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Photo Oxidation – a Light Induced Stored Food Distress

Photo oxidation is a chemical reaction, where, a substance reacts with oxygen under the influence of light (IUPAC, 1997). Photo oxidation of stored food products brings about nutritional changes, variations in color, smell and flavor and thus, poses a serious challenge to the food industry.

Moreover, oxidation of lipids in the stored food and the subsequent dietary end products is detrimental to human health (Kanner, 2007).

Precisely, photo-oxidation reaction starts with the formation of Singlet Oxygen, a high energy variant of the normal oxygen in the presence of light, especially, in the ultraviolet range. This singlet oxygen reacts readily with polyunsaturated fatty acids (lipids) that are abundantly available in foods such as walnuts, peanut butter, olive oil, sardines, soybeans, tuna, wild salmon and whole grain wheat to form hydroxyperoxide molecules.

Hydroxyperoxide, in turn, triggers a chain lipid oxidation reaction that culminates in the formation of plentiful lipid peroxide free radicals and hydroxyperoxide molecules (Gueraud et al, 2010).

These hydroxyperoxide molecules, apart from initiating further lipid oxidation reactions, also form secondary oxidation products in the stored foods causing bad odor, reduction in flavor, diminution in the nutritional quality and appearance (Long and Picklo, 2010).

Further, some of these secondary oxidation products have been shown to be cytotoxic, mutagenic, neurotoxic and carcinogenic substances that can upset the genetic framework of human cells causing cancer and various other diseases (Cohn, 2002 and Drake et al, 2004).

Technically, such entities that initiate an oxidation reaction are termed pro-oxidant factors and research evidence has shown that light, high temperature and oxygen are important pro-oxidant factors that initiate lipid oxidation in stored food.

Interestingly, the temperature has a close statistical correlation with light (Frankel, 2005), where, an increase in light leads to a corresponding rise in temperature by radiation. This is more factual and relevant in food display racks and shelves in a commercial scenario, where, vague fluorescent lights discharging high levels of ultraviolet and infrared radiations are employed.

Thus, these non-specific fluorescent lights, apart from initiating a photo oxidation reaction, also, increase the storage temperature by radiation and, thereby, augment oxidation of the food items, bringing about bad reek, reduction in taste, decrease in the nutritional quality and color.

Moreover, any increase in storage temperature of food items inevitably takes the food to the ambit of microbial contamination, causing complete wastage of the stock, huge economic loss and legal liability during food borne disease outbreaks.

Photo oxidation of stored food is perhaps an obscure concept, but photo oxidation of food, obviously augmented by offensive non-food grade lighting is amendable and such food- grade light alterations are inescapable demands of commercial situations today.

The key to this commercial display illumination predicament, thus, lies in the prudent use of food-grade display lightings that would not only deter photo oxidation, but also thwart an increase in storage temperature brought about by offensive radiation.

Promolux low radiation balanced spectrum LED and fluorescent lights are recent market innovations in this arena that effectively impede photo and lipid oxidation of perishable food by utilizing an inventive blend of food-grade phosphors and coatings.

References

  • Cohn, J.S., Oxidized fat in the diet, postprandial lipaemia and cardiovascular disease. Curr Opin Lipidol, 2002. 13(1): p. 19-24.
  • Drake, J., et al., 4-Hydroxynonenal oxidatively modifies histones: implications for Alzheimer’s disease. Neurosci Lett, 2004. 356(3): p. 155-8.
  • Esterbauer, H., R.J. Schaur, and H. Zollner, Chemistry and biochemistry of 4-hydroxynonenal, malonaldehyde and related aldehydes. Free Radic Biol Med, 1991. 11(1): p. 81-128.
  • Frankel, E.N., Lipid Oxidation, ed. E.N. Frankel. Vol. 10. 2005, Bridgewater, UK: The Oily Press.
  • Gueraud, F., et al., Chemistry and biochemistry of lipid peroxidation products. Free Radic Res, 2010. 44(10): p. 1098-124.
  • Hu, W., et al., The major lipid peroxidation product, trans-4-hydroxy-2-nonenal, preferentially forms DNA adducts at codon 249 of human p53 gene, a unique mutational hotspot in hepatocellular carcinoma. Carcinogenesis, 2002. 23(11): p. 1781-9.
  • IUPAC. Compendium of Chemical Terminology, 2nd ed. (the “Gold Book”). Compiled by A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford (1997). XML on-line corrected version: http://goldbook.iupac.org (2006-) created by M. Nic, J. Jirat, B. Kosata; updates compiled by A. Jenkins. ISBN 0-9678550-9-8. doi: 10.1351/goldbook.
  • Kanner, J., Dietary advanced lipid oxidation endproducts are risk factors to human health. Mol Nutr Food Res, 2007. 51(9): p. 1094-101.
  • Long, E.K. and M.J. Picklo, Sr., Trans-4-hydroxy-2-hexenal, a product of n-3 fatty acid peroxidation: make some room HNE. Free Radic Biol Med, 2010. 49(1): p. 1-8.
  • Son, Y., et al., Mitogen-Activated Protein Kinases and Reactive Oxygen Species: How Can ROS Activate MAPK Pathways? J Signal Transduct, 2011. 2011: p. 792639.
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