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In this study, the effects of metal halide (MH), incandescent (INC), ultraviolet-B (UV-B), ultraviolet-C (UV-C) and fluorescent (FL) light sources on some of the ...
Research & Development 63

Effects of light sources on physicochemical/color properties and oxidative/microbiological stability of ground beef during storage at 4 °C By Hasan Ibrahim Kozan and Cemalettin Sariçoban In this study, the effects of metal halide (MH), incandescent (INC), ultraviolet-B (UV-B), ultraviolet-C (UV-C) and fluorescent (FL) light sources on some of the quality characteristics of ground beef samples were investigated at 4 °C for four storage days. The parameters of pH, TBARS, metmyoglobin, free fatty acid, color characteristics and microbiological contents from ground beef samples were also analysed. Both, the light sources and the storage process, affected significantly all analyzed parameters. Ground beef samples, exposed to UV-C and UV-B lights had the highest pH values. Each color parameter of ground beef samples exposed to UV-C light was the highest. While total mesophyllic aerobic counts increased under MH and INC lights, psychrophilic aerobic bacteria counts decreased. We conclude that UV lamps can prolong the shelf life of ground beef and thus provide an economic incentive.

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eat and meat products are important sources of proteins, fats, essential amino acids, minerals, vitamins and other nutrients. Minced meat is a popular unprocessed meat product because of its functionality and serviceability for further products. Also, it can be easily prepared for consumption. However, it is very vulnerable to spoilage because of the extended surface area in the grinding process. Thus, minced meat stored under refrigeration temperatures has a very low shelf life. Various studies have been developed to improve the quality and extend the shelf life of minced meat (ESMER KIZILIRMAK et al., 2011; AYARI et al., 2012). Modified atmosphere packaging, natural or synthetic additives for food preservation, refrigeration, ionizing irradiation, coating, canning and pressurizing can be listed as some of the most effective methods used to extend the shelf life of minced meat to control the rate of deteriorative changes (LIMBO et al., 2010). The reasons for the deteriorative changes can be examined through two components: As endogenous factors, such as pH value or the degree of acidity of the meat, aw value or the amount of moisture available in the product, and the concentration of nutrients that influence types and growth of bacteria; and exogenous factors, such as oxygen (from the air), microorganisms, temperature, light, packaging properties and evaporation and desiccation (LAMBERT et al., 1991; BLIXT and BORCH, 1999). The appearance of food products plays a major role in their acceptability and the purchase decisions. CARPENTER et al. (2001) stated that appearance influences consumer purchase decisions. ROGERS et al. (2014) pointed out that the beef industry has directed significant efforts into the development of systems that promote shelf life and color stability. It has been observed that fluorescent, metal halide and incandescent lamps are now used in the retail stores marketing meat products, especially in the cold meat sections of delicatessen stores (BARBUT, 2001). It has been reported that UV light is much more effective in inducing discoloration and reducing oxidation of lipid and pigments than visible light (ANDERSEN and SKIBSTED, 1991). Food store managers usually keep the meat display area well-lit to attract consumers; however, different types of light sources can be used. The three main sources include incandescent (INC), fluorescent

Keywords ,Ground meat ,Light sources ,Microbial characteristics ,Quality characteristics

(FL), and metal halide (MH) lamps. FL bulbs radiate about one-fifth of the heat produced by INC bulbs of the same light output (KROPF, 1980), and, therefore, FL bulbs can be placed inside the display cooler. A source such as MH is the most efficient one for illuminating a large area, but it does not produce a full visible spectrum. The objective of this study was to determine the effect of light sources of various lamps, such as MH, INC, FL, UV-B and UV-C, on the physicochemical properties and color, the stability of oxidative compounds and the microbiological quality of ground beef during storage at 4 °C.

Materials and methods Raw Material Fresh beef was purchased in the form of boneless rounds from a local supermarket in Konya, Turkey. The fresh beef was transported to the Food Engineering Department in the Faculty of Agriculture of Selçuk University under hygienic conditions and processed immediately upon arrival. After the visible fat and connective tissue were removed, the fresh beef was cut into small pieces. To make the product homogeneous, the fresh beef pieces were cut into small cubes and minced with a meat grinder (Kitchenaid Classic Model K45SS, USA) using 8 mm (coarse) and 3 mm (fine) plates simultaneously to obtain ground beef. The diet history and production practices of the beef were unknown.

Methods Preparation of samples and storage conditions After grinding the beef, the samples were assigned to one of the following six treatments: The ground beef meat was divided into 24 samples (6 treatments × 4 storage times) in smaller portions (about 500 g each) and transferred into sterile plates. All samples were stored in a cold storage chamber at 4 °C, simulating retail conditions at supermarkets. The light exposure was performed in a cold storage chamber at 4 °C, with different light sources placed in a distance of approximately 18 cm over the shelves. The light sources included: Metal halide (Philips MHN-TD 220 V, 70 W × 87 LE, Poland), incandescent (Osram 60 W, 220 V, 60 W × 15 LE, Germany), ultraviolet-B (Ushio 8 W, 220 V, 283.3 mm × 16 mm, Hungary), ultraviolet-C (Philips 8 W, 220 V, 283.3 mm × 16 mm, Hungary) and fluorescent (Philips 8 W × 60 LE, 220 V, 283.3 mm × 16 mm, Hungary). The positions of the samples in the cabinet were rotated every 24 h to minimize light intensity differences and possible temperature varia-

Received: 20 March 2016 | reviewed: 13 July 2016 | revised: 25 July 2016 | accepted: 26 July 2016 FLEISCHWIRTSCHAFT International 4/2016