Location: Wenatchee, Washington2013 Annual Report
1a. Objectives (from AD-416):
Determine interrelationship between controlled atmosphere (CA), relative humidity (RH), and SmartFresh (MCP) on apple cuticle structure, function and disorder.
1b. Approach (from AD-416):
Previously, work done at the ARS laboratory in Wenatchee indicated preharvest treatments that increased ethylene production in ‘Granny Smith’ apples also increased fruit epicuticular wax production during storage. Similarly, treatments that reduced postharvest ethylene production were associated with a delay in fruit epicuticular wax production during storage. Ethylene is implicated in apple epicuticular wax production. Wax production is necessary for “healing” the microcracking associated with normal fruit growth and cuticle expansion. Degree of microcracking “healing” by the time storage conditions are achieved influences fruit cuticle water vapor permeance, which, together with ambient conditions, establishes desiccation potential of fruit in storage. Moisture loss of fruit in storage followed by rewetting during water-based fruit processing may be implicated in cuticle cracking around lenticels, and disorders associated therewith. This project will focus on the interrelationship of fruit ethylene production, fruit cuticle water vapor permeance and ambient water vapor pressure during storage and the impact these have on physiological storage disorders.
3. Progress Report:
This serves as a final report for project 5350-43000-006-07T. This project relates to objective 3 of the associated in-house project, which seeks to identify factors that influence postharvest fruit quality and development of market limiting physiological disorders. The project focused on the interrelationship of fruit ethylene regulation, fruit cuticle water vapor permeance and ambient water vapor pressure during storage and the impact these have on physiological storage disorders. Previously, work conducted at the ARS laboratory in Wenatchee indicated ethylene is implicated in epicuticular wax production in apple: 1) preharvest treatments that increase ethylene production in ‘Granny Smith’ apples also increase fruit epicuticular wax production during storage and 2) treatments that reduce postharvest ethylene production were associated with a delay in fruit epicuticular wax production during storage. Wax production is necessary for “healing” the microcracking associated with normal fruit growth and cuticle expansion. By the time apple storage temperature and atmosphere are achieved, degree of healing influences fruit cuticle water vapor permeance, which, together with ambient conditions, establishes desiccation potential of fruit in storage. Moisture loss from fruit in storage followed by rewetting during water-based fruit processing may be implicated in cuticle cracking around lenticels, and disorders associated therewith. Beginning in 2008, experiments were conducted to examine the effect of storage humidity on quality of fruit with and without prestorage treatment with the ethylene action inhibitor 1-MCP. In one experiment, ‘Gala’ apples were treated immediately after harvest by dipping fruit for 2 minutes in increasing rates of EpiShield--a natural wax formulation that reduces moisture loss in storage. Treatment with EpiShield was followed by treatment with SmartFresh (1-MCP) and storage for 8 months at 33 °F. Apples treated with EpiShield plus 1-MCP showed reduced lenticel breakdown (LB) compared with fruit treated only with 1-MCP. The following year, experiments were conducted to examine the effect of relative humidity (RH) and modified atmosphere storage on moisture loss (shrivel) of fruit with or without prestorage treatment with 1-MCP. ‘Golden Delicious’ apples were treated 24 h after harvest with 1-MCP and placed in controlled atmosphere (CA) or regular atmosphere (RA) storage at 33 °F for 8 months. RH was maintained at either 90% or 100%. At 90% humidity, all fruit showed signs of shrivel regardless of whether fruit were kept in CA or RA storage, whereas at 100% RH none of the fruit showed these symptoms. There was no treatment effect from 1-MCP on fruit shrivel. Fruit treated with 1-MCP were the least ripe (greenest) when stored at 100% RH under CA conditions, followed by those stored at 100% RH under RA conditions. At 90% RH in RA storage, fruit treated with 1-MCP were no different than untreated fruit. The results indicate RH affects fruit weight as well as ripening under certain storage conditions. In 2010, experiments were conducted to examine the effect of pre-sizing and 1-MCP treatment on moisture loss (shrivel) and LB of fruit stored at 33 °F for 8 months under 75 or 100% relative humidity (RH). Data indicate: 1) pre-sizing (10 minutes in a water bath kept at 90 °F) had no effect on fruit quality; 2) lower storage RH was associated with increased internal ethylene concentration; 3) lower storage RH reduced fruit firmness by about 30%; 4) 1-MCP treatment masked the effects of higher storage RH on internal ethylene concentration and flesh firmness. In 2011, experiments were conducted using ‘Lady Alice’ apples (similar to ‘Pink Lady’) to examine the effect on quality of 1-MCP, time in storage, oxygen (O2) level and post-harvest soap/wax treatment, in conventional vs. organic orchards. Results indicate after 90 days, fruit stored at air without 1-MCP were the least firm of all treatments. After 180 days, fruit treated with 1-MCP and then kept at room temperature showed delayed ethylene production for an additional 12-14 days. Oxygen level during cold storage had little effect on firmness measured 24 h after removal from 33 °F. On the other hand, 1-MCP-treated fruit were 1-2 lbs firmer in 80% of treatments. Fruit stored in air had the lowest incidence of lenticel breakdown and black lenticel. These results suggest ‘Lady Alice’ treated with 1-MCP may be stored in air instead of low O2 to maintain equal or better quality than fruit kept in CA. In addition to preharvest cultural management, accurate measurement and control of apple storage conditions are paramount in maintaining consistent high quality fruit. This work showed that many factors must be considered when storing apples longer than three months: cultivar, preharvest treatment, ripening stage at harvest, pre-storage treatment (e.g. Smartfresh, Epishield), ambient temperature, water vapor pressure and atmosphere composition.