Proximate composition, lipid quality and heavy metals content in the muscle of two carp species

A. Merdzhanova*, V. Panayotova, D.A. Dobreva, K. Peycheva

Department of Chemistry, Faculty of Pharmacy, Medical University, 9000 Varna, Bulgaria (Manuscript received 2 August 2018; accepted for publication 12 October 2018)

Abstract. The aim of the presented study was to characterize the quality of edible tissue of freshwater common carp (Cyprinus carpio) and bighead carp (Aristichthys nobilis), based on their proximate and lipid composition (lipid classes, fatty acid profile, fat soluble vitamins, carotenoids and cholesterol). Health risk assessment was evaluated based on the analysis of some toxic elements (As, Cd, Ni, Pb and total Hg). Proximate composition (moisture, crude protein and total lipid) was determined using standard procedures. Lipids were subsequently separated into neutral (NL) and polar lipids: Phospho- (PL) and Glycolipids (GL) by means of column and thin-layer chromatography. Lipid classes were derivatized into fatty acid methyl esters (FAMEs) which were analysed by gas chromatography–mass spectrometry (GC-MS). Vitamins A, D3 and E, beta-carotene, astaxanthin and cholesterol were analysed simultaneously using high performance liquid chromatography (HPLC). Heavy metals (As, Pb, Cd, Hg and Ni) were determined by optical emission spectrometry with inductively coupled plasma (ICP-OES) following a microwave digestion procedure. Protein content was higher in bighead carp (18.5%) and lower for common carp (15.5%), whereas lipid content showed opposite trend. Similarities in lipid classes distribution were observed for both species: NL>GL>PL. Neutral lipids constituted approximately 70% of TL in both species, as FAs profile was dominated by monounsaturated fatty acids (MUFA), whereas polyunsaturated FAs (PUFA) prevailed in polar fractions. Omega-3 PUFAs were higher in all lipid classes compared to omega-6 PUFAs. Cholesterol content was low (17-24 mg.100-1g ww). Astaxanthin was detected only in bighead carp, whereas beta-carotene, vitamin D3 and vitamin A showed similar concentrations in both samples. Vitamin E content was higher in bighead carp (10.4 mg.100 g-1 w.w.). Trace elements content was higher in bighead carp showing a maximum value of As (0.312 mg.kg-1 w.w). All determined toxic elements were found below the recommended value in carp muscle. The results of the present study confirmed the high quality and safety of common carp and bighead carp meat. These freshwater species are valuable sources of essential nutrients such as proteins, vitamin D3 and long chain omega-3 PUFAs. Together with the nutrients, the information for low concentrations of toxic elements makes them valuable components of a healthy human diet.