Potato researchers aim to decrease the risk that the crop will sustain bruise-related “cutting black” during storage.

Pressure bruising is among the industry’s leading causes of lost revenue, especially in the fresh potato market, according to a news release from the University of Idaho. Pressure bruises affect 10-20% of potatoes coming out of storage.

A $42,470 grant from the Northwest Potato Research Consortium is funding the work by UI Extension potato post-harvest physiologist Gustavo Teixeira, UI Extension potato storage specialist Nora Olsen and USDA Agricultural Research Service research plant physiologist Munevver Dogramaci.

The researchers started a study testing three compounds for their potential to block bruised tissue from darkening. Though the products are not labeled for use on potatoes in the U.S., the work could lead to more in-depth studies that prompt registering them for potatoes.

“That is a huge potential for these products if we get good results,” Teixeira said.

Potatoes are firm when they enter storage but lose water through respiration. After eight or nine months, the weight of the pile can start to flatten those near the bottom. Once the potatoes are removed and exposed to oxygen, bruises usually darken within four days and make them less desirable.

The goal is to control the cutting black, not the pressure bruise, Teixeira said.

“We are inducing the pressure bruise, and at the end of storage after about eight months, we are going to apply products,” he said.

Researchers on Sept. 19 placed concrete blocks on piles of Russet Burbank potatoes to simulate typical storage conditions.

The potatoes will be stored for eight months. For five days before coming out of storage, some will be treated with 1-Methylcoclopropene (1MCP), nitric oxide or diphenylamine (DPA) in gas form.

DPA and 1MCP are both widely used in the U.S. apple and pear industries — DPA to control browning resulting from superficial scald, and 1MCP to help extend shelf life, according to the university. In Europe, 1MCP also is used to reduce potato shrinkage.

Bruises darken as part of the process plants use to heal wounds. Stimulating wound healing is a function of ethylene, one of the first hormones a vegetable produces when it is damaged. Teixeira and his team intend to apply 1MCP to block ethylene action in bruised potatoes.

DPA is an antioxidant, which can prevent the initiation of browning by reacting with oxygen, according to UI.

A control group of potatoes exposed to pressure bruise using the concrete blocks will remain untreated, as will a group that will not be subjected to simulated pile pressure.

Researchers plan to spend about three months evaluating data, starting in early May.

If their tests produce encouraging results, they’ll likely test combinations of the compounds in a follow-up experiment, according to UI.