Investigation into the qualitative changes of fillet of broiler chickens fed by diet containing eugenol and butyric acid glycerides

Introduction: Chicken meat is considered as an easily available source of high-quality protein and other necessary nutrients which are essential for body functioning. In order to meet the consumers’ growing demands for high-quality protein, the poultry industry focused on selection of fast-growing broilers, which reach a body mass of about 2.5 kg within 6-week-intensive fattening. Relatively low sales prices of chicken meat, in comparison to other types of meat, speak in favor of the increased chicken meat consumption. In addition, chicken meat is known by its nutritional quality, as it contains significant amount of high-quality and easily digestible protein and a low portion of saturated fat. Composition of chicken meat can be influenced through modification of chicken feed composition (addition of different types of oils or essential oils, vitamins, microelements and amino acids), to produce enriched meat with functional ingredients (n-3 PUFA, carnosine, selenium and vitamin E). By this way, chicken meat becomes a foodstuff with added value, which, in addition to high-quality nutritional composition, also contains ingredients that are beneficial to human health. Eugenol is the major constituent [70% to 90%] in the aromatic oil extract from cloves (Syzygium aromaticum), also found in lower concentrations in cinnamon and other aromatic spices. In vitro, eugenol has been shown to have antibacterial, antifungal, antioxidant and antineoplastic activity. Butyric acid is a short-chain organic acid with a direct influence on stimulating the growth of enterocytes, as it is also used as an energy source for these cells. Thus, they help to improve intestinal integrity, acting as a barrier to pathogens and increasing nutrient absorption capacity, which consequently improves animal performance Butyric acid glycerides (mono-, di- and triglycerides of butyric acid) and are stable at pH and are therefore released directly into the intestine and being more efficient than the free butyric acid salts. The main aim of this research was to investigate the effect of adding glycerides of butyric acid and eugenol essence to the diet of broilers on meat chemical and qualitative properties.
Material and methods: To achieve this goal, 300 broiler chickens of commercial strain Ross 308 were selected in a completely random design. Six experimental diets including experimental diets containing two levels of butyric acid glycerides (0 and 0.2% w/w) and three levels of eugenol (0, 500, 1000 mg per kg of diet) and the control diet in the form of five replicates and 10 pieces. After 42 days, the broilers were slaughtered, cleaned, and fillets were moved to zip pack packaging, maintained at refrigerator until tests. The assays including chemical compounds, L*a*b* color parameters, volatile nitrogen substances (TVN) and thiobarbituric acid (TBA) were conducted on the fillets at programed times during 60 days of storgae. The data from the tests were analyzed by means of one-way Analysis of variance (one-way ANOVA) with SAS statistical software.
Results and discussion: The results of the data analysis showed that the addition of eugenol along with glycerides of butyric acid in the diet of broilers had no significant effect on the moisture and ash content of the fillets (p>0.05), while fat and protein extent of some treatments decreased significantly (p<0.05). L* values of T3 (fed by 1000 ppm eugenol) and T6 (fed by 0.2% w/w butyric acid glycerides and 1000 ppm eugenol) samples were highest and lowest, respectively. The b* values of all enriched diets were higher than that of the control. There was no significant difference among a* of all samples. The reason for decreasing L* of the samples fed by glycerides of butyric acid was pertain to higher pH of them, which cause to increase the intracellular water content and increasing light absorbance of chicken fillets. Overall color difference (ΔE) of the fillets collectd from the chickens fed by only eugenol (T2) and only 0.2% w/w butyric acid glycerides (T4) were highest and lowest, respectively. TBA values were not affected significantly by treatments, whereas storage time had a significant influence. Treatments containing 0.2% w/w butyric acid glycerides and eugenol indicated relatively lower TBA value than other treatments, and with increasing eugenol contents TBA more decreased due to antioxidant components (carvacrol, thymol, etc) of the essence. Similar to TBA, TVN values of the fillets increased significantly during 60 days of storage, without significant observation among different treatments at the same time. Against to TBA, chickens fed by only eugenol showed a decreased TVN values compared to other treatments.
Conclusion: According to the results, adding eugenol and glycerides of butyric acid to the diet of broiler chickens decreased fat content of fillets, which maybe considered as a beneficial function. Redness of meat (a*) wich is attended by consumers was not greatly influenced by diet. Oxidative resistance of fillets measured by TBA assays relatively improved specially by feeding butyric acid glycerides. The fillets ghatherd from broilers fed by only eugenol showed to some extent reduced proteolytic activity during storage. Consequently, incorporation of eugenol and butyric acid glycerides to broilers diet could improve the chemical traits of fillets, and to select an appropriate diet other physicochemical, textural and sensory properties of the fillets should be determined. Also, other edible sections of broilers such as legs and individual muscles, physiological properties of carcass and gastrointestinal microbial flora can be evaluated to better understanding the diet changing effects.