with the first harvest rating. The FHW, expressed as Streif Index coefficients via the regression of Streif Index (Y) on day of year (X), was then calculated as the 3-year final harvest mean with the upper and lower window limits being determined by the standard deviation of the mean. The lower to upper FHW boundaries ranged from 4.18 to 5.34, 4.12 to 5.46, 4.51 to 5.68, 5.23 to 5.99, and 1.38 to 2.34 for Redmax, Marshall and Summerland `McIntosh', Redcort `Cortland' and Wilmuta `Jonagold', respectively. The practical utility of the Streif Index method lies in the ease with which apple fruit maturity at harvest can be evaluated for its suitability for long-term CA storage.
H.P. Vasantha Rupasinghe, Dennis P. Murr, Jennifer R. DeEll, and Murray D. Porteous
Flesh softening is a major quality parameter that can limit long-term storage of apple cultivars. This study investigated the combined effects of preharvest AVG (Retain™) application, 1-methylcyclopropene (1-MCP; EthylBloc™) exposure at harvest, and commercial controlled atmosphere (CA) storage (2.0% O2 + 2.5% CO2) on flesh softening of `Empire' apple. Treatments were assigned in a split-split-plot experimental design; AVG and no AVG application as the main-plot, CA and air storage as the sub-plots, and 0, 0.1 0.5, 1.0 mL·L–1 1-MCP as the sub-sub-plots. Apples were removed from storage at 70 and 140 days after harvest and kept up to an additional 2 weeks at 20 °C for post-storage assessment of ripening. Preharvest AVG application of `Empire' fruit delayed maturation slightly as determined by starch index at harvest, but did not affect fruit size at harvest nor flesh softening in storage. All levels of 1-MCP were equally effective in controlling fruit softening both in air and CA, as 1-MCP-treated fruit were ≈2.5 kg firmer than untreated fruit. This firmness advantage was still evident even after 2 weeks at 20 °C, with CA-stored fruit holding their firmness the best. When all three technologies were combined, treated fruit were overall 156% firmer than control fruit (no AVG, no 1-MCP, air-stored). As well, ethylene production and emanation of aroma volatiles were reduced significantly in these fruit. Therefore, the synergism of AVG, 1-MCP and long-term CA storage could potentially hold flesh firmness and other ripening parameters of apples to values near those found at harvest.
Jennifer R. DeEll, Clément Vigneault, Frédérique Favre, Timothy J. Rennie, and Shahrokh Khanizadeh
The objective of this research was to evaluate the effects of vacuum cooling and temperature on the quality and storage life of mung bean sprouts (Vigna radiata L. Wilczek). Sprouts in micro-perforated bags were either not precooled or vacuum cooled to 9, 6, or 3 °C, and stored for 7 days at 1, 3, or 6 °C. Vacuum-cooled bean sprouts lost more weight than sprouts not precooled, and the weight loss was greater when the sprouts were cooled to lower temperatures. However, the total loss never exceeded 5% and no apparent signs of shrivel were observed. Vacuum cooling resulted in greater product freshness after 4 days of storage, but the effect was nonsignificant after 7 days. Storage temperature had greater influence on bean sprout quality than did cooling temperature, with greater freshness and whiter hypocotyls at the lower temperatures. However, blackening of cotyledons increased as the storage temperature decreased.
H.P. Vasantha Rupasinghe*, Dennis P. Murr, Jennifer R. DeEll, and Joseph Odumeru
Wounding during processing triggers physiological reactions that limits shelf-life of fresh-cut apples. Exposure of `Empire' and `Crispin' apples at harvest to the ethylene antagonist 1-methylcyclopropene (1-MCP, SmartFresh™) on the maintenance of fresh-cut apple quality was evaluated in combination with post-cut dipping of NatureSeal™. Efficacy of 1-MCP on fresh-cut physiology and quality depended on the storage duration and apple cultivar. Ethylene production and respiration of apple slices were inhibited by 1-MCP but not by NatureSeal. Total volatiles produced by fresh-cut apples was not affected by the treatments. 1-MCP influenced the quality attributes of fresh-cut apple slices prepared from apples stored either 4 months in cold storage or 6 months in controlled atmosphere. Enzymatic browning and softening of the cut-surface, total soluble solids, and total microbial growth were suppressed by 1-MCP in `Empire' apples. Overall, the influence of 1-MCP on quality attributes in `Crispin' apple slices was marginal. NatureSeal consistently maintained the firmness of fresh-cut apple slices held at 4 °C for up to 21 days. The additive effect of 1-MCP in the maintenance of apple quality is an advantage for processing and marketing of fresh-cut apples.
Cindy B.S. Tong, Hsueh-Yuan Chang, Jennifer K. Boldt, Yizhou B. Ma, Jennifer R. DeEll, Renae E. Moran, Gaétan Bourgeois, and Dominique Plouffe
Multiple types of flesh browning can occur as storage disorders in ‘Honeycrisp’ apple (Malus ×domestica Borkh.) fruit. Predicting its occurrence is hindered by differing definitions of the types of browning, incomplete understanding of their etiologies, and difficulty in assessing harvest maturity of ‘Honeycrisp’ fruit. In 2013, of ‘Honeycrisp’ fruit grown, harvested over multiple weeks, and stored in Maine, Minnesota, Ontario, and Quebec, only the Quebec fruit developed diffuse flesh browning. A detailed comparison showed that the Quebec fruit differed in size, but not in other quality attributes, from fruit of the other locations. The Quebec fruit experienced lower temperatures during active fruit growth and were increasing in cell size up to harvest. Analyses of climate data from 2009 to 2015 indicated that accumulated growing degree-days (GDD) 50–60 day after full bloom (DAFB) could account for 31% of the variation in diffuse flesh browning, and seasonal GDD <500 are associated with a greater likelihood of injury. Fruit that exhibited diffuse flesh browning had higher magnesium and lower fructose levels than unaffected fruit. As these measurements were made after browning was assessed, the timing of the onset of these characteristics in relation to browning cannot be determined.
Shahrokh Khanizadeh, Johanne Cousineau, Martine Deschênes, Audrey Levasseur, Odile Carisse, Jennifer DeEll, Louis Gauthier, and J. Alan Sullivan
Shahrokh Khanizadeh, Yvon Groleau, Audrey Levasseur, Odile Carisse, Djamila Rekika, Jennifer DeEll, Jean-Pierre Privé, Inteaz Alli, and Henk Kemp
`SuperMac' (Malus ×domestica Borkh) is being released as a replacement for `Spartan', which is presently being grown in Eastern Canada for its excellent shelf life. However, it is susceptibility to scab [Venturia inaequalis (Cke) Wint.], the most common apple disease. This new cultivar produces larger fruit than `Spartan' and is resistant to apple scab. It is very attractive (Fig. 1), has a pleasant taste and an excellent shelf life, and keeps very well and longer compared with the `Spartan'. `SuperMac' is a `McIntosh'-type apple. The tree is hardy to –30 °C, and the fruit and leaves are resistant to the common races of apple scab resulting from the presence of the V f gene derived from Malus floribunda 821.
Shahrokh Khanizadeh, Yvon Groleau, Audrey Levasseur, Marie-Thérèse Charles, Rong Tsao, Raymond Yang, Jennifer DeEll, Cheryl R. Hampson, and Peter Toivonen
Shahrokh Khanizadeh, Martine Deschênes, Audrey Levasseur, Odile Carisse, Rong Cao, Raymond Yang, Jennifer DeEll, J. Alan Sullivan, and Jean-Pierre Privé
`Clé des Champs' is a new June-bearing strawberry cultivar (Fragaria ×ananassa Duch.) bred for Eastern Central Canada and climates similar to Quebec conditions. `Clé des Champs' was released for pick-your-own and shipping because it has very attractive light red, glossy (Fig. 1), and firm fruit, which have an excellent shelf life compared with `Kent'.