CHEMICAL, GENETIC AND CONSUMER PROFILING OF HEIRLOOM TOMATOES - THE UNDERLYING CHEMISTRY OF A GREAT TASTING TOMATO
Location: Plant Genetic Resources
Project Number: 1910-21000-019-21
Specific Cooperative Agreement
Start Date: Aug 01, 2012
End Date: Jul 31, 2013
We will screen flavor chemical composition and conduct consumer evaluation (taste tests) for 27 heirloom varieties of tomato. Fruits will be brought to the laboratory for physicochemical, sensory, and consumer preference measurements. Flavor is one of the most highly demanded consumer traits of tomato at present, and the lack of flavor is one of the most commonly heard complaints associated with modern varieties of tomato.
Previously 27 heirloom varieties of tomato were evaluated and this project will complete the evaluation of another 27 heirloom varieties to give a dataset for 74 heirloom tomatoes. Since flavor is the major concern of fresh market tomato, germplasm used is primarily from fresh market tomatoes.
Tomato seeds were obtained from Seeds of Change (Santa Fe, NM), Totally Tomatoes (Randolph, WI) or Victory Seed Co. (Molalla, OR). Most varieties selected are described as heirloom, open-pollinated. A few modern hybrid varieties Tasti-Lee, Florida 47) were also selected for comparison. Plants will be grown in the field at the University of Florida North Florida Research and Education Center-Suwannee Valley in the spring or fall seasons. Plants will be grown using commercial Florida protocols, i.e., raised beds with plastic mulch, drip irrigation and staking. Depending on the variety, a minimum of 50 plants separated into six plant randomized blocks will be grown.
Volatile compound identification is determined by GC-MS and coelution with known standards (Sigma-Aldrich, St. Louis, MO). We routinely quantify ~60 volatiles (Table 1), including all of the compounds believed to significantly contribute to tomato flavor. Sugars, acids, glutamic acid and Brix are determined as described in Vogel et al. (2010). Samples are analyzed using citric acid, malic acid, glutamic acid and glucose/fructose analysis kits (R-Biopharm, Marshall, MI, USA) according to the manufacturer’s instructions. Average values are calculated from five biological replicates. Soluble solids ('Brix) are measured using a handheld refractometer.
Fully ripe fruit are harvested for taste panels. Any fruits with defects are culled out. A random subset of the fruit is selected for biochemical analysis. A group of 100 tomato consumers are recruited for each season to evaluate all the varieties. All panelists go through a training session to familiarize them with the scaling and procedures. Tomatoes are sliced into wedges (or in halves for grape/cherry types) and each panelist is given two pieces for evaluation. Where appropriate, color differences can be masked with artificial lighting. Panelists rate their overall liking as well as their liking for the texture on a hedonic scale. This scale assesses the liking for tomatoes in the context of all pleasure/displeasure experiences: 0=neutral, -100=strongest disliking of any kind experienced, and +100=strongest liking of any kind experienced. Panelists then rate their perceived intensities of overall tomato flavor, sweetness, sourness, saltiness and umami. This scale assesses taste and flavor sensations in the context of all sensory experience: 0=no sensation, 100=strongest sensation of any kind experienced. The scales were devised to provide valid comparisons across subjects and sessions and the method has proven to be highly reproducible in comparing many varieties over multiple seasons.