Retail Produce Display Lighting
Fruits and vegetables react in many different ways to light from artificial sources. The most significant category of products in the produce segment is root vegetables. Radishes, carrots, beets, turnips (rutabagas) and others will begin to green under the influence of visible and non-visible radiation from in-store lighting.
"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 ... birth defects."
Of critical importance is the potato category which produces toxic levels of the glycoalkaloid solanine during the greening process.
Glycoalkaloids are toxic to humans; the lethal dose is 3-6 mg per kg of body mass.
Improper display and lighting of potatoes contributes to accelerated greening and represents a substantial food safety and economic risk to food retailers and consumers.
Produce departments and farmers markets can protect the appearance and shelf life of organic and non-organic fruits and vegetables on display by using a low radiation light source like PROMOLUX lighting.
Fruit and Vegetable General Processing. Chapter 3: Deterioration Factors and Their Control. Mircea Enachescu Dauthy. FAO Agricultural Services Bulletin No. 119, Rome 1995. Read the full article here.
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.
Green Potatoes: the Problem and the Solution. Alexander D. Pavlista. Cooperative Extension, Institute of Agriculture and Natural Resources, University of Nebraska-Lincoln. G01-1437-A. Read the full article here.
"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 so lanine 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."
Greening Potatoes: The Problem. Alexander D. Pavlista. University of Nebraska-Lincoln’s Potato Education Guide.
"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."
Potato Glycoalkaloid Toxicity: Solanine. Andrew Montario. Cornell University. Read the full article here.
"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."
Potato Greening and Glycoalkaloid Accumulation. Everard Edwards. Abstract of Ph.D. Thesis for The Nottingham Trent University: The Accumulation of Chlorophylls and Glycoalkaloids in Stored Tubers.
"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. from the World Potato Congress Newsletter, July 1999. Read the full article here.
"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."
Greening of Potatoes. Wayne Vandre. University of Alaska Fairbanks. Read the full article here.
"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."
Potato : Green Tubers and Sprouts. Updated by Cherlin Johnson, M.D. Medical Encyclopedia, Medline Plus: A Service of the National Library of Medicine and the National Institutes of Health. Read the full article here.
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). Symptoms: hypothermia (lower than normal body temperature), paralysis, shock, fever, slowed breathing, dilated pupils, vision changes, stomach or abdominal pain, vomiting, diarrhea, slow pulse, headache, delirium, loss of sensation, hallucinations.