Retail Produce Display Lighting

Light is one of the major factors responsible for the deterioration of fresh and dehydrated produce.

When fruits and vegetables are processed and stored, their quality is compromised by lipid oxidation, a chemical reaction that affects the color, flavor, odor, and nutritional value of the food.

If factors such as exposure to light and heat are controlled, the rate of photo-oxidation can be reduced and nutrient loss can be prevented.

"Greening is strongly affected by the cumulative effects of light quality, duration, and intensity."

"As a rule, fluorescent light above 75 foot-candles exposure at room temperature (68° F) for three to five days will start the greening process; however, light intensity as low as 5 foot-candles and light durations as short as 12 hours can cause greening of a few potato varieties such as Kennebec."

"In potato tubers, the greening is a sign that there may be an increase in the presence of glycoalkaloids, especially the substance solanine."

"Unlike chlorophyll, light is not needed for solanine formation, but, with light, glycoalkaloid formation is increased."

"When potato tubers are exposed to light, the solanine content in the peel may increase as much as ten times. Toxic levels for people are about one-hundredth of an ounce for a 200-lb person."

"But, with UV light-exposed whole tubers in which solanine had increased ten-fold, only two pounds could cause a reaction. Potentially high levels for a 100-lb and 50-lb person would be 16 and 8 ounces of a fully green potato, respectively."

"Potatoes containing more than 0.1 percent solanine (.01 oz / 10 oz potato) are considered unfit for eating."

"The green indicates an increase in the presence of glycoalkaloids, especially, in potato, the substance 'solanine' (see structure). When the potato greens, solanine increases to potentially dangerous levels."

"Unlike chlorophyll, light is not needed for solanine formation but is substantially promoted by it."

"As a rule, fluorescent light above 75 foot-candles exposure at room temperature, 68F, for three to five days will start the greening process. Light intensity may be as low as 5 foot-candles and light durations as short as 12 hours can cause greening of a few potato varieties such as Kennebec."

"It is a less commonly known fact that potatoes produce compounds called glycoalkaloids that have been shown to be toxic to both man and to animals."

"At high enough levels the glycoalkaloid found in potatoes known as solanine can cause irritation of the gastrointestinal tract, impairment of the nervous system, and it is believed that they can cause teratogenic or birth defects. Neurological signs can include ataxia, convulsions, coma, muscle weakness, and involuntary urination."

"Exposure to light causes potato tubers to green, due to the conversion of amyloplasts to chloroplasts, and accumulate toxic steroidal glycoalkaloids. The two major alkaloids, comprising 95% of the total (TGA), are a-solanine and a-chaconine. The consumption of potatoes with high TGA concentrations can cause illness and even death."

"Glycoalkaloids are toxic to humans; the lethal dose is considered to be 3-6 mg per kg body mass."

"On exposure to light the potato tuber will produce elevated levels of these protective glycoalkaloids, with the highest levels being in the sprouts as they emerge from the tuber."

"In a recent paper delivered at a Pediatrics Congress (Symposium of Congential Malformations) held in Barquisimeto-Lara, Venezuela, Ruben Dario Cortez said that there is a relationship between the consumption of damaged and green potatoes, and neural tube defects."

"The concern with greened potatoes should not be the color but the fact that solanine, a potentially toxic alkaloid, develops in the same area along with the chlorophyll. Greened potatoes, therefore, are often higher in solanine than those not greened. The bitter taste associated with greened potatoes is caused by the solanine, not the chlorophyll."

"Potatoes also develop more greening under light exposure, when temperatures are higher, e.g., 68 °F versus 41 °F. Retail packaging can also contribute to increased greening. Consumers want to be able to view produce prior to purchase. Packaging materials have changed over time from burlap and other opaque materials to transparent bags which allow exposure to light during retail storage and display."

Definition: Poisoning caused by consumption of green tubers and/or new sprouts of the potato plant.

Poisonous Ingredient: solanine (very toxic even in small quantities).