The Science Behind the Spud: Why Grocery Stores Are Tucking in Potatoes at Night
Grocery stores are tucking in potatoes at night to block light exposure, a practice rooted in science. This simple act prevents the production of chlorophyll and a bitter toxin called solanine, preserving quality, ensuring customer safety, and reducing costly food waste.
It’s a common sight during late-night shopping or early morning restocking: grocery store employees carefully covering produce displays. While it may seem like a simple tidying ritual, the practice of tucking in potatoes at night is a crucial step rooted in plant science, aimed at preventing spoilage, preserving quality, and reducing significant financial loss from food waste.
Preventing Greening and Toxin Formation
The primary driver behind covering potatoes is to block them from prolonged exposure to light, whether from the sun or a store’s fluorescent fixtures. When potatoes are exposed to light, they begin a process of photosynthesis, producing chlorophyll, the same pigment that makes leaves green. While the green color itself is harmless, its presence is a clear indicator of a more serious issue.
“The greening of a potato signals that conditions have been right for the formation of something more concerning: a class of chemical compounds called glycoalkaloids,” stated Dr. Nora Olsen, a Professor and Potato Specialist at the University of Idaho’s Department of Plant Sciences. The main glycoalkaloid in potatoes is solanine.
In small amounts, solanine gives potatoes a slightly bitter taste. However, if concentrations become high enough, it can cause gastrointestinal distress in humans, with symptoms including nausea, vomiting, and diarrhea. While a person would need to consume a very large quantity of highly greened potatoes to experience severe effects, retailers prioritize customer safety and satisfaction by preventing the process from starting.
“It’s a quality control measure that directly impacts consumer safety and perception,” according to a report on post-harvest handling from Cornell University’s College of Agriculture and Life Sciences. The report emphasizes that light exposure, combined with warmer temperatures, accelerates the production of these compounds. Covering the potatoes effectively “turns off the lights,” halting the chemical reaction.
The Economic Case for Tucking in Potatoes at Night
Beyond safety and quality, covering potatoes is a sound business decision. Produce departments operate on thin margins, and spoilage—known in the industry as “shrink”—is a major source of lost revenue. Potatoes that turn green are often unsellable, leading directly to food waste.
According to data from the non-profit organization ReFED, which studies food loss, retail food waste in the United States accounts for billions of dollars in lost profits annually. Fresh produce, including potatoes, represents a significant portion of this loss.
Calculating the Cost of Spoilage
- Direct Loss: Every potato that turns green and must be discarded is a direct loss of inventory.
- Labor Costs: Employees must spend time culling the spoiled potatoes from displays, a task that takes them away from other duties like stocking shelves or assisting customers.
- Consumer Confidence: Consistently seeing green or poor-quality potatoes can erode customer trust in a store’s produce section, potentially driving them to competitors.
“Simple, low-cost interventions can have a major impact on a store’s bottom line,” said a spokesperson for the National Grocers Association. “Covering potatoes is a textbook example of an inexpensive practice that protects inventory, reduces waste, and maintains the high-quality appearance that shoppers expect.”
Best Practices for Retailers and Consumers
The industry standard involves using opaque tarps or blankets to ensure no light penetrates the potato display overnight. This practice is most common for loose potatoes sold in open bins, which are most susceptible to ambient light. Bagged potatoes offer some protection, but even they can green if left under intense display lighting for extended periods.
Experts advise that consumers can apply the same logic at home. The U.S. Department of Agriculture (USDA) recommends storing potatoes in a cool, dark, and well-ventilated place, such as a pantry or cellar. Storing them in a paper bag can also help block light while allowing air to circulate. It is not recommended to store potatoes in the refrigerator, as the cold temperature can cause the starch to convert to sugar, resulting in a sweet taste and undesirable browning when cooked.
If a potato does have minor green spots, they can be safely removed. “For potatoes that are only slightly green, you can simply peel the skin and cut away the green-tinted flesh before cooking,” advised Dr. Olsen in a University of Idaho publication. However, if a potato is extensively green or has a bitter taste after cooking, it should be discarded. The nightly ritual of covering potatoes is more than just store maintenance. It is a critical, science-backed procedure that ensures the potatoes on store shelves are safe, high-quality, and appealing, ultimately benefiting both the retailer’s finances and the consumer’s dinner table.
