UGA Variety Trial Quality Report 2022–2023 Crop Season

Each season the University of Georgia, 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 (VOVRC), and once they are harvested and dried, they 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 2022–2023 growing season, as well as compares the performance of each variety over the past three growing seasons.

Materials and Methods

There were 50 onion varieties analyzed as part of the 2022–2023 variety trial. Each variety was grown at the VOVRC in quadruplicate plots. Harvested onions from each plot were dried and submitted to the lab individually. Cores taken from 10 onions within each replicate were composited and pressed to collect the onion juice, 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 2022–2023 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 trials, the pyruvic acid (pungency) content ranged from 3.6–6.0 µmol/ml, which is a decrease of 13% compared to the past growing season. Lachrymatory factor ranged from 2.2–4.8 µmol/ml, which was a decrease of 32.5% compared to the last season. Finally, methyl thiosulfinates ranged from 3.1–18.1 nmol/ml which was a slight increase of 8% compared with the past two growing seasons.

Overall, the flavor quality of the variety trial onions was significantly improved as compared to the past few seasons. This could be attributed to the wetter growing season, which may have leached more sulfur after bulb initiation. The cumulative variety flavor quality rankings are also provided below for this year’s data, 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