UGA Variety Trial Quality Report 2023–2024 Crop Season

Each season the UGA, Agricultural and Environmental Services Laboratories (AESL) evaluates the flavor-associated compounds in the short-day onions grown in the variety trial. These onion varieties are submitted by the participating seed companies, grown at the Vidalia Onion and Vegetable Research Center, and once harvested and dried, are submitted to the AESL for analysis of the pungency-related compounds: pyruvic acid, lachrymatory factor (LF), and methyl thiosulfinates.

Due to the association of Vidalia onions with low pungency and sweet flavor, this annual evaluation provides useful information about the relative flavor quality of these onion varieties. Furthermore, results are used to evaluate Yellow Granex varieties before officially qualifying them to be grown as sweet Vidalia onions in the region.

This publication summarizes the flavor analysis results from the 2023–2024 growing season, as well as comparing the performance of each variety over the past three growing seasons.

Materials and Methods

There were 53 onion varieties analyzed as part of the 2023–2024 variety trial. Each variety was grown at the research center in quadruplicate plots. Harvested onions from each plot were graded, dried, and submitted to the lab individually. Cores taken from 10 onions within each replicate were composited and pressed to collect the onion juice, which was analyzed following procedures described in Kim et al. (2017).

Results and Discussion

The following tables compare the concentrations of flavor-associated compounds in onions grown as a part of the 2023–2024 variety trial. It should be noted that as the three measured parameters decrease, the onions are considered to have a superior flavor quality. In this year’s Yellow Granex variety trials, the pyruvic acid (pungency) content ranged from 2.5–6.0 µmol/ml, which is a decrease of 12% compared to the past two growing seasons. Lachrymatory factor ranged from 0.5–2.1 µmol/ml, which was a decrease of 83% compared to the last two seasons. Finally, methyl thiosulfinates ranged from 2.7–16.6 nmol/ml which was a decrease of 79% compared to the previous growing seasons.

Overall, the flavor quality of the variety trial onions was significantly improved as compared to the past two seasons. This could be attributed to the increased rainfall prior to bulb initiation, which may have leached more sulfur from the soil. This year’s data on the cumulative variety flavor quality rankings are also provided along with the average rating of Yellow Granex onion varieties grown over the past three seasons.

For additional information regarding the performance of a given variety, please contact your Extension agent or the Vidalia Onion and Vegetable Research Center. We would like to thank the participating seed companies as well as the Vidalia Onion Committee for their support of this trial.

Reference

Kim, H.-Y., Jackson, D., Adhikari, K., Riner, C., & Sanchez-Brambila, G. (2017). Relationship between consumer acceptability and pungency-related flavor compounds of Vidalia onions. Journal of Food Science, 82(10), 2396–2402. https://doi.org/10.1111/1750-3841.13915

Tables