Quality improvement of common carp (Cyprinus carpio L.) meat fortified with n-3 PUFA
Introduction
Fish in the human diet are a source of easily digestible proteins, nutritious fats and fat-soluble vitamins (D, A), as well as micro- and macro-elements (e.g. I, Ca, Se). Fish lipids are particularly valuable because of their favorable fatty acid profile, including the high proportion of long-chain fatty acids, especially n-3 and n-6 EFA (essential fatty acid). Fatty acids EPA (20:5, n-3, eicosapentaenoic acid) and DHA (22:6, n-3, docosahexaenoic acid) have a very positive effect on health and are recommended for the reduction of cardiovascular disease (Calder, 2006; Calder and Yaqoob, 2009, 2010). Despite the high nutritional value of fish, consumption is far below levels recommended by nutritionists. The World Health Organization, together with Food and Agriculture Organization (WHO/FAO, 2003), recommend regular consumption of fish (1–2 times a week), including one portion of oily fish providing 200–500 mg of EPA and DHA. Despite these recommendations, most consumers globally eat fish less than once a week (Skibniewska et al., 2009; Pieniak et al., 2010; Dymkowska-Malesa et al., 2014; Maciel et al., 2019). One of the reasons for the lower popularity of fish (compared with meat) are their specific sensory features (i.e. smell, taste). Proteins and lipids (and post-mortem transformation of these compounds) are responsible for palatability, and fish lipids are particularly susceptible to oxidative changes due to their high content of unsaturated FA (fatty acids) which contribute strongly to the deterioration of the sensory quality and taste (Fauconneau et al., 1995).
Carp (Cyprinus carpio L.) is the main freshwater fish species bred in many European, Asian and Latin American countries. Carp contains 11.8–18% protein and 6.8–12.4% fat, the latter of which consists of 24.3–30.0% SFA (saturated fatty acids) and 70.0–75.7% unsaturated fatty acids, including 48.6% MUFA (monounsaturated fatty acids) and 21.5% PUFA (polyunsaturated fatty acids). Carp lipids are composed of 1.3–6.7% of n-3 FA, including ΣEPA + DHA constituting 0.5–4.3% of FA, and 1.3–14.8% n-6 FA (Grela et al., 2010; Woźniak et al., 2013; Ljubojevic et al., 2013). The variable nutrient content of carp is due to different living conditions and food sources. Therefore, these factors can be used by breeders to alter the nutritional make-up of carp. The nutritional quality of this species can be improved for human consumption by selecting the right feed composition and enrichment with nutrients, particularly those present in smaller amounts (e.g., EPA and DHA). Indeed, breeding experiments have shown that feeding common carp with mixed feed affects proximate composition (Manjappa et al., 2002; Aprodu et al., 2012) and fatty acid profile, including the EPA and DHA contents (Buchtová et al., 2007; Aprodu et al., 2012). Increased EPA and DHA in carp can be achieved by the introduction of fats into feed from different natural sources, including microalgae (e.g. Schizochytium sp.), fish or vegetables oils. The use of microalgal oils from Schizochytrium sp. for fortification is considered safe, as no reports have revealed potential exposure to toxic chemicals or pathogens (Ryan et al., 2010). Microalgal oil is recognized by the Food and Drug Administration of the United States of America (FDA) as permitted for use in infant formulae, and food and dietary supplements (Fedorova-Dahms et al., 2011). However, there is a lack of information about the effects of increased EPA and DHA in carp on culinary quality.
The aim of this study was to assess the quality of carp fed with feed enriched with the EPA + DHA fatty acids from natural sources and to check whether using such blends would increase the nutritional value of carp fillets without compromising their structure, texture and sensory quality parameters.
Section snippets
Experimental diets
The trial comprised four experimental diets (Table 1). A control diet, mimicking a commercial feed formulation for common carp, with moderate levels of fishmeal (5%) and high levels of plant raw materials and vegetable oils (rapeseed and soybean) as sole fat sources. In comparison, in the three test diets (CB1, CB2 and CB3), half of the fishmeal was replaced with a blend of microalgae (Spirulina sp., Chlorella sp.), macroalgae (Laminaria digitata) and salinized yeast. Additionally, fat
Proximate composition and fat characteristics of fillets
A highly significant (P ≤ 0.01) effect of carp feeding on the chemical composition (Table 2) and fat characteristics (Table 3) of fillets was achieved. Fillets from fish fed fortified feeds were characterized by a lower protein content and greater amounts of dry matter and fat, compared with the controls. No significant differences in ash content were found. The percentage of total MUFA was significantly (P ≤ 0.01) lower and total PUFA significantly (P ≤ 0.01) higher in fillets from fish fed
Discussion
Feeding carp with fortified feeds significantly affected the proximate chemical compositions and fat profiles of their fillets. The highest protein content in the control fillets was probably due to the feed containing twice as much fishmeal as the fortified feeds (CB1–CB3). Mazurkiewicz et al. (2011) did not show significant differences in the crude protein content of carp fed with different proportions of meal (fish, soybean, wheat) and rapeseed oil. Yet, together with an increase in meals
Conclusion
Feeding carp with feeds enriched with algae and fish fats improved significantly the nutritional value of fillets without compromising quality. Compared with the control fillets, the fillets of fish fed with fortified feeds had lower protein and higher fat contents and better fatty acid profiles, especially the most valuable total n-3 PUFA, EPA and DHA, as well as lighter color, greater redness and low to medium intensity of fishy odor and taste. Yet, none differed in instrumental or sensory
CRediT authorship contribution statement
M. Sobczak: Conceptualization, Writing - review & editing, Investigation, Supervision. R. Panicz: Conceptualization, Writing - review & editing, Validation. P. Eljasik: Writing - original draft, Investigation, Visualization. J. Sadowski: Resources. A. Tórz: Formal analysis. J. Żochowska-Kujawska: Writing - review & editing. V. Barbosa: Writing - review & editing. V. Domingues: Investigation. A. Marques: Writing - review & editing. J. Dias: Resources.
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgements
This research is part of the EU Horizon2020 project SEAFOODTOMORROW. This project has received funding from the European Union's Horizon 2020 funding programme, Grant Agreement no. 773400 (SEAFOODTOMORROW). This output reflects the views of the author(s), and the European Commission cannot be held responsible for any use that might be made of the information contained therein.
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