EFFECTS OF DIETARY ALPHA-TOCOPHERYL ACETATE ON LIPID OXIDATION FARMED RAINBOW TROUT (ONCORHYNCHUS MYKISS) FILLETS

George Liviu Mihalca¹, Ovidiu Tiţa¹, Ana Mihalca², Zsuzsana J. Sándor³

¹”Lucian Blaga” University, 550012,Str. Ion Raţiu, Nr.5-7, Sibiu, România, mihalca.liviu@yahoo.com
²”Ţara Bârsei” College of Prejmer, Prejmer, str. Brasovului, nr. 160A
³Research Institute for Fisheries, Aquaculture and Irrigation, Szarvas, Hungary

Abstract

Keywords: Trout fillets; Aquatic foods; Lipid oxidation; Total fat; Antioxidant; Omega-3 fatty acids

Flaxseed oil (FO) contains highest concentration of ω-3 fatty acid (FA) among plant-derived oils. Therefore, flaxseed oil may be used to supplement trout diets in order to increase the ω-3 FA content in fillets. However, the ω-3 FA are highly unsaturated, and therefore, susceptible to oxidation in fish fillets. Lipid oxidation causes meat quality deterioration, typically associated with development of rancidity. Hence, the FO-supplemented trout diets may need to be enhanced with higher concentration of an antioxidant to counteract lipid oxidation of fillets. The objective of this research was to determine lipid oxidation and potential strategies to increase oxidative stability of the fillets recovered from omega-3-enhanced farmed rainbow trout fed diets supplemented with FO and α-TA.

In the feeding experiment a trout diet was supplemented with 0, 8.5, or 15 g/100 g of flaxseed oil (FO). To prevent lipid oxidation of fillets, FO-supplemented diets were also enhanced with 0, 400, and 900 mg/kg of alpha-tocopheryl acetate (α-TA). Total fat, moisture content, and lipid oxidation of fillets were determined following fish harvest on days 0, 30, 60, 90, and 120. The experiment took place at Hărman Farm of Doripesco SA, Romania. A gravity-fed flow-through raceway system composed of four levels was used for this study. Each level had two parallel lanes and each lane had five tanks. Tanks were stocked with 75 rainbow trout fingerlings (age 11–12 months, average weight 240 g/fish, and average length 27 cm) per tank (size 91 x 122 x 91 cm). Rainbow trout were fed with dry pelleted diets mentioned above twice a day, feed was stored at 4 ⁰C. Trout fillet were homogenized in a laboratory blender and stored at -80 ⁰C until analysis Fat content in fillets was determined according to Soxhlet extraction method (AOAC, 1995). Oxidative rancidity of fillets was measured by a 2-TBARS assay of malondialdehyde (MDA) as described by Jaczynski and Park (2003).

Regardless of supplementing trout diets with FO or α-TA, no (P>0.05) difference of the total fat in fillets was measured. The effect of retarding lipid oxidation in fillets was recorded after supplementing trout with α-TA for 60 days. Our results indicate that regardless of FO level in trout diet, 900 mg/kg of α-TA can prevent lipid deterioration of fillets. However, to achieve more pronounced antioxidant effect in the ω-3- enhanced trout fillets, a synergetic effect of antioxidants and anaerobic packaging with α-TA supplementation should be investigated.

References

AOAC. (1995). Official methods of analysis (16th ed.). Washington, DC: AOAC

Jaczynski, J., and Park, J. W. (2003). Physicochemical properties of surimi seafood as affected by electron beam and heat. Journal of Food Science, 68, 1626–1630

Researches realized within the project POSDRU/6/1.5/S/26 funded of the Social European Fund by the Sectorial Operating Programm ”DEVELOPMENT OF THE HUMAN RESOURCES 2007 – 2013”