Retail Dairy Display Lighting

"Oxidized Light-Induced: Odor, taste of burnt-protein, burnt-feathers, or medicinal or plastic-like taste. May progress to metallic-oxidized type flavor due to fat oxidation."

"Cause - exposure of milk to sunlight or fluorescent lights resulting in protein degradation and/or lipid oxidation. Milk in unprotected or transparent milk jugs/bottles is more susceptible though this defect may occur in paper packaging if the light is intense and exposure time is sufficient."

"It is well known that milk, if exposed to either sunlight or artificial light (i.e., fluorescent lighting found in most dairy cases), can develop flavor changes and nutrient losses, especially of riboflavin (vitamin B2), vitamin A (particularly added vitamin A), vitamin C (which is present in low quantities in milk), and added vitamin D."

"The extent of flavor changes and nutrient losses depends on several variables. Among these are the light intensity, illuminance and wavelength, the distance between the light source and milk container, container material, amount exposed surface area, surface to volume ratio, temperature, and duration of exposure."

"In terms of nutrition, loss of riboflavin is directly related to the amount of ultraviolet light transmitted through the container."

"Vitamin C or ascorbic acid is particularly light-sensitive. In milk, the rate of destruction of vitamin C is proportional to the amount of light transmitted through the container."

"In a study in Pennsylvania, almost half of 449 samples of milk in translucent plastic jugs were reported to have developed pronounced light-induced off-flavors within 36 hours."

"Light-oxidized defect develops in milk as a result of its exposure to sunlight or to fluorescent lighting (wavelengths below 620 nm) common in store dairy cases. Light initiates a chemical reaction in milk that modifies specific proteins and fats, resulting in the characteristic off-flavors. Certain vitamins (i.e. riboflavin and vitamin A) are also susceptible to light-induced degradation in a similar manner."

"Exposure to sunlight for as little as 10-15 minutes (5 minutes in very intense light) is sufficient to cause the defect, while longer exposure times are generally required for fluorescent lighting. The closer the milk is to the fluorescent light source (or the more intense the light), the quicker the development of the off-flavor.

"In general, the defect is more common in milk packaged in transparent glass or plastic, though it can also occur in milk in paper cartons if there is sufficient light intensity and exposure time."

"Fluorescent lighting in retail dairy display cases induces vitamin A degradation and 'light-oxidized' flavor defects in milk products packaged in light-transmissible (i.e. high-density polyethylene - HDPE) containers."

"Based on the results of this study, trained panelists were able to detect oxidized flavor after 15 to 30 minutes of light exposure while consumers required between 54 minutes and 2 hours."

"One way to have good-tasting milk is to protect it from light."

"Both natural and artificial light can induce quality defects that consumers notice -- and don't like. Light exposure causes chemical reactions in milk that can modify the proteins and fats that are present to produce many negative flavors, ranging from burnt protein (burnt feathers or hair) to cardboard or metallic. The resulting off-flavors are dependent upon various factors such as exposure time, intensity and wavelength of light, and composition of the milk."

"Ice cream contains a high percentage of fat compared with other food products; therefore, ice cream might deteriorate during storage under strong lighting in grocery stores. Light-induced oxidation could potentially cause serious problems in the quality and safety of ice cream."

"A vanilla ice cream sample developed a strong putrid flavor during distribution...Elevated levels of hexanal and dimethyl disulfide clearly indicate the sample was light-abused."

"Ice cream sampled from roughly half the cartons (round 1.5 gallon paperboard with a clear plastic lid) developed the defect, which formed on the top surface of the ice cream but not in ice cream from the carton interior."

"Reinspection of the warehouse showed samples were stored in close proximity to high-intensity lights. Lighting adjustments were made, remedying the problem."

"Another useful tactic is to control lighting conditions in supermarket dairy cases."

"Oxidative rancidity causes the breakdown of fat-soluble vitamins and essential fatty acids (linoleic, linolenic), and is also responsible for the development of off flavors and odors. The warmed-over flavor common in reheated leftovers is the effect of oxidative rancidity, as is the cardboard taste of ice cream left too long in a freezer."

"The presence of oxygen, metal ions, especially copper and iron, and the exposure to light will increase the rate of oxidation."

"Approximately two to five percent of the top or front pieces of Cheddar or Colby cheese in supermarket retail display cases show definite evidence of pink discoloration and potential oxidized flavor. Consumer rejection of the discolored cheese alone represents a projected loss of $30 to $40 million dollars per year to the dairy industry."

"'When confronted with cheese that has turned pink, the consumer will either purchase a white cheese instead, or no cheese at all,' [said Bill Wendorff, food science professor at the University of Wisconsin at Madison]...'the economic impact of the pink cheese on the top of the pile is that all the packages of cheese underneath the pink one remain untouched and unsold.'"

"Wendorff identified three major factors that cause discoloration. The primary culprit is the fluorescent lighting in retail cases that catalyzes the pinking effect."

"High-intensity lighting in retail display cases ranged from 300 to 600 foot candles in power. Wendorff and his team tested cheeses at 250 foot candles and found that in some cases, pinking occurred within two days at that level of light intensity. 'One can only assume that the spoilage occurs more rapidly as the light intensity increases,' said Wendorff."

"Researchers have found that the application of an antimicrobial preservative such as natamycin to cheese reduces the incidence of mold growth."

"Natamycin is extremely sensitive to ultraviolet (UV) light. 'Cheese products are exposed to high-intensity fluorescent lighting in the retail dairy case, resulting in natamycin degradation on the cheese by the time of purchase by consumers,' said Marcy [of Virginia Polytechnic Institute and State University]."

"Researchers Joseph E. Marcy, Ph.D., and John L. Koontz - with funding from America's dairy farmers - [are] inhibiting mold growth on the surface of cheeses by leveraging natamycin, an antimicrobial preservative approved by the Food & Drug Administration (FDA) for use in the food industry. Natamycin is particularly beneficial when used on shredded cheeses, which are especially prone to mold."

"'In terms of stability, natamycin is extremely sensitive to ultraviolet (UV) light,' said Marcy, professor of food science & technology at Virginia Polytechnic Institute and State University in Blacksburg, VA. 'Cheese products are exposed to high-intensity fluorescent lighting in the retail dairy case, resulting in natamycin degradation on the cheese by the time of purchase by consumers.'"