Research Summary


 Project Title: Non-Destructive Detection of Sun Stress Compromised Apples 

PI: David Rudell

Co-PI: Carolina Torres 

 Sun stress results in significant annual loss not only due to injury in the orchard but also injuries that appear during the cold chain including sunscald and lenticel blotch. Detection of these disorders before they enter the cold chain could afford producers the capacity to segregate fruit for removal, immediate marketing, or different storage strategy to eliminate injured fruit. Our earlier work has identified fruit compounds present prior to symptom development that may be detected non-destructively. Two non-destructive techniques, near infrared spectroscopy and UV reflectance, have been tested and shown promise, and at least one other technique may also have utility. We will use the same destructive chemical analysis techniques used to identify fruit compounds associated with peel disorder risk to validate the accuracy of the non-destructive techniques. Then, we will validate the use of the non-destructive technique(s) by identifying symptomless, yet sun stressed, apples prior to storage and wait for and symptoms to develop during storage. This project’s goal will be to develop a means for sorting symptomless sun stressed fruit from fruit that are less likely to develop sun stress disorders, thereby minimizing or eliminating sun-related postharvest disorders from the cold chain and retail. 

Hyperspectral image detecting sun stress in Granny Smith apples

Project Title: Postharvest System Optimization for Organic Apple Storage

PI: Carolina Torres 

Co-PI: Jim Mattheis 

Organic tree fruit production in WA is steadily growing. Apples are the most important crop (in value) under this production system with approx. 16% of the WA apple acreage and 14% of the 2018 crop being grown under the USDA organic standard. Not only production has been and continues to be a challenge, but also maintaining the fruit quality long term in storage, which is critical to keep crop profitability. Today, most of cold storage for organic pome fruit is done using traditional (CA) or dynamic controlled atmosphere storage (DCA). Nevertheless, there is not enough information on how to combine postharvest storage systems and technologies to maximize fruit quality for extended storage periods. Organic fruit cannot be treated with 1-methyl cycle propene (1-MCP), an ethylene action inhibitor, at harvest as it can conventionally-grown apples. This poses a bigger challenge to organic fruit that requires a tighter control of maturity advancement prior and at harvest in order to achieve good results with different postharvest systems. This has becoming even more important as unpredictable climate events, such as heat waves, occur every season, changing ripening rates pre-and postharvest.  

Evaluation of CA in organic apples

Project Title: New Active Ingredients for Pear Superficial Scald Control 

 PI: David Rudell 

Co-PI: Carolina Torres 

Co-PI: Jim Mattheis 


 Management for superficial scald control continues to be an industry challenge. The uncertainty of continued availability of ethoxyquin, market access issues related to its use, and ripening issues with 1-MCP treated fruit all contribute to a need for alternative scald control methods. A new chemistry, developed by Dr. Carolina Torres, has been shown to control scald on ‘Packham’ (patent pending). The formulation contains purified squalane from vegetable oil, which is likely the active ingredient. Squalane is an oily triterpane related to many triterpene cellular membrane, wax, and, possibly, cuticular components. The mode of action is unknown although preliminary evidence indicates it does not act as an antioxidant like ethoxyquin or DPA. If so, this is a unique mode of action which, if determined, may yield new information to find additional active ingredients, risk assessment protocols, and cold chain management strategies to eliminate superficial scald from the pear cold chain. We propose to determine the efficacy and best use of the existing squalane-based formulation as well as analyze the mode of action. To accomplish this, we will treat multiple ‘d’Anjou’ lots from different growing regions and store them in air or CA storage evaluating appearance as well as fruit quality over commercially relevant storage durations. Multiple seasons and harvest maturities will be included in location. We will exhaustively analyze peel chemistry at critical points in the cold chain to determine changes squalane addition may provoke focusing on cellular membrane, wax, and cutin chemistry to determine mode of action. We expect to deliver information describing best use of this formulation in relation to current CA storage and cold chain management practices, and an improved understanding of pear scald. Our goal is to eliminate superficial scald from the pear supply chain.

Superfical scald control in pear

Project Title: Effect of Dump Tank Composition on Lenticel Breakdown Disorder 

PI: Carolina Torres 

Co-PI: Faith Critzer 

Lenticel breakdown (LB) is an important skin disorder on apples that usually appears after fruit has been processed and packed. Although it is a multi-factorial disorder, where environmental conditions in the orchard, mineral imbalances, and harvest maturity play an important role, translated into susceptibility variation between sites and seasons, processing practices after storage have a major effect on the disorder’s development. Amongst postharvest packing conditions, dump tank temperature, brushing and soap/detergent type are critical. Given that dry and hot growing environments affect lenticel morphology on the fruit, and therefore, lenticel breakdown potential postharvest; climate change events may increase fruit susceptibility in the future. 

In susceptible fruit, abrasive treatments on the packing line, along with chemicals and mineral residues in the water used in dump tanks and flumes can trigger LB appearance. The extent to which these residues on the water cause/exacerbate LB after processing is still poorly understood, mainly due to the multi-factorial nature of this disorder, and the different practices carried out by different operations and new active ingredients. There is also little or no information on the effect of new antimicrobial compounds commercially available today regarding LB incidence. 

In order to study the effect of current makeup of water used in packinghouses operations on LB development, we will be using the information obtained by the ‘Critical limits for antimicrobials in dump tank systems’ project led by Dr. Faith Critzer, and coordinate activities alongside. 

Flume and tank water composition are related to postharvest LBD


Project Title: Survey of Pear Packers on Storage and Handling of d’Anjou Pears 

 PI: Carolina Torres 

CO-PI: Chris Hedges 

 Eating quality on pears is key to maintain and increase its consumption. In winter pears, like Anjou, this is a challenge, especially after short-term storage, because their chilling requirement to ripen and their variable maturity stage at harvest. Today, the WA pear industry has different handling practices for this variety with variable success especially in early season fruit. There is a need in the industry to develop universal metrics and standards to define “good” vs. “bad” fruit, additionally to identify and define the best storage practices being used. This is an opportunity to better understand how the industry can extend the storage and marketing season and still deliver high eating quality fruit. A survey will help to identify best practices to help the industry. Previous survey was carried out by Dr. G. Kupferman in the 90s (Tree Postharvest Journal, 1998), since then, new technologies, such as 1-MCP, have changed some of those practices, as well as the fruit outcome. Therefore, a new survey will update some of this information together with anonymous fruit quality.

Survey of storage and handling of d’Anjou Pears 

Project TitleNutrient Management for High Quality Sweet Cherries 

PI: Bernardita Sallato 

Co-PI: Matthew Whiting 

Co-PI: Carolina Torres 

Tree nutrition affects sweet cherry fruit quality, yield, and susceptibility to biotic and abiotic stresses. Macronutrients such as nitrogen can reduce fruit firmness and affect flavor; potassium affects internal water balance and dry matter content; calcium is fundamental for fruit firmness, cracking and shelf life. Micronutrients are required in very low quantities, but their deficiencies can lead to innumerable malfunctions and fruit quality problems. In addition to the independent role of each essential nutrient, their internal balance is key in determining overall fruit quality, nutrient uptake and distribution. There are many examples of fruit disorders associated with nutrient imbalances (e.g. bitter pit and lenticel breakdown in apples, cork spot in pears), yet little is known on the role of fruit nutrient content on sweet cherry quality and storability. Currently, nutrient management in sweet cherry is based on leaf tissue standards, useful in preventing deficiencies or toxicities. These standards were developed by determining nutrient concentration at maximum growth and have not taken fruit quality into account (i.e., there are no nutritional standards related to optimizing fruit quality). The goal of this project is to improve nutrient management strategies from an understanding of the nutritional composition of good and poor quality fruit. We propose to undertake a prospective analysis of orchard growing conditions, tree and soil health, irrigation management and nutrient composition and its relationship with the quality parameters; size, firmness and storability. This research approach will allow an in-depth analysis of fruit nutritional content and fruit quality, identify predictors, determine nutrient extraction/demand and begin to develop fruit-specific nutritional management strategies for sweet cherry. 

Nutrition is related to postharvest quality in sweet cherries

Project Title:  Efficient Heat Stress Management for Improved Apple Fruit Quality

PI: Lav Khot 

Co-PI: Bernardita Sallato 

Co-PI: Carolina Torres 

Co-PI: R. Troy Peters 


 This project aims to investigate efficient heat stress monitoring and management strategies in Honeycrisp and WA-38 apple cultivars with goal of reducing in-field and post-harvest crop losses. We will evaluate water-energy efficient evaporative cooling system that will use fogging type emitters (from Jain Irrigation, USA) to cool orchard micro-climate using about 15 to 18 GPM/A of water. This is critical as growers struggle to manage combination of evaporative cooling and deficit irrigation during fruit maturation stages for these two premium fresh market cultivars. In our preliminary trials in WA-38 cultivar, proposed evaporative cooling system was tested in 2020 season for its effectiveness in heat stress management. Results are encouraging with documented improvement in fruit coloration compared to conventional cooling approaches; additional fruit quality analysis is in progress.  

In this 3-year project, Hancock Farmland Services (at Prosser, WA) commercial blocks will be used for experimentation. We will compare the fogging system with overhead netting established by the cooperator. Throughout the season, we will monitor these replicate blocks for heat stress using a localized orchard climate/crop physiology sensing system (CPSS) developed by our team (through NSF/USDA-NIFA funded project). CPSS details with season long test results are in Ranjan et al. (2020) Computers and Electronics in Agriculture, 175, 105558. On this project, we will evaluate the impact of orchard sub-block climate variations and of sunburn management treatments on sunburn incidence, tree vigor, fruit quality and storability.  

Additionally, we will use two seasons data and grower knowledge to manage heat stress in sub-treatment blocks, for both cultivars, through evaporative cooling system actuated by sensing system (year 3). The CPSS is capable of real-time fruit surface temperature monitoring and actuation of evaporative cooling at set threshold with user override option. We will test the robustness of this system and pertinent improvements in crop quality and resource usage.  

Our team has a synergy of collaboration and cooperation to have successful project deliverables. Overall, the project outcomes will lead towards energy/water use efficient apple crop stress (sunburn) management. This will lead towards improved pack-outs and ultimately in grower profit margins. 

Heat stress management in apple orchards