Location: Commodity Protection and Quality Research
2018 Annual Report
Objectives
Objective 1: Integrate pre- and postharvest approaches to enhance fruit flavor quality and enable commercial methods to extend postharvest life of fresh fruit.
• Sub-objective 1A: Identify factors influencing the development of postharvest off-flavor formation in mandarins.
• Sub-objective 1B: Develop pre- and postharvest integrated practices using reduced-risk or generally-recognized-as-safe substances and advanced packaging technologies to control postharvest diseases and maintain fruit quality of blueberries.
• Sub-objective 1C: Develop pre- and postharvest integrated practices using reduced-risk or generally-recognized-as-safe substances to control postharvest diseases and maintain fruit quality of table grapes.
Objective 2: Enable new commercial postharvest methods to remove or reduce fungicide residues on fresh fruit.
• Sub-objective 2A: Develop postharvest treatments with generally-recognized-as-safe substances to remove or reduce fungicide residues on blueberries.
Approach
The goal of this project is to maintain/improve fruit quality and prolong storage and shelf life of fresh fruits. The emphasis is on the integration of pre- and postharvest practices using reduced-risk fungicides or substances that are generally recognized as safe for decay control and fruit quality preservation. Field and laboratory experiments will be conducted on different varieties to identify biochemical, physiological and anatomical factors that influence off-flavor development in mandarin citrus after harvest. Field and cold storage experiments will be conducted to evaluate various pre- and postharvest practices using reduced-risk or generally-recognized-as-safe substances and advanced packaging technologies to control postharvest diseases and maintain fruit quality of blueberries and table grapes. Initially effective individual pre- and postharvest practices will be identified, and in the later phase of the project integrations of effective pre- and postharvest practices will be developed and evaluated. The effects of postharvest fumigation treatments with generally-recognized-as-safe substances on fungicide residues on blueberry fruit will be evaluated, and effective treatments will be developed as mitigation measures for removal or reduction of fungicide residues on blueberry fruit.
Progress Report
In research under Sub-objective 1A, new and more accurate methodologies were utilized in mandarins to measure peel permeability to gas exchange to more fully understand the effect of fruit maturation on off-flavor development during storage. As previously found, the two satsumas tested developed lower internal oxygen and more off-flavor toward the end of the harvest season. Peel gas permeability was relatively constant throughout the season and was likely not the cause of the lowering in internal oxygen in more mature fruit. Respiration, however, was enhanced with maturation and may be playing an important role in decreasing internal oxygen. This was also suggested by the testing of ‘W. Murcott,’ another type of mandarin, for which respiration declined as the season progressed. In the case of this variety, internal oxygen levels dropped to a lesser degree with maturation and off-flavor did not develop.
In research under Sub-objective 1B, post-harvest fumigation of blueberry fruit with continuous ozone at concentrations ranging from 0 to 1 parts per million (ppm) during cold storage was evaluated. Ozone concentrations ranging from 0.05 to 1 ppm significantly reduced the incidence of Alternaria rot compared to control, and ozone concentrations at 0.3 to 1 ppm provided significantly better control than ozone lower than 0.3 ppm. All ozone treatments significantly suppressed spread of gray mold, and ozone at 0.2 to 1 ppm significantly reduced the incidence of gray mold compared to the control.
In research under Sub-objective 1B, sulfur dioxide-emitting packaging liners, sheets, or bags with modified atmosphere capability were evaluated for control of post-harvest diseases and maintenance of postharvest fruit quality of blueberries. Commercially harvested blueberry fruit were packed in clamshells wrapped with the tested packaging materials and stored at 0 degrees Celsius (°C) for three or six weeks. One sulfur dioxide-emitting liner with modified atmosphere capability significantly reduced the incidence of decay, suppressed the spread of gray mold caused by Botrytis cinerea, and prevented weight loss of the fruit compared to the control.
In research under Sub-objective 1B, pre-harvest reduced-risk fungicides in combination with post-harvest continuous ozone fumigation at low doses (0.3 and 1 ppm) for control of post-harvest diseases are being tested in the 2018 season. Fungicides Switch (a mixture of fludioxonil and cyprodinil) and fenhexamid were applied to the fruit before harvest. After harvest, part of the fruit was inoculated with either Alternaria alternata or Botrytis cinerea, and part of the fruit that was not artificially inoculated was used for assessing treatment effects on decay resulting from natural infections. Fruit were then stored at 0°C either in air or continuous ozone at 0.3 or 1 ppm. Post-harvest evaluation will be conducted as time progresses.
In research under Sub-objective 1B, integrated approaches consisting of pre-harvest reduced-risk fungicides and post-harvest sulfur dioxide-emitting pads (either single-stage slow releasing or dual-stage releasing) for control of post-harvest diseases in blueberries are being conducted in the 2018 season. Fungicides Switch (a mixture of fludioxonil and cyprodinil) and fenhexamid were applied to the fruit before harvest. After harvest, part of the fruit was inoculated with either Alternaria alternata or Botrytis cinerea, and part of the fruit that was not artificially inoculated was used for assessing treatment effects on natural infections. Fruit were packed into clamshells and placed in cardboard boxes, and one sulfur dioxide-releasing pad was placed on each of the two layers of clamshells in the box. Clamshells were wrapped with a plastic bag in each box. Fruit were then stored at 0°C for decay development. Post-harvest evaluation will be conducted as time progresses.
In research under Sub-objective 2A, effects of ozone fumigation at high doses on fungicide residues on blueberry fruit were evaluated. Blueberry fruit were treated in the lab with various fungicides and subjected to ozone fumigation at 2,000 ppm or 5,000 ppm for two hours. Ozone fumigation did not cause visible phytotoxicity on the fruit compared to the nonfumigated control. Ozone treatments significantly reduced fungicide residues on blueberry fruit, except the fungicide captan. Residue reduction rate was 52.7-62.7%, 59.7-76.4%, 23.5-22.8% and 26.8-42.4% for azoxystrobin, cyprodinil, fenhexamid and fludioxonil, respectively, compared to those on the fruit that were not treated with ozone.
Accomplishments
1. Rate of respiration is linked with flavor quality loss in mandarins. Mandarins can dramatically lose flavor quality in storage and disappoint consumers, but the factors influencing this problem are not well known. ARS researchers in Parlier, California, harvested different mandarin varieties at various time points from early to late season and observed that, in certain varieties, respiration rates increase with fruit maturation, and that these varieties develop bad flavor in storage. In the absence of this rise in respiration, flavor remained good throughout the time of storage. This finding increases our understanding of why this storage disorder occurs and may suggest ways to stop its occurrence.
2. Peroxyacetic acid controls post-harvest diseases of blueberries. Post-harvest fruit rot diseases limit the storage and shelf life of fresh blueberries. ARS researchers in Parlier, California, conducted research and determined that peroxyacetic acid applied as a post-harvest dip treatment significantly reduced post-harvest fruit rot diseases such as gray mold and Alternaria rot, and there were no significant differences in fruit quality such as sugar content and fruit firmness between the treated and non-treated fruit. Taste panel tests also showed that there were no significant differences in visual acceptance, flavor, and fruit texture between the treated and non-treated fruit. Peroxyacetic acid is a generally recognized as safe (GRAS) product and can be used in organic production. These research findings suggest that peroxyacetic acid can be used to extend the storage and shelf life of fresh blueberries.
Review Publications
Saito, S., Xiao, C. 2017. Evaluation of sulfur dioxide-generating pads and modified atmosphere packaging for control of postharvest diseases in blueberries. Acta Horticulturae. 1180:123-128. https://doi.org/10.17660/ActaHortic.2017.1180.17.
Saito, S., Xiao, C. 2017. Prevalence of postharvest diseases of mandarin fruit in California. Plant Health Progress. 18(4):204-210. https://doi.org/10.1094/PHP-08-17-0048-RS.
Aguilar, C.G., Mazzola, M., Xiao, C. 2018. Control of bull’s-eye rot of apple caused by Neofabraea perennans and Neofabraea kienholzii using pre- and postharvest fungicides. Plant Disease. 102(5):905-910. https://doi.org/10.1094/PDIS-09-17-1363-RE.
Xiao, C., Saito, S. 2017. Prevalence and incidence of postharvest diseases of blueberries in California. Acta Horticulturae. 1180:129-134. https://doi.org/10.17660/ActaHortic.2017.1180.18.
Arpaia, M., Collin, S., Sievert, J., Obenland, D.M. 2018. ‘Hass’ avocado quality as influenced by temperature and ethylene prior to and during final ripening. Postharvest Biology and Technology. 140:76-84. https://doi.org/10.1016/j.postharvbio.2018.02.015.
Obenland, D.M., Campisi-Pinto, S., Arpaia, M. 2017. Determinants of sensory acceptability in grapefruit. Scientia Horticulturae. 231:151-157. https://doi.org/10.1016/j.scienta.2017.12.026.
