Food Safety and Retail Display Lighting
"...spoiled food is not just an issue of quality, it is also often a question of food safety."
The field of food safety has become an increasingly important issue for governments, manufacturers, food retailers and consumers. One component of food safety is the impact of light on fresh foods.
Light and temperature damage food presentations through discoloration and oxidation, the development of foul smells and changes in taste, causing a significant reduction in the shelf life of the food product and jeopardizing food safety.
"Probably the single most important factor in preventing microbial food spoilage is temperature."
The food safety references on this site refer to research papers and articles that share the common theme of how food safety and shelf life are connected to holding temperatures. A small variation in holding temperature can dramatically increase the bacterial count on food products to levels that are unhealthy and unsafe.
"...surveys of retail outlets have shown product surface temperatures to be 4 to 25° F higher than the temperature of the retail case."
For example, healthy and fresh seafood has on average a bacterial count of 2,000 microorganisms per square inch. When seafood is not kept at the right temperature, the bacterial count can increase to several million in just four hours, rendering that food unsafe for consumption. Researchers have found evidence that the light source used can make a very significant difference on the surface temperature of displayed food.
Studies at Texas A & M have shown that the air just 2 inches above a bed of ice in an unrefrigerated display case may be at room temperature. Similarly, researchers at Virginia Tech have recorded as much as a 25° F difference between the bottom and the top of a stack of flounder filets piled on ice.
This is a very dangerous condition when you realize that the shelf life of fish filets is reduced by three days if the temperature of the product is increased from 32° F to 34° F. If a 2° F increase can make such a difference in the shelf life, imagine the risk factor when the surface temperature is 25° F higher than the appropriate temperature for seafood, which is 32° F or lower.
"With UV light-exposed whole [potato] tubers in which solanine had increased ten-fold, only two pounds could cause a reaction."
The food borne illnesses are not limited to meat, seafood and dairy products but they include such staple foods as potatoes.
"...solanine can cause irritation of the gastrointestinal tract, ... convulsions, coma, muscle weakness, and involuntary urination."
There is considerable research available that shows that potatoes when exposed to light develop solanine, which is toxic and very harmful to the immune system.
Food Safety Studies
Color and Oxidative Properties of Irradiated Beef. Donald Kropf and Curtis Kastner. K-State Research and Extension Program Updates and Highlights. MF-2313, January 1998. Kansas State University Agricultural Experiment Station and Cooperative Extension Service.
"Meat and poultry products are primary sources of foodborne illness worldwide."
"A report by the Council for Agricultural Science and Technology has estimated that foodborne diseases in the United States caused by pathogenic bacteria may cause as many as 9,000 deaths each year and 6.5 million to 33 million cases of diarrheal disease. The annual economic losses associated with foodborne disease may be as large as $5 billion to $6 billion."
Retail Seafood Temperature Control. Robert J. Price, Ph.D. Seafood Network Information Center. Department of Food Science & Technology, University of California, Davis. UCSGEP 90-5 August 1990.
"Temperature control is the most effective way to slow bacterial growth, delay seafood spoilage, and maintain seafood quality."
"Bacteria are the major cause of seafood spoilage. Millions of bacteria are on the surface, on the gills, and in the gut of living fish and shellfish. After harvest, bacteria invade the flesh of fish and shellfish through the gills, along blood vessels, and directly through the skin and belly cavity lining. These bacteria grow and multiply in the flesh. They produce the 'fishy' smelling and tasting compounds associated with old seafood. If food-poisoning bacteria are present, they can multiply and cause illness."
Food Safety: Federal Oversight of Seafood Does Not Sufficiently Protect Consumers. Report to the Committee on Agriculture, Nutrition, and Forestry, US Senate. January 2001. GAO United States General Accounting Office, Washington, D.C. 20548
"Contaminated food products cause an estimated 76 million foodborne illnesses annually in the United States, according to the Centers for Disease Control and Prevention (CDC). Seafood (finfish and crustaceans) represented about 15 percent of the documented foodborne illness outbreaks in the United States, according to CDC's data for 1997, the latest year for which such data are available. Seafood-related illnesses could result in a variety of problems, ranging from mild gastrointestinal discomfort to neurological damage or death."
"In 1999, FDA analyzed a total of 769 domestic seafood samples (of which 473 were analyzed for the presence of biological hazards) and found that 94, or 20 percent, contained hazards such as salmonella, listeria, and scombrotoxin. FDA officials said that, unlike meat and poultry, seafood is affected by a variety of microbiological and chemical pathogens and that there is no single widespread bacterial hazard, such as salmonella, in meat and poultry."
"While all seafood may not be affected by a single widespread hazard, such as salmonella, some species of seafood are often affected by specific hazards. For example, tuna, mahi-mahi, and bluefish are likely to produce histamines when not kept at the proper temperature. The resulting illness - scombroid poisoning - causes nausea, diarrhea, sweating, and headaches. Similarly, subtropical and tropical fish, including grouper and snapper, accumulate a naturally occurring toxin, called 'ciguatoxin.' Ciguatera poisoning involves a combination of gastrointestinal neurological and cardiovascular disorders. Scombrotoxin and ciguatoxin, which cannot be eliminated by cooking, contributed to over 88 percent of all confirmed food illness outbreaks for seafood reported by CDC in 1997."
Fruit and Vegetable General Processing. Chapter 3: Deterioration Factors and Their Control. Mircea Enachescu Dauthy. FAO Agricultural Services Bulletin No. 119, Rome 1995.
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.
FoodHandler Safety Byte 6. Why Does Food Spoil? Lacie Thrall. Food Safety.
"It is important to remember that some of the conditions that accelerate spoilage, such as inappropriate temperature and moisture control, also encourage the growth of pathogenic microorganisms that cause foodborne illness. Consequently, spoiled food is not just an issue of quality, it is also often a question of food safety. "
The Color of Meat and Poultry. Food Safety and Inspection Service, United States Department of Agriculture.
"Exposure to light and oxygen causes oxidation to take place, which causes the breaking down of color pigments formed during the curing process. Chemicals in the cure and oxygen, as well as energy from ultraviolet and visible light, contribute to both the chemical breakdown and microbial spoilage of the product."
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.
"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.
"With UV light-exposed whole tubers in which solanine had increased ten-fold, only two pounds could cause a reaction."
"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, 68° F, 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.
"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."
Glycoalkaloids. from the World Potato Congress Newsletter, July 1999.
"Glycoalkaloids are toxic to humans; the lethal dose is considered to be 3-6 mg per kg body mass."
The Influence of Storage and Display Conditions on the Retail Properties and Case-life of Display-ready Pork Loin Roasts. L.E. Jeremiah & L.L. Gibson. Meat Science, vol. 47, no. 1/2 (1997): 17-27.
"Since cold-tolerant bacteria capable of spoiling meat continue to grow to at least -3° C, their growth on unfrozen meat can not be prevented and as the meat temperature increases the growth rate of the bacteria also increases."
"Increasing the storage temperature by only a degree or two has a profound effect on product storage life in any type of preservative packaging utilized. Therefore, any temperature increase, above the optimum, produces a proportional decrease in storage life. For example, storage at commercial (2° C), as opposed to optimum (-1.5° C) temperatures reduces product storage life by 50% (Gill and Shand, 1993)."
"In addition, surveys of retail outlets have shown product surface temperatures to be 4 to 25° C higher than the temperature of the retail case (Holland, 1979), and a product surface temperature of 10° C was not uncommon under retail conditions (Greer, 1984)."
Improved Quality of Retail Beef Through Control of Bacterial Spoilage. G. Gordon Greer. Technical Bulletin 1984-13E. Lacombe, Alberta: Research Branch Agriculture Canada, 1984.
“The growth rate of a typical beef spoilage bacteria can double as the temperature of incubation increases from 1 to 5° C and can triple with a further increase to 10° C. Increased bacterial growth means reduced case life.”
“The actual surface temperature of steaks on retail display is much higher than that recorded at the blower thermometer. In this particular case, the blower thermometer indicated a temperature of -0.5° C while displayed steak surface temperatures were on the average about 8° C higher (7.3° C).”
“Another important consideration is the intensity and duration of display illumination. The display case in the studies described herein was illuminated with 150 watt incandescent, cool-beam floodlights to give a light intensity of about 80 foot-candles at the meat surface. Lighting was automatically timed to illuminate the display case for 12 hours/day."
"During this 12 hour period of illumination steak surface temperatures were found to be higher than in the absence of illumination. This is a type of ‘greenhouse effect’ in that the heat produced by radiant energy is absorbed by the meat and trapped between the polyvinyl wrap and the meat surface. Thus, although display illumination enhances the appearance of beef it is detrimental to keeping quality."
Marketing Guidelines for a Retail Seafood Department: Customer Needs, Management, Quality Assurance and Merchandising, Charles W. Coale et al. Sponsored by Sea Grant at Virginia Tech, Mid-Atlantic Fisheries Development Foundation, Inc., and National Marine Fisheries Service. VPI-SG-88-01.
"Texas A & M specialists have observed that the air just two inches above a bed of ice in an unrefrigerated case may be at room temperature. Similarly, researchers at Virginia Tech have recorded as much as a 25° F difference between the bottom and top of a stack of flounder fillets piled on ice. Obviously this is not acceptable."
Rapid and Quantitative Detection of the Microbial Spoilage of Meat by Fourier Transform Infrared Spectroscopy and Machine Learning. David I. Ellis, David Broadhurst, Douglas B. Kell, Jem J. Rowland, Royston Goodacre. Applied and Environmental Microbiology, vol. 68, no. 6 (June 2002): 2822-2828.
Consumers have "fears over microbiological food safety issues, especially the incidence of Salmonella spp. and Campylobacter spp."
"Muscle foods, such as meat and poultry, are described as spoiled if organoleptic changes make them unacceptable to the consumer. These organoleptic characteristics may include changes in appearance (discoloration), the development of off odors, slime formation, changes in taste, or any other characteristic which makes the food undesirable for consumption. While endogenous enzymatic activity within muscle tissue postmortem can contribute to changes during storage, it is generally accepted that detectable organoleptic spoilage is a result of decomposition and the formation of metabolites caused by the growth of microorganisms."
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."
Greening of Potatoes. Wayne Vandre. University of Alaska Fairbanks.
"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."
Food Spoilage and You. George Schuler, William Hurst, Estes Reynolds and James Christian; revised by P.T. Tybor. Bulletin 906. Cooperative Extension Service, The University of Georgia College of Agricultural & Environmental Sciences.
"Probably the single most important factor in preventing microbial food spoilage is temperature. Generally speaking, the cooler the food can be kept, the longer shelf life it will have."
Meat, Poultry and Shellfish Safety. Susan Osaki and C. Gavranich. University of California Cooperative Extension. Publication #31-446.
"All raw meat, poultry and shellfish are contaminated with bacteria some of which may cause food poisoning; therefore these foods require careful handling and proper cooking to guarantee their safety."
"Temperature control is the key to safe handling. Shellfish should never be allowed to stand at room temperature for more than two hours. Bacteria that cause food spoilage or illness, or both, multiply rapidly at room temperature. Refrigerator temperatures of 40° F or less significantly slow the growth of spoilage bacteria and stop the growth of food poisoning bacteria."