Chemical and Quality Evaluation of Some Alternative Lipid Sources for Aqua Feed Production Babalola T.O.O1* and D.F

Home , Acid value

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

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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. The peroxide concentrations in PKO and CO than GNO. It was not value of lard was significantly (P < 0.05) higher than detected in SBO, L, SFO and CF. Palmitic acid (16:0) values for other vegetable oils and animal fat occurred at similar concentration in L and GNO. sources. However, peroxide values in PKO, PO, SO, However, 16:0 concentrations in PO was higher than SBO, FO, GNO and CO were similar and significantly other lipid sources. Oleic acid (18:1n-9) also occurred lower than the value in other lipid sources. at similar levels in SBO, L and PO, the lowest The acid values of the oils ranged from 1.38 in CO to concentration of this fatty acid occurred in CO (4.18 14.04 NaOH/g in PKO and were significantly g/100g). Linoleic acid (18:2n-6) was highest in SFO different. Acid value of FO was not significantly (67.27 g/100g), followed by SO (53.94 g/100g) and different from that of MSO but was significantly higher MSO (50.46 g/100g) which are similar and lowest in than those of CO and SO and lower than those of PKO (1.98 g/100g). linolenic acid (18:3n-3) was CF, PO, L, SFO, GNO, SBO, and PKO. highest in SO (6.78 g/100g) and was not detected in SBO, L and CO. Eicosanoic acid (20:0) was highest The FFA content of CO and PKO was significantly in GNO (1.37 g/100g) and was not detected in FO, higher than that of the other lipid sources. SO had the PKO, L and CO. Arachidonic acid (20:4n-6) was least value which was significantly different from detected only in CF, while eicosapentaenoic acid was others. detected in FO, and CF. FO had the highest The FFA values for FO, CF and MSO are similar and concentration (9.39 g/100g) while CF has the lowest significantly lower than those of PKO, SBO, L, PO, concentration (0.15 g/100g). Docosanoic acid (22:0) SFO, CO and GNO. occurred only in SO and GNO. Among the long chain polyunsaturated fatty acids (LcPUFA) of C22, 22:4n-6 The iodine value of SFO, FO and SO were occurred only in CF, 22:5n-3 in FO and CF, and comparable and higher, while a lower value that was 22:6n-3 in FO and CO. Analyses demonstrated not significantly different were observed in GNO, CO highest concentration of saturated fatty acids in CO and MSO. The saponification number of the oils was and PKO, followed by SBO, PO, L and GNO, while significantly different. The highest saponification SFO had the lowest content. The bulk of the number was obtained in MSO. The saponification unsaturated fatty acid in SBO, L and PO are of the values are in the following order MSO > PKO > CF ≥ monounsaturated group. Although the highest CO = GNO = FO. The values for SBO, L, SO, PO, concentration of polyunsaturated fatty acids was and SFO were similar. found in SFO, it is predominantly of the n-6 PUFA Thiobarbituric acid reactive substances of the oils group. This is also reflected in its higher levels of n- were significantly different and showed low 6/n-3 fatty acid ratio. Substantial levels of n-3 PUFA concentrations. The highest content was obtained in was observed in FO, SO and GNO. The SO and CF while PKO had the lowest value which was not GNO are exceptional high in the n-3 fatty acid significantly different from that of PO, SO, FO, SBO content of the 18:3n3 among the vegetable oil and and CO. animal fats. However, the n-3 fatty acids of FO were predominantly of the LcPUFA of 20 and 22 carbons. Fatty acid composition of the oils: The fatty acid composition of fish oil, two terrestrial animal fats and

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Table 1 Chemical property of the different lipid sources. Lipid source* Peroxide value Acid value(mg FFA (as percentage Iodine value Saponification Thiobarbituric acid reactive mEqKg-1 NaOH/g oil) oleic acid) (mg/100g) number (mg substances (mg/kg) KOH/g oil)

FO 1.48b 4.87c 2.51cd 109.20e 201.33cd 0.016de

PKO 1.40ab 14.04j 7.05i 35.73b 345.33b 0.011e

SBO 1.00 a 11.21i 5.65h 65.67d 125.33d 0.016de

L 5.70f 8.41fg 4.23fg 67.73d 135.00d 0.056c

SO 1.37ab 2.70ab 1.54a 120.60ef 134.67d 0.015de

PO 1.2ab 6.91ef 3.55ef 50.70c 133.33d 0.013e

SFO 2.04c 9.21gh 4.82gh 125.17f 151.33d 0.025d

CO 1.55b 1.38a 7.33i 16.93a 237.67cd 0.017de

GNO 1.54b 10.28hi 5.26h 13.27a 209.00cd 0.160b

CF 4.28d 6.37de 3.08de 56.63cd 293.00c 0.429a

MSO 4.97e 4.17bc 2.05bc 22.30a 416.67a 0.052c

SEM 0.07 0.34 0.17 2.30 64.08 0.002

Values in the same column followed by the same letter are not significantly different at P > 0.05 *Lipid source as explained in the text

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Table 2 Fatty acid composition of the different lipid sources* (g/100g of total FA) Fatty acid molar% FO PKO SBO L SO PO SFO CO GNO CF MSO 12:0 ND 54.45 ND ND 0.14 0.18 ND 49.85 1.64 ND 0.02 14:0 9.10 14.61 ND 2.04 0.36 1.07 0.13 16.57 0.67 0.88 0.09 16:0 10.63 12.39 4.96 29.78 11.91 39.38 6.06 10.16 31.04 12.15 9.69 18:0 2.45 1.40 41.26 12.99 3.12 4.96 2.91 7.28 2.28 7.44 6.25 20:0 ND ND 1.18 ND 0.09 0.27 0.25 ND 1.37 0.35 0.27 22:0 ND ND ND ND 0.08 ND ND ND 3.08 ND ND 16:1n-9 11.45 ND ND ND ND ND ND ND ND ND 0.10 16:1n-7 ND 2.50 ND ND ND 0.11 0.12 0.25 ND ND ND 18:1n-9 11.81 12.09 46.55 45.23 23.58 43.93 21.65 4.18 19.81 30.95 32.56 18:1n-7 10.06 ND ND ND ND 1.64 1.49 ND ND 1.97 ND 20:1n-9 ND ND ND ND ND ND ND ND 1.24 ND 0.15 22:1n-9 ND ND ND ND ND ND ND ND 0.11 ND 0.21 18:2n-6 8.26 1.98 6.05 9.95 53.94 8.24 67.27 10.49 38.22 42.48 50.46 18:3n-6 9.07 ND ND ND ND ND ND ND ND ND ND 20:3n-6 2.02 ND ND ND ND ND ND ND ND 0.03 ND 20:4n-6 ND ND ND ND ND ND ND ND ND 0.04 ND 22:4n-6 ND ND ND ND ND ND ND ND ND 0.01 ND 18:3n-3 5.03 0.57 ND ND 6.78 0.22 0.10 ND 0.54 3.50 0.20 20:5n-3 9.39 ND ND ND ND ND ND ND ND 0.15 ND 22:5n-3 1.73 ND ND ND ND ND ND ND ND 0.04 ND 22:6n-3 8.99 ND ND ND ND ND ND 0.30 ND ND ND ∑SAT 22.18 82.85 47.40 44.81 15.70 45.76 9.35 83.82 40.08 20.82 16.32 ∑MUFA 33.32 14.59 46.55 45.23 23.58 45.57 23.14 4.43 21.16 32.95 33.02 ∑PUFA 44.50 2.55 6.05 9.95 60.72 8.46 67.37 10.79 38.76 46.06 50.66 ∑UNSAT 77.82 17.14 52.60 55.18 84.30 54.03 90.65 15.22 59.92 79.01 83.68 ∑n-6 19.35 1.98 6.05 9.95 53.94 8.24 67.27 10.49 38.22 42.56 50.46 ∑n-3 25.14 0.57 0.00 0.00 6.78 0.22 0.10 0.62 0.54 3.68 0.20 n-6/n-3 0.77 3.47 0.00 0.00 7.96 37.46 672.7 16.92 70.78 11.57 252.30 n-3/n-6 1.30 0.29 0.00 0.00 0.13 0.03 0.00 0.06 0.01 0.09 0.00 ND = not detected *Lipid sources as explained in the text

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DISCUSSION Formation of free fatty acid might be an important measure of rancidity in foods. FFA is formed due to Peroxide value (PV) is a measure of the hydrolysis of triglycerides and may be promoted by concentration of peroxides and hydroperoxides reaction of oil with moisture (Frega et al., 1999). This formed in the initial stages of lipid oxidation. PV is is a problem mainly encountered in products based one of the most widely used tests for the on lauric oils, such as coconut and palm kernel oil. measurement of oxidative rancidity and or The free fatty acids are liberated from the parent oils, deterioration of oils and fats. In this study peroxide which comprise large amounts of capric, lauric and values of less than 10 were obtained for all lipid myristic acids. These acids have a distinct soapy sources examined, mainly because they were flavour and have lower flavour threshold values than obtained fresh and has not been exposed to air and the longer chain fatty acids found in other oils and light - the agent of autoxidation – for a prolonged fats (Rossell, 1994). The result of this study shows time. Similar lower peroxide values of less than 10 that coconut oil and palm kernel oil had a higher FFA was obtained in canola oil, corn oil, coconut oil, grape value of 7.05 and 7.33 respectively. Free fatty acid seed oil, olive oil, palm olein, peanut oil, rapeseed oil, values of less than 5 obtained for FO, L, SO, PO, rice bran oil, sunflower oil, soybean oil, sesame oil, SFO, CF and MSO are within allowable limits for safflower oil and walnut oil by Gan et al. (2005). edible oils (Eckey, 1954), while the values for GNO However, higher value above this level was obtained and SBO are slightly above. The high FFA in PKO in hazelnut oil and extra virgin olive oil by the same and CO is comparable to that of cotton seed oil author. It has been showed that off-flavours, (Shahidi, 2004). This indicates that these oils with nutritional losses and other deteriorative changes in FFA values above the allowable limits may undergo oil arise by reaction with atmospheric oxygen, i.e., oxidation and aquafeed produced with such oils may oxidative rancidity, or by hydrolytic reactions become rancid. catalyzed by lipases from food or from microorganisms (Shahina et al., 2004). The low free fatty acid and acid value of SO, MSO and FO suggests their application as good edible oil. The peroxide value (PV), anisidine value (AV) and Free fatty acid and acid value of L, SFO, GNO, SBO free fatty acids (FFA) are good guides to the quality and PKO are high, indicating that they would require of oil. Good quality oil should have a PV less than 10 refining to make them suitable for edible purposes, units before off-flavours are encountered (Rossell, and may be better utilized for industrial purposes. 1994). The peroxide value of less than 2.10 meq/kg Free fatty acid is also related to smoke point in FO, PKO, SBO, SO, PO, SFO, CO and GNO in (Akintayo and Bayer, 2002). In this study, SO and this study compare favourably with 2.50 meq/kg in MSO with low free fatty acids value suggest high cotton seed oil (Popoola and Yangomoduo, 2006) smoke point, as such, they could be suitable for stir- and is not far from 1.50 meq/kg in groundnut oil fry cooking. The low free fatty acid in MSO may (Atasie et al., 2009). All the oils used in this study had explain the reason why it is used for various edible acceptable levels of PV which were less than 10 purposes from frying to soup ingredient in the South- units. The lower peroxide values of the lipids suggest western part of Nigeria. that the oil can be stored for a long period without deterioration. According to Ojeh (1981), oils with high In the tropics, where vegetable oils are the most peroxide values are unstable and easily become common dietary lipids, it has been shown that it is rancid. Oils become rancid when the peroxide value desirable to ensure that the free fatty acid contents of ranges from 20.0 to 40.0 mg/g oil. cooking oils lie within limits of 0.0–3.0% (Bassir, 1971). The low level of FFA in SO and MSO similar Acid value is used as an indicator for edibility of oil to those obtained by Gan et al. (2005) suggests that and suitability for use in the paint industry. The total the oils could be a good edible oil that will store for a acidity, expressed as acid value of CO, SO, MSO long time without spoilage via oxidative rancidity. and FO compares favourably with values for sesame, soybean and rape acid (Pearson 1976) and is similar Iodine value is a measure of overall unsaturation and to the values reported for the pulp and seed of D. is widely used to characterize oils and fats. It is edulis (Ajayi & Oderinde, 2002). These values are defined as the number of grams of iodine absorbed within the allowable limits for edible oils (Eckey, by 100 g of fat. The high iodine value in FO, SO and 1954). The nutritional value of a fat/oil depends, in SFO shows that these oils are rich source of some respects, on the amount of free fatty acids that polyunsaturated fatty acids that possess health develops. benefits, such as regulating blood cholesterol levels

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and lowering elevated blood pressure. High iodine abundant fatty acids in vegetable oils were lauric shows that the oils have the good qualities of edible acid (PKO and CO), palmitic acid (PO and GNO) oil and drying oil purposes (Eromosele et al., 1997). stearic (in SBO), oleic (in SBO and PO) and linoleic In contrast, GNO had the lowest iodine value of (in SO, SFO, GNO and MSO), which together 13.27. composed about 99.0% of the total fatty acids (Table 2). SO, SFO, GNO and MSO contained a high The saponification number of SBO, PO, SO, L and amount of linoleic acid (38.22 – 67.27 g/100g), which SFO are low (125.33 – 151.33 mg KOH/g); hence makes them especially prone to oxidation. These oils these oils are not likely to be suitable for soap are a rich source of polyunsaturated fatty acids that making. However, the saponification value of 209.00 possess favourable nutritional implications and health mg KOH/g for GNO makes GNO and other vegetable benefits, such as regulating blood cholesterol levels, oils with higher vales useful in soap making. The lowering elevated blood pressure and beneficial saponification values of SFO, FO, GNO and CO were physiological effects in the prevention of coronary comparable to the one obtained for safflower, heart disease and cancer (Oomah et al., 2000). High sunflower and corn oil (O’Brien, 2004) with average ratio polyunsaturated/saturated fatty acids are saponification numbers ranging between 191 and regarded favourably in the reduction of the serum 250 (Gunstone et al., 1994). cholesterol and atherosclerosis and the prevention of Thiobarbituric acid reactive substances (TBARS) heart diseases (Rudel et al., 1998; Ruggeri et al., values of the oils in this study were low (less than 1998). 0.5mg/kg oil). The lower value obtained in PKO, PO The appreciable concentration of oleic acid in the and SO substantiates the occurrence of the vegetable oils makes them desirable in terms of protective action of natural antioxidant in the oil nutrition (Corbett, 2003). High concentration of against peroxidation. This corroborates the assertion unsaturated fatty acids has also been linked with high of Nuernberg et al. (2002) that the possibility of a iodine value in oils. A comparative high iodine value sample to slow the formation of peroxidative of 120.60 and 125.17 in SO and SFO respectively degradation products (MDA) is an indication of its due to their high unsaturated fatty acids (Table 3.2) antioxidative capacity. shows that the oils has the good qualities of edible oil The presence of (TBARS) in a sample of oil or meat (Eromosele et al., 1997). indicates that lipid peroxidation has taken place and The fatty acid profile of fats and oils has a large the level of TBARS shows the amount of peroxidation bearing on their quality. The fatty acid profile affects that has already occurred (Lukaszewicz et al., 2004). the shelf-life, flavour and the stability of the oil. The The main thiobarbituric acid reactive substance that ratio of oleic to linoleic acid is a measure of oil is measured is the malonaldehyde, which is a stability (Worthington and Hammons, 1977), and it is secondary product formed as a result of lipid a critical factor in determining oil quality (Sanders et peroxidation (Ulu, 2004). TBARS values tend to have al, 1992). Shelf-life and flavour are determined, in a good correlation with sensory testing when being part; by how quickly oxidative rancidity occurs. used to detect rancidity of foods (Fernández et al., According to Mercer et al. (1990), oxygen reacts with 1997; Rhee and Myers, 2003; Campo et al., 2006), the double bonds of unsaturated fatty acids and making it a good choice of an assay to pair with shows that linoleic (18:2) is more susceptible than sensory testing. oleic (18:1), this is evident in the lower concentrations This test can also detect aldehydes, alk-2-enals and of peroxide and TBARS of PKO that has the lowest alk-2,4-dienals produced during lipid oxidation, concentration of linoleic acid. Others especially SFO although malonaldehyde is the primary substance had higher value of PV and TBARS. Palm oil has that is detected with this assay. Thiobarbituric acid been shown to have higher resistance to oxidative reacts with these substances to produce a red colour changes as a result of its higher saturated fatty acid that is measured using a spectrophotometer (at 532 content (Edem, 2002). The saturated and nm) (Inoue et al., 1998). monounsaturated fatty acids (mainly oleic) occur in relatively uniform concentrations in PO. This will be The fatty acid composition of oil is its most useful utilized by fish as an energy source leading to chemical feature. Many of the chemical tests for oil improved growth performance as obtained in other identity or purity can be related to their fatty acid fish species (Ng et al., 2003). The appreciable content (Pritchard, 1991). The results obtained concentration of n-3 and/or n-6 fatty acids in SO, PO, similar to that of Dhifi et al. (2004) show that the most

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SFO, CO, GNO, CF and MSO implies that these oil Campo, M. M., G.R. Nute, S.I. Hughes, M. Enser, J.D. sources will be ideal substitutes for FO in the diet of Wood and R.I. Richardson. (2006). Flavour perception H. longifilis, producing fish with higher weight and of oxidation in beef. Meat Sci. 303 – 311. fillet n-3 and n-6 PUFA similar to FO fed fish; Corbett, P. (2003). It is time for an oil change! because of the innate ability of freshwater fish to Opportunities for high oleic vegetables oils. Inform 14: elongate and desaturate 18C fatty acids. The results 480 – 481. of this study shows that the vegetable oils and the Dhifi, W., I. Hamrouni, S. Ayachi, T. Chahed, M. Saïdani terrestrial animal fats used possess good qualities and B. Marzouk. (2004). Biochemical characterization that makes them suitable as alternative lipids in diet of some Tunisian Olive oils. Journal of Food Lipids 11: of tropical freshwater fishes. 287 – 296. ACKNOWLEDGEMENTS Duncan, D.B. (1955). Multiple range and multiple (F) test. Biometrics, 11:1-42. The authors are grateful to Mr M.A.B. Adebayo of Department of Chemistry, University of Ilorin, Nigeria, Eckey, E. W. (1954). Vegetable fats and oils. New York: for technical assistance. Reinhold publ. Corporation. P. 347 REFERENCES Edem, D.O. (2002). Palm oil: biochemical, physiological, nutritional, hematological, and toxicological aspects: a Ajayi, I. A. and R. A. Oderinde. (2002). Studies on the oil review. Plant Foods Hum Nutr. 57:319–41. characteristics of Dacryodes edulis pulp and seed. Eromosele, I.C., C.O. Eromosele, P. Innazo and P. Njerim. Discovery and Innovation. 14: 20 – 24. (1997). Short communication: studies on some seeds Akintayo, E.T and E. Bayer. (2002). Characterisation and and seed oils. Bioresour. Technol. 64: 245 – 247. some possible uses of Plukenetia conophora and Fernández, J., J.A Pérez-Álvarez and J.A. Fernández- Adenopus breviflorus seeds and seed oils. López. (1997). Thiobarbituric acid test for monitoring Bioresource Technology 85: 95 – 97. lipid oxidation in meat. Food Chem. 59: 345-353. AOAC. (2000). Official method of analysis. Arlington, VA: Fonseca-Madrigal, J., V. Karalazos, P.J. Campbell, J.G. Association of Official Analytical Chemists (Official Bell and D.R. Tocher. (2005). Influence of dietary method 920.160 and 985.29). palm oil on growth, tissue fatty acid compositions, and AOCS. (2004). Official methods and recommended fatty acid metabolism in liver and intestine in rainbow practices of the American Oil Chemists’ Society. 5th trout (Oncorhynchus mykiss). Aquac. Nutr. 11: 241– ed. Champaign, Ill: AOCS (Method Cd 8-53 and Ca 250. 5a-40). Fontagné, S., D. Bazin, J. Brèque, C. Vachot, C. Bernarde, Atasie, V.N., T.F. Akinhanmi and C.C. Ojiodu. (2009). T. Rouault and P. Bergot. (2006). Effects of dietary Proximate analysis and physico-chemical properties oxidized lipid and vitamin A on the early development of groundnut (arachis hypogaea l.). Pak. J. Nutr. 8: and antioxidant status of Siberian sturgeon (Acipenser 194 – 197. baeri ) larvae. Aquaculture. 257: 400 – 411. Bassir, O. (1971). Handbook of practical biochemistry (2nd Frega, N., M. Mozzon and G. Lercker. (1999). Effects of ed.). Ibadan, Nigeria: Ibadan University Press. free fatty acids on oxidative stability of vegetable oil. Journal of the American Oil Chemists Society. 76(3): Bell, J.G., R.J. Henderson, D.R. Tocher and J.R. Sergent. 325 – 329. (2004). Replacement of dietary fish oil with increasing levels of linseed oil: modification of flesh fatty acid Gan, H.L., Y.B. Che Man, C.P. Tan, I. NorAini and S.A.H. composition in Atlantic salmon (Salmo salar) using a Nazimah. (2005). Characterisation of vegetable oils fish oil finishing diet. Lipids 39: 223 – 232. by surface acoustic wave sensing electronic nose. Food Chemistry 89: 507 – 518. Bell, J.G., J. McEvoy, D.R. Tocher, F. McGhee, P.J. Campbell and J.R.Sargent. (2001). Replacement of Geurden I., A. Cuvier, E. Gondouin, R.E. Olsen, K. fish oil with rapeseed oil in diets of Atlantic salmon Ruohonen, S. Kaushik and T. Boujard. (2005). (Salmo salar) affects tissue lipid compositions and Rainbow trout can discriminate between feeds with hepatocyte fatty acid metabolism. J. Nutr. 131: 1535– different oil sources, Physiology and Behaviour 85: 1543. 107 – 114. Boran, G., H. Karacam and B. Boran. (2006). Changes in Gunstone, F.D., L.H. John and B.P. Fred. (1994). The Lipid the quality of fish oils due to storage temperature and Handbook, 2nd ed. Chapman & Hall Chemical time. Food Chem. 98: 693 – 698. Database, United States.

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