Polar and neutral lipid composition and fatty acids profile in selected fish meals depending on raw material and grade of products

Highlights

• High content of essential polyunsaturated fatty acids were recorded in homogenous meals.

• Significant differences were detected in odd and branched-chain fatty acids content.

• High content of phospholipids in homogenous meals were detected.

• Production technique determines the quality of the food products.

• Selected fish meals are a valuable functional ingredient of food or nutraceutical.

Abstract

Fish and fish products are widely distributed feed in aquaculture and agriculture. However, still little is known on the lipid composition of them, potential differences in the lipid profiles of various meals depending on fish composition of meal and process technology. Therefore, the aim of this study was to determine the characteristics of polar and neutral lipids in selected meals. The thirteen fish meals were analyzed using two mass spectrometry technique coupled with gas chromatography and liquid chromatography. The highest lipid content was detected in mixed meal prepared from many species – multi fish meal – (mackerel, trout, sprat, herring, perch, silver carp etc.). In our article for the first time such precise fatty acid profile including atypical acids, e.g. branched fatty acid, was described in fish meals. Polyunsaturated fatty acids (PUFA) dominated in Norsea Mink (Nsm), Mauretania Grade (MG), Human Grade Batch (HGB) and Low Temperature (LT) products, what was associated with the processing technique and whole fish was used for meal production. These products were also abundant in phospholipids. Meals did not subjected to extrusion process and without addition of antioxidant were characterized by low levels of n-3 PUFA and small diversity of polar and neutral lipids.

Introduction

Millions of tonnes of fish meal are produced and used in commercial diets for fish, dairy cattle, mink, poultry and swine (Aberoumand, 2010). In fish feed industry exist two types of animal feed, produced from whole fresh industrial fish and from fish offal (Jensen, Fiskeindustri, & Denmark, 1990). In 2008 world production of fish meal amounted about 5 million tons (Penven, Perez-Galvez, & Bergé, 2013) and currently, the supply is stable at 6.0 to 6.5 million tons annually (Miles and Chapman, 2006). In order to produce 1 ton of dry fish meal, 4 to 5 tons of whole fish are required (Miles and Chapman, 2006). Fish meals can be divided into 3 categories: fish meal made from fish, which are not suitable for human consumption (sandeel, Norway pout), fish meal made from fish, which can be consumed by human (blue whiting, sprat, capelin) and fish meal produced from fish, which are commonly consumed by human, but any surplus may be used for fish meal production (herring, mackerel) (Karalazos, 2007).

Balance of amino acids, fatty acids and phospholipids are essential for optimum growth, development and reproduction (Miles and Chapman, 2006, Usydus et al., 2011). Until now, authors mainly analyzed content of protein and amino acids composition in fishery products and in commonly available specification of fish products are presented mainly: total amount of protein, fat, water, salt, volatile nitrogen, minerals. Despite application of fish meal in agriculture and aquaculture and beneficial effects of fish meal, we still lack an accurate characteristics of their lipids. Only few previous studies analyzed the profiles of polar (PL) and neutral lipids in fish meal (Vik et al., 2015). Importantly, lipid content and stability of fish meal depends on storage conditions and processing, seasonal variations and fishery location (Samuelsen, Mjøs, & Oterhals, 2014) as well as presence of natural antioxidant (Bragadóttir, Pálmadóttir, & Kristbergsson, 2004). Other conditions, such as species of fish and part of organism intended for meal production will determine the dominant group of lipids (Jensen et al., 1990).

Therefore, the objective of this research was to identify the composition of molecular species of specific lipid classes in fish meal, which is produced in various technology process from whole fish (homogeneous meal) and from by-products of several species of fish (mixed meal). Characterization of lipids comprises a new information about the lipid composition in fish products. Two mass spectrometry (MS) technique was used. The total number of FAs was analyzed by using gas chromatography–mass spectrometry (GC–MS) technique with electron ionization (EI). Diacylglycerols (DAGs), triacylglycerols (TAGs), lysophospholipids (LPLs), phospholipids (PLs), ceramides and sphingomyelins were recorded using a liquid chromatography-electrospray-tandem mass spectrometry (LC-ESI-MS²) technique with Ultra Ion Trap and detector MS via diode array detector (DAD).