OXIDATIVE STABILITY OF CHICKEN MEAT AFTER PROPOLIS EXTRACT APPLICATION IN THEIR DIETS

In the experiment, the effect of the addition of propolis extract in a feed mixture for chicken broilers Hubbard JV on oxidative stability of breast and thigh muscles during refrigerated storage was investigated. In the experiment were included 90 pieces of one day-old chicks, which were divided into 3 groups (control, E1 and E2). Chickens were fed by ad libitum system until the age of 42 days. These feed mixtures were made without antibiotics preparation and coccidiostats. Propolis extract in an amount of 150 mg.kg (E1) and 450 mg.kg (E2) was added into feed mixtures for experimental groups. During whole period of refrigerated storage were higher values of MDA determined in control group compare to experimental groups. The higher average MDA value determined in breast muscels of broiler chicken hybrid combination Hubbard JV was in samples of control group (0.157 mg.kg) compared to experimental groups E1 (0.140 mg.kg) and E2 (0.130 mg.kg) after 6-month of refrigerated storage. Significantly higher values of MDA were determined in control group compare to second experimental group from fourth month to the end of storage. The significantly lower value of MDA was determinated in first experimental group compare to control only at 6 month of storage. Trend of thigh muscle oxidation stability of chicken hybrid combination Hubbard JV was during 6 months of refrigerated storage similar than in breast muscle. The higher average MDA value determined in thigh muscels was in samples of control group (0.170 mg.kg) compared to experimental groups E1 (0.150 mg.kg) and E2 (0.139 mg.kg) after 6-month of refrigerated storage. Significantly higher values of MDA were determined in control group compare to second experimental group from fourth month to the end of storage. Higher amount of MDA in thigh muscle compare to breast muscle is due to by higher amount of fat occurred in thigh muscle.


INTRODUCTION
Lipids play important role in technological, nutritional and sensory function of food. However they are liable to undergo autooxidation that leads to the formation of a number of undesirable compounds. In an effort to retard this process, various antioxidants are employed. The application of synthetic antioxidants has recently been restricted because there is suspiction that they are carcinogenic. For this reason a growing interest has been paid to the research of natural antioxidants, among which spices occupy an important position (Pokorny et al., 2001).
Lipid oxidation is a major cause of meat quality deterioration. Lipid oxidation is an important determinant of shelf life of meat and meat products. Antioxidants are natural or synthetics substances used to prevent lipid oxidation. Meat protection, primarily against lipid components, is possible by addition of antioxidants to feed mixes. This is the way to ensure oxidative stability of meat fats during the postslaughter proccessing of carcasses and storage of meat The post mortem oxidation of lipids decreases the nutritional value and the sensory quality of meat. It has been shown, in chickens, that dietary fat sources have major impact on the composition and the melting point of fat in tissues (Hrdinka et al., 1996).
Propolis is a resinous, rubbery and balsamic substance collected by honey bees from the buds of flowers, trees and other plant sources. Propolis contains resins, aromatic and ethereal oils, flavonoid pigment, vanillin, isovanilin, caffeic, benzoic and ascorbic acids as well as benzyl alcohol and cinnamic acid Certainly, it is possible to state, that plant extract, propolis and the other natural supplements are considered as an alternative to the antibiotic and they have wide range of possible uses; consequently, influence of these products on human and animal health is curently evaluted and determined with regard to growth of organic farming (Tekeli et al., 2011). For this reason, the present study was aimed to investigate the effect of propolis extract Slovak multifloral addition to feed mixtures for oxidative stability of meat in the process of installation of Hubbard JV chickens.

MATERIAL AND METHODOLOGY
The experiment was realized at the test station of poultry (Slovak Agricultural University in Nitra). The experiment enrolled 90 one day old chicks of hybrid combination Hubbard JV and was formed into 3 groups: control group (C) and two experimental groups (E1, E2) of 30 pcs chickens in each group. Custom feeding insisted 42 days. Chickens were fed to 21 th day of age an ad libitum with the same starter feed mixture HYD-01 (powdery form) and from 22 nd to 42 th day of age fed with the growth feed mixture HYD-02 (powdery form). The feed mixture HYD-01 and HYD-02 have been produced without antibiotic preparations and coccidiostats. Nutritional value of feed mixtures (Table 1) given during the experiment was the same in each group, but to the experimental groups were added propolis extracts at a dose of 150 (E1) and 450 mg.kg -1 (E2). Propolis extract was prepared from minced propolis (Krell, 1996). Weighed 150 g propolis was the volume of 80% ethanol, 500 cm 3 .
Extraction was carried out in a water bath at 80 °C under reflux for 60 minutes. After cooling was extract centrifuged. The supernatant was evaporated on a rotary vacuum evaporator at a water bath at temperature of 40 -50 °C and then weighed. Residue in an amount of 15 and 45 g was dissolved in 1000 cm 3 of ethanol concentration of 80% and applied to 100 kg of the feed mixture.
At the end of feeding (day 42 th ) from each group were selected 10 pieces of chicken for slaughter analysis. To determine changes in lipid degradation (determination of thiobarbiturates numbers, TBA) the samples of chickens were boned and thigh and breast muscle packed into polyethylene bags and stored for 6 months at -18 °C. TBA value expressed in number of malondialdehyde were measured in the process of first storage day of 1 st , 2 nd , 3 rd , 4 th , 5 th and 6 th months. TBA number was determined by Marcinčák et al. (2004). Absorbance of samples was measured on UV-VIS spectrophotometer T80 (PG Limeted Instruments, UK) at a wavelength of 532 nm, the translation results on the amount of malondialdehyde (MDA) in 1 kg samples.
Results of the experiment was evaluated with statistical program Statgraphics Plus version 5.1 (AV Trading Umex, Dresden, Germany), were calculated variation-statistical values (mean, standard deviation) and to determine the significant difference between groups was used variance analyze with subsequent Scheffe test.

RESULTS AND DISCUSSION
The results of the oxidation stability determined in breast and thigh muscle of chickens Hubbard JV during 6 months storage at -18 °C are shown in Table 2. Our results are in accordance with Marcinčák et al. (2010) who, after slaughtering and processing of poultry samples also recorded low values of MDA. During refrigerated storage of the breast and thigh muscles (6 months) were detected increased content of MDA in comparison to the first day of storage. During whole period of refrigerated storage were higher values of MDA determined in control group compare to experimental groups. The higher average MDA value determined in breast muscels of broiler chicken hybrid combination Hubbard JV was in samples of control group (0.157 mg.kg -1 ) compared to experimental groups E1 (0.140 mg.kg -1 ) and E2 (0.130 mg.kg -1 ) after 6-month of refrigerated storage. Significantly higher values of MDA were determined in control group compare to second experimental group from fourth month to the end of storage. The significantly lower value of MDA was determinated in first experimental group compare to control only at 6 month of storage.
Trend of thigh muscle oxidation stability of chicken hybrid combination Hubbard JV was during 6 months of refrigerated storage similar than in breast muscle. The higher average MDA value determined in thigh muscels was in samples of control group (0.170 mg.kg -1 ) compared to experimental groups E1 (0.150 mg.kg -1 ) and E2 (0.139 mg.kg -1 ) after 6-month of refrigerated storage.
Significantly higher values of MDA were determined in control group compare to second experimental group from fourth month to the end of storage. Higher amount of MDA in thigh muscle compare to breast muscle is due to by higher amount of fat occurred in thigh muscle  reported that a higher concentration of antioxidants in poultry meat has the effect of reducing lipid oxidation, ie. there is a reduction in MDA values during chilling and refrigeration storage, which was confirmed by our findings.

CONCLUSION
Results achieved in the experiment show that the addition of propolis extract in feed mixture for broiler chickens had a significantly (p ≤0.05) positive impact on the reduction of oxidative processes in the breast and thigh muscles during refrigerated storage.