When Green is Not Good

July 24th, 2012 | Simcha Weinstein | Comments Off on When Green is Not Good

If you’re overseeing and managing a produce department, you understand that your product is deteriorating every moment that it is on the rack. Time is not friendly to fresh food, and your job is to take a live food that has been separated from its life force (soil, sun, and water) and make it look appealing and desirable to shoppers. When viewed in this light, it captures the high level of intensity and skill that’s involved in creating and maintaining an attractive and effective produce department.

Of all the products that you carry, potatoes may be the single item that most challenges our ability to sustain a product once it has been harvested. A question that I hear a fair amount, and one that certainly qualifies as an FAQ categorization is “how do I keep potatoes from turning green?” This is indeed a problem, and one that can quickly sour a customer to your otherwise superb produce offerings. So let’s look at what causes the greening, and also what steps we can take to at least reduce the problem, and perhaps outright solve it all together.

It’s important to understand what creates the problem in the first place. Exposure to light, whether in the field, in storage, on the shelves, or at a home, can cause “greening” in potatoes. It’s actually a very natural process and occurs because of the formulation of chlorophyll. Chlorophyll is primarily found in leaves and near the surface of the potato and is responsible for a plant’s ability to make food through photosynthesis.

Greening is strongly affected by the cumulative effects of light quality, duration, and intensity. Chlorophyll is green because it reflects green light, while absorbing red, yellow, and blue light. Under green lighting practically no greening will occur, while very little occurs under blue lights. Fluorescent lights (which are mostly used) induce more greening than incandescent lighting, although we do not endorse incandescent lighting, and the manufacturing of incandescent bulbs are basically on their way out. Incandescent lighting is far less energy efficient than fluorescent lighting, consuming about 75% more energy. The incandescent bulbs do release considerably less ultraviolet light than fluorescent bulbs which increases greening. From an environmental perspective, however, fluorescent lighting is the far better choice and what we recommend, but strictly as a matter of fact concerning the issue of greening potatoes, incandescents fair better. Of course, from an ecological perspective LED lighting is the way to go.

Obviously, the less light directly hitting the potatoes, the less likely they are to green. But temperature can play a role as well. The temperature during light exposure is a key factor since greening is an enzymatic response and enzyme activity increases as temperature increases. There is no greening when potatoes are kept at 40° F or below. It’s important not to store them below 40° as cracking may occur if potatoes get too cold. Greening is most rapid at temperatures between 65-70° F. At temperatures higher than 70° F, the greening actually slows down, but again there is a trade-off as your potatoes are much more likely to decay and turn bad at higher temperatures. On average, typical grocery store lighting will induce greening within a week if the potatoes are not refrigerated or kept cool.

There are several steps that can be taken to minimize the greening process:

1) Turn the lights off at night (at least over your potato display) when you put your department “to sleep”. Cover the potatoes with burlap.

2) Locate your potato displays in areas of low light if possible; and keep away from windows and strongly lit areas.

3) Do not use spotlights on your potato display.

4) Keep your potatoes cool. Displaying at 40-42° F will not harm your potatoes and will dramatically reduce the greening process. For many, this may be the one key step that reduces this issue.

One last consideration to discuss about green potatoes – are they poisonous, or can they make you ill if you eat them? By itself, chlorophyll is not harmful. As the levels of chlorophyll increase, however, it’s an indication that levels of solanine (responsible for the bitter taste in a green potato) have increased as well. Potatoes naturally produce small amounts of solanine as a defense against insects, but the levels increase with prolonged exposure to light and warm temperatures. It is the occurrence of solanine that can cause illness when eating green potatoes. Studies indicate that a 100-pound person would have to eat about 16 ounces of a fully green potato to get sick from solanine. That is the weight of a large baked potato. Solanine formation usually occurs in the skin and is rarely found more than 1/8 of an inch deep into the potato.

There is no doubt that greening potatoes are an issue. Unfortunately, there is no one silver bullet remedy that eliminates the problem. There are, however, some effective steps that can be taken to minimize this issue, and even though there may be a few trade-offs to consider as you move forward, it is possible to have beautiful “non-green”, healthy potatoes on display in your produce area.

Good luck with your potato adventure, and even though it’s what we’re mostly about conceptually – going green is not always the way to go.