OXIDATIVE STABILITY OF CHICKEN THIGH MEAT AFTER TREATMENT OF ABIES ALBA ESSENTIAL OIL

In the present work, the effect of the Abies alba essential oil in two different concentrations on oxidative stability of chicken thigh muscles during chilled storage was investigated. In the experiment were chickens of hybrid combination Cobb 500 after 42 days of the fattening period slaughtered. All the broiler chickens were fed with the same feed mixtures and were kept under the same conditions. The feed mixtures were produced without any antibiotic preparations and coccidiostatics. After slaughtering was dissection obtained fresh chicken thigh with skin from left half-carcass which were divided into five groups (n = 5): C control air-packaged group; A1 vacuum-packaged experimental group; A2 vacuum-packaged experimental group with ethylenediaminetetraacetic acid (EDTA) solution 1.50% w/w; A3 vacuum-packaged experimental group with Abies alba oil 0.10% v/w and A4 vacuum-packaged experimental group with Abies alba oil 0.20% v/w. The Abies alba essential oil was applicate on ground chicken things and immediately after dipping, each sample was packaged using a vacuum packaging machine and storage in refrigerate at 4 ±0.5 °C. Thiobarbituric acid (TBA) value expressed in number of malondialdehyde was measured in the process of first storage day of 1, 4, 8, 12 and 16 day after slaughtering and expressed on the amount of malondialdehyde (MDA) in 1 kg sample. The treatments of chicken things with Abies alba essential oil show statistically significant differences between all testing groups and control group, where higher average value of MDA measured in thigh muscle of broiler chickens was in samples of control group (0.4380 mg.kg) compared to experimental groups A1 (0.124 mg.kg), A2 (0.086 mg.kg), A3 (0.082 mg.kg) and A4 (0.077 mg.kg) after 16-day of chilled storage. Experiment results show that the treatment of chicken thigh with Abies alba essential oil positively influenced on the reduction of oxidative processes in thigh muscles during chilling storage and use of essential oil is one of the options increase shelf life of fresh chicken meat.


INTRODUCTION
For chicken meat products, freshness, as one of the most important quality attributes, has attracted attention from producers and consumers and has a strong relationship with product sales and consumption (Rzepka et al., 2013).
The production and consumption of chicken meat has become very popular worldwide owing to its desirable nutritional characteristics, such as high protein, low fat and relatively high concentrations of polyunsaturated fatty acids (PUFAs) compared to beef or pork (Brenes and Roura, 2010).However, the higher level of PUFAs in muscle membranes increases the susceptibility of oxidative deterioration of lipid (Engberg et al., 1996), which impairs the organoleptic characteristics and shortens the shelf-life of meat and meat products.Lipid oxidation is a major cause of meat quality deterioration, resulting in rancidity and the formation of undesirable odours and flavours, which lowers the functional, sensory and nutritive values of meat products; and therefore, consumer acceptability (Bou et al., 2004).In meat, lipid peroxidation is initiated by the abstraction of hydrogen radicals from unsaturated fatty acids, induced by light (Boselli et al., 2005), heat, metal ions (Kanner et al., 1988), or other oxidizing agents.The reaction of oxygen with preformed free radicals results in accelerated lipid peroxidation (Frankel, 1984), which leads to the formation of secondary by-products from PUFA such as MDA and the potential appearance of lower sensory scores.
The antioxidants can be of synthetic or natural origin.Synthetic antioxidants such as butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), tert-butylhydroquinone (TBHQ), and propyl gallate (PG) have been widely used in meat and poultry products (Biswas et al., 2004;Jayathilakan et al., 2007).But the demand for natural antioxidants, especially of plant origin has increased in the recent years due to the growing concern among consumers about these synthetic antioxidants because of their potential toxicological effects (Juntachote et al., 2006;Naveena et al., 2008;Nunez de Gonzalez et al., 2008).
One option for reducing lipid oxidation is the use of various natural plant antioxidants presented in essential oils.
Essential oils (EOs) are aromatic oily liquids obtained from plant material (flowers, buds, seeds, leaves, twigs, bark, herbs, wood, fruits and roots).They can be obtained by expression, fermentation, enfleurage or extraction but the method of steam distillation is most commonly used for commercial production of EOs (Van de Braak and Leijten, 1999).EOs obtained from various herbs are widely used in cosmetics and food manufacturing and can be used for prolonging the shelf-life of food for their antimicrobial (Skandamis et al Antioxidants can slow the oxidative reactions of both lipids and pigments in meat, and much interest has been focused on natural antioxidants due to negative public perception of synthetic additives (Cuppett et al., 1997).Frankel (1996) commented that the use of natural antioxidants has increased according to a presumption of their safety.Natural plant-derived antioxidants are primarily composed of polyphenolic compounds (Shahidi et al., 1992), and antioxidants containing 2 or more phenolic hydroxyl groups have been found to be effective antioxidants (Dziedzic and Hudson, 1984).Plant phenolics are multi-functional antioxidants that can act as reducing agents (free radical terminators), metal chelators, and singlet O2 quenchers.Namiki (1990) listed several common natural antioxidants used commercially in food, for example, tocopherols, ascorbic acid, soybean products, oat products, components of crude vegetable oils, amino acids, peptides and proteins, guaiac gum, flavonoids, spices, and herbs.
One possible use EOs from another source e.g.trees from the family Pinaceae, which includes many of the well-known conifers of commercial importance such as cedars, firs, hemlocks, larches, pines and spruces.Trees are rich in polyphenolic compounds, and might serve as a source of potentially useful substances, if their antimicrobial properties and safety can be established In this study we aimed to investigate the combined effect of ethylenediaminetetraacetate acid (EDTA) and plant essential oil (Abies alba) on the oxidative stability of fresh chicken thighs stored under vacuum packaging (VP), at 4 ±0.5 °C for a period of 16 days.

MATERIAL AND METHODOLOGY
The experiment was implemented in the local poultry station (Hydinaren a.s., Zamostie).The tested were broiler chickens of hybrid combination Cobb 500 both sexes.All the broiler chickens were fed with the same feed mixtures and were kept under the same conditions.The feed mixtures were produced without any antibiotic preparations and coccidiostatics.At the end of the fattening period (42.day) were chickens slaughtered for analysis in laboratory of Slovak University of Agriculture in Nitra.After slaughtering was dissection obtained fresh chicken thighs with skin from left half-carcass, which were divided into five groups (n = 5):  Air-packaged (C, control group): chicken thigh fresh meat was packaging to polyethylene backs and stored aerobically in refrigerator at 4 ±0.5 °C for a period of 16 days;  Vacuum-packaged (VP) (A1, experimental group): chicken thigh fresh meat was packaging to polyethylene backs and stored anaerobically in vacuum and in refrigerator at 4 ±0.5 °C for a period of 16 days;  VP with EDTA solution 1.50% w/w (A2, experimental group): chicken thigh fresh meat was treated with EDTA for 1 min and packaging to polyethylene backs and stored anaerobically in vacuum and in refrigerator at 4 ±0.5 °C for a period of 16 days;  VP with Abies alba oil 0.10% v/w (A3, experimental group): chicken thigh fresh meat was treated with Abies alba oil for 1 min and packaging to polyethylene backs and stored anaerobically in vacuum and in refrigerator at 4 ±0.5 °C for a period of 16 days;  VP with Abies alba oil 0.20% v/w, (A4, experimental group): chicken thigh fresh meat was treated with Abies alba oil for 1 min and packaging to polyethylene backs and stored anaerobically in vacuum and in refrigerator at 4 ±0.5 °C for a period of 16 days.Immediately after dipping, each sample was packaged using a vacuum packaging machine type VB-6 (RM Gastro, Czech Republic).
Ethylenediaminetetraacetic acid (EDTA) (C10H14N2O8.Na2.2H2O) was 99.5% purity, analytical grade, (Invitrogen, USA).A stock solution of 500 mM concentration was prepared by diluting 186.15 g.L -1 distilled water.A final concentration of 50 mM EDTA solution was prepared from the stock solution.The pH of the solution was adjusted to 8.0 with the addition of the appropriate quantity of NaOH solution.The amount of EDTA added to the treat chicken thighs was 0.28 g.kg -1 .Essential oil (Calendula, Nova Lubovna, Slovakia) were added to the coated chicken thigh surface (both sides) of each sample using a micropipette so as to achieve a 0.1% and 0.2% v/w final concentration of essential oils.TBA value expressed in number of malondialdehyde (MDA) was measured in the process of first storage day of 1 st , 4 th , 8 th , 12 th and 16 th day.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 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 analyse with subsequent Scheffe test.

RESULTS AND DISCUSSION
The results of the oxidation stability of fresh chicken thigh muscles of chicken Cobb 500 after application EDTA and plant essential oil (Abies alba) during 16 days storage at 4 ±0.5 °C are shown in Table 1 and Figure  The higher average value of MDA measured in thigh muscle in 0 day of experiment was in samples of vacuumpackaged chicken thighs group with Abies alba oil 0.10% v/w group A3 (0.027 mg.kg -1 ) compared to experimental groups A1 (0.021 mg.kg -1 ), A2 (0.024 mg.kg -1 ), A4 (0.026 mg.kg -1 ) and air-packaged control group (0.023 mg.kg -1 ).We have not found statistically significant differences between testing groups chicken thighs.During chilled storage of the thigh muscles were detected increased content of malondialdehyde in comparison to the first day of storage.On the fourth day of storage were measured below the values of malondialdehyde in all experimental groups (0.042 mg.kg -1groups A3, A4 and 0.055 mg.kg -1group A1) opposite control group C (0.071 mg.kg -1 ).We have found statistically significant differences (p ≤0.05) between control group C and tested groups A2, A3 and A4.A similar trend of improving the oxidation stability after eight days of refrigerate storage in the thigh muscle of hybrid combination Cobb 500 we found in the experimental groups (0053 mg.kg -1 -A4 to 0069 mg.kg -1 -A1) compared with control group C (0.172 mg.kg -1 ).
After 12 days of thigh muscle storage was statistic significantly (p ≤0.05) improved the oxidative stability of all test groups chicken things (0.066 mg.kg -1 -A4 to 0.081 mg.kg -1 -A1) compared to the control group C (0.246 mg.kg -1 ).We have found statistically significant differences (p ≤0.05) between control group C and tested groups and between tested group A1 and groups A2, A3 and A4.
During testing period of chilled storage were higher values of malondialdehyde measured in control group C compare to experimental groups.The higher average value of MDA measured in thigh muscle of broiler chickens Cobb 500 was in samples of control group C (0.438 mg.kg -1 ) compared to experimental groups A1 (0.124 mg.kg -1 ), A2 (0.086 mg.kg -1 ), A3 (0.082 mg.kg -1 ) and A4 (0.077 mg.kg -1 ) after 16-day of chilled storage.At the end of the test period we have found statistically significant differences between all testing groups and control group of chicken thighs.
Table 1 Effect of Abies alba essential oil on the concentration of MDA (mg.kg -1 ) in thigh muscle (mean ±SD) (n = 5).Overall, we can state that such addition Abies alba essential oil as well as the packaging method (system of vacuum packing) improved the oxidative stability of chicken thigh stored cooling at 4 ±0.5 °C for a period of 16 days.

Day
Due to consumer preferences, chicken dark meat is typically in an overabundance; thus, finding value-added options for dark chicken meat is of interest to the poultry industry.One reason ground chicken meat shelf life is limited is the rapid loss of fresh appearance.
Meat containing unsaturated fatty acids is very sensitive to lipid oxidation especially during storage, because polyunsaturated fatty acid esters are easily oxidized by molecular oxygen.This kind of oxidation is called autoxidation and proceeds by a free radical chain mechanism (Brewer, 2011  2013) stated that the degradation pathways of fatty substances play one of the main causes of foods deterioration and unpleasant odours.This factor is also responsible for the loss of sensory properties.
Rhee et al. (1996) observed that raw poultry meat is less prone to lipid oxidation than beef or pork meat because of its lower iron content.

CONCLUSION
The essential oil from natural sources can be used as alternatives to chemical additives which could extend the meat and meat products shelf life.Results achieved in the experiment show that the treatment of chicken thigh with Abies alba essential oil in concentration 0.10% v/w and 0.20% v/w with combination vacuum packaging had positive influence on the reduction of oxidative processes in thigh muscles during chilling storage at 4 ±0.5 °C in comparative with tested groups -control air-packaged group, vacuum-packaged experimental group and vacuumpackaged experimental group with EDTA solution 1.50% w/w.The use of essential oil is one of the options increase shelf life of meat.

1 .
Oxidation of lipids can occur in both fresh and cooked meats (Min and Ahn, 2005; Jo et al., 2006), and can have significant impact to meat industry.

(
Economou et al., 1991; Yanishlieva and Marinova, 1995; Man and Jaswir, 2000), also Abies alba essential oil exhibits substantiating positive effect on oxidation stability of lipids in meat.Botsoglou et al. (2007) reported that a higher concentration of antioxidants in poultry meat has the effect of reducing lipid oxidation, i.e. there is a reduction in malondialdehyde values during chilling storage.Sampaio et al. (2012) examined the effect of combinations of sage, oregano and honey on lipid oxidation in cooked chicken meat (thigh and breast) during refrigeration at 4 ±0.5 °C for 96 h as measured by TBARs numbers.The analysis of variance on the TBARs data indicated that the TBARs values were significantly affected by natural antioxidants throughout refrigeration (p <0.05).Analysis their data showed that all of the three combinations of natural antioxidants tested would be beneficial for reducing the velocity of lipid oxidation in both chicken meats during storage, what are corroborated by other authors who have added honey and herbs and thereby inhibited the development of lipid oxidation in cooked meats during refrigeration time (McKibben and Engeseth, 2002; Juntachote et al., 2007a).