UGA Variety Trial Quality Report 2021–2022 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 2021–2022 growing season, as well as compares the performance of each variety over the past three growing seasons.

Materials and Methods

There were 53 onion varieties analyzed as part of the 2021–2022 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 2021–2022 variety trial. It should be noted that as the three measured parameters decrease, the onions are considered to have a more superior flavor quality.

In this year’s trials, the pyruvic acid (pungency) content ranged from 3.7–7.4 µmol/ml, which is an increase of 32% compared to the past two growing seasons. Lachrymatory factor ranged from 2.9–6.7 µmol/ml, which was an increase of 43% compared to past two seasons.

Finally, methyl thiosulfinates ranged from 8.0–42 nmol/ml, which was a slight increase of 8% compared with the past two growing season. Overall, the pungency of the variety trial onions was approximately 30% higher as compared to the past two seasons. This could be attributed to the hotter, drier growing season.

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