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Trial rates garlic-handling practices

Storing garlic correctly is critical to producing the best-quality product.

Kara Lynn Dunn

June 8, 2023

5 Min Read
Garlic is pictured here with tops on in layers on a wagon in a high tunnel
EVALUATING BEST PRACTICES: Garlic is pictured here with tops on in layers on a wagon in a high tunnel. Cornell Extension vegetable specialist Christy Hoepting recently conducted a garlic curing and storage trial that compared 21 unique curing and storage practices. Photos by Christy Hoepting

Storage crops require specific handling protocols to ensure product quality, and New York garlic growers are eager to know what works best.

With funding from the New York Farm Viability Institute, Cornell Extension vegetable specialist Christy Hoepting recently conducted a garlic curing and storage trial that compared 21 unique curing and storage practices.

Commercially grown German hard neck garlic was mechanically undercut, harvested by hand and quickly divided into equal 100-bulb samples. After harvest, participating growers received five mesh bags with 10 garlic plants of equal quantities of bulb sizes and colors, ranging from white through pink.

The growers handled the samples just as they did the rest of their garlic, through curing and storage. Tops were left on or trimmed to length per each grower’s usual practice. A temperature and relative humidity data logger was secured inside one sample bag for each entry.

The plants or bulbs were hung, boxed, layered or piled in different configurations with highly variable temperature and ventilation. Locations included barns or sheds, high tunnels or greenhouses, or outside.

The post-curing and storage samples were collected Oct. 1-9 for evaluation. Data were recorded on bulb density, color, firmness, wrapper leaf tightness, shrinkage and overall quality. Bulbs with any sign of fusarium, other rot or eriophyid mites were culled from the trial. Bulbs with black surface mold only on the outer wrapper leaves were recorded but not culled.

Clove samples were stored in paper bags at room temperature (warm and dry conditions) for 118 days and in plastic bags in a refrigerator (cool, humid conditions) for 72 days to evaluate clove color and firmness, and visual evidence of fusarium.

Best and worst

Two of the top three highest-ranking treatments were garlic cured in a high tunnel covered with shade cloth, with sides rolled up — and doors open for natural, passive ventilation. They were then stored in a pile five layers deep just inside an open door of a steel barn, Hoepting explains.

“The only difference between the two treatments was that one had the tops on and the other was topped to leave 1.5-inch neck. They were cured and stored at the same farm,” she adds. “The temperatures during curing were some of the hottest in the trial, with an average of 75 degrees F and a maximum of 123 degrees. The relative humidity had more hours at less than 40% than most other treatments and averaged 65%.”

During storage, the temperatures did not drop below 50 degrees and did not exceed 90 degrees and averaged 65 degrees. The relative humidity during storage did not drop below 45% and averaged 76%.

The treatment cured with the tops on had the least shrink and densest bulbs out of storage; above-average, white-colored bulbs; tight wrapper leaves; and overall highest bulb quality scoring. This treatment was evaluated with a below-average 8% rate of fusarium infection and 4% of bulbs with eriophyid mites. The fusarium average was 6% following cold storage of the cloves, but an above-average 27% rate of clove coverage after storage at room temperature.

Across the trial, clove coverage with fusarium after storing in paper at room temperature was three times higher (average 21%) than cloves stored in plastic under refrigeration (average 7%), although there were no significant differences among these treatments.

The researchers intentionally established the worst treatment by placing it in a damp basement with no ventilation. As expected, it had the highest rate of fusarium and black mold, and the softest bulbs.

The second-worst result experienced cooler temperatures and higher humidity, with wider swings in both, during both curing and storage.

This treatment had the highest shrinkage percentage, the lowest bulb density and the brownest bulbs. However, the bulbs were very firm with very tight wrapper leaves. The specific treatments for curing and storing were not available as the sample bag was returned without its label.

Ninety-one percent of the garlic cloves stored in warm and dry conditions in paper bags at room temperature — averaging 63 degrees and 41% relative humidity — for the evaluation of fusarium were infested with eriophyid mites. The mites were not detected in cloves stored in plastic bags in a refrigerator.

Should you top?

To determine whether, and to what extent, topping might affect quality, the researchers worked with two farms to compare untopped garlic to plants topped to 6 inches or a 1.5-inch neck before curing.

“We did not see any consistent differences between topping and not topping,” Hoepting explains.

Similarly, seven treatments with passive curing with no or only natural ventilation averaged better bulb quality than the seven treatments that were actively cured with fans or other mechanical ventilation.

The project produced a large amount of data that is still being analyzed to identify more specific postharvest factors for best results, particularly related to fusarium development under different conditions.

For now, Hoepting suggests, “If you are happy with the quality of your garlic, continue your usual practices. If your garlic has softer bulbs and looser wrapper leaves than you like, consider adjusting your curing or storage conditions.”

For more information, contact Christy Hoepting at 585-721-6953 or email [email protected]. Hoepting’s survey was conducted in collaboration with Cornell AgriTech plant pathologist Frank Hay.

Dunn writes from her farm in Mannsville, N.Y.

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