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ARS Home » Southeast Area » Fort Pierce, Florida » U.S. Horticultural Research Laboratory » Citrus and Other Subtropical Products Research » Research » Research Project #445765

Research Project: Quality Evaluation of Citrus Hybrids Tolerant to HLB for Juice Processing

Location: Citrus and Other Subtropical Products Research

Project Number: 6034-41430-007-020-R
Project Type: Reimbursable Cooperative Agreement

Start Date: Feb 12, 2024
End Date: Jun 30, 2024

The overall objective is to identify citrus scions/hybrids tolerant to HLB that produce fruit that can be processed in juice, for either orange or grapefruit juice. Specific objectives include: 1. Define orange and mandarin flavor, as well as off-flavor using sensory evaluation and chemical analysis 2. Identify scions/hybrids tolerant to HLB and producing fruit and juice having orange flavor 3. Identify hybrids that have a tendency to develop delayed bitterness after juicing

The breeder will select no more than 50 hybrids per season for quality evaluation. Ten to 25 fruits will be brought to the laboratory for processing. A standardized processing method will be used. Fruit will be manually washed, sanitized and let air dry. Fruit will be separated into 4 batches to account for 4 biological replications and juiced using the Zulay press. Juice will then be pasteurized, one batch following standard commercial practices (90-91 °C for 15-20 seconds), or 75 °C for 10 min to induce fast formation of the bitter compounds limonin and nomilin. Juice pasteurized following commercial practices will be stored at -20 °C until ready for sensory evaluation and chemical analysis. A trained panel comprised of six to ten panelists, a core of them having taste orange juice each season for over 10 years, will meet to agree on methods of evaluation and descriptors before each season. They will practice on juice from the previous year to make sure they agree on the terminology and reference standards. Suggested descriptors: sweet, sour and bitter (reference standards sucrose (8%), citric acid (0.2%) and quinine hydrochloride (11.5 ppm) in solution); orange, mandarin and grapefruit flavor (reference standard: juice from minimized pasteurized processing); off flavor including “poncirus” (reference standard: peel from poncirus fruit, stored frozen at -80 °C), cardboard, metallic, and others to be discussed with the panel. Samples will be served as 45 mL in 4 oz cups with lids, at 16 °C. Sensory evaluation will be performed in isolated booths under red lighting and positive air pressure to minimize odors from outside. Samples will be evaluated in duplicate as much as sample volume allows. Sample presentation design will be randomized using Compusense® Cloud, which will also be used for data recording. Samples pasteurized for 10 minutes will be analyzed for titratable acidity, soluble solids, limonin and nomilin. Volatiles will be analyzed from the juice tasted by the panel. For non-volatile analysis, juice will first be centrifuged to remove any pulp and pectin that would interfere with refractometer reading. Titratable analysis will be performed with a Metrohm autotitrator equipped with a 32-cups sample changer; soluble solids will be read with an ATAGO RX-5000¿ refractometer; juice for limonoids analysis will be passed through a C-18 filter, and analyzed by HPLC-MSMS; volatiles will be analyzed by GC-MS using the SPME sampling technique. All samples will be analyzed keeping the 4 biological replications. Data will be collected and statistically analyzed using SAS, JMP or XLStats.