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Color of Cured Meats in Grocery Store Merchandisers

Curing solutions, which are injected into the meat with a needle or rubbed on the surface of raw meat, usually contain nitric oxide (NO) which reacts with the meat pigment myoglobin to form nitric oxide myoglobin (MbNO), also known as nitrosylmyoglobin or nitrosomyoglobin, a bright red pigment. Even a small amount of nitrite, such as the amount left on an improperly cleaned utensil, can cause the nitric oxide myoglobin pigment to form on other meats such as cooked beef.

This pigment is not very stable, however. If the cured meat is exposed to display light and oxygen, the pigment becomes oxidized and breaks down, forming metmyoglobin nitrite and turning the cured meat gray. Heat can also contribute to nitrite burn, a series of three chemical reactions in which metmyoglobin nitrite reacts with excess nitrous acid to form nitrimetmyoglobin, which reduces to nitrimyoglobin (MbN), which in turn becomes the green pigment nitrihemin when exposed to heat. The green/gray color of cured meats can also be triggered when the meat is contaminated by metals from moulds or smoke sticks.

To stabilize the color, cured meats are often vacuum packaged, and one study recommended storing the meat in the dark prior to display. Protecting cured meats from harmful visible spectrum and ultraviolet light, elevated temperatures, and oxygen can help prevent cured meats from turning gray or green.

Ultraviolet and visible spectrum light can also cause the color of cured products (raw or cooked) to fade to a degree in proportion to the intensity of the light multiplied by the length of exposure to light beginning at 200 foot candle hours.

Cured meats such as hams are very sensitive to the effects of ultraviolet light. The typical pale gray color of raw hams is directly related to pigment transformation and fading triggered by the radiation from ultraviolet and visible spectrum light. With prolonged exposure to light (UV and visible light), oxygen, and the salts and chemicals in the cure, raw cured meats break down chemically and spoil, turning green in the process.

The cured color is much more stable after the meat has been cooked because this process changes the pigment nitric oxide myoglobin to the pink pigment nitric oxide myochromogen, also known as nitrosylmyochrome, nitrosohemochrome, or nitrosylhemochrome. However, the pigment of cooked cured meat is still very sensitive to the discoloring effects of light, temperature, and oxygen, and even cooked cured meats tend to be sold in vacuum packages.

Frozen bacon has a short shelf life compared to other frozen meats because it is sensitive to various oxidative reactions which affect the bacon’s color, appearance, and flavor. The pigment in bacon, nitric oxide myoglobin, reacts with sodium nitrite to form the grey pigment metmyoglobin nitrite, a process that is accelerated by high levels of the salt sodium chloride especially in leaner bacon.

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Promolux True Color Definition Lamps

Promolux Safe Spectrum balanced full spectrum lamps emit lower levels of heat and ultraviolet radiation than regular supermarket fluorescent lamps, thus reducing the rate of meat decomposition. Compared to other fluorescent lighting, Promolux lamps emit 86% lower UV B radiation, a shorter wavelength that penetrates and causes heating, and 52% lower UV A radiation, a longer wavelength that tends to affect surfaces.

Because Promolux lamps are designed for true color definition, they have a more balanced visible spectrum than other fluorescent lamps. The yellow and green wavelengths that are predominant in regular fluorescent lighting are the most damaging wavelengths in the visible spectrum. Promolux lamps emit a more balanced range of wavelengths, including more of the red and blue wavelengths and more moderate levels of the yellow and green wavelengths. It is impossible to create a natural light that does not have any yellow or green wavelengths, so light sources will always be damaging to some extent.

However, in a study conducted by the University of Zaragoza, meat that was displayed under Promolux low UV balanced spectrum lamps stayed nearly as fresh as meat kept in the dark, while meat that was displayed under regular fluorescent lighting quickly turned brown and began to decompose.