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Slaughter yield, proximate and fatty acid composition and sensory properties of rapfen (Aspius aspius L) with tissue of bream (Abramis brama L) and pike (Esox lucius L)
ARTICLE IN PRESS JOURNAL OF FOOD COMPOSITION AND ANALYSIS Journal of Food Composition and Analysis 19 (2006) 176–181 www.elsevier.com/locate/jfca
Original Article
Slaughter yield, proximate and fatty acid composition and sensory properties of rapfen (Aspius aspius L) with tissue of bream (Abramis brama L) and pike (Esox lucius L) Tomasz Z˙ mijewskia,, Roman Kujawab, Barbara Jankowskaa, Aleksandra Kwiatkowskaa, Andrzej Mamcarzb a University of Warmia and Mazury in Olsztyn, Faculty of Food Science, Chair of Tissue Technology and Chemistry, Poland University of Warmia and Mazury in Olsztyn, Faculty of Environmental Sciences and Fisheries, Chair of Lake and River Fisheries, Poland
b
Received 29 April 2004; received in revised form 11 February 2005; accepted 22 March 2005
Abstract The manuscript presents a comparative analysis of slaughter yield, sensory traits and proximate and fatty acid composition of a little-known rapfen (Aspius aspius L) with bream (Abramis brama L) and pike (Esox lucius L). The experimental fish of each species were obtained under natural conditions between July and August. The rapfen was characterized by the highest slaughter yield of gutted and deheaded carcass (74.57%). The slaughter yields of fillet with skin (59.44%) and deskinned fillet (51.26%) were similar to those reported for pike, but higher than those of bream. Aroma and consistency of evaporated meat carcass obtained similar scores, whereas differences were demonstrated between flavour, colour and juiciness of rapfen and bream, and between colour and juiciness of rapfen and pike. The fat contents of rapfen and bream carcasses were similar (2.52% and 3.63%, respectively) and higher than that of pike (0.64%). The contents of protein (18.00–18.83%) and ash (0.99–1.01%) were alike in the three species examined. The concentrations of polyunsaturated fatty acids (PUFA) in 100 g carcasses of rapfen and bream were similar, and higher than in pike. The carcasses of the fish species examined differed in terms of the concentrations of monounsaturated fatty acids (MUFA). The total concentrations of n-6 fatty acids were different in rapfen, bream and pike, whereas concentrations of n-3 acids were higher than those reported for pike. Rapfen carcass had the highest concentration of docosahexaneoic acid (DHA; 22:6 n-3). r 2005 Elsevier Inc. All rights reserved. Keywords: Slaughter yield; Principal components; Fatty acids; Sensory evaluation; Rapfen; Bream; Pike
1. Introduction Fish tissue possesses high nutritional value and is therefore a particularly recommended dietary component. Fish tissue is the main source of long-chain polyunsaturated fatty acids n-3 (n-3 LC-PUFA) with beneficial or even therapeutic effects on human health (Kinsella, 1986; Garcia, 1998; Kolanowski et al., 1999; Corresponding author. Tel.: +48 89 523 32 95; fax: +48 89 523 36 94. ˙ mijewski). E-mail address: [email protected] (T. Z
0889-1575/$ - see front matter r 2005 Elsevier Inc. All rights reserved. doi:10.1016/j.jfca.2005.03.006
Ackman, 2000). In addition, fish tissue protein is characterized by a very desirable composition of amino acids. This tissue is also a rich source of group B vitamins and is rich in vitamins A and D. Additionally, fish are a good source of micro- and macro-elements (calcium, phosphorus, iodine, selenium, fluorine, and manganese) (Brown, 1986; Ko"akowska and Ko"akowski, 2000). The chemical composition of fish tissue can be modified by several factors such as feed, development phase, territory, catch season and ontogenic traits. Due to the development of aquaculture, it is possible to maintain and increase the biomass of popular fish
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species as well as the dissemination of other species of currently limited economic importance (Witkowski, 1996; Kujawa et al., 1998; Mamcarz et al., 2001). Rapfen can serve as an example of such a species (Aspius aspius L.). This freshwater fish is well known to anglers but has rarely been available on the market. This is the only carnivorous cyprinoid fish feeding on small fish (Brylin´ska, 1986). Although it belongs to cyprinoid fish, its growth rate is high and it reaches commercial body weight (1.5 kg) after 4 years (Martyniak and Heese, 1994). Large-scale activities aiming at restitution of this species have recently been undertaken in Poland, and catches of rapfen have significantly increased. Therefore, the objective of this study was to determine the slaughter yield, sensory traits, and proximate and fatty acid composition of a little-known rapfen and to compare the results obtained with parameters of two popular species of freshwater fish. Comparative analyses were carried out with bream (Abramis brama L), which like rapfen belongs to the same family (Cyprinidae), and with pike (Esox lucius L), which—also like rapfen—is a carnivorous fish.
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sample mineralization at a temperature of 550–600 1C (AOAC, 1975). 2.3. Determination of fatty acid profile Cold extraction of tissue lipids according to Folch et al. (1957) was used for quantitative and qualitative analysis of fatty acid composition. The fatty acids were methylated with the use of the mix of chloroform: methanol: sulphuric acid (100:100:1) (Peisker, 1964). Chromatographic separation was done with an Agilent Technologies 6890 N gas chromatograph with a flameionizing detector (FID) and a 30 m capillary column with an internal diameter of 0.32 mm, liquid phase Supelcowax 10, film thickness 0.25 mm. Separation conditions: helium carrier gas, flow rate of 1 mL/min. Temperature of the detector was 250 1C; of the injector, 225 1C; and of the column, 180 1C. Signals from the detector were registered by a Philips unit with a 1 mV scale at a tape rate of 10 mm min1. The individual fatty acids were identified by comparing their retention times with the standards of Supelco (Bellefonte, PA, USA).
2. Material and methods 2.4. Sensory assessment 2.1. Preparation of experimental material The experimental fish were obtained in natural conditions (Lake Maro´z, northern Poland) between July and August. Of each species catch, 8 fish with similar body weights were selected for analyses. The fish were then killed and their body weights (BW71 g) and body lengths (Lc71 mm) were determined. The condition factor was calculated according to the formula K ¼ ðBW 100Þ=Lc3 . After evisceration and deheading, the fish were filleted and the fillets were deskinned. The obtained gutted carcass, gutted and deheaded carcass, fillet with skin, and fillet without skin were weighed (71 g), and their percentage in the total body weight of fish was calculated. The weight of gonads was also determined (GW71 g) and a gonadosomatic index was calculated based on the following formula GSI ¼ (BW/GW) 100. One of the deskinned fillets of each fish served as analytical material for determination of proximate composition and fatty acid profile analysis. The second fillet, after thermal treatment, was used for sensory assessment. 2.2. Determination of proximate composition Water content was determined by the sample drying technique at a temperature of 105 1C; crude protein content with the use of the Kjeldahl method with 6.25 multiplier; fat content with the Soxhlet method (with petroleum ether as the solvent), and ash content by
Fillets with skin to be used for sensory assessment were evaporated to an internal temperature of 72 1C. Immediately after the thermal treatment, 5 cm of the fillet was cut out beginning with the section touching the head. Next, 6 samples 2.0 cm wide were cut out from the central section. A sample evaluated by each assessor originated from the same part of the fillet. This procedure was designed to minimize potential differences likely to result from the evaluation of different parts of the fillet. The assessment was carried out by a 6person panel, and all assessors evaluated all species examined (rapfen, pike, bream). The sensory evaluation was carried out in three separate sessions. The assessors performing the sensory assessment met the minimum sensory competence required in the current calibrating tests; they were selected, trained, tested, and monitored according to ISO guidelines (ISO, 1993). The assessors were experienced in sensory evaluation and were acquainted with the accepted system of sensory assessment. Colour, odour, consistency, juiciness and flavour were determined on a 5-point scale using half-scores according to the modified method for the evaluation of food products with the use of the scaling method (ISO, 1987) (see Table 1). The evaluation was carried out in a laboratory adjusted to sensory analyses; individual stations were separate from one another. Each sensory assessment station was lit with standardized lighting (T ¼ 6500 1C) (ISO, 1988).
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178 Table 1 Sensory evaluation scores Score (in points)
Colour
Odour
Texture
Juiciness
Flavour
5
Homogeneous, typical for cooked fish of certain species Homogeneous, somewhat dark
Typical, clearly perceptible
Firm, particularly tender
Very juicy
2
Somewhat too soft or somewhat too hard, very tender Semi-soft or hard, tender Soft or hard, fibrous
Juicy
Somewhat unhomogeneous, dark Unhomogeneous
Typical, poorly perceptible or very strong Poorly perceptible, foreign Perceptible, foreign
Desirable, typical, intense, no foreign aftertastes Desirable, typical, weak, no foreign aftertastes
1
Very unhomogeneous
Strong foreign
Very soft or very hard, fibrous
4
3
2.5. Statistical analysis The results presented for fish of particular species are means 7S.E.M. obtained in the analysis of 8 fish. The differences between the mean values of parameters examined (biological factors: slaughter field, proximate composition, fatty acid composition, sensory assessment) were calculated using one-factor analysis of variance (ANOVA). Use was also made of the SNK test (Student–Newman–Keuls) and statistically significant differences were reported at Po0:01. Calculations were made with the use of Statistica 6.0 PL software.
3. Results and discussion Table 2 presents the condition factor, gonadosomatic index and slaughter field of carcasses and fillets for rapfen, bream and pike, whose total weight accounted for 16807180 g; 1483791 g, and 1248752 g, respectively. The fish differed in the condition factor, 0.91 for rapfen, 1.15 for bream, and 0.64 for pike. On the other hand, the gonadosomatic index was the same in all fish species and ranged from 2.01 to 2.69. The slaughter yield of the gutted carcass of the experimental species did not significantly differ. However, rapfen had the highest yield of gutted and deheaded carcass. This value was 3.28% greater than in bream and 4.48% greater than in pike. High yields of fillet with skin and skinned fillet were also obtained in rapfen, totalling 59.4470.43 and 51.2670.38%, respectively, and were similar to those of pike. These same indicators for bream resulted in significantly lower yields. The above relations agree with the data obtained by Litwin´czuk et al. (2000) and Bykowski and Dutkiewicz (1996), who found that the yields of carcass and tissue are higher in pike than in bream. The literature does not contain any reference to rapfen.
Low juiciness Dry Very dry
Typical with slight foreign aftertaste Clearly perceptible foreign aftertaste Atypical, strong foreign aftertaste
One of the factors exerting a substantial effect on the yield is the degree of gonad development. In all fish species analysed, the gonads were in the first phases of development, which is indicated by the fishing period and low GSI values. Hence, their percentage in the total weight of fish was not high, and the slaughter yields of the gutted carcasses of rapfen, bream and pike were differentiated. However, the small head percentage in the rapfen total body weight in comparison to bream and pike determined the highest yield of gutted and deheaded carcass in this fish. Similar yields of rapfen and pike fillets indicated a similar percentage of skin and muscle system in these fish, which were different in bream. The high tissue yield (over 50%) indicates a high slaughter value of rapfen, which is greater than in other cyprinoid fish. The tissue obtained from the experimental fish was characterized by a varied content of fat and water. The rapfen and bream tissue contained significantly higher amounts of fat. The varied content of fat was compensated by the content of water. The content of protein was similar for the three species and ranged from 18.00% to 18.83%. In addition, the ash level in the three species was similar and was approximately 1% (Table 3). Based on a sensory evaluation, the odour and texture of the fish tissue evaluated received very similar scores. In addition, the flavour of rapfen and pike tissue was evaluated similarly. However, rapfen tissue colour scored lower than bream or pike tissue. It was darker and was evaluated as slightly uneven. The evaluated fish tissue differed in juiciness, which was the highest for bream and the poorest for pike (Fig. 1). The results obtained confirmed a reverse correlation between the fat and water contents, which is common for many fish species (Ko"akowska and Ko"akowski, 2000). According to the classification provided by the above-mentioned authors and the Polish norm (PN, 1999), rapfen—like bream—may be classified in the
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Table 2 Biological factor, carcass and fillet yields (mean7S.E.M.) Factor
Rapfen (n ¼ 8)
Bream (n ¼ 8)
Pike (n ¼ 8)
Total mass (BW) (g) Body lenght (Lc) (mm) Condition factor (K) Gonadosomatic index (GSI) (%) Gutted carcass (%)d Gutted and deheaded carcass (%)d Fillet, with skin (%)d Fillet, skinned (%)d
1680 7180 47.88a72.01 0.91a70.02 2.07a70.25 91.19a70.35 74.57a70.36 59.44a70.43 51.26a70.38
1483 791 41.45b70.54 1.15b70.02 2.01a70.20 88.49a70.75 71.29b70.73 48.83b70.89 37.87b70.52
1248a752 50.50a71.17 0.64c70.01 2.69a70.21 91.02a70.69 70.09b70.71 57.83a71.01 48.92a70.70
a
a
Values in the same line with different letters are significantly different at Po0:01. d Yield with relation to the total mass.
Table 3 Chemical composition (%) of fish tissue (mean7S.E.M.) Component
Rapfen (n ¼ 8)
Bream (n ¼ 8)
Pike (n ¼ 8)
Water Protein Fat Ash
77.64a70.35 18.83a70.15 2.52a70.29 1.01a70.01
77.37a70.27 18.00a70.28 3.63a70.34 1.00a70.01
80.32b70.14 18.06a70.14 0.64b70.13 0.99a70.01
Values in the same line with different letters are significantly different at Po0:01.
Fig. 1. Sensory evaluation of fish tissue.
group of semi-fat fish (fat content of fish tissue 2–7%), and—like pike—in the group of lean fish (fat content lower than 2%). The fat content in fish tissue contributes to its organoleptic properties, texture and flavour. Fat, rich tissue is juicy, while lean tissue is dry and perceived as thickly fibrous. This was explicitly confirmed in a study comparing the sensory properties
of wild and farmed fish, which differed in fat content (Jahncke et al., 1988; Orban et al., 1997; Grigoriakis et al., 2003) or of fish of the same species with different fat contents (Johansson et al., 2000). A comparison of sensory properties in the above-described study confirmed that pike tissue, with the lowest fat content, was the least juicy.
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A lipid analysis enabled the classification and quantitative determination of 33 fatty acids as well as the sum of saturated fatty acids (SFA), monounsaturated fatty acids (MUFA), polyunsaturated fatty acids (PUFA), n-3 acids, n-6 acids and n-3/n-6 ratio (Table 4). It was demonstrated that the total sum of SFA in 100 g carcass of rapfen and bream did not differ, and was higher than that of pike carcass. This was due to higher concentrations of three quantitatively dominating saturated fatty acids compared to pike carcass: myristic (14:0), palmitic (16:0), and stearic acids (18:0). As a consequence, the percentage of unsaturated fatty acids appeared to be similar in rapfen and bream and the lowest in pike. The MUFA concentration of rapfen Table 4 Fatty acid profile (mg 100 g1) in fish tissue (mean7S.E.M.) Fatty acid
Rapfen (n ¼ 8)
Bream (n ¼ 8)
Pike (n ¼ 8)
14:0 14:1 15:0 16:0 16:1 16:2 16:4 17:1 18:0 18:1 cis 9 18:1 cis 11 18:2 n-6 18:3 n-5 18:3 n-6 18:3 n-4 18:3 n-3 18:4 20:0 20:1 n-11 20:1 n-9 20:1 n-7 20:2 20:4 n-6 20:4 n-3 20:5 n-3 22:0 22:1 n-11 22:1 n-9 22:2 21:5 22:5 n-3 22:5 n-6 22:6 n-3 S SFA S MUFA S PUFA S n-3 S n-6 S n-3/S n-6
58.43a73.10 11.09a70.61 8.63a70.63 253.6a75.0 179.8a74.7 12.00a70.82 1.66a70.12 16.48a70.78 56.08a72.40 320.9a715.9 65.20a71.45 72.98a73.31 4.18a70.31 4.08a70.41 3.85a70.21 54.76a72.92 19.39a72.08 2.72a70.08 0.43a70.01 16.29a71.06 2.75a70.23 9.53a70.40 6.21a70.46 73.97a71.96 106.7a72.7 — 1.10a70.04 0.55a70.02 3.51a70.12 6.83a70.46 14.55a71.91 36.28a71.13 207.8a711.2 379.5a77.6 613.6a722.5 638.3a711.9 457.8a711.3 119.6a73.7 3.86a70.17
77.67a710.09 23.92b73.14 12.74a71.57 380.3a733.8 349.2b743.7 31.36b73.25 2.99a70.36 27.80a73.26 98.41a77.27 557.2a747.6 149.4b716.6 160.5b720.6 10.81b71.20 8.49a71.18 6.28a70.68 63.82a76.78 17.00a71.61 7.88a70.56 14.80b71.46 19.89a71.57 4.47a70.49 15.73a71.47 11.28a71.45 79.70a77.14 153.0a712.5 1.69a70.42 0.39a70.04 1.49a70.13 4.58a70.67 8.18a70.95 10.26a70.70 38.71a73.60 134.1b78.5 578.7a752.5 1151b7115 752.4a764.8 440.9a732.4 219.0b726.0 2.15b70.14
5.68b70.41 0.95c70.16 1.17b70.10 59.96b74.80 16.51c71.57 1.36c70.13 0.22b70.02 2.04b70.27 21.02b71.77 40.10b73.47 8.67c70.58 11.67c71.02 0.59c70.04 0.67b70.06 0.54b70.06 7.36b70.67 3.00b70.30 0.33a70.02 0.21a70.01 1.50b70.17 0.41a70.04 1.26b70.09 0.93b70.12 18.77b71.66 19.09b71.83 0.14a70.02 0.30a70.03 0.96a70.34 0.50b70.04 1.26b70.07 4.23b70.28 7.43b70.54 83.25c77.22 88.25b77.07 71.04c76.11 162.1b713.8 132.7b711.5 20.69c71.68 6.41c70.12
FA, fatty acid; SFA, saturated FA; MUFA, monounsaturated FA; PUFA, polyunsaturated FA. Values in the same line with different letters are significantly different at Po0:01.
carcass was intermediate when compared to those of bream and pike, whereas the concentration of PUFA was higher than that of pike and comparable with that of bream. It is also worth emphasizing that rapfen was characterized by similar percentages of MUFA and PUFA acids, whereas the carcasses of bream were predominated by MUFA, and those of pike, by PUFA. The total sum of n-3 fatty acids reaching 457.8711.3 mg 100 g1 for rapfen did not differ from that reported for bream, namely 440.9732.4 mg 100 g1, but appeared to be higher than that reported for pike, 132.7711.5 mg 100 g1. The concentrations of individual n-3 acids, including linolenic (18:3n-3), eicosatetraenoic (20:4n-3), and docosapentaenoic acid (EPA, 22:5n-3), in the carcass of rapfen approximated those determined in bream carcass and were higher than those determined in pike carcass. A significant difference between rapfen and the other two fish species was observed in the concentration of docosahexaenoic acid (DHA; 22:6n-3). The total sum of n-6 acids was different in the carcasses of all fish species examined, which resulted from a differentiated concentration of linoleic acid (18:2n-6) in rapfen, bream and pike, as well as various concentrations of arachidonic acid (20:4n-6) and docosapentaenoic acid (22:5n-6) in rapfen and bream compared to pike. Carcasses of the analysed fish also had a different n-3/ n-6 ratio. The highest value, 6.4170.12, was reported for pike, whereas the lowest, 2.1570.14, was for bream. Because of the positive, health-promoting effects of long-chain n-3 fatty acids on the human body, their contents are especially important to consumers (Hunter and Roberts, 2000; Uayu and Valenzuela, 2000). The results obtained indicate that although the concentrations of EPA and DPA acid in rapfen are similar to those of bream, they are higher than the values reported for pike. In addition, the rapfen carcass has the highest concentration of DHA. Thus, despite the fact that bream contains more fat (by 1% and more), rapfen appears a more valuable source of this particular fatty acid for consumers. A comparison with pike carcasses, which had the lowest fat content, is even more to the advantage of rapfen, since a 100 g portion of pike carcass had only half the DHA concentration as the carcass of rapfen. The results obtained also indicated that although the n-3/n-6 ratio of rapfen carcass does not reach the value reported for pike, it is still higher than that observed in bream. This was confirmed by data obtained by Bieniarz et al. (2000), who found that freshwater carnivorous fish can be characterized by greater n-3/n-6 fatty acid ratio than phytophagous and benthophagous cyprinoid fish (tench, ide, crucian carp, grass carp). Only the n-3/n-6 acid ratio determined for bream falls into the narrow range of values determined for freshwater fish by
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Henderson and Tocher (1987) and Aggelousis (1991). Data determined for the other experimental species are in line with the values given by Ko"akowska et al. (2000) for freshwater fish caught in Polish waters.
4. Conclusions Based on the results obtained, rapfen is characterized by a very good yield. The skinned fillet weight is over 50% of rapfen body weight. Although rapfen tissue is similar to bream tissue in terms of the total fat content, the percentage of PUFA and particularly DHA, which is valuable in the human diet, as well as the n-3/n-6 acid ratio, are greater in rapfen tissue. However, in this respect, rapfen tissue does not match pike tissue. References Ackman, R.G., 2000. Fish is more than a brain food. IIFET Proceedings. Aggelousis, G., 1991. Fatty acid composition of the lipids from eight freshwater fish species from Greece. Journal of Food Composition and Analysis 4, 68–76. AOAC, 1975. Official Methods of Analysis of the Association of Official Analytical Chemists. AOAC, Washington, DC. Bieniarz, K., Ko"dras, M., Kamin´ski, J., Mejza, T., 2000. Fatty acids and cholesterol in some freshwater fish species in Poland. Folia Universitatis Agriculturae Stetinensis 27, 21–44. Brown, W.D., 1986. Fish muscle as food. In: Bechtel, P.J. (Ed.), Muscle as Food. Academic Press INC, Orlando, pp. 406–445. Brylin´ska, M., 1986. The Freshwater Fishes of Poland. PWN, Warszawa. Bykowski, P., Dutkiewicz, D., 1996. Freshwater fish processing and equipment in small plants. FAO Fisheries Circular No. 905, Rome. Folch, H., Less, M., Stanley, H.A., 1957. A simple method for isolation and purification of total lipids from animal tissues. Journal of Biological Chemistry 226, 497–499. Garcia, D.J., 1998. Omega-3 long-chain PUFA nutraceuticals. Food Technology 52, 44–49. Grigoriakis, K., Taylor, K.D.A., Alexis, M.N., 2003. Organoleptic and volatile aroma compounds comparsion of wild and cultured gilthead sea bream (Sparus aurata): sensory differences and possible chemical basis. Aquaculture 225, 109–119. Henderson, R.J., Tocher, D.R., 1987. The lipid composition and biochemistry of freshwater fish. Progress in Lipid Research 26, 281–347. Hunter, B.J., Roberts, D., 2000. Potential impact of the fat composition of farmed fish on human health. Nutrition Research 20, 1047–1058.
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ISO 4121, 1987. Sensory analysis—methodology—evaluation of food products by methods using scales. ISO 8589, 1988. Sensory analysis—general guidance for design of test rooms. ISO 8586-1, 1993. Sensory analysis—general guidance for the selection, training and monitoring of assesors—Part 1: Selected assessors. Jahncke, M., Hale, M.B., Gooch, J.A., Hopkins, J.S., 1988. Comparsion of pond-raised and wild red drum (Sciaenops ocellatus) with respect to proximate composition, fatty acid profiles, and sensory eveluations. Journal of Food Science 53, 286–287. Johansson, L., Kiessling, A., Kiessling, K.H., Berglund, L., 2000. Effects of altered ration levels on sensory characteristics, lipid content and fatty acid composition of rainbow trout (Oncorhynus mykiss). Food Quality and Preference 11, 247–254. Kinsella, J.E., 1986. Food components with potential therapeutic benefits: the n-3 polyunsatureted fatty acids of fish oils. Food Technology 40, 89–97. Ko"akowska, A., Ko"akowski, E., 2000. XXXI Scientific Session of the Committee for Food Technology and Chemistry. PAN, Poznan´, pp. 14–15. Ko"akowska, A., Szczygielski, M., Bienkiewicz, G., Zienkowicz, L., 2000. Some of fish species as a source of n-3 polyunsaturated fatty acids. Acta Ichthyologica et Piscatoria 30, 59–70. Kolanowski, W., S´widerski, F., Berger, S., 1999. Possibilities of fish oil application for food products enrichment with omega-3 PUFA. International Journal of Food Sciences and Nutrition 50, 39–49. Kujawa, R., Mamcarz, A., Kucharczyk, A., 1998. Biotechnology of reproduction and breeding of asp (Aspius aspius L.). Czech Journal of Animal Science 43, 396–401. Litwin´czuk, A., Kro´l, J., Ska"ecki, P., Olesiuk, E., 2000. Utility value and chemical composition of fish meat from the Ł˛ecznaW"odawa lake district. Annals of UMCS Section EE 18, 175–181. Mamcarz, A., Kujawa, R., Furga"a-Selezniow, G., Kucharczyk, D., 2001. Preliminary results of larval and asp (Aspius aspius L.) rearing in the illuminated cages. European Aquaculture Society, Special Publication 30, 328–331. Martyniak, A., Heese, T., 1994. Growth rate and age composition of asp Aspius aspius (L., 1758) from Pierzcha"y Reservoir. Acta Ichthyologica et Piscatoria 24, 55–67. Orban, E., Sinesio, F., Paoletti, F., 1997. The functional properties of proteins, texture and the sensory characteristic of frozen bream (Sparus aurata) from different farming systems. LebensmittelWissenschaft & Technologie 30, 214–217. Peisker, K., 1964. Rapid semi-micro method for methyl esters from triglicerides using chloroform, methanol, sulphuric acid. Journal of the American Oil Chemists’ Society 11, 87–90. PN-A-86770, 1999. Fish and fishery products–terminology. Uayu, R., Valenzuela, A., 2000. Marine oils: the health benefits of n-3 fatty acids. Nutrition 16, 680–684. Witkowski, A., 1996. Introduced fish species in Poland: pros and cons. Archives of Polish Fisheries 4, 101–112.
Original Article
Slaughter yield, proximate and fatty acid composition and sensory properties of rapfen (Aspius aspius L) with tissue of bream (Abramis brama L) and pike (Esox lucius L) Tomasz Z˙ mijewskia,, Roman Kujawab, Barbara Jankowskaa, Aleksandra Kwiatkowskaa, Andrzej Mamcarzb a University of Warmia and Mazury in Olsztyn, Faculty of Food Science, Chair of Tissue Technology and Chemistry, Poland University of Warmia and Mazury in Olsztyn, Faculty of Environmental Sciences and Fisheries, Chair of Lake and River Fisheries, Poland
b
Received 29 April 2004; received in revised form 11 February 2005; accepted 22 March 2005
Abstract The manuscript presents a comparative analysis of slaughter yield, sensory traits and proximate and fatty acid composition of a little-known rapfen (Aspius aspius L) with bream (Abramis brama L) and pike (Esox lucius L). The experimental fish of each species were obtained under natural conditions between July and August. The rapfen was characterized by the highest slaughter yield of gutted and deheaded carcass (74.57%). The slaughter yields of fillet with skin (59.44%) and deskinned fillet (51.26%) were similar to those reported for pike, but higher than those of bream. Aroma and consistency of evaporated meat carcass obtained similar scores, whereas differences were demonstrated between flavour, colour and juiciness of rapfen and bream, and between colour and juiciness of rapfen and pike. The fat contents of rapfen and bream carcasses were similar (2.52% and 3.63%, respectively) and higher than that of pike (0.64%). The contents of protein (18.00–18.83%) and ash (0.99–1.01%) were alike in the three species examined. The concentrations of polyunsaturated fatty acids (PUFA) in 100 g carcasses of rapfen and bream were similar, and higher than in pike. The carcasses of the fish species examined differed in terms of the concentrations of monounsaturated fatty acids (MUFA). The total concentrations of n-6 fatty acids were different in rapfen, bream and pike, whereas concentrations of n-3 acids were higher than those reported for pike. Rapfen carcass had the highest concentration of docosahexaneoic acid (DHA; 22:6 n-3). r 2005 Elsevier Inc. All rights reserved. Keywords: Slaughter yield; Principal components; Fatty acids; Sensory evaluation; Rapfen; Bream; Pike
1. Introduction Fish tissue possesses high nutritional value and is therefore a particularly recommended dietary component. Fish tissue is the main source of long-chain polyunsaturated fatty acids n-3 (n-3 LC-PUFA) with beneficial or even therapeutic effects on human health (Kinsella, 1986; Garcia, 1998; Kolanowski et al., 1999; Corresponding author. Tel.: +48 89 523 32 95; fax: +48 89 523 36 94. ˙ mijewski). E-mail address: [email protected] (T. Z
0889-1575/$ - see front matter r 2005 Elsevier Inc. All rights reserved. doi:10.1016/j.jfca.2005.03.006
Ackman, 2000). In addition, fish tissue protein is characterized by a very desirable composition of amino acids. This tissue is also a rich source of group B vitamins and is rich in vitamins A and D. Additionally, fish are a good source of micro- and macro-elements (calcium, phosphorus, iodine, selenium, fluorine, and manganese) (Brown, 1986; Ko"akowska and Ko"akowski, 2000). The chemical composition of fish tissue can be modified by several factors such as feed, development phase, territory, catch season and ontogenic traits. Due to the development of aquaculture, it is possible to maintain and increase the biomass of popular fish
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species as well as the dissemination of other species of currently limited economic importance (Witkowski, 1996; Kujawa et al., 1998; Mamcarz et al., 2001). Rapfen can serve as an example of such a species (Aspius aspius L.). This freshwater fish is well known to anglers but has rarely been available on the market. This is the only carnivorous cyprinoid fish feeding on small fish (Brylin´ska, 1986). Although it belongs to cyprinoid fish, its growth rate is high and it reaches commercial body weight (1.5 kg) after 4 years (Martyniak and Heese, 1994). Large-scale activities aiming at restitution of this species have recently been undertaken in Poland, and catches of rapfen have significantly increased. Therefore, the objective of this study was to determine the slaughter yield, sensory traits, and proximate and fatty acid composition of a little-known rapfen and to compare the results obtained with parameters of two popular species of freshwater fish. Comparative analyses were carried out with bream (Abramis brama L), which like rapfen belongs to the same family (Cyprinidae), and with pike (Esox lucius L), which—also like rapfen—is a carnivorous fish.
177
sample mineralization at a temperature of 550–600 1C (AOAC, 1975). 2.3. Determination of fatty acid profile Cold extraction of tissue lipids according to Folch et al. (1957) was used for quantitative and qualitative analysis of fatty acid composition. The fatty acids were methylated with the use of the mix of chloroform: methanol: sulphuric acid (100:100:1) (Peisker, 1964). Chromatographic separation was done with an Agilent Technologies 6890 N gas chromatograph with a flameionizing detector (FID) and a 30 m capillary column with an internal diameter of 0.32 mm, liquid phase Supelcowax 10, film thickness 0.25 mm. Separation conditions: helium carrier gas, flow rate of 1 mL/min. Temperature of the detector was 250 1C; of the injector, 225 1C; and of the column, 180 1C. Signals from the detector were registered by a Philips unit with a 1 mV scale at a tape rate of 10 mm min1. The individual fatty acids were identified by comparing their retention times with the standards of Supelco (Bellefonte, PA, USA).
2. Material and methods 2.4. Sensory assessment 2.1. Preparation of experimental material The experimental fish were obtained in natural conditions (Lake Maro´z, northern Poland) between July and August. Of each species catch, 8 fish with similar body weights were selected for analyses. The fish were then killed and their body weights (BW71 g) and body lengths (Lc71 mm) were determined. The condition factor was calculated according to the formula K ¼ ðBW 100Þ=Lc3 . After evisceration and deheading, the fish were filleted and the fillets were deskinned. The obtained gutted carcass, gutted and deheaded carcass, fillet with skin, and fillet without skin were weighed (71 g), and their percentage in the total body weight of fish was calculated. The weight of gonads was also determined (GW71 g) and a gonadosomatic index was calculated based on the following formula GSI ¼ (BW/GW) 100. One of the deskinned fillets of each fish served as analytical material for determination of proximate composition and fatty acid profile analysis. The second fillet, after thermal treatment, was used for sensory assessment. 2.2. Determination of proximate composition Water content was determined by the sample drying technique at a temperature of 105 1C; crude protein content with the use of the Kjeldahl method with 6.25 multiplier; fat content with the Soxhlet method (with petroleum ether as the solvent), and ash content by
Fillets with skin to be used for sensory assessment were evaporated to an internal temperature of 72 1C. Immediately after the thermal treatment, 5 cm of the fillet was cut out beginning with the section touching the head. Next, 6 samples 2.0 cm wide were cut out from the central section. A sample evaluated by each assessor originated from the same part of the fillet. This procedure was designed to minimize potential differences likely to result from the evaluation of different parts of the fillet. The assessment was carried out by a 6person panel, and all assessors evaluated all species examined (rapfen, pike, bream). The sensory evaluation was carried out in three separate sessions. The assessors performing the sensory assessment met the minimum sensory competence required in the current calibrating tests; they were selected, trained, tested, and monitored according to ISO guidelines (ISO, 1993). The assessors were experienced in sensory evaluation and were acquainted with the accepted system of sensory assessment. Colour, odour, consistency, juiciness and flavour were determined on a 5-point scale using half-scores according to the modified method for the evaluation of food products with the use of the scaling method (ISO, 1987) (see Table 1). The evaluation was carried out in a laboratory adjusted to sensory analyses; individual stations were separate from one another. Each sensory assessment station was lit with standardized lighting (T ¼ 6500 1C) (ISO, 1988).
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178 Table 1 Sensory evaluation scores Score (in points)
Colour
Odour
Texture
Juiciness
Flavour
5
Homogeneous, typical for cooked fish of certain species Homogeneous, somewhat dark
Typical, clearly perceptible
Firm, particularly tender
Very juicy
2
Somewhat too soft or somewhat too hard, very tender Semi-soft or hard, tender Soft or hard, fibrous
Juicy
Somewhat unhomogeneous, dark Unhomogeneous
Typical, poorly perceptible or very strong Poorly perceptible, foreign Perceptible, foreign
Desirable, typical, intense, no foreign aftertastes Desirable, typical, weak, no foreign aftertastes
1
Very unhomogeneous
Strong foreign
Very soft or very hard, fibrous
4
3
2.5. Statistical analysis The results presented for fish of particular species are means 7S.E.M. obtained in the analysis of 8 fish. The differences between the mean values of parameters examined (biological factors: slaughter field, proximate composition, fatty acid composition, sensory assessment) were calculated using one-factor analysis of variance (ANOVA). Use was also made of the SNK test (Student–Newman–Keuls) and statistically significant differences were reported at Po0:01. Calculations were made with the use of Statistica 6.0 PL software.
3. Results and discussion Table 2 presents the condition factor, gonadosomatic index and slaughter field of carcasses and fillets for rapfen, bream and pike, whose total weight accounted for 16807180 g; 1483791 g, and 1248752 g, respectively. The fish differed in the condition factor, 0.91 for rapfen, 1.15 for bream, and 0.64 for pike. On the other hand, the gonadosomatic index was the same in all fish species and ranged from 2.01 to 2.69. The slaughter yield of the gutted carcass of the experimental species did not significantly differ. However, rapfen had the highest yield of gutted and deheaded carcass. This value was 3.28% greater than in bream and 4.48% greater than in pike. High yields of fillet with skin and skinned fillet were also obtained in rapfen, totalling 59.4470.43 and 51.2670.38%, respectively, and were similar to those of pike. These same indicators for bream resulted in significantly lower yields. The above relations agree with the data obtained by Litwin´czuk et al. (2000) and Bykowski and Dutkiewicz (1996), who found that the yields of carcass and tissue are higher in pike than in bream. The literature does not contain any reference to rapfen.
Low juiciness Dry Very dry
Typical with slight foreign aftertaste Clearly perceptible foreign aftertaste Atypical, strong foreign aftertaste
One of the factors exerting a substantial effect on the yield is the degree of gonad development. In all fish species analysed, the gonads were in the first phases of development, which is indicated by the fishing period and low GSI values. Hence, their percentage in the total weight of fish was not high, and the slaughter yields of the gutted carcasses of rapfen, bream and pike were differentiated. However, the small head percentage in the rapfen total body weight in comparison to bream and pike determined the highest yield of gutted and deheaded carcass in this fish. Similar yields of rapfen and pike fillets indicated a similar percentage of skin and muscle system in these fish, which were different in bream. The high tissue yield (over 50%) indicates a high slaughter value of rapfen, which is greater than in other cyprinoid fish. The tissue obtained from the experimental fish was characterized by a varied content of fat and water. The rapfen and bream tissue contained significantly higher amounts of fat. The varied content of fat was compensated by the content of water. The content of protein was similar for the three species and ranged from 18.00% to 18.83%. In addition, the ash level in the three species was similar and was approximately 1% (Table 3). Based on a sensory evaluation, the odour and texture of the fish tissue evaluated received very similar scores. In addition, the flavour of rapfen and pike tissue was evaluated similarly. However, rapfen tissue colour scored lower than bream or pike tissue. It was darker and was evaluated as slightly uneven. The evaluated fish tissue differed in juiciness, which was the highest for bream and the poorest for pike (Fig. 1). The results obtained confirmed a reverse correlation between the fat and water contents, which is common for many fish species (Ko"akowska and Ko"akowski, 2000). According to the classification provided by the above-mentioned authors and the Polish norm (PN, 1999), rapfen—like bream—may be classified in the
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Table 2 Biological factor, carcass and fillet yields (mean7S.E.M.) Factor
Rapfen (n ¼ 8)
Bream (n ¼ 8)
Pike (n ¼ 8)
Total mass (BW) (g) Body lenght (Lc) (mm) Condition factor (K) Gonadosomatic index (GSI) (%) Gutted carcass (%)d Gutted and deheaded carcass (%)d Fillet, with skin (%)d Fillet, skinned (%)d
1680 7180 47.88a72.01 0.91a70.02 2.07a70.25 91.19a70.35 74.57a70.36 59.44a70.43 51.26a70.38
1483 791 41.45b70.54 1.15b70.02 2.01a70.20 88.49a70.75 71.29b70.73 48.83b70.89 37.87b70.52
1248a752 50.50a71.17 0.64c70.01 2.69a70.21 91.02a70.69 70.09b70.71 57.83a71.01 48.92a70.70
a
a
Values in the same line with different letters are significantly different at Po0:01. d Yield with relation to the total mass.
Table 3 Chemical composition (%) of fish tissue (mean7S.E.M.) Component
Rapfen (n ¼ 8)
Bream (n ¼ 8)
Pike (n ¼ 8)
Water Protein Fat Ash
77.64a70.35 18.83a70.15 2.52a70.29 1.01a70.01
77.37a70.27 18.00a70.28 3.63a70.34 1.00a70.01
80.32b70.14 18.06a70.14 0.64b70.13 0.99a70.01
Values in the same line with different letters are significantly different at Po0:01.
Fig. 1. Sensory evaluation of fish tissue.
group of semi-fat fish (fat content of fish tissue 2–7%), and—like pike—in the group of lean fish (fat content lower than 2%). The fat content in fish tissue contributes to its organoleptic properties, texture and flavour. Fat, rich tissue is juicy, while lean tissue is dry and perceived as thickly fibrous. This was explicitly confirmed in a study comparing the sensory properties
of wild and farmed fish, which differed in fat content (Jahncke et al., 1988; Orban et al., 1997; Grigoriakis et al., 2003) or of fish of the same species with different fat contents (Johansson et al., 2000). A comparison of sensory properties in the above-described study confirmed that pike tissue, with the lowest fat content, was the least juicy.
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A lipid analysis enabled the classification and quantitative determination of 33 fatty acids as well as the sum of saturated fatty acids (SFA), monounsaturated fatty acids (MUFA), polyunsaturated fatty acids (PUFA), n-3 acids, n-6 acids and n-3/n-6 ratio (Table 4). It was demonstrated that the total sum of SFA in 100 g carcass of rapfen and bream did not differ, and was higher than that of pike carcass. This was due to higher concentrations of three quantitatively dominating saturated fatty acids compared to pike carcass: myristic (14:0), palmitic (16:0), and stearic acids (18:0). As a consequence, the percentage of unsaturated fatty acids appeared to be similar in rapfen and bream and the lowest in pike. The MUFA concentration of rapfen Table 4 Fatty acid profile (mg 100 g1) in fish tissue (mean7S.E.M.) Fatty acid
Rapfen (n ¼ 8)
Bream (n ¼ 8)
Pike (n ¼ 8)
14:0 14:1 15:0 16:0 16:1 16:2 16:4 17:1 18:0 18:1 cis 9 18:1 cis 11 18:2 n-6 18:3 n-5 18:3 n-6 18:3 n-4 18:3 n-3 18:4 20:0 20:1 n-11 20:1 n-9 20:1 n-7 20:2 20:4 n-6 20:4 n-3 20:5 n-3 22:0 22:1 n-11 22:1 n-9 22:2 21:5 22:5 n-3 22:5 n-6 22:6 n-3 S SFA S MUFA S PUFA S n-3 S n-6 S n-3/S n-6
58.43a73.10 11.09a70.61 8.63a70.63 253.6a75.0 179.8a74.7 12.00a70.82 1.66a70.12 16.48a70.78 56.08a72.40 320.9a715.9 65.20a71.45 72.98a73.31 4.18a70.31 4.08a70.41 3.85a70.21 54.76a72.92 19.39a72.08 2.72a70.08 0.43a70.01 16.29a71.06 2.75a70.23 9.53a70.40 6.21a70.46 73.97a71.96 106.7a72.7 — 1.10a70.04 0.55a70.02 3.51a70.12 6.83a70.46 14.55a71.91 36.28a71.13 207.8a711.2 379.5a77.6 613.6a722.5 638.3a711.9 457.8a711.3 119.6a73.7 3.86a70.17
77.67a710.09 23.92b73.14 12.74a71.57 380.3a733.8 349.2b743.7 31.36b73.25 2.99a70.36 27.80a73.26 98.41a77.27 557.2a747.6 149.4b716.6 160.5b720.6 10.81b71.20 8.49a71.18 6.28a70.68 63.82a76.78 17.00a71.61 7.88a70.56 14.80b71.46 19.89a71.57 4.47a70.49 15.73a71.47 11.28a71.45 79.70a77.14 153.0a712.5 1.69a70.42 0.39a70.04 1.49a70.13 4.58a70.67 8.18a70.95 10.26a70.70 38.71a73.60 134.1b78.5 578.7a752.5 1151b7115 752.4a764.8 440.9a732.4 219.0b726.0 2.15b70.14
5.68b70.41 0.95c70.16 1.17b70.10 59.96b74.80 16.51c71.57 1.36c70.13 0.22b70.02 2.04b70.27 21.02b71.77 40.10b73.47 8.67c70.58 11.67c71.02 0.59c70.04 0.67b70.06 0.54b70.06 7.36b70.67 3.00b70.30 0.33a70.02 0.21a70.01 1.50b70.17 0.41a70.04 1.26b70.09 0.93b70.12 18.77b71.66 19.09b71.83 0.14a70.02 0.30a70.03 0.96a70.34 0.50b70.04 1.26b70.07 4.23b70.28 7.43b70.54 83.25c77.22 88.25b77.07 71.04c76.11 162.1b713.8 132.7b711.5 20.69c71.68 6.41c70.12
FA, fatty acid; SFA, saturated FA; MUFA, monounsaturated FA; PUFA, polyunsaturated FA. Values in the same line with different letters are significantly different at Po0:01.
carcass was intermediate when compared to those of bream and pike, whereas the concentration of PUFA was higher than that of pike and comparable with that of bream. It is also worth emphasizing that rapfen was characterized by similar percentages of MUFA and PUFA acids, whereas the carcasses of bream were predominated by MUFA, and those of pike, by PUFA. The total sum of n-3 fatty acids reaching 457.8711.3 mg 100 g1 for rapfen did not differ from that reported for bream, namely 440.9732.4 mg 100 g1, but appeared to be higher than that reported for pike, 132.7711.5 mg 100 g1. The concentrations of individual n-3 acids, including linolenic (18:3n-3), eicosatetraenoic (20:4n-3), and docosapentaenoic acid (EPA, 22:5n-3), in the carcass of rapfen approximated those determined in bream carcass and were higher than those determined in pike carcass. A significant difference between rapfen and the other two fish species was observed in the concentration of docosahexaenoic acid (DHA; 22:6n-3). The total sum of n-6 acids was different in the carcasses of all fish species examined, which resulted from a differentiated concentration of linoleic acid (18:2n-6) in rapfen, bream and pike, as well as various concentrations of arachidonic acid (20:4n-6) and docosapentaenoic acid (22:5n-6) in rapfen and bream compared to pike. Carcasses of the analysed fish also had a different n-3/ n-6 ratio. The highest value, 6.4170.12, was reported for pike, whereas the lowest, 2.1570.14, was for bream. Because of the positive, health-promoting effects of long-chain n-3 fatty acids on the human body, their contents are especially important to consumers (Hunter and Roberts, 2000; Uayu and Valenzuela, 2000). The results obtained indicate that although the concentrations of EPA and DPA acid in rapfen are similar to those of bream, they are higher than the values reported for pike. In addition, the rapfen carcass has the highest concentration of DHA. Thus, despite the fact that bream contains more fat (by 1% and more), rapfen appears a more valuable source of this particular fatty acid for consumers. A comparison with pike carcasses, which had the lowest fat content, is even more to the advantage of rapfen, since a 100 g portion of pike carcass had only half the DHA concentration as the carcass of rapfen. The results obtained also indicated that although the n-3/n-6 ratio of rapfen carcass does not reach the value reported for pike, it is still higher than that observed in bream. This was confirmed by data obtained by Bieniarz et al. (2000), who found that freshwater carnivorous fish can be characterized by greater n-3/n-6 fatty acid ratio than phytophagous and benthophagous cyprinoid fish (tench, ide, crucian carp, grass carp). Only the n-3/n-6 acid ratio determined for bream falls into the narrow range of values determined for freshwater fish by
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Henderson and Tocher (1987) and Aggelousis (1991). Data determined for the other experimental species are in line with the values given by Ko"akowska et al. (2000) for freshwater fish caught in Polish waters.
4. Conclusions Based on the results obtained, rapfen is characterized by a very good yield. The skinned fillet weight is over 50% of rapfen body weight. Although rapfen tissue is similar to bream tissue in terms of the total fat content, the percentage of PUFA and particularly DHA, which is valuable in the human diet, as well as the n-3/n-6 acid ratio, are greater in rapfen tissue. However, in this respect, rapfen tissue does not match pike tissue. References Ackman, R.G., 2000. Fish is more than a brain food. IIFET Proceedings. Aggelousis, G., 1991. Fatty acid composition of the lipids from eight freshwater fish species from Greece. Journal of Food Composition and Analysis 4, 68–76. AOAC, 1975. Official Methods of Analysis of the Association of Official Analytical Chemists. AOAC, Washington, DC. Bieniarz, K., Ko"dras, M., Kamin´ski, J., Mejza, T., 2000. Fatty acids and cholesterol in some freshwater fish species in Poland. Folia Universitatis Agriculturae Stetinensis 27, 21–44. Brown, W.D., 1986. Fish muscle as food. In: Bechtel, P.J. (Ed.), Muscle as Food. Academic Press INC, Orlando, pp. 406–445. Brylin´ska, M., 1986. The Freshwater Fishes of Poland. PWN, Warszawa. Bykowski, P., Dutkiewicz, D., 1996. Freshwater fish processing and equipment in small plants. FAO Fisheries Circular No. 905, Rome. Folch, H., Less, M., Stanley, H.A., 1957. A simple method for isolation and purification of total lipids from animal tissues. Journal of Biological Chemistry 226, 497–499. Garcia, D.J., 1998. Omega-3 long-chain PUFA nutraceuticals. Food Technology 52, 44–49. Grigoriakis, K., Taylor, K.D.A., Alexis, M.N., 2003. Organoleptic and volatile aroma compounds comparsion of wild and cultured gilthead sea bream (Sparus aurata): sensory differences and possible chemical basis. Aquaculture 225, 109–119. Henderson, R.J., Tocher, D.R., 1987. The lipid composition and biochemistry of freshwater fish. Progress in Lipid Research 26, 281–347. Hunter, B.J., Roberts, D., 2000. Potential impact of the fat composition of farmed fish on human health. Nutrition Research 20, 1047–1058.
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