AGRICULTURE AND BIOLOGY JOURNAL OF NORTH AMERICA ISSN Print: 2151-7517, ISSN Online: 2151-7525, doi:10.5251/abjna.2011.2.6.935.943 © 2011, ScienceHuβ, http://www.scihub.org/ABJNA Chemical and quality evaluation of some alternative lipid sources for aqua feed production Babalola T.O.O1* and D.F. Apata 2 1National Institute for Freshwater Fisheries Research, New-Bussa, Nigeria 2Department of Animal Production, University of Ilorin, Ilorin, Nigeria * Author for correspondence: E-mail:[email protected] ABTSTRACT A study was carried out on fish oil, two terrestrial animal fats (lard and chicken fat) and eight vegetable oils (palm kernel, sheabutter, soybean, palm, coconut, sunflower, groundnut and melon seed oils) to investigate their chemical and quality characteristics and the possibility of using them as alternative lipids in aquafeed. The results showed that the peroxide value of lard was significantly (P < 0.05) higher than values obtained in the other vegetable oils and animal fat sources; acid values of the oils ranged from 1.38 in coconut oil to 14.04 NaOH/g in palm kernel oil and were significantly different; the iodine value of sunflower oil, fish oil and soybean oil were comparable and higher, while a lower value that was not significantly different were observed in groundnut oil, coconut oil and melon seed oil. Thiobarbituric acid reactive substances of the oils were significantly different and showed low concentrations. The main fatty acids predominating in terms of relative abundance in the vegetable oils and animal fats examined are Lauric, palmitic, oleic and linoleic acids. Substantial levels of n-3 PUFA was observed in soybean oil and groundnut oil. The soybean oil and groundnut oil are exceptional high in the n-3 fatty acid content of the 18:3n-3 among the vegetable oils and would be a good lipid sources for tropical freshwater fishes. Keywords: animal fats; fatty acids; lipid oxidation; vegetable oil sustainable. However, the chemical characteristics of INTRODUCTION vegetable oils, specifically the fatty acid composition, could pose a problem. This is because most of the Lipids provide energy for fish. They also serve as a plant – based oils currently being investigated for the source of fat-soluble vitamins and essential fatty replacement of fish oil in aquafeeds, especially palm acids. Essential fatty acids are used to produce oil (PO), soybean oil (SO) and sunflower oil (SFO) hormone-like substances, such as prostaglandins are completely devoid of EPA and DHA (Bell et al., and leukotrienes that have a number of regulatory 2004; Geurden et al., 2005; Rinchard et al., 2006). functions including immune and inflammation Therefore, the sole use of these alternative lipid response. The fatty acids in the diets of fish can sources is limited. affect the fatty acid profile of their tissues (Fonseca- Madrigal et al., 2005). Lipid quality may be reduced by a degenerative oxidation process which lipid undergoes. Fish oil is a primary lipid used in aquafeed. It is high Polyunsaturated fatty acids are especially susceptible in fatty acids that are not common in many plant and to lipid peroxidation (Fernández et al.,1997). animal based oils. Fatty acids in fish oil include Vegetable oils may be oxidized in storage, making polyunsaturated fatty acids such as eicosapentaenoic them unappealing to the aquaculture industry, as acid (EPA) and docosahexaenoic acid (DHA), they higher shelf life is desirable for aquafeeds. Fish oil are commonly considered to be highly desirable for experiences similar problem with oxidation (Boran et use in aquaculture and in human nutrition. Current al., 2006). Exposure to oxygen, heat and light can research indicates that vegetable oils are good accelerate the oxidation process of oils (Ulu, 2004). alternative energy source fish as an energy source for growth (Ng et al., 2007; Stubhang et al., 2007). Peroxidations of oils lead to by-products that Consequently, much of the fish oil (FO) used in negatively affect the palatability and health benefits of aquafeeds might be wasteful in terms of its usage as the diets (Fontagné et al., 2006). Oils in aquafeeds energy source and could be replaced by vegetable are known to affect the carcass quality of the fish to oils, which are readily available, cost effective and which they are fed (Bell et al., 2001). Agric. Biol. J. N. Am., 2011, 2(6): 935-943 Lipid oxidation involves a complete set of reaction, oxidation (Pike, 1994). The determination of acid which may differ depending on the condition under values was as outlined by Ajayi and Oderinde (2002). which a lipid is stored. There are two main categories Free fatty acid content in the oil was determined by of methods used to test for lipid oxidation; predictive using a modified FFA method (AOCS, 1997 revised test and oxidation indicator assay. Predictive test are 2004). The saponification value (SV) was determined assays that are used to determine the amount of by AOAC (2000) method 920.160. In duplicate, about oxidation that could potentially occur in a sample. 2 g of the oil sample was added to a flask with 30 ml Two commonly used predictive tests are the oxidative of ethanolic KOH, and then attached to a condenser stability index and the iodine value assay (Nilson, for 30 min to ensure that the sample was fully 2008). The tests are used to determine the amount of dissolved. After the sample was cooled, 1 ml of oxidation that could potentially occur in a sample, phenolphthalein was added and titrated with 0.5 M oxidation indicator tests are used to determine the HCl until a pink endpoint was reached. The results amount of oxidation that has already occurred were expressed as milliEquivalents (mEq) of active (Lukaszewicz et al., 2004). These can be used to oxygen per kg of oil. determine the quality of oil in a sample. Three The TBA-reactive substances (TBARS) were commonly used oxidation indicator tests are the determined on oil samples as described by (Menoyo thiobarbituric acid reactive substances assay, the et al., 2002). Oil samples (2 g) were weighed into a peroxide value assay and the anisidine value assay test tube with 18 ml of 3.86% perchloric acid and (Nilson, 2008). were homogenized with a Brinkman Polytron7 for 15 Information on the composition and quality s at high speed. The homogenate was filtered characteristics of locally sourced lipids is scarce. The through a Whatman #1 filter paper. The filtrate (2 ml) objective of this study was to determine the fatty was mixed with 2 ml of 20 mM TBA in distilled water acids composition and quality characteristics of some and incubated in a boiling water bath for 30 min. After tropical vegetable oils and animal fats. The results cooling, the absorbance of filtrate was determined at will provide information on the potential of these 531 nm against blank containing 2 ml distilled water different lipids as alternative sources of lipid for and 1 ml of 20 mM TBA solution. The TBA numbers aquafeed. were expressed as milligrams of malonaldehyde per kilogram of oil. MATERIALS AND METHODS Fatty acid analysis: Fatty acid analysis was Materials: Fish oil (cod liver oil, FO), two terrestrial performed on three samples of each oil. The animal fats (lard (L) and chicken fat (CF)) and eight extraction of total lipids and preparation of fatty acid vegetable oils (sheabutter oil (SBO), palm kernel oil methyl esters was performed according to Sukhija (PKO), soybean oil (SO), palm oil (PO), sunflower oil and Palmquist (1988). Fatty acid analysis was carried (SFO), coconut oil (CO), groundnut oil (GNO) and out on a Perkin Elmer gas chromatograph (Model melon seed oil (MSO)) were the lipid sources used 8700) fitted with an automatic sampler (Model AS for this study. Commercially refined cod liver oil was 2000B) and FID detector. The conditions used were purchased from a local pharmaceutical shop, the following: Omegawax fused silica capillary soybean oil, palm oil, palm kernel oil, sheabutter oil, column (30 m x 0.25 mm I.D., 0.25 µm film thickness) coconut oil, sunflower oil, melon seed oil and (Supelco, Bellafonte, PA), temperature programmed groundnut oil were purchased from a local market in 0 0 from 100 to 250 C at 3 C/min, held for 10 min. Ilorin, Nigeria, lard and chicken fat were obtained Carrier gas was helium at 1.0 ml/min, inlet pressure from a local meat processing company in Ogbomoso, 12 psi. Fatty acids methyl esters were identified in Nigeria, melted and stored in an amber glass bottle TM comparison to an external standard (Supelco 37 until analysis.. component FAME Mix). Chemical analysis: Three samples of the lipid Statistical analysis: The chemical characteristics sources were analysed for their chemical and quality data was statistically treated using ANOVA and characteristic using the following standard Duncan’s multiple range test at P < 0.05 (Duncan, procedures: The peroxide value was determined by 1955) 0.05 was applied as a multiple sample the official AOCS Peroxide Value (PV) method Cd 8– comparison analysis. SPSS version 13.0 (SPSS Inc., 53 (AOCS, 1997, revised 2004). This iodometric Chicago, IL, USA) computer programs was used for titration method measures the peroxides and statistical analysis. hydroperoxides that are the initial products of lipid 936 Agric. Biol. J. N. Am., 2011, 2(6): 935-943 RESULTS eight vegetable oils are presented in Table 2. Lauric, Chemical properties of lipids: The results of the palmitic, oleic and linoleic acids are the four fatty peroxide value, acid value, free fatty acid iodine value acids predominant in terms of relative content in the saponification number and thiobarbituric reactive vegetable oils and animal fats examined. Among substances of fish oil, vegetable oils and terrestrial these, lauric acid (12:0) occurred at higher animal fats are presented in Table 1.