LIGHT INDUCED CHANGES ON A MEAT MODEL SYSTEM

The appearance of fresh meat and meat products is the most important factor that influence the consumers’ selection. In fact, whereas food flavour and consistency affect subsequently purchase decisions, meat colour plays a direct role in the freshness perception and acceptability of the product at the purchase moment. The meat colour basically depends on the redox state of the myoglobin: the physiologically active species are the purple reduced pigment (deoxymyoglobin) and the oxygenate bright cherry-red form (oxymyoglobin), whereas the oxidized specie (metmyoglobin) appears brown-red. During storage, meat is characterized by a continuous dynamic conversion among the above mentioned three different myoglobin states. However the appearance of the meat surface is not affected only by the real product colour but also by the lighting conditions where it is observed. For this reason, in stores are generally used the lamp typologies able to improve the natural colour of meat. Nevertheless, often, the marketing specialist choices do not consider the potential damage induced on food by electromagnetic radiations. In fact, it is known that light causes the deterioration of lipids, vitamins, proteins and natural pigments which result in off-flavours, loss of nutrients and colour fading. The aim of this work was to investigate the effect of different light storage conditions on the quality evolution of a meat model system. For the experimental phase, fresh minced beef meat was homogenized with a phosphate buffer in order to obtain a final solution with a pH of 7. To avoid the microbial growth during all the experimental time, chloramphenicol was added as preservative. The obtained model system was stored in clear glass vials under two different modified atmospheres. A set of vials was closed under 60 kPa of oxygen and 40 kPa of carbon dioxide, while another set was conditioned under 3 kPa of oxygen and 97 kPa of carbon dioxide. These conditions were chosen to emulate modified atmosphere and under vacuum packaging. During storage, the samples were exposed to constant temperature under lighting conditions produced by different light sources commonly used by retailers to illuminate meat products. In particular, a cool white lamp (Osram Dulux El Longlife 30W/840) and a nature® lamp (with high emission in the red region of the visible spectrum) were chosen. For each selected light source, the light intensity that reached the samples was recorded under real storage conditions. A series of sample was kept in the dark as reference. At different times, the samples were analysed in triplicate in order to monitor the changes occurred in the meat model system. The changes in the vial headspace gas composition, the amount of different myoglobin species and the colour (CIE L*a*b* parameters) of the model system were evaluated during time. Moreover, the lipid degradation phenomena were investigated by means of the determination of oxidation products