ENHANCEMENT OF FRUIT AND FRUIT PRODUCT FLAVOR QUALITY USING ANALYTICAL/SENSORY METHODS

Determine sensory threshold values in orange juice for numerous important volatile flavor components of citrus. Investigate the effect of other juice components on aroma theresholds, such as pectin, sugar and flavonoids. Develop analytical techniques using gas chromatography, mass- spectometry, olfactometry and electronic sensors to quantitatively monitor changes in citrus, tomatoes, tropical fruits and their products during processing and storage. Use multivariate analysis techniques to correlate sensory and analytical data to help processors produce and objectively evaluate value-added flavor fractions and juice products. Screen citrus and tomato breeding lines for flavor, color and nutritional quality traits to develop molecular markers. This project aims to determine the components that comprise flavor quality of citrus and tomato as well as the effect of genetics, harvest maturity or postharvest handling/processing. Volatile work on tangerine breeding lines with the University of Florida (UF) citrus breeder and the USDA-ARS breeding program in Ft. Pierce, FL was continued. The study with UF breeding lines completed its third year for selected hybrids, and showed strong seasonal and genetic effects, especially for aroma compounds and carotenoid content. Five of the hybrids were analyzed by gas-chromatography-olfactometry (GC-O) (smelling aroma compounds as they exit the GC), which gave additional information on the aroma activity of the volatile compounds previously identified by gas-chromatography-mass- spectrometry (GC-MS). Two of the citrus varieties with distinct differences in volatile production and used as parents in the breeding program were analyzed for deoxyribonucleic acid (DNA) expression by the UF collaborator. Investigation of the effect of citrus greening disease (Huanglongbing, HLB) on orange juice quality was scaled up to pilot size sampling with 15-20 trees per batch. Sensory evaluation tests indicated that when the juice was made with fruit that was not severely affected by the disease, there were no differences from juice that was made with fruit from unaffected trees. Only severely affected fruit imparted a negative flavor to the juice, and those are unlikely to enter the processed juice under commercial conditions because of their small size: they would not be harvested, often drop off the tree or if harvested, would be sorted out on the processing line. Data obtained from chemical and sensory analyses during the previous season were modeled to understand the main reasons for flavor differences between healthy and HLB juice and resulted in two publications. Determination of thresholds for detection of compounds imparting bitterness in juice is under way. This work is important for juice processors to predict the effect of this new and spreading disease on orange juice flavor. Data from tomato lines that have been studied over the past 10 years were combined into a database to relate chemical and sensory relationships using a special method in collaboration with University of Florida. Tomatoes subjected to different temperature treatments were analyzed for flavor using trained panel and chemical analysis. Differences were found in that chilling reduced flavor, but heating may protect against chilling-induced injury and reduced decay. Analysis of flavor pathway enzyme activity and gene expression was completed and submitted for publication. Strawberry breeding lines were evaluated by a USDA-ARS sensory panel, as well as sugars, acids and volatiles. Changes of volatiles, sugars and acids, and sensory over the harvest season were evaluated for two lines of blueberries, strawberries and tomatoes. Blueberries from a breeding program of the University of Florida were evaluated by a trained taste panel. This project was combined with another project and has completed the OSQR process. Significant Activities that Support Special Target Populations Work on tangerine hybrids will soon result in release of new fruit varieties. This will benefit citrus fresh fruit growers on small rural farms. Accomplishments 01 Effect of Huanglongbing Disease on Orange Juice Flavor: Huanglongbing (H is a devastating disease for the citrus industry. In addition to debilitating trees, fruit quality was anecdotally reported to be affecte but no chemical or sensory studies had been done. ARS researchers in Winter Haven, FL conducted research to determine whether fruit harvested from HLB-affected trees would impact fruit and juice quality. It was sho that only fruit that were severely affected by the disease imparted a negative flavor to the juice. When fruit with normal appearance, harvest from HLB-affected trees were juiced, the juice flavor was not different from juice made from fruit harvested from healthy trees. It is important to the citrus processors to now know that they only need to sort out symptomatic fruit (small, green and lopsided fruit) from their processin line to maintain juice quality. Studies are now ongoing to determine threshold levels of HLB-induced off-flavors in normal juice. 02 Quality of Tangerine and Orange Juices: Some orange and tangerine fruits that may not be appropriate for the fresh fruit market, but have good flavor, may be successful as a juice product. ARS researchers at Winter Haven and Fort Pierce, FL conducted a study over the season on one orang one tangerine and one orange-tangerine hybrid line. The Navel orange exhibited delayed bitterness, while the tangerine line showed some evidence of delayed bitterness 24 hours after juicing and after freezing the juice while the hybrid did not. The delayed bitterness phenomenon ma determine the suitability of some citrus varieties for juice products. 03 Inheritance of Tangerine Quality: Knowing inheritability of components o quality is important for the breeder to select parents in a breeding program. In a tangerine breeding program, ARS scientists from Winter Hav and Fort Pierce, FL analyzed hybrids that had sweet orange in their parentage and found that they showed a distinct flavor profile, with mor fruity ester and orangey sesquiterpene aromas. Hybrids of tangerine line had more aldehydes and less aroma volatiles in general. Overall, hybrids with sweet orange in their background were described as having more �floral� and �orange� flavor. 04 Internal Flavor Injury of Tomato Due to Chilling: Chilling tomato fruits causes an internal chilling injury that results in a reduction of aroma for which the mechanism is not known. A study on enzymes in the pathway certain important (aldehyde) tomato aroma compounds, which decrease due chilling, was conducted by ARS scientists at Winter Haven, FL and showed that the activities of most enzymes that produce these aromas were reduc and sometimes the genes that code for those enzymes were downregulated, but not in all cases.