QUALITY, SHELF-LIFE AND HEALTH BENEFITS FOR FRESH, FRESH-CUT AND PROCESSED PRODUCTS FOR CITRUS AND OTHER TROPICAL/SUBTROPICAL-GROWN FRUITS AND VEGETABLES

Phenotypes for fruit quality in citrus, tomatoes, strawberry, peaches and avocados will be screened for flavor markers: volatiles, sugars and acids, and sensory characteristics by gathering chemical and sensory data on a wide range of genetically variable breeding lines (or hybrids). In the long term, plant breeders will identify genes associated with fruit quality traits and map them on the genome to aid in marker-assisted selection. For advanced selections or commercial cultivars of peach and avocado, fruit will be harvested multiple times during maturation and ethylene and respiration rate will be measured at harvest and in stored fruit. For the effect of citrus greening or Huanglongbing (HLB) disease on orange fruit/juice flavor, fruit or juice will be obtained from collaborators, or from groves undergoing various field treatments (pesticides, growth regulators, antibiotics or thermotherapy), or from trees grown on different rootstocks to study a wide range of HLB flavor symptoms. Juices will be tested for CLas infection by qPCR and for levels of sugars, acids, volatiles, flavonoids, limonoids and for flavor perception using sensory evaluation. Taste panels will serve as the biosensors for compounds isolated from HLB-affected orange juice to determine compounds responsible for these putative off-flavor taste attributes. The electronic nose and electronic tongue will be used to screen for HLB-induced off-odor or flavor. The effect of HLB on the flavor quality of grapefruit and tangerines will be investigated. HLB- induced off-flavor can be managed by blending, by modifying juice processes or by adding citrus-derived natural compounds (volatiles or non- volatiles) to mask or bind off-flavor compounds. Studies will be conducted on several citrus types using fungicide sprays (strobulorins, Topsin) targeting D. natalensis to determine if the HLB-induced fruit drop and postharvest stem end rot can be reduced. This is the final report for Project No. 6034-41430-006-00D. Objective 1. Citrus hybrids showing tolerance to Huanglongbing (HLB) were obtained from an ARS collaborator for four consecutive years. Fruit were evaluated by a trained sensory panel, and chemically analyzed for flavor volatiles, sugars, acids and bitter limonoids. On the fourth year, plans were made to initiate blends with juices from promising selections to achieve optimum taste. However, the restriction of research due to Covid 19 only allowed for harvest and freezing of samples. No analyses were performed in 2020. Strawberry selections from the University of Florida (UF) breeding program were evaluated each year for three or four months (December to March) by a trained taste panel, and fruit were analyzed for firmness, sugars, acids and volatiles. These data help the breeder selecting hybrids with high quality, discarding those with negative sensory attributes. Two cultivars were released during the Plan period resulting from the collaboration with UF. Analysis of the five-year data show that genotypes, followed by season, strongly effect sensory perception. Statistical models revealed which volatiles increased perception of sweetness and strawberry flavor. Genetic studies of target volatiles are underway to facilitate the selection of strawberry cultivars with higher sweetness and flavor through marker-assisted selection. Volatile production in different tissue (structure) of the tomato fruit was measured in four commercial cultivars. In general, the pericarp tissue showed the highest volatile concentration, with the highest aldehydes and herbaceous-like compounds. Compounds with floral and fruity characters were more abundant in the inner fruit tissue, i.e. septa and columella, and locular gel and seeds. Distinct volatile profiles were found in different cultivars. Peaches from a breeding collection at ARS (Byron, Georgia) were collected for three seasons and flavor volatiles were analyzed. The objective is to compare aroma volatile profiles in peach and nectarine genotypes with different melting/non-melting and yellow/white flesh. A subset of samples including 15 cultivars/hybrids with different degrees of skin hair were assessed for their volatile profile. The only volatile which was detected in the nectarines but not in peaches was hexanol, indicating alcohol hedydrogenase (ADH) and hexanol are potential markers for peach-to- nectarine mutants. However, overall peach-to-nectarine mutants showed broad pleiotropic effects for fruit size, taste, and aroma, in addition to hairlessness. Twenty one papaya accessions from the UF tropical fruit breeding program were evaluated for aroma volatiles by gas chromatography-mass spectrometry (GC-MS), revealing a large variation among samples. A subset of samples were evaluated by GC-olfactometry to pinpoint which volatile compounds may potentially contribute to aroma and flavor. These results provides the breeder potential to select hybrids with high eating quality. Avocadoes from the ARS varietal collection were harvested monthly or bi- monthly, and let ripened at room temperature (20 C). Once ripe, fruit were tasted by expert panels. This study establishes maturity windows for unknown cultivars or hybrids. Some hybrids seemed to show tolerance to laurel wilt and phytophthora root rot. A collection of photos was taken for future use. Objective 2.Thyme oil, thymol, carvacrol and Thyme Guard (a commercial formulation containing thyme oil) were most effective at controlling decay of Florida strawberries, on both inoculated or naturally infected fruit. Formulations with microencapsulated slow release volatiles applied to sachet in clamshells and fruit stored at low temperatures (i.e. 5 C) controlled Botrytis gray mold and Rhizopus soft rot without affecting fruit quality. Likewise, a new formulation of chlorine dioxide vapor was effective at controlling strawberry decay. Covid 19 restrictions did not allow commercially simulated tests. Experiments on fresh-cut mangoes and winter melon quality were finalized in the previous period. Objective 3a. â¿¿Valenciaâ¿¿ oranges were juiced using two types of commercial extractors, a reamer and a squeezer type. The physical and chemical properties of the juices were compared. Juice processed by squeezing the fruit contained higher limonoids, flavonoids and carotenoids resulting in higher nutritional value but slight bitter taste. Juice processed with a reamer had more peel oil, specifically because food service/juice stand type was used where peel oil was not removed prior to juicing. A good quality juice will depend on the raw material as well as methods of processing. Grapefruits free from HLB (grown in a â¿¿Citrus Under Protective Screenâ¿