1a. Objectives (from AD-416)
1. Evaluate the effect of genetics on microbial stability and composition of flavor and healthful compounds - sugars, acids, volatiles, carotenoids, total phenolics, pectin and fiber – in citrus, tomato, and subtropical-bred small fruit breeding lines. 2. Relate chemical composition to sensory flavor and pathogen resistance data from Objective 1 to determine which compounds are important for flavor or have anti-microbial properties. a) Modeling for quality evaluation. b) Modeling for shelf life as limited by decay and identify natural compounds with antimicrobial activity. 3. Develop pre- and postharvest treatment protocols for reducing specific decay pathogens using sanitizers, antimicrobials, such as plant (including citrus) essential oils, with or without coatings and/or other surface treatments and storage atmospheres to minimize postharvest losses and maximize shelf life of the of citrus, tomato, berries and select tropicals for both intact and fresh-cut products. a) Pre-harvest treatments to reduce postharvest pathogens and to enhance postharvest quality. b) Postharvest treatments to prevent decay and transference of fruit surface microbes.
1b. Approach (from AD-416)
Evaluate advanced breeding lines for citrus tomato and small fruits to determine optimal harvest maturity, microbial stability, and overall flavor quality. Evaluate diverse breeding material for citrus, tomato, and strawberry to determine desirable flavor aromas and tastes. Flavor analyses will be done using sensory panels as well as chemical analyses using gas chromatography (GC) mass spectroscopy (MS), GC-olfactometry, and electronic nose for aroma compounds and liquid chromatography (HPLC), HPLC-MS and microplate readers for sugars, acids, vitamin C, carotenoids, phenolic and antioxidant analyses coupled with flame ionization, refractive index and ultraviolet light and photo diode array among other detectors. Sensory panels will consist of consumer or trained descriptive panels to determine preference and fundamental flavor information. Multivariate and other statistics will be used to relate chemical to sensory data. Storage of commodities under study will be done using simulated commercial or abusive conditions for monitoring of quality and decay. Causal decay organisms will be indentified and pre- and postharvest treatments to reduce their population will be tested including pre-harvest deployment of wax-based sprays, sanitizers, and nutrients as well as use of postharvest sanitizers, anti-microbial agents or antagonists with or without coatings. Produce will also be subjected to short-term antimicrobial atmospheres of low oxygen, high carbon dioxide alone or combined with other anti-microbial volatile compounds. Effect of disease (Huanglongbing) on orange juice flavor will also be analyzed and identification and threshold of off-flavor compounds determined.
3. Progress Report
Significant progress was made under Objective 1. New mandarin/tangerines hybrids were harvested at 3-4 week intervals to determine optimum harvest for eating quality as fresh fruit. A taste panel could perceive the increase in sweetness and juiciness and decrease in sourness and bitterness with maturity. The possibility of processing two complex citrus hybrids for a unique citrus juice beverage was investigated. Collaboration with University of Florida (UF) tomato and strawberry breeders was continued to evaluate new hybrids by sensory evaluation and chemical analysis. Data from tomato lines that have been studied over the past 10 years were combined into a database to determine chemical and sensory relationships. A new experiment was designed to understand the inheritability of the aroma volatile methylanthranilate (MA) in strawberries. MA provides a unique fruit flavor to strawberries when present in substantial amount. Collaboration with the UF blueberry breeder was established to relate firmness by sensory descriptive analysis with instrumental measurements and determine the genetic control of the “crisp” character. Flavor of orange juice made with fruit from trees infected with Huanglongbing (HLB) disease and undergoing field nutritional sprays was evaluated. Under Objective 2a, analyses of chemical components of commodities evaluated for eating quality were performed. In order to further understand what causes off flavor in juice from HLB-infected trees, taste thresholds were determined for two bitter compounds of orange juice, limonin and nomilin, and the perception of these compounds in model solutions was examined. This work is important for juice processors to predict the effect of this new and spreading disease on orange juice flavor. Further, a study was initiated to detect the presence of causal organism in orange juice made with fruit from HLB-infected trees. Under Objective 2b, a soil fungus, Trichoderma viridie was isolated and tested as a potential antagonist against citrus canker, as well as a commercial strain of Pseudomonas syringae. Under Objective 3a, field sprays of potassium sorbate and a commercial sanitizer were performed on blueberries. The commercial sanitizer, ‘Treewash’, significantly reduced decay. The effect of such preharvest sprays on yield and eating quality was also measured. Postharvest treatments were performed under Objective 3b. Newly designed clamshells were tested with blueberries, strawberries and litchee fruit and significantly extended shelf life of these crops in comparison with commercial clamshells. New formulations of chlorine dioxide were tested for removal of Escherichia coli on blueberries, citrus and fresh-cut mangoes. The slow-release formulation and liquid formulation incorporated into a coating both showed significant reduction of pathogen on inoculated fruit, and increased fruit quality. Experimental trials with alkaline sanitizing washes significantly reduced postharvest decay in papaya, whole and fresh-cut. This project replaced projects 6621-43000-002-00D (bridging project for 6621-43000-001-00D) and 6621-41440-004-00D (bridging project for 6621-41440-003-00D).
1. Perception threshold of limonin and nomilin in orange juice. Previous year studies by ARS researchers in Winter Haven, Florida, showed that limonin and nomilin are two compounds that induce bitterness or off-flavor in orange juice made with fruit severely affected with Huanglongbing (HLB). We showed this year that these two compounds tasted in a model orange juice had a synergistic effect, with nomilin enhancing limonin bitterness more than limonin increased nomilin bitterness. This information is of interest to the industry to determine what is the maximum acceptable level of these two compounds in juice, especially in light of a likely increase in diseased fruit entering the juice stream.
2. Historical trend of old and new strawberry cultivars from the University of Florida (UF) breeding program. In order to learn trends in variety development over the last 50 years, a field study was designed that compared 10 cultivars and two new selections. Data showed that fruit size increased with year of release of the cultivar, and fruit color became redder for cultivars released up to 2002. ARS scientists from Winter Haven, FL, found that there was seasonal effect on sugars, acids and volatiles, which affect eating quality, but there was no trend due to year of release of cultivar. This information is useful for the breeder to understand how quality traits were selected over the years and their response to environment. This will save effort and money in the future breeding program and help breeders take new directions.
3. Release of a new strawberry cultivar. In collaboration with ARS researchers from Winter Haven, Florida, the University of Florida released a new strawberry cultivar, Medallion™. This cultivar is adapted to climates with mild winters and produces large bright red fruit. Taste quality has been consistently less sour and sweeter than current commercial cultivars. New cultivars with improved market potential benefit Florida strawberry growers.
4. Use of a preharvest wax spray to reduce incidence of canker disease on citrus fruit. Florida fresh citrus is under an international quarantine because fruit with citrus canker or fruit from a grove with canker cannot be sold to the European Union (EU). The EU is a valuable market, especially to grapefruit growers. Using commercial groves as models, ARS researchers from Winter Haven, Florida, developed a spray program using a natural carnauba wax mixed with copper hydroxide, which was found to decrease the incidence of citrus canker. Fresh citrus growers in Florida are using this spray to increase marketable fruit.
Nunes, M.C.N., Emond, J-P., Dea, S., Yagiz, Y. 2011. Distribution center and retail conditions affect the sensory and compositional quality of bulk and packaged slicing cucumbers. Postharvest Biology and Technology. 59:280-288.