Offensive lighting in commercial food display cases can be defined as the lighting that promotes rapid oxidation of the stored food by photo oxidation and radiation, causing, bad odor, reduction in flavor, diminution in the nutritional quality and appearance (Long and Picklo, 2010).
Photo oxidation is a chemical reaction, where, a substance reacts with oxygen under the influence of light. Radiation is the process of conversion of light energy into heat energy in a space.
Although, ultraviolet radiation has been proved an effective tool in the eradication of microorganisms like bacteria, fungi and virus in the stored refrigerated food, ultraviolet radiation has been, also, shown to have a deleterious effect on the chemical composition, especially, on the biogenic amines of stored food products (Lazaro et al, 2014).
The presence of excess biogenic amines can indicate microbial spoilage and high levels of biogenic amines are toxic (Santos and Silla, 1996).
Various aldehydes and ketones from lipid oxidation have been shown to produce biogenic amines throughout the shelf life of the anchovies and the levels of amines are proportional to the light and temperature abuse (Dehaut et al, 2014).
Recent investigations have shown that photo oxidation can instigate up to 19% decrease in polyunsaturated fatty acids (PUFA) and a marked increase in peroxides (PV), thiobarbituric acid reactive substances (TBAR) and cholesterol oxidation products (COPs) in sardine muscles (Cardinia et al, 2013).
Light and temperature mediated browning, lipid breakdown, reduction in the levels of total sugars, tryptophan, and methionine on stored fish products have been well documented (Rosa et al, 2012). This includes the recent elucidation of light induced changes in color of the skin and eyes of the snapper (Pagrus auratus) and Gurnard (Chelidonichthys kumu) during storage over a period of 12 days (Balaban et al, 2014).
Interestingly, the light produced in the conventional electric lighting is actually a product of the conversion of electric energy into light energy.
This energy conversion occurs by a process known as emission and the wavelength of the light produced depends on the chemical component(s) of the lamp that includes the type of filament(s), coating and the gases utilized. The emission characteristics of each component are unique and hence, the color and spectral features of every electric lamp.
Although the visible part of the emission spectrum falls between a wavelength of 380 and 780 nm, the visible spectrum of the normal, non-specific fluorescent lamps, includes the spectral features of mercury, the inert gases such as neon, argon, and the phosphor coating apart from the ultraviolet and infrared lines (Astronuc, 2004).
The predominant ones in a non-specific fluorescent are those of the violet-blue at a wavelength of 435.8 nm and the slightly yellowish green at 546.1 nm. The other negligible spectral lines include the deep violet lines at 404.7 and 407.8 nm, the blue-green lines at 491.6 and 496 nm, and the yellow lines at 577 and 579.1 nm (Klipstein, 2015).
On the other hand, specific display lights that are favorable in terms of an extended shelf life are those that produce appropriate specific spectral lines that neither induce photo oxidation nor contribute to temperature rise by radiation photon flow. Promolux offers an assortment of such specific food display lights that extend the shelf life of fish.
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