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Whole Fish Displays in Supermarket Display Cases

When fresh, most whole fish have silvery or brightly colored metallic scales and bright to pinkish red gills. Most retail display lighting will distort these colors, and emit high levels of damaging radiation which encourages the exponential growth of bacteria and the decomposition of the fish.

Fresh fish smells like a fresh ocean breeze or grass, or has no odor at all. The flesh bounces back if poked, and is firmly attached to the rib bones near the belly cavity. The eyes are shiny, clear, and usually full.

Decomposition of Whole Fish in Seafood Department Cabinets

Visible spectrum and UV radiation from most fish display case lighting heats the surface of the fish, accelerating the growth of surface bacteria and the decomposition of the fish. When fish are stored in dark cool places for the same amount of time, they remain fresh.

Within a few hours of increased temperatures, bacteria can multiply to astronomical numbers. High surface temperatures also dehydrate the fish, leading to weight loss and lost profit if the fish are sold by weight.

When fish are exposed to oxygen and light, even in sub-freezing temperatures, the fat oxidizes, turning rancid and producing a strongly fishy smell, a yellow or brown discoloration, and a cardboardy taste.

There are two processes that cause whole fish to decompose: the escape of digestive enzymes from the belly cavity, and the growth of bacteria. The bacteria that live in the fish’s intestines, gills, and surface slime release enzymes that begin the decomposition process. The rate of this decomposition is determined by the type and number of bacteria initially found on the fish, and the temperature of the fish. Marine fish tend to decompose more quickly than freshwater fish because their osmoregulation system provides an ideal food source for bacteria.

Meanwhile, the enzymes excreted by the fish’s digestive system eventually break down the walls of the belly cavity and cause the fish to decompose even at temperatures well below freezing, and even if the fish has no bacteria at all. Once the tissue is broken down by the enzymes, however, it is consumed by bacteria, and this accelerates bacterial growth.

As whole retail fish decompose, the muscle turns mushy, soft, and flabby, losing its bounce when poked, and the flesh pulls away from the bones especially near the belly cavity. The eyes become dull, sunken, and cloudy or opaque. The skin color fades and forms yellow or brown patches, and thick mucus forms over the gills, which also turn brown or grey. The fish smells strongly fishy, putrid, or ammonia-like, and the gills smell sour.

For seafood science references and excerpts click here.

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Promolux True Color Definition Lamps

Compared to other fluorescent lighting, Promolux Safe Spectrum 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.

Yellow and green wavelengths are the most damaging wavelengths in the visible spectrum, and their predominance in regular fluorescent lighting can distort the natural colors of finfish and make ice beds look green or yellow. 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, since Promolux Safe Spectrum lamps minimize the emission of damaging visible spectrum and UV wavelengths, using Promolux lamps will prolong the display shelf life of whole fish and maximize their fresh appearance, enticing customers to buy while the fish are fresh.