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Fatty acid composition and degradation level of the oils used in canned fish as a function of the different types of fish
Journal of Food Composition and Analysis 24 (2011) 1117–1122
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Original Article
Fatty acid composition and degradation level of the oils used in canned fish as a function of the different types of fish Francesco Caponio *, Carmine Summo, Antonella Pasqualone, Tommaso Gomes Dipartimento di Biologia e Chimica Agro-Forestale ed Ambientale (DIBCA), Sezione di Scienze e Tecnologie Alimentari, Universita` degli Studi, Via Amendola, 165/a, I-70126 Bari, Italy
A R T I C L E I N F O
A B S T R A C T
Article history: Received 14 January 2011 Received in revised form 21 January 2011 Accepted 28 January 2011 Available online 12 February 2011
An experimental investigation was carried out to assess the fatty acid composition and the degradation level of the covering oil present in canned fish. The most commonly marketed canned fish types were considered (tuna, sardines, anchovies, mackerels), as well as different kinds of covering oil: extra virgin olive oil, olive oil, refined seed oil. A total of 68 samples were analyzed. Two-way analysis of variance, followed by Fisher’s Least Significant Difference test for multiple comparisons, and principal component analysis were carried out to compare the effect of both type of oil used and kind of fish on oil quality. The obtained results showed the lowest extent of both hydrolytic and oxidative degradation in samples containing extra virgin olive oil. In particular, the contents of triacylglycerol oligopolymers, imputable to secondary oxidative degradation, were equal to 0.17%, 0.50% and 0.74% for extra virgin olive oil, olive oil and refined seed oil, respectively. Olive oil showed significantly higher hydrolytic degradation, with diacylglycerols equal to 3.37%, but lower oxidative degradation and trans isomers content than refined seed oil. Finally, the type of fish did not seem to influence the extent of oxidative and hydrolytic degradation, with the only exception of sardines’ covering oil. This oil, characterized by the highest polyunsaturated fatty acid content, showed the highest values of oxidized triacylglycerols (1.32%) and specific absorption at 232 (K232, 4.030), indices of primary oxidative degradation. ß 2011 Elsevier Inc. All rights reserved.
Keywords: Canned fish Oxidative degradation Hydrolytic degradation Tuna Sardines Anchovies Mackerels HPSEC analysis Food analysis Food composition
1. Introduction Interest in fish consumption has increased in recent years due to the wide range of health benefits related to the high content of polyunsaturated fatty acids (PUFAs), especially eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), of this kind of food. PUFA, in particular n-3 and n-6, are considered essential fatty acids and have been shown to have curative and preventive effects on cardiovascular and inflammatory diseases and cancer. Moreover, they play an important role in the neurodevelopment of infants and in fat glycemic control (Karmali et al., 1984; Kinsella et al., 1990; Nettleton, 1995; Rambjor et al., 1996; Conner, 1997; Mozaffarian et al., 2005). In addition to fresh product, canned fish enables a delayed consumption of this appreciated kind of food. Among the different types of fish, the most used in canning manufacture are tuna, sardines, anchovies, mackerels, and oil is usually adopted as liquid medium. In fact, oil has a preserving effect and contributes to make the product more palatable. Its protective action lies in the ability to insulate products from air, rather than in an active bacteriostatic or bactericidal action. Among the different types of oil, the most
* Corresponding author. Fax: +39 080 5443467. E-mail address: [email protected] (F. Caponio). 0889-1575/$ – see front matter ß 2011 Elsevier Inc. All rights reserved. doi:10.1016/j.jfca.2011.01.019
commonly used in canning are: olive oil (OO, made up of refined olive oil blended with virgin oil other than ‘lampante’ oil, in an undefined ratio) and refined seed oils (RSOs), while extra virgin olive oil (EVOO, obtained from the fruits of Olea europaea L. by mechanical or other physical means that do not lead to any chemical changes) is seldom applied, and only in case of tuna. This situation is probably related to the commercial value of tuna, higher than that of the other types of fish considered. Then, merely from an economic point of view, the use of EVOO, the most expensive oil if compared to RSO and OO, is justified only for tuna. Various studies regarded the assessment of the genuineness of the liquid medium used in the production of in-oil canned fish (Bizzozzero and Carnelli, 1996; Cavallaro et al., 1996; Vitucci et al., 1999; Rossi et al., 2001). Caponio et al. (2003a) assessed the oxidative degradation of the oils used as covering media in canned tuna. This study was performed also to take into account the harmful effects caused by some intermediate and final products of oxidative degradation of the oil on consumers’ health (Billek, 2000; Saguy and Dana, 2003). More recently, Selmi et al. (2008) assessed the changes of lipid quality and histamine level during processing and storage of canned tuna, whereas Gladyshev et al. (2009) evaluated the content of essential PUFA in three canned fish species. Moreover, several studies were carried out in order to evaluate the metal traces in canned fish (Mol, 2010; Rahimi et al., 2010; Miklavcˇicˇ et al., 2011). However, no studies are reported
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about the degradation level of covering oils in other types of commonly marketed canned fish, as well as about the influence of the type of fish on the overall quality of oils utilized as liquid medium. The aim of this study was, therefore, to assess the fatty acid composition and the degradation level of the covering oils present in the most commonly marketed types of canned fish, as well as to assess the influence of fish on oil quality. 2. Materials and methods 2.1. Reagents and samples Analytical grade absolute ethanol, diethyl ether, phenolphthalein, sodium hydroxide, glacial acetic acid, chloroform, potassium iodine, starch, sodium thiosulphate, petroleum ether, methanol, hexane, hydrochloric acid; spectroscopy grade isooctane; high pressure liquid chromatography (HPLC) grade dichloromethane were used. All reagents were purchased from J.T. Baker (Deventer, Holland). Fatty acid methyl ester standard (189-19, purity >99%) were purchased from Sigma–Aldrich (St. Louis, MO, USA). Sixty-eight samples of in-oil canned fish were purchased at different retailers: 34 tuna cans (seven canned in EVOO, 18 in OO and nine in RSO); 11 sardine cans (seven canned in OO and four in RSO); 16 anchovies cans (eight canned in OO and eight in RSO); seven mackerel cans (five were canned in OO and two in RSO). In the laboratory, for each sample the oil/dripped fish ratio (w/w) was determined. First, the oil was drained from the cans and the remaining dripped fish was manually squeezed with a fork. Both the oil and the dripped fish were weighted. Then, the oil recovered from each can was filtered on anhydrous sodium sulphate using filter paper circles 5893 Blauband (Schleicher & Schu¨ll, Dassel, Germany). Fatty acid composition, trans isomers content, and degree of hydrolytic and oxidative degradation were determined for each oil sample. Reference standards (fish oil from menhaden, F8020; highly refined and low acidity olive oil, O1514; sunflower seed oil from Helianthus annuus, S5007) were purchased from Sigma–Aldrich and submitted to the same determinations as the drained oil samples to determine the oxidative and hydrolytic degradation.
2.3. Hydrolytic and oxidative degradation determination Analyses of the free fatty acids, the peroxide value, and specific absorptions were carried out for each sample according to the official methods of European Communities 2568/91 (Official Journal of the European Communities, 1991). The polar compounds (PCs) were separated by silica gel column chromatography according to the Association of Official Analytical Chemists method no. 982.27 (2003). After being recovered in dichloromethane they were analyzed by means of High Performance Size-Exclusion Chromatography (HPSEC) using dichloromethane as eluant at flow rate of 1 mL/min. The HPSEC system, consisted of a PerkinElmer series 200 pump (Norwalk, CT, USA) with Rheodyne injector, a 50 mL loop, a PerkinElmer PL-gel guard column of 5 cm length 7.5 mm i.d., and a series of three PerkinElmer PL-gel column of 30 cm length 7.5 mm i.d. each. The columns were packed with highly cross-linked styrene-divinylbenzene copolymer with particle of 5 mm and a pore diameter of 500, 500 and 100 A˚, respectively. The refractive index detector was a PerkinElmer series 200A. Peaks identification and quantification were carried out as described elsewhere (Gomes and Caponio, 1999; Caponio et al., 2003b). 2.4. Statistical analysis All the determinations were carried out in duplicate. Analysis of variance (ANOVA), followed by Fisher’s Least Significant Difference
2.2. Fatty acid composition and trans isomer determination Fatty acid and trans isomer determinations were carried out by gas-chromatographic analysis of fatty acid methyl esters, according to the official methods (Official Journal of the European Communities, 1991; American Oil Chemists’ Society, 1993). In particular, the oil was treated with methanol/hydrochloric acid (98/2, v/v), in a sealed phial, at 100 8C for 40 min. After cooling, the phial was opened and 2 mL of distilled water and 1 mL of hexane were added. Then, 1 mL of the hexane fraction was injected. The gas-chromatographic system was composed of a Fisons (Milan, Italy) High Resolution Gas-Chromatography (HRGC) mega 2 series, equipped with a flame ionization detector (FID) and a Supelco SPTM 2340 fused silica capillary column (Bellefonte, PA, USA), 0.25 mm i.d. 60 m length and 0.20 mm film thickness. The temperature of the split injector was 210 8C, with a splitting ratio of 1:100; the detector temperature was 220 8C. The oven temperature was programmed from 160 to 200 8C, with increments of 1.3 8C/min and final isothermal of 15 min. Hydrogen was utilized as carrier gas. The identification of each fatty acid was carried out by comparing the retention time with that of the corresponding standard methyl ester. Several analyses carried out on the same sample produced a repeatability coefficient of per cent variation (CV%) of about 5%.
Fig. 1. Mean values, standard error and results of statistical analysis (p < 0.05) of the ratio oil/dripped fish (w/w) 100, according to both the type of oil used as liquid medium (A) and the type of fish (B). (a–c) Different letters indicate significant differences. Extra virgin olive oil, obtained from the fruits of Olea europaea L. by mechanical or other physical means that do not lead to any chemical changes; olive oil, made up of refined olive oil blended with virgin oil other than ‘lampante’ oil; seed oils, represented by sunflower, soybean and corn oils.
F. Caponio et al. / Journal of Food Composition and Analysis 24 (2011) 1117–1122
(LDS) test for multiple comparisons, and principal component analysis (PCA) were carried out on the experimental data by the XLStat software (Addinsoft SARL, New York, NY). 3. Results and discussion Fig. 1 shows the mean values, standard error and the results of statistical analysis of the percent ratio oil/dripped fish (w/w) according to both the different type of oil used (A), and the
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different kind of fish (B). Regarding the oils (Fig. 1A), the data showed increasing ratio values comparing the fish product in EVOO with those in OO, and in RSO, although significant differences (p < 0.05) were detected only comparing the latter to the first two types of fish product. The presence of a lower amount of preserving liquid medium might be attributed to the greater commercial value of EVOO as compared to OO and, especially, to RSO. Regarding the type of fish (Fig. 1B), the canned anchovies showed significantly higher mean values (p < 0.05) of
Table 1 Mean values, standard deviations and results of statistical analysisa of fatty acids, as percent of total fatty acids, of the different types of covering oils recovered from the examined fish cans. Fatty acids
Extra virgin olive oilsb (n = 7) Mean value
C14:0 C15:0 C16:0 C16:1 C17:0 C17:1 C18:0 C18:1 C18:2 C18:3 C18:4 C20:0 C20:1 C20:4 C20:4 C20:5 C22:0 C22:5 C22:6 C24:0
w6 w3
w3 w3
Olive oilsc (n = 38) SD
nd nd 12.96 1.30 0.06 0.11 2.55 72.55 8.63 0.65 nd 0.35 0.26 nd 0.01 0.04 0.03 nd 0.46 0.02
Mean value
SD
*
– – 2.38 0.48 0.01 0.03 0.30 3.32 1.30 0.03 – 0.05 0.06 – 0.03 0.05 0.03 – 0.25 0.02
Seed oilsd (n = 23)
0.29 0.03* 12.44* 1.41* 0.16* 0.17* 2.92 70.55* 8.56 0.87 0.10* 0.39 0.35* 0.01* 0.04* 0.48* 0.07* 0.05* 1.09* 0.04*
0.60 0.06 2.18 0.88 0.16 0.09 0.61 6.52 2.36 1.59 0.20 0.05 0.14 0.01 0.08 0.92 0.10 0.11 1.07 0.03
Mean value
SD
*
0.56 0.05* 10.69* 0.66* 0.17* 0.11* 3.85 27.21 50.47 3.75 0.20* 0.30* 0.25* 0.01* 0.05* 0.77* 0.09* 0.07* 0.63* 0.11*
1.06 0.08 2.88 0.97 0.20 0.13 0.62 10.71 10.03 2.61 0.46 0.06 0.09 0.02 0.11 1.44 0.07 0.14 0.95 0.06
SD, standard deviation; nd, not detected (the limit of detection is 0.005%). a One way analysis of variance considering the effect of the fish variable on each type of oil. b Oil obtained from the fruits of Olea europaea L. by mechanical or other physical means that do not lead to any chemical changes. c Refined olive oil blended with virgin oil other than ‘lampante’ oil. d Sunflower, soybean and corn oils. * Significant influence of the independent variable at p < 0.05.
Table 2 Mean values and results of two-way analysis of variance, followed by Fisher’s Least Significant Difference test for multiple comparisons, of the analytical data of the different types of oils recovered from the examined fish cans as a function of both the type of covering oil and kind of fish. Parameters
Model (p value)
Type of oil EVOO (n = 7)
Fatty acid composition (as percent of total fatty acids) C14:0–C17:1 <0.001 14.44AB C18:0–C20:1 <0.001 84.91AB C20:4–C24:0 <0.001 0.56B SFA <0.001 15.98A MUFA <0.001 74.13A PUFA <0.001 9.79B PUFA-(C18:2 + C18:3) <0.001 0.51B Total trans fatty acids <0.001 0.00B Hydrolytic and oxidative degradation determination FFA (g/100 g) 0.155 0.70A PV (mequiv. O2/kg) 0.265 8.8A K232 <0.001 1.79B K270 <0.001 0.34B DK <0.001 0.06AB PCs (g/100 g) <0.001 3.28C TAGP (g/100 g) <0.001 0.17C ox-TAG (g/100 g) <0.001 0.60B DAG (g/100 g) <0.001 2.23B
Type of fish OO (n = 38)
So (n = 23)
Tuna (n = 34)
Sardines (n = 11)
Anchovies (n = 16)
Mackerels (n = 7)
14.48A 83.43B 1.77A 16.33A 72.16A 11.19B 1.76A 0.32B
12.24B 85.50A 1.73A 15.82A 28.23B 55.42A 1.73A 0.77A
12.40bc 86.79a 0.61c 14.98c 61.55a 23.27b 0.52c 0.36a
20.32a 73.26c 5.79a 21.41a 47.80b 30.17a 6.09a 0.60a
11.61c 87.19a 0.91c 14.69c 50.79b 34.25a 0.81c 0.49a
14.26b 82.68b 2.02b 16.71b 61.60a 20.65b 2.13b 0.51a
0.56A 3.5B 2.35B 0.64B 0.03B 5.57A 0.50B 0.79B 3.37A
0.52A 3.0B 3.99A 1.70A 0.10A 4.88B 0.74A 1.56A 1.71B
0.47b 3.5a 2.52b 0.90b 0.05b 4.92b 0.58a 0.93b 2.75a
0.41b 3.0a 4.03a 1.01ab 0.04b 5.08ab 0.66a 1.32a 2.18b
0.77a 5.2a 2.82b 1.23a 0.08a 5.73a 0.51a 1.14ab 2.98a
0.74ab 2.7a 2.99b 0.84b 0.04b 5.17ab 0.45a 0.94b 2.66ab
EVOO, extra virgin olive oil obtained from the fruits of Olea europaea L. by mechanical or other physical means that do not lead to any chemical changes; OO, olive oil obtained from refined olive oil blended with virgin oil other than ‘lampante’ oil; So, seed oils represented by sunflower, soybean and corn oils. SFA, saturated fatty acids; MUFA monounsaturated fatty acids; PUFA, polyunsaturated fatty acids; FFA, free fatty acids; PV, peroxide value; K232, specific absorption at 232 nm; K270, specific absorption at 270 nm; DK, K270 (K274 + K266)/2; PCs, polar compounds; TAGP, triacylglycerol oligopolymers; ox-TAG, oxidized triacylglycerols; DAG, diacylglycerols. Different letters mean significant difference at p < 0.05. Uppercase letters are used to compare the samples considering the effect of the type of oil; lower letters are used to compare the samples considering the effect of the type of fish.
F. Caponio et al. / Journal of Food Composition and Analysis 24 (2011) 1117–1122
Table 3 Oxidative and hydrolytic degradation of the reference standards.a
showed the lowest values of C20:4–C24:0 and PUFA-(C18:2 + C18:3); on the contrary, sardine cans showed the highest values of these indices, due to a greater extent of the diffusive phenomena (Tarley et al., 2004). Moreover, respect to the other types of canned fish, the covering oils in sardine cans showed higher contents of saturated fatty acids (SFA) and C14:0–C17:1. PUFA were higher in anchovies and sardines, the sum C18:0–C20:1 prevailed in anchovies and tuna, while MUFA in tuna and mackerels. Finally, unsaturated fatty acids’ trans isomers were detected only in refined oils (RSO and OO), whereas in EVOO were absent. Their mean values were significantly (p < 0.05) higher in RSO than in OO. This might be due to a higher amount of PUFA in RSO than in OO. Nutritionists address a great attention towards this category of substances, rarely observed in natural vegetable oils, because the presence of trans isomers, in association with a scarcity of essential fatty acids, 1
A
PUFA
Total trans fatty acids
0.5
Anchovies
0.25
Fish oil
Olive oil
Sunflower oil
FFA (g/100 g) PV (mequiv. O2/kg) K232 K270 DK PCs (g/100 g) TAGP (g/100 g) ox-TAG (g/100 g) DAG (g/100 g)
0.27 12.6 0.53 0.13 0.01 7.50 1.37 2.24 2.90
0.09 8.3 0.16 0.02 0.00 5.80 0.36 1.49 3.55
0.08 11.1 0.15 0.08 0.01 3.87 0.37 1.25 1.73
FFA, free fatty acids; PV, peroxide value; K232, specific absorption at 232 nm; K270, specific absorption at 270 nm; DK, K270 (K274 + K266)/2; PCs, polar compounds; TAGP, triacylglycerol oligopolymers; ox-TAG, oxidized triacylglycerols; DAG, diacylglycerols. a Fish oil from menhaden, F8020; highly refined and low acidity olive oil, O1514; sunflower seed oil from Helianthus annuus, S5007 (Sigma–Aldrich, St. Louis, MO, USA).
C18:0-C 20:1
PUFA-
(C18:2+C18:3) Sardines 0 C20:4-C 22:6
Tuna
Mackerels
SFA
-0.25
Extra virgin olive oil
C 14:0-C17:1 -0.5 -0.75 Olive oil
MUFA
-1 -0.75
-1
-0.5
-0.25
0
0.25
0.5
0.75
1
PC1 (57.46 %)
B
4
SoT
3 2
SoT
SoT
SoSa
SoSa SoSa SoM SoSa
SoT
SoA SoA SoT SoA SoA SoASoA SoT SoA SoT SoA SoT SoT
SoM
1 OA 0 OA OM OT OT OT OT OM OT OT OA OA ET OT OT OA OT ET OM ET OM OM OA OA OT OT OT OT OT OT OT ET ETOA ET ET
OSa OSa OSa OSaOSa OSa
-1 OSa -2
Parameters
Seed oils
0.75
PC2 (30.28 %)
the oil/dripped fish ratio than those found in the other types of fish products. These findings could be imputable to the different processing technology of the examined samples (Pirati, 1971; Pellegrino and Tortonese, 2001), as well as to the nature of anchovy flesh. Table 1 reports the mean values and standard deviations of percent fatty acid composition of covering oils recovered from the examined samples, as well as the results of one-way ANOVA. The overall data obtained indicate the presence of characteristic fatty acids of fish, in particular C20:5 and C22:6 (Osman et al., 2001; Tarley et al., 2004; Selmi et al., 2008), confirming the findings of other authors about an interchange between fish lipid fraction and covering oil (Bizzozzero and Carnelli, 1996; Cavallaro et al., 1996; Vitucci et al., 1999; Rossi et al., 2001). Moreover, the statistical analysis evinced that the fatty acid composition of liquid medium was significantly (p < 0.05) influenced by the fish variable due to diffusion of fish lipids into covering oil. In particular, sardines were the most responsible for this variability (data not shown). Besides, for the categories EVOO and OO, the observed compositional data confirmed the expected composition for oils derived from O. europaea correct marketing categorization of the oil. The high variability observed in case of RSO was due to the different botanical origins of the starting oily seeds (Merrien et al., 1996). Table 2 shows the analytical data of canned fish as a function of both the type of covering oil and kind of fish, as well as the results of two-way ANOVA (followed by Fisher’s LSD test for multiple comparisons), whereas in Table 3 the results of the analyses assessing the oxidative and hydrolytic degradation of the reference standards are reported. The ANOVA models were significant for all the examined parameters (p < 0.001), with the exception of the models for free fatty acids and peroxide value. This pointed out that both type of oil and type of fish were responsible for most of data variability. Regarding the type of oil, the differences in fatty acid composition were related to the different botanical nature of the various categories of oil used. In particular, the mean values of monounsaturated fatty acids (MUFA) were significantly higher in EVOO and OO than in RSO. On the contrary, PUFA percentage was significantly (p < 0.05) higher in RSO than in EVOO and OO. Moreover, significantly (p < 0.05) different mean values were observed comparing the sums of C14:0–C17:1 and C18:0–C20:1 obtained for OO and RSO. The detected values of long-chain fatty acids C20:4–C24:0 and PUFA-(C18:2 + C18:3), that include those fatty acids typically present in fish, indicated a diffusion from fish flesh to covering oils. These indices were significantly (p < 0.05) lower in EVOO than in OO and RSO. This could be due to the different fish/ oil ratio of samples as well as to the different fat content of fishes (Pirati, 1971; Pellegrino and Tortonese, 2001). Tuna samples
PC2 (30.28 %)
1120
SoT
-3 -4 -5 -8
-7
-6
-5
-4
-3
-2
-1
0
1
2
3
4
5
PC1 (57.46 %) Fig. 2. Results of the principal components analysis of the data regarding the fatty acid composition and trans isomers content of the covering oil of the fish cans. Plots of variables loadings (A) and observations scores (B) for first two principal components (SFA, saturated fatty acids; MUFA, monounsaturated fatty acids; PUFA, polyunsaturated fatty acids; E, extra virgin olive oil, obtained from the fruits of Olea europaea L. by mechanical or other physical means that do not lead to any chemical changes; O, olive oil, made up of refined olive oil blended with virgin oil other than ‘lampante’ oil; So, seed oils, represented by sunflower, soybean and corn oils; Sa, sardines; M, mackerels; T, tuna; A, anchovies).
F. Caponio et al. / Journal of Food Composition and Analysis 24 (2011) 1117–1122
100
4.5 4
Eigenvalues
3 60 2.5 2 40 1.5 1
Cumulative variability (%)
80
3.5
20
0.5 0
0 P C1 P C2
P C3
P C4
P C5
P C6
P C7
P C8
OO than in EVOO. In fact, TAGP are mainly formed during the refining process, that involves the exposure to high temperatures (Dobarganes et al., 1988; Carlson, 1996; Hodgson, 1996; Hopia, 1993; Gomes and Caponio, 1998; Gomes et al., 2003a). The unexpected presence of TAGP also in EVOO could be due to the step of thermal stabilization of canned fish. In fact, usually these substances are absent in freshly extracted EVOO and may increase up to about 0.1% during shelf-life, depending to storage conditions (Caponio et al., 2005). The significantly (p < 0.05) lower peroxide value detected in refined oils than in EVOO did not indicate a really low oxidative degradation level of OO and RSO, but was due to the fact that these oils come, entirely (RSO) or in part (OO), from a refining process. In fact, during refining the hydroperoxides are degraded and/or modified by the catalytic action of bleaching earth (Hodgson, 1996). Regarding the fish variable, it was observed that the sardines’ covering oil showed the highest values of ox-TAG and K232, indices 1
A
P Cs
0.75
P C9
Fig. 3. Results of the principal components analysis of the data regarding the oxidative and hydrolytic degradation of the covering oil of fish cans. Plot of eigenvalues (bars) and cumulative variability (line).
FFA
DA G
0.5 PV
PC2 (21.02 %)
Olive oil
TA GP K270
Anchovies
0.25
o x-TA G K232
ΔK 0
Mackerels
Sardines Seed oil
-0.25
Tuna Extra virgin olive oil
-0.5 -0.75 -1 -1
-0.75
-0.5
-0.25
0
0.25
0.5
0.75
1
PC1 (42.39 %)
B
5 O 4
So
O
So
3 So
So
PC2 (21.02 %)
can provoke metabolic imbalance as well as cardiovascular diseases. In particular, their intake increase low density lipoprotein (LDL) levels similarly to those caused by SFA, but unlike SFA, trans isomers simultaneously reduce high density lipoprotein (HDL) levels (Koletzko and Decsi, 1997; Morrison et al., 2008). The fish variable did not appear to affect the content of trans isomers in a significant way. Fig. 2 shows the score plot (A) and the loading plot (B) of PCA of fatty acid compositional data. The first two variables accounted for about 88% of total variability. In particular, PC1 explained over 57% of variability, enabling to distinguish sardines’ covering oil – characterized by high amounts of SFA, short and medium chain fatty acids (C14:0–C17:1), and fatty acids typical of fish lipids – from covering oils of other canned fish types, with high values of the sum C18:0–C20:1. PC2 explained about 30% of variability and discriminate the canned fish samples on the basis of the type of oil used. In the upper part of Fig. 2 are grouped fish canned in RSO, characterized by higher content of PUFA and trans isomers than the other types, while in the lower part are present those covered by OO and EVOO, that showed higher levels of MUFA than RSO samples. Considering the indices of oxidative and hydrolytic degradation, data in Table 2 indicate that the PCs – comprising all the substances having a polarity higher than that of the unaltered triacylglycerols – were significant (p < 0.05) higher in OO than in RSO and, above all, in EVOO. The HPSEC analysis of the PCs pointed out that diacylglycerols (DAG) were the most abundant class of substances. DAG were significantly (p < 0.05) higher in OO than in EVOO and in RSO, evidencing a higher hydrolytic degradation of OO. As a consequence, OO showed the highest content of PCs. Regarding FFA, no significant difference was observed among samples. This indicated the limited reliability of FFA determination to evaluate the actual extent of hydrolytic degradation of refined oils (OO and RSO), and pointed out the need of determining the DAG content. In fact, FFA are removed during the neutralization phase of the refining process of oils (Hodgson, 1996). Regarding the oxidative degradation, RSO showed the greatest extent of both primary and secondary oxidation, with significantly (p < 0.05) higher mean values of K232, K270, DK, oxidized triacylglycerols (ox-TAG), and triacylglycerol oligopolymers (TAGP) than the other oils. This result confirms the observations of the same authors in a previous work about canned tuna (Caponio et al., 2003a). Moreover, considering the olive oils, the levels of TAGP were found to be significantly (p < 0.05) higher in
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2
O O
1 O
So
O O O OO O OO O O O O OOOO
O
O So
O
So
So
So
0 So
O OO O O O O OO OEE O O O OE E E E E
-1
-2
So SoSoSo SoSo So So So So So So So
-3 -5
-4
-3
-2
-1
0
1
2
3
4
5
6
PC1 (42.39 %) Fig. 4. Results of the principal components analysis of the data regarding the degree of oxidative and hydrolytic degradation of the covering oil of the fish cans. Plots of variables loadings (A) and observations scores (B) for first two principal components (PCs, polar compounds; TAGP, triacylglycerol oligopolymers; ox-TAG, oxidized triacylglycerols; DAG, diacylglycerols; FFA, free fatty acids; PV, peroxide value; K232, specific absorption at 232 nm; K270, specific absorption at 270 nm; DK, K270— (K274 + K266)/2; E, extra virgin olive oil, obtained from the fruits of Olea europaea L. by mechanical or other physical means that do not lead to any chemical changes; O, olive oil, made up of refined olive oil blended with virgin oil other than ‘lampante’ oil; So, seed oils, represented by sunflower, soybean and corn oils).
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of primary oxidative degradation. These findings were probably due to the highest content of PUFA-(C18:2 + C18:3). TAGP levels, considered a reliable index of secondary oxidative degradation of oils and fats (Gomes et al., 2003b; Bilancia et al., 2007; Caponio et al., 2007), were not significantly different among samples, indicating that the fish variable did not influence this parameter. The other indices did not show a univocal behaviour. The differences among them were probably due to the different type of raw material used. Fig. 3 plots the eigenvalues and the cumulative variability explained by the principal components of data regarding both the hydrolytic and oxidative degradation of examined oils. First three principal components allow to explain about 75% of total variability. About 42% of total variability was explained by PC1, while PC2 and PC3 accounted for about 21% and 12% of total variability, respectively. Fig. 4 plots the observation scores and the variable loadings of the first two principal components. These principal components accounted mainly for the variability due to the different typologies of oils used as covering medium of canned fish and to the variations of oxidative degradation. In particular, PC1 pointed out the differences among the fish canned in RSO and those in EVOO or OO. This principal component was positively correlated with the amounts of K232, K270, ox-TAG, TAGP and DK, that characterize the RSO. The PC2, instead, helped to discriminate the samples canned in EVOO from those in OO. The latter were characterized by high contents of DAG and PCs. Finally, the fish variable did not show to influence the extent of oxidative and hydrolytic degradation of covering oils. 4. Conclusions On the whole, the covering oil of canned fish showed a high level of oxidative degradation when constituted by RSO and a high hydrolytic degradation in case of OO. The samples canned in EVOO presented a lower extent of both hydrolytic and oxidative degradation. Finally, the type of fish did not seem to influence the extent of oxidative and hydrolytic degradation, with the only exception of sardines’ covering oil. This oil, characterized by the highest PUFA content, showed the highest values of ox-TAG and K232, indices of primary oxidative degradation. References American Oil Chemists’ Society, 1993. In: Firestone, D. (Ed.), Official Methods and Recommended Practices of the AOCS. 4th ed. AOCS Press, Washington, DC, USA (Method Chapter 1–91). Association of Official Analytical Chemists, 2003. In: Horwitz, W. (Ed.), Official Methods of Analysis of AOAC International. 17th ed. Arlington, VA, USA, AOAC Press. Bilancia, M.T., Caponio, F., Sikorska, E., Pasqualone, A., Summo, C., 2007. Correlation of triacylglycerol oligopolymers and oxidised triacylglycerols to quality parameters in extra virgin olive oil during storage. Food Research International 40, 855–861. Billek, G., 2000. Health aspects of thermoxidized oils and fats. European Journal of Lipid Science and Technology 102, 587–593. Bizzozzero, N., Carnelli, L., 1996. Fatty acid composition and trans unsaturation of the covering oil of canned mackerels and tunas. Industrie Alimentari 35, 680– 683. Caponio, F., Bilancia, M.T., Pasqualone, A., Sikorska, E., Gomes, T., 2005. Influence of the exposure to light on extra virgin olive oil quality during storage. European Food Research and Technology 221, 92–98. Caponio, F., Gomes, T., Pasqualone, A., Summo, C., 2007. Use of the high performance size exclusion chromatography analysis for the measurement of the degree of hydrolytic and oxidative degradation of the lipid fraction of biscuits. Food Chemistry 102, 232–236. Caponio, F., Gomes, T., Summo, C., 2003a. Quality assessment of edible vegetable oils used as liquid medium in canned tuna. European Food Research and Technology 216, 104–108.
Caponio, F., Gomes, T., Summo, C., 2003b. Assessment of the oxidative and hydrolytic degradation of oils used as liquid medium of in-oil preserved vegetables. Journal of Food Science 68, 147–151. Carlson, K.F., 1996. Deodorization. In: Hui, Y.H. (Ed.), Bailey’s Industrial Oil & Fat Products. John Wiley & Sons Inc., New York, USA, pp. 339–390. Cavallaro, A., Bizzozzero, N., Carnelli, L., 1996. Fatty acid composition and trans unsaturation of the covering oil of canned sardines. Industrie Alimentari 35, 801–805. Conner, W.E., 1997. The beneficial effects of omega-3 fatty acids: cardiovascular disease and neurodevelopment. Current Opinion in Lipidology 8, 1–3. Dobarganes, M.C., Pe´rez-Camino, M.C., Ma´rquez-Ruiz, G., 1988. High performance size exclusion chromatography of polar compounds in heated and non-heated fats. Fat Science Technology 90, 308–311. Gladyshev, M.I., Sushchik, N.N., Makhutova, O.N., Kalachova, G.S., 2009. Content of essential polyunsaturated fatty acids in three canned fish species. International Journal of Food Sciences and Nutrition 60, 224–230. Gomes, T., Caponio, F., 1998. Evaluation of the state of oxidation of olive-pomace oils. Influence of the refining process. Journal of Agricultural and Food Chemistry 46, 1137–1142. Gomes, T., Caponio, F., 1999. Effort to improve the quantitative determination of oxidation and hydrolysis compound classes in edible vegetable oils. Journal of Chromatography A 844, 77–86. Gomes, T., Caponio, F., Delcuratolo, D., 2003a. Fate of oxidized triglycerides during refining of seed oils. Journal of Agricultural and Food Chemistry 51, 4647–4651. Gomes, T., Caponio, F., Delcuratolo, D., 2003b. Non conventional parameters for quality evaluation of refined oils with special reference to commercial class olive oil. Food Chemistry 83, 403–408. Hodgson, A.S., 1996. Refining and bleaching. In: Hui, Y.H. (Ed.), Bailey’s Industrial Oil & Fat Products. John Wiley & Sons Inc., New York, USA, pp. 157–212. Hopia, A., 1993. Analysis of high molecular weight autoxidation products using high performance size exclusion chromatography: II. Changes during processing. Food Science and Technology 26, 568–571. Karmali, R.A., Marsh, J., Fuchs, C., 1984. Effect of n-3 fatty acids on growth of rat mammary tumor. Journal of the National Cancer Institute 75, 457–462. Kinsella, J.E., Lokesh, B., Stone, R.A., 1990. Dietary n-3 polyunsaturated fatty acids and amelioration of cardiovascular disease: possible mechanisms. American Journal of Clinical Nutrition 52, 1–28. Koletzko, B., Decsi, T., 1997. Metabolic aspects of trans fatty acids. Clinical Nutrition 16, 229–237. Merrien, A., Pouzet, A., Morin, O., Uzzan, A., 1996. Sources of main fats and relevant monographs. In: Karleskind, A. (Ed.), Oils & Fats Manual. Intercept Ltd., Hampshire, UK, pp. 117–323. Miklavcˇicˇ, A., Stibilj, V., Heath, E., Polak, T., Tratnik, J.S., Klavzˇ, J., Mazej, D., Horvat, M., 2011. Mercury, selenium, PCBs and fatty acids in fresh and canned fish available on the Slovenian market. Food Chemistry 124, 711–720. Mol, S., 2010. Determination of trace metals in canned anchovies and canned rainbow trouts. Food and Chemical Toxicology, doi:10.1016/j.fct.2010.11.005. Morrison, J.A., Glueck, C.J., Wang, P., 2008. Dietary trans fatty acid intake is associated with increased fetal loss. Fertility and Sterility 90, 385–390. Mozaffarian, D., Bryson, C.L., Lemaitre, R.N., Siscovick, D.S., Burke, G.L., 2005. Fish intake and risk of incident heart failure. Journal of the American College of Cardiology 45, 2015–2021. Nettleton, J.A., 1995. Omega-3 Fatty Acids and Health. Chapman and Hall, New York. Official Journal of the European Communities, 1991. Regulation no. 2568/91, L. 248 of September 5. Osman, H., Suriah, A.R., Law, E.C., 2001. Fatty acid composition and cholesterol content of selected marine fish in Malaysian waters. Food Chemistry 73, 55–60. Pellegrino, C., Tortonese, E., 2001. Pesci marini e prodotti alimentari derivati. Edagricole, Bologna, Italy. Pirati, D., 1971. Le conserve di tonno. Artegrafica Silva, Parma, Italy. Rahimi, E., Hajisalehi, M., Kazemeini, H.R., Chakeri, A., Khodabakhsh, A., Derakhshesh, M., Mirdamadi, M., Ebadi, A.G., Rezvani, S.A., Kashkahi, M.F., 2010. Analysis and determination of mercury, cadmium and lead in canned tuna fish marketed in Iran. African Journal of Biotechnology 9, 4938–4941. Rambjor, G.S., Walen, A.I., Windsor, S.L., Harris, W.S., 1996. Eicosapentaenoic acid is primarily responsible for hypotriglyceridemic effect of fish oil in humans. Lipids 31, S45–S49. Rossi, M., Colonello, A., Alamprese, C., 2001. Influence of lipid interchange between canned sardines and covering olive oil on some oil genuineness features. Italian Journal of Food Science 13, 159–171. Saguy, I.S., Dana, D., 2003. Integrated approach to deep fat frying: engineering, nutrition, health and consumer aspects. Journal of Food Engineering 56, 143– 152. Selmi, S., Monser, L., Sadok, S., 2008. The influence of local canning process and storage on pelagic fish from tunisia: fatty acid profiles and quality indicators. Journal of Food Processing and Preservation 32, 443–457. Tarley, C.R.T., Visentainer, J.V., Matsushita, M., de Souza, N.E., 2004. Proximate composition, cholesterol and fatty acids profile of canned sardines (Sardinella brasiliensis) in soybean oil and tomato sauce. Food Chemistry 88, 1–6. Vitucci, V., Pierri, P., Maffei, F., 1999. Olive oil used for covering canned fish. Study for a chemiometric pattern based on the triglycerides analysis. Industrie Alimentari 38, 926–929.
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Journal of Food Composition and Analysis journal homepage: www.elsevier.com/locate/jfca
Original Article
Fatty acid composition and degradation level of the oils used in canned fish as a function of the different types of fish Francesco Caponio *, Carmine Summo, Antonella Pasqualone, Tommaso Gomes Dipartimento di Biologia e Chimica Agro-Forestale ed Ambientale (DIBCA), Sezione di Scienze e Tecnologie Alimentari, Universita` degli Studi, Via Amendola, 165/a, I-70126 Bari, Italy
A R T I C L E I N F O
A B S T R A C T
Article history: Received 14 January 2011 Received in revised form 21 January 2011 Accepted 28 January 2011 Available online 12 February 2011
An experimental investigation was carried out to assess the fatty acid composition and the degradation level of the covering oil present in canned fish. The most commonly marketed canned fish types were considered (tuna, sardines, anchovies, mackerels), as well as different kinds of covering oil: extra virgin olive oil, olive oil, refined seed oil. A total of 68 samples were analyzed. Two-way analysis of variance, followed by Fisher’s Least Significant Difference test for multiple comparisons, and principal component analysis were carried out to compare the effect of both type of oil used and kind of fish on oil quality. The obtained results showed the lowest extent of both hydrolytic and oxidative degradation in samples containing extra virgin olive oil. In particular, the contents of triacylglycerol oligopolymers, imputable to secondary oxidative degradation, were equal to 0.17%, 0.50% and 0.74% for extra virgin olive oil, olive oil and refined seed oil, respectively. Olive oil showed significantly higher hydrolytic degradation, with diacylglycerols equal to 3.37%, but lower oxidative degradation and trans isomers content than refined seed oil. Finally, the type of fish did not seem to influence the extent of oxidative and hydrolytic degradation, with the only exception of sardines’ covering oil. This oil, characterized by the highest polyunsaturated fatty acid content, showed the highest values of oxidized triacylglycerols (1.32%) and specific absorption at 232 (K232, 4.030), indices of primary oxidative degradation. ß 2011 Elsevier Inc. All rights reserved.
Keywords: Canned fish Oxidative degradation Hydrolytic degradation Tuna Sardines Anchovies Mackerels HPSEC analysis Food analysis Food composition
1. Introduction Interest in fish consumption has increased in recent years due to the wide range of health benefits related to the high content of polyunsaturated fatty acids (PUFAs), especially eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), of this kind of food. PUFA, in particular n-3 and n-6, are considered essential fatty acids and have been shown to have curative and preventive effects on cardiovascular and inflammatory diseases and cancer. Moreover, they play an important role in the neurodevelopment of infants and in fat glycemic control (Karmali et al., 1984; Kinsella et al., 1990; Nettleton, 1995; Rambjor et al., 1996; Conner, 1997; Mozaffarian et al., 2005). In addition to fresh product, canned fish enables a delayed consumption of this appreciated kind of food. Among the different types of fish, the most used in canning manufacture are tuna, sardines, anchovies, mackerels, and oil is usually adopted as liquid medium. In fact, oil has a preserving effect and contributes to make the product more palatable. Its protective action lies in the ability to insulate products from air, rather than in an active bacteriostatic or bactericidal action. Among the different types of oil, the most
* Corresponding author. Fax: +39 080 5443467. E-mail address: [email protected] (F. Caponio). 0889-1575/$ – see front matter ß 2011 Elsevier Inc. All rights reserved. doi:10.1016/j.jfca.2011.01.019
commonly used in canning are: olive oil (OO, made up of refined olive oil blended with virgin oil other than ‘lampante’ oil, in an undefined ratio) and refined seed oils (RSOs), while extra virgin olive oil (EVOO, obtained from the fruits of Olea europaea L. by mechanical or other physical means that do not lead to any chemical changes) is seldom applied, and only in case of tuna. This situation is probably related to the commercial value of tuna, higher than that of the other types of fish considered. Then, merely from an economic point of view, the use of EVOO, the most expensive oil if compared to RSO and OO, is justified only for tuna. Various studies regarded the assessment of the genuineness of the liquid medium used in the production of in-oil canned fish (Bizzozzero and Carnelli, 1996; Cavallaro et al., 1996; Vitucci et al., 1999; Rossi et al., 2001). Caponio et al. (2003a) assessed the oxidative degradation of the oils used as covering media in canned tuna. This study was performed also to take into account the harmful effects caused by some intermediate and final products of oxidative degradation of the oil on consumers’ health (Billek, 2000; Saguy and Dana, 2003). More recently, Selmi et al. (2008) assessed the changes of lipid quality and histamine level during processing and storage of canned tuna, whereas Gladyshev et al. (2009) evaluated the content of essential PUFA in three canned fish species. Moreover, several studies were carried out in order to evaluate the metal traces in canned fish (Mol, 2010; Rahimi et al., 2010; Miklavcˇicˇ et al., 2011). However, no studies are reported
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about the degradation level of covering oils in other types of commonly marketed canned fish, as well as about the influence of the type of fish on the overall quality of oils utilized as liquid medium. The aim of this study was, therefore, to assess the fatty acid composition and the degradation level of the covering oils present in the most commonly marketed types of canned fish, as well as to assess the influence of fish on oil quality. 2. Materials and methods 2.1. Reagents and samples Analytical grade absolute ethanol, diethyl ether, phenolphthalein, sodium hydroxide, glacial acetic acid, chloroform, potassium iodine, starch, sodium thiosulphate, petroleum ether, methanol, hexane, hydrochloric acid; spectroscopy grade isooctane; high pressure liquid chromatography (HPLC) grade dichloromethane were used. All reagents were purchased from J.T. Baker (Deventer, Holland). Fatty acid methyl ester standard (189-19, purity >99%) were purchased from Sigma–Aldrich (St. Louis, MO, USA). Sixty-eight samples of in-oil canned fish were purchased at different retailers: 34 tuna cans (seven canned in EVOO, 18 in OO and nine in RSO); 11 sardine cans (seven canned in OO and four in RSO); 16 anchovies cans (eight canned in OO and eight in RSO); seven mackerel cans (five were canned in OO and two in RSO). In the laboratory, for each sample the oil/dripped fish ratio (w/w) was determined. First, the oil was drained from the cans and the remaining dripped fish was manually squeezed with a fork. Both the oil and the dripped fish were weighted. Then, the oil recovered from each can was filtered on anhydrous sodium sulphate using filter paper circles 5893 Blauband (Schleicher & Schu¨ll, Dassel, Germany). Fatty acid composition, trans isomers content, and degree of hydrolytic and oxidative degradation were determined for each oil sample. Reference standards (fish oil from menhaden, F8020; highly refined and low acidity olive oil, O1514; sunflower seed oil from Helianthus annuus, S5007) were purchased from Sigma–Aldrich and submitted to the same determinations as the drained oil samples to determine the oxidative and hydrolytic degradation.
2.3. Hydrolytic and oxidative degradation determination Analyses of the free fatty acids, the peroxide value, and specific absorptions were carried out for each sample according to the official methods of European Communities 2568/91 (Official Journal of the European Communities, 1991). The polar compounds (PCs) were separated by silica gel column chromatography according to the Association of Official Analytical Chemists method no. 982.27 (2003). After being recovered in dichloromethane they were analyzed by means of High Performance Size-Exclusion Chromatography (HPSEC) using dichloromethane as eluant at flow rate of 1 mL/min. The HPSEC system, consisted of a PerkinElmer series 200 pump (Norwalk, CT, USA) with Rheodyne injector, a 50 mL loop, a PerkinElmer PL-gel guard column of 5 cm length 7.5 mm i.d., and a series of three PerkinElmer PL-gel column of 30 cm length 7.5 mm i.d. each. The columns were packed with highly cross-linked styrene-divinylbenzene copolymer with particle of 5 mm and a pore diameter of 500, 500 and 100 A˚, respectively. The refractive index detector was a PerkinElmer series 200A. Peaks identification and quantification were carried out as described elsewhere (Gomes and Caponio, 1999; Caponio et al., 2003b). 2.4. Statistical analysis All the determinations were carried out in duplicate. Analysis of variance (ANOVA), followed by Fisher’s Least Significant Difference
2.2. Fatty acid composition and trans isomer determination Fatty acid and trans isomer determinations were carried out by gas-chromatographic analysis of fatty acid methyl esters, according to the official methods (Official Journal of the European Communities, 1991; American Oil Chemists’ Society, 1993). In particular, the oil was treated with methanol/hydrochloric acid (98/2, v/v), in a sealed phial, at 100 8C for 40 min. After cooling, the phial was opened and 2 mL of distilled water and 1 mL of hexane were added. Then, 1 mL of the hexane fraction was injected. The gas-chromatographic system was composed of a Fisons (Milan, Italy) High Resolution Gas-Chromatography (HRGC) mega 2 series, equipped with a flame ionization detector (FID) and a Supelco SPTM 2340 fused silica capillary column (Bellefonte, PA, USA), 0.25 mm i.d. 60 m length and 0.20 mm film thickness. The temperature of the split injector was 210 8C, with a splitting ratio of 1:100; the detector temperature was 220 8C. The oven temperature was programmed from 160 to 200 8C, with increments of 1.3 8C/min and final isothermal of 15 min. Hydrogen was utilized as carrier gas. The identification of each fatty acid was carried out by comparing the retention time with that of the corresponding standard methyl ester. Several analyses carried out on the same sample produced a repeatability coefficient of per cent variation (CV%) of about 5%.
Fig. 1. Mean values, standard error and results of statistical analysis (p < 0.05) of the ratio oil/dripped fish (w/w) 100, according to both the type of oil used as liquid medium (A) and the type of fish (B). (a–c) Different letters indicate significant differences. Extra virgin olive oil, obtained from the fruits of Olea europaea L. by mechanical or other physical means that do not lead to any chemical changes; olive oil, made up of refined olive oil blended with virgin oil other than ‘lampante’ oil; seed oils, represented by sunflower, soybean and corn oils.
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(LDS) test for multiple comparisons, and principal component analysis (PCA) were carried out on the experimental data by the XLStat software (Addinsoft SARL, New York, NY). 3. Results and discussion Fig. 1 shows the mean values, standard error and the results of statistical analysis of the percent ratio oil/dripped fish (w/w) according to both the different type of oil used (A), and the
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different kind of fish (B). Regarding the oils (Fig. 1A), the data showed increasing ratio values comparing the fish product in EVOO with those in OO, and in RSO, although significant differences (p < 0.05) were detected only comparing the latter to the first two types of fish product. The presence of a lower amount of preserving liquid medium might be attributed to the greater commercial value of EVOO as compared to OO and, especially, to RSO. Regarding the type of fish (Fig. 1B), the canned anchovies showed significantly higher mean values (p < 0.05) of
Table 1 Mean values, standard deviations and results of statistical analysisa of fatty acids, as percent of total fatty acids, of the different types of covering oils recovered from the examined fish cans. Fatty acids
Extra virgin olive oilsb (n = 7) Mean value
C14:0 C15:0 C16:0 C16:1 C17:0 C17:1 C18:0 C18:1 C18:2 C18:3 C18:4 C20:0 C20:1 C20:4 C20:4 C20:5 C22:0 C22:5 C22:6 C24:0
w6 w3
w3 w3
Olive oilsc (n = 38) SD
nd nd 12.96 1.30 0.06 0.11 2.55 72.55 8.63 0.65 nd 0.35 0.26 nd 0.01 0.04 0.03 nd 0.46 0.02
Mean value
SD
*
– – 2.38 0.48 0.01 0.03 0.30 3.32 1.30 0.03 – 0.05 0.06 – 0.03 0.05 0.03 – 0.25 0.02
Seed oilsd (n = 23)
0.29 0.03* 12.44* 1.41* 0.16* 0.17* 2.92 70.55* 8.56 0.87 0.10* 0.39 0.35* 0.01* 0.04* 0.48* 0.07* 0.05* 1.09* 0.04*
0.60 0.06 2.18 0.88 0.16 0.09 0.61 6.52 2.36 1.59 0.20 0.05 0.14 0.01 0.08 0.92 0.10 0.11 1.07 0.03
Mean value
SD
*
0.56 0.05* 10.69* 0.66* 0.17* 0.11* 3.85 27.21 50.47 3.75 0.20* 0.30* 0.25* 0.01* 0.05* 0.77* 0.09* 0.07* 0.63* 0.11*
1.06 0.08 2.88 0.97 0.20 0.13 0.62 10.71 10.03 2.61 0.46 0.06 0.09 0.02 0.11 1.44 0.07 0.14 0.95 0.06
SD, standard deviation; nd, not detected (the limit of detection is 0.005%). a One way analysis of variance considering the effect of the fish variable on each type of oil. b Oil obtained from the fruits of Olea europaea L. by mechanical or other physical means that do not lead to any chemical changes. c Refined olive oil blended with virgin oil other than ‘lampante’ oil. d Sunflower, soybean and corn oils. * Significant influence of the independent variable at p < 0.05.
Table 2 Mean values and results of two-way analysis of variance, followed by Fisher’s Least Significant Difference test for multiple comparisons, of the analytical data of the different types of oils recovered from the examined fish cans as a function of both the type of covering oil and kind of fish. Parameters
Model (p value)
Type of oil EVOO (n = 7)
Fatty acid composition (as percent of total fatty acids) C14:0–C17:1 <0.001 14.44AB C18:0–C20:1 <0.001 84.91AB C20:4–C24:0 <0.001 0.56B SFA <0.001 15.98A MUFA <0.001 74.13A PUFA <0.001 9.79B PUFA-(C18:2 + C18:3) <0.001 0.51B Total trans fatty acids <0.001 0.00B Hydrolytic and oxidative degradation determination FFA (g/100 g) 0.155 0.70A PV (mequiv. O2/kg) 0.265 8.8A K232 <0.001 1.79B K270 <0.001 0.34B DK <0.001 0.06AB PCs (g/100 g) <0.001 3.28C TAGP (g/100 g) <0.001 0.17C ox-TAG (g/100 g) <0.001 0.60B DAG (g/100 g) <0.001 2.23B
Type of fish OO (n = 38)
So (n = 23)
Tuna (n = 34)
Sardines (n = 11)
Anchovies (n = 16)
Mackerels (n = 7)
14.48A 83.43B 1.77A 16.33A 72.16A 11.19B 1.76A 0.32B
12.24B 85.50A 1.73A 15.82A 28.23B 55.42A 1.73A 0.77A
12.40bc 86.79a 0.61c 14.98c 61.55a 23.27b 0.52c 0.36a
20.32a 73.26c 5.79a 21.41a 47.80b 30.17a 6.09a 0.60a
11.61c 87.19a 0.91c 14.69c 50.79b 34.25a 0.81c 0.49a
14.26b 82.68b 2.02b 16.71b 61.60a 20.65b 2.13b 0.51a
0.56A 3.5B 2.35B 0.64B 0.03B 5.57A 0.50B 0.79B 3.37A
0.52A 3.0B 3.99A 1.70A 0.10A 4.88B 0.74A 1.56A 1.71B
0.47b 3.5a 2.52b 0.90b 0.05b 4.92b 0.58a 0.93b 2.75a
0.41b 3.0a 4.03a 1.01ab 0.04b 5.08ab 0.66a 1.32a 2.18b
0.77a 5.2a 2.82b 1.23a 0.08a 5.73a 0.51a 1.14ab 2.98a
0.74ab 2.7a 2.99b 0.84b 0.04b 5.17ab 0.45a 0.94b 2.66ab
EVOO, extra virgin olive oil obtained from the fruits of Olea europaea L. by mechanical or other physical means that do not lead to any chemical changes; OO, olive oil obtained from refined olive oil blended with virgin oil other than ‘lampante’ oil; So, seed oils represented by sunflower, soybean and corn oils. SFA, saturated fatty acids; MUFA monounsaturated fatty acids; PUFA, polyunsaturated fatty acids; FFA, free fatty acids; PV, peroxide value; K232, specific absorption at 232 nm; K270, specific absorption at 270 nm; DK, K270 (K274 + K266)/2; PCs, polar compounds; TAGP, triacylglycerol oligopolymers; ox-TAG, oxidized triacylglycerols; DAG, diacylglycerols. Different letters mean significant difference at p < 0.05. Uppercase letters are used to compare the samples considering the effect of the type of oil; lower letters are used to compare the samples considering the effect of the type of fish.
F. Caponio et al. / Journal of Food Composition and Analysis 24 (2011) 1117–1122
Table 3 Oxidative and hydrolytic degradation of the reference standards.a
showed the lowest values of C20:4–C24:0 and PUFA-(C18:2 + C18:3); on the contrary, sardine cans showed the highest values of these indices, due to a greater extent of the diffusive phenomena (Tarley et al., 2004). Moreover, respect to the other types of canned fish, the covering oils in sardine cans showed higher contents of saturated fatty acids (SFA) and C14:0–C17:1. PUFA were higher in anchovies and sardines, the sum C18:0–C20:1 prevailed in anchovies and tuna, while MUFA in tuna and mackerels. Finally, unsaturated fatty acids’ trans isomers were detected only in refined oils (RSO and OO), whereas in EVOO were absent. Their mean values were significantly (p < 0.05) higher in RSO than in OO. This might be due to a higher amount of PUFA in RSO than in OO. Nutritionists address a great attention towards this category of substances, rarely observed in natural vegetable oils, because the presence of trans isomers, in association with a scarcity of essential fatty acids, 1
A
PUFA
Total trans fatty acids
0.5
Anchovies
0.25
Fish oil
Olive oil
Sunflower oil
FFA (g/100 g) PV (mequiv. O2/kg) K232 K270 DK PCs (g/100 g) TAGP (g/100 g) ox-TAG (g/100 g) DAG (g/100 g)
0.27 12.6 0.53 0.13 0.01 7.50 1.37 2.24 2.90
0.09 8.3 0.16 0.02 0.00 5.80 0.36 1.49 3.55
0.08 11.1 0.15 0.08 0.01 3.87 0.37 1.25 1.73
FFA, free fatty acids; PV, peroxide value; K232, specific absorption at 232 nm; K270, specific absorption at 270 nm; DK, K270 (K274 + K266)/2; PCs, polar compounds; TAGP, triacylglycerol oligopolymers; ox-TAG, oxidized triacylglycerols; DAG, diacylglycerols. a Fish oil from menhaden, F8020; highly refined and low acidity olive oil, O1514; sunflower seed oil from Helianthus annuus, S5007 (Sigma–Aldrich, St. Louis, MO, USA).
C18:0-C 20:1
PUFA-
(C18:2+C18:3) Sardines 0 C20:4-C 22:6
Tuna
Mackerels
SFA
-0.25
Extra virgin olive oil
C 14:0-C17:1 -0.5 -0.75 Olive oil
MUFA
-1 -0.75
-1
-0.5
-0.25
0
0.25
0.5
0.75
1
PC1 (57.46 %)
B
4
SoT
3 2
SoT
SoT
SoSa
SoSa SoSa SoM SoSa
SoT
SoA SoA SoT SoA SoA SoASoA SoT SoA SoT SoA SoT SoT
SoM
1 OA 0 OA OM OT OT OT OT OM OT OT OA OA ET OT OT OA OT ET OM ET OM OM OA OA OT OT OT OT OT OT OT ET ETOA ET ET
OSa OSa OSa OSaOSa OSa
-1 OSa -2
Parameters
Seed oils
0.75
PC2 (30.28 %)
the oil/dripped fish ratio than those found in the other types of fish products. These findings could be imputable to the different processing technology of the examined samples (Pirati, 1971; Pellegrino and Tortonese, 2001), as well as to the nature of anchovy flesh. Table 1 reports the mean values and standard deviations of percent fatty acid composition of covering oils recovered from the examined samples, as well as the results of one-way ANOVA. The overall data obtained indicate the presence of characteristic fatty acids of fish, in particular C20:5 and C22:6 (Osman et al., 2001; Tarley et al., 2004; Selmi et al., 2008), confirming the findings of other authors about an interchange between fish lipid fraction and covering oil (Bizzozzero and Carnelli, 1996; Cavallaro et al., 1996; Vitucci et al., 1999; Rossi et al., 2001). Moreover, the statistical analysis evinced that the fatty acid composition of liquid medium was significantly (p < 0.05) influenced by the fish variable due to diffusion of fish lipids into covering oil. In particular, sardines were the most responsible for this variability (data not shown). Besides, for the categories EVOO and OO, the observed compositional data confirmed the expected composition for oils derived from O. europaea correct marketing categorization of the oil. The high variability observed in case of RSO was due to the different botanical origins of the starting oily seeds (Merrien et al., 1996). Table 2 shows the analytical data of canned fish as a function of both the type of covering oil and kind of fish, as well as the results of two-way ANOVA (followed by Fisher’s LSD test for multiple comparisons), whereas in Table 3 the results of the analyses assessing the oxidative and hydrolytic degradation of the reference standards are reported. The ANOVA models were significant for all the examined parameters (p < 0.001), with the exception of the models for free fatty acids and peroxide value. This pointed out that both type of oil and type of fish were responsible for most of data variability. Regarding the type of oil, the differences in fatty acid composition were related to the different botanical nature of the various categories of oil used. In particular, the mean values of monounsaturated fatty acids (MUFA) were significantly higher in EVOO and OO than in RSO. On the contrary, PUFA percentage was significantly (p < 0.05) higher in RSO than in EVOO and OO. Moreover, significantly (p < 0.05) different mean values were observed comparing the sums of C14:0–C17:1 and C18:0–C20:1 obtained for OO and RSO. The detected values of long-chain fatty acids C20:4–C24:0 and PUFA-(C18:2 + C18:3), that include those fatty acids typically present in fish, indicated a diffusion from fish flesh to covering oils. These indices were significantly (p < 0.05) lower in EVOO than in OO and RSO. This could be due to the different fish/ oil ratio of samples as well as to the different fat content of fishes (Pirati, 1971; Pellegrino and Tortonese, 2001). Tuna samples
PC2 (30.28 %)
1120
SoT
-3 -4 -5 -8
-7
-6
-5
-4
-3
-2
-1
0
1
2
3
4
5
PC1 (57.46 %) Fig. 2. Results of the principal components analysis of the data regarding the fatty acid composition and trans isomers content of the covering oil of the fish cans. Plots of variables loadings (A) and observations scores (B) for first two principal components (SFA, saturated fatty acids; MUFA, monounsaturated fatty acids; PUFA, polyunsaturated fatty acids; E, extra virgin olive oil, obtained from the fruits of Olea europaea L. by mechanical or other physical means that do not lead to any chemical changes; O, olive oil, made up of refined olive oil blended with virgin oil other than ‘lampante’ oil; So, seed oils, represented by sunflower, soybean and corn oils; Sa, sardines; M, mackerels; T, tuna; A, anchovies).
F. Caponio et al. / Journal of Food Composition and Analysis 24 (2011) 1117–1122
100
4.5 4
Eigenvalues
3 60 2.5 2 40 1.5 1
Cumulative variability (%)
80
3.5
20
0.5 0
0 P C1 P C2
P C3
P C4
P C5
P C6
P C7
P C8
OO than in EVOO. In fact, TAGP are mainly formed during the refining process, that involves the exposure to high temperatures (Dobarganes et al., 1988; Carlson, 1996; Hodgson, 1996; Hopia, 1993; Gomes and Caponio, 1998; Gomes et al., 2003a). The unexpected presence of TAGP also in EVOO could be due to the step of thermal stabilization of canned fish. In fact, usually these substances are absent in freshly extracted EVOO and may increase up to about 0.1% during shelf-life, depending to storage conditions (Caponio et al., 2005). The significantly (p < 0.05) lower peroxide value detected in refined oils than in EVOO did not indicate a really low oxidative degradation level of OO and RSO, but was due to the fact that these oils come, entirely (RSO) or in part (OO), from a refining process. In fact, during refining the hydroperoxides are degraded and/or modified by the catalytic action of bleaching earth (Hodgson, 1996). Regarding the fish variable, it was observed that the sardines’ covering oil showed the highest values of ox-TAG and K232, indices 1
A
P Cs
0.75
P C9
Fig. 3. Results of the principal components analysis of the data regarding the oxidative and hydrolytic degradation of the covering oil of fish cans. Plot of eigenvalues (bars) and cumulative variability (line).
FFA
DA G
0.5 PV
PC2 (21.02 %)
Olive oil
TA GP K270
Anchovies
0.25
o x-TA G K232
ΔK 0
Mackerels
Sardines Seed oil
-0.25
Tuna Extra virgin olive oil
-0.5 -0.75 -1 -1
-0.75
-0.5
-0.25
0
0.25
0.5
0.75
1
PC1 (42.39 %)
B
5 O 4
So
O
So
3 So
So
PC2 (21.02 %)
can provoke metabolic imbalance as well as cardiovascular diseases. In particular, their intake increase low density lipoprotein (LDL) levels similarly to those caused by SFA, but unlike SFA, trans isomers simultaneously reduce high density lipoprotein (HDL) levels (Koletzko and Decsi, 1997; Morrison et al., 2008). The fish variable did not appear to affect the content of trans isomers in a significant way. Fig. 2 shows the score plot (A) and the loading plot (B) of PCA of fatty acid compositional data. The first two variables accounted for about 88% of total variability. In particular, PC1 explained over 57% of variability, enabling to distinguish sardines’ covering oil – characterized by high amounts of SFA, short and medium chain fatty acids (C14:0–C17:1), and fatty acids typical of fish lipids – from covering oils of other canned fish types, with high values of the sum C18:0–C20:1. PC2 explained about 30% of variability and discriminate the canned fish samples on the basis of the type of oil used. In the upper part of Fig. 2 are grouped fish canned in RSO, characterized by higher content of PUFA and trans isomers than the other types, while in the lower part are present those covered by OO and EVOO, that showed higher levels of MUFA than RSO samples. Considering the indices of oxidative and hydrolytic degradation, data in Table 2 indicate that the PCs – comprising all the substances having a polarity higher than that of the unaltered triacylglycerols – were significant (p < 0.05) higher in OO than in RSO and, above all, in EVOO. The HPSEC analysis of the PCs pointed out that diacylglycerols (DAG) were the most abundant class of substances. DAG were significantly (p < 0.05) higher in OO than in EVOO and in RSO, evidencing a higher hydrolytic degradation of OO. As a consequence, OO showed the highest content of PCs. Regarding FFA, no significant difference was observed among samples. This indicated the limited reliability of FFA determination to evaluate the actual extent of hydrolytic degradation of refined oils (OO and RSO), and pointed out the need of determining the DAG content. In fact, FFA are removed during the neutralization phase of the refining process of oils (Hodgson, 1996). Regarding the oxidative degradation, RSO showed the greatest extent of both primary and secondary oxidation, with significantly (p < 0.05) higher mean values of K232, K270, DK, oxidized triacylglycerols (ox-TAG), and triacylglycerol oligopolymers (TAGP) than the other oils. This result confirms the observations of the same authors in a previous work about canned tuna (Caponio et al., 2003a). Moreover, considering the olive oils, the levels of TAGP were found to be significantly (p < 0.05) higher in
1121
2
O O
1 O
So
O O O OO O OO O O O O OOOO
O
O So
O
So
So
So
0 So
O OO O O O O OO OEE O O O OE E E E E
-1
-2
So SoSoSo SoSo So So So So So So So
-3 -5
-4
-3
-2
-1
0
1
2
3
4
5
6
PC1 (42.39 %) Fig. 4. Results of the principal components analysis of the data regarding the degree of oxidative and hydrolytic degradation of the covering oil of the fish cans. Plots of variables loadings (A) and observations scores (B) for first two principal components (PCs, polar compounds; TAGP, triacylglycerol oligopolymers; ox-TAG, oxidized triacylglycerols; DAG, diacylglycerols; FFA, free fatty acids; PV, peroxide value; K232, specific absorption at 232 nm; K270, specific absorption at 270 nm; DK, K270— (K274 + K266)/2; E, extra virgin olive oil, obtained from the fruits of Olea europaea L. by mechanical or other physical means that do not lead to any chemical changes; O, olive oil, made up of refined olive oil blended with virgin oil other than ‘lampante’ oil; So, seed oils, represented by sunflower, soybean and corn oils).
1122
F. Caponio et al. / Journal of Food Composition and Analysis 24 (2011) 1117–1122
of primary oxidative degradation. These findings were probably due to the highest content of PUFA-(C18:2 + C18:3). TAGP levels, considered a reliable index of secondary oxidative degradation of oils and fats (Gomes et al., 2003b; Bilancia et al., 2007; Caponio et al., 2007), were not significantly different among samples, indicating that the fish variable did not influence this parameter. The other indices did not show a univocal behaviour. The differences among them were probably due to the different type of raw material used. Fig. 3 plots the eigenvalues and the cumulative variability explained by the principal components of data regarding both the hydrolytic and oxidative degradation of examined oils. First three principal components allow to explain about 75% of total variability. About 42% of total variability was explained by PC1, while PC2 and PC3 accounted for about 21% and 12% of total variability, respectively. Fig. 4 plots the observation scores and the variable loadings of the first two principal components. These principal components accounted mainly for the variability due to the different typologies of oils used as covering medium of canned fish and to the variations of oxidative degradation. In particular, PC1 pointed out the differences among the fish canned in RSO and those in EVOO or OO. This principal component was positively correlated with the amounts of K232, K270, ox-TAG, TAGP and DK, that characterize the RSO. The PC2, instead, helped to discriminate the samples canned in EVOO from those in OO. The latter were characterized by high contents of DAG and PCs. Finally, the fish variable did not show to influence the extent of oxidative and hydrolytic degradation of covering oils. 4. Conclusions On the whole, the covering oil of canned fish showed a high level of oxidative degradation when constituted by RSO and a high hydrolytic degradation in case of OO. The samples canned in EVOO presented a lower extent of both hydrolytic and oxidative degradation. Finally, the type of fish did not seem to influence the extent of oxidative and hydrolytic degradation, with the only exception of sardines’ covering oil. This oil, characterized by the highest PUFA content, showed the highest values of ox-TAG and K232, indices of primary oxidative degradation. References American Oil Chemists’ Society, 1993. In: Firestone, D. (Ed.), Official Methods and Recommended Practices of the AOCS. 4th ed. AOCS Press, Washington, DC, USA (Method Chapter 1–91). Association of Official Analytical Chemists, 2003. In: Horwitz, W. (Ed.), Official Methods of Analysis of AOAC International. 17th ed. Arlington, VA, USA, AOAC Press. Bilancia, M.T., Caponio, F., Sikorska, E., Pasqualone, A., Summo, C., 2007. Correlation of triacylglycerol oligopolymers and oxidised triacylglycerols to quality parameters in extra virgin olive oil during storage. Food Research International 40, 855–861. Billek, G., 2000. Health aspects of thermoxidized oils and fats. European Journal of Lipid Science and Technology 102, 587–593. Bizzozzero, N., Carnelli, L., 1996. Fatty acid composition and trans unsaturation of the covering oil of canned mackerels and tunas. Industrie Alimentari 35, 680– 683. Caponio, F., Bilancia, M.T., Pasqualone, A., Sikorska, E., Gomes, T., 2005. Influence of the exposure to light on extra virgin olive oil quality during storage. European Food Research and Technology 221, 92–98. Caponio, F., Gomes, T., Pasqualone, A., Summo, C., 2007. Use of the high performance size exclusion chromatography analysis for the measurement of the degree of hydrolytic and oxidative degradation of the lipid fraction of biscuits. Food Chemistry 102, 232–236. Caponio, F., Gomes, T., Summo, C., 2003a. Quality assessment of edible vegetable oils used as liquid medium in canned tuna. European Food Research and Technology 216, 104–108.
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