1. Introduction
In global aquaculture, the production of interspecific hybrids within the Siluridae family has been successfully carried out for many years. Hybrids often combine the features of parental lines that are desired by breeders, i.e., rapid growth rate, low FCR (feed conversion rate), increased tolerance to low concentration of dissolved oxygen in water, or higher resistance to pathogens (e.g.,
Edwardsiella ictaluri). The most known hybrid in this group of animals is channel x blue catfish (
I. punctatus (Rafinesque, 1818) ×
I. furcatus (Lesueur, 1840)), in which traits exceed even those observed in individuals of the pure channel catfish line [
1]. Another well-known intergeneric hybrid is crossbred between the
Heterobranchus longifilis (Valenciennes, 1840) and
Clarias gariepinus (Burchell, 1822), the so-called “heteroclarias”. This hybrid is becoming popular because the fish show very fast growth, inherited from the species
H. longifilis [
2]. In semi-intensive systems, fry of hybrids (mean weight 7.5 g) within 24 weeks reached an average harvest weight of 880 g [
3]. In addition, heteroclarias has a higher capacity to grow in unfavorable farming conditions, efficiently utilizes diverse feeds, and has increased disease resistance. The unique breeding features of the
C. gariepinus ×
H. longifilis hybrid have increased the interest in global aquaculture, which is associated with the development of fish processors interested in new ways to use this raw material. The literature data show that consumers highly rate the quality of meat of
C. gariepinus [
4,
5] due to the high content of protein (17.35%) and low calorific value (491 kJ). The meat of this species has an intense red color and a low free leakage, is tender, boneless, and devoid of intense fishy flavor. These factors mean that African catfish meat is characterized by high culinary and processing suitability [
5]. Due to its inherent characteristics, catfish meat can gain the interest of new consumers currently not interested in the consumption of fish. The aversion to the taste, smell, and texture of fish, as well as the fear of ingesting bones contribute to low fish intake [
6,
7]. However, no information was found in the available literature on the quality characteristics of
H. longifilis meat. It is, therefore, difficult to estimate the effect of these “parental” species on the culinary and processing quality of heteroclarias meat (hybrids of
C. gariepinus ×
H. longifilis). Moreover, in the scientific literature, there is a low number of data available for heteroclarias, and they are mostly related to the zootechnical parameters. Therefore, it seems that determining the culinary and processing qualities of the new raw meat material will contribute its proper use.
Catfish and its hybrids are important worldwide. The total production of African catfish officially reported by FAO is 246,476 t during 2015 [
8]; however, it is expected that the production will increase in the following years. Therefore, detailed characteristics of catfish and its hybrids’ meat is of utmost importance to aquaculture and fish processing sectors in those countries in which catfish production is very popular, such as Nigeria, Netherlands, Brazil, and Hungary. This approach is also in line with the Sustainable Development Goals (SDGs) set in 2015 by the United Nations which indicate the need of sustainable food production. [
9]. The aim of the study was to assess selected parameters of nutritional and culinary quality of heteroclarias hybrid meat obtained from crossing female
C. gariepinus with male
H. longifilis. The preliminary results obtained in our study may help the fish sector to introduce new raw materials and products on the market that are sensorily appealing to consumers who have to eat seafood products to maintain healthy growth and development, i.e., children and seniors.
4. Discussion
Hybrid production has its economic justification. In aquaculture, it allows for better culture parameters, i.e., higher growth rates, fillet yield, and lower mortality due to diseases. The study showed that the studied fish groups did not differ significantly in body, carcass, and fillet weight, but a significantly higher carcass and fillet yield was shown for heteroclarias (68.3 and 53.9%, respectively) compared to
C. gariepinus (60.4 and 49.1%). According to the literature data, the yields of
C. gariepinus carcasses and fillets were at the level of 66.75–69.95% and 42.69%, respectively [
5,
19], and were similar to those found in our study, whereas the higher dressing percentage of heteroclarias confirms its higher utility value compared to
C. gariepinus.
The consumer acceptance of raw materials and fish products depends on, among other things, their nutritional value and sensory properties, especially color, tastiness, and texture [
20,
21]. In turn, the chemical usefulness of the raw material is determined by its chemical composition, losses during storage and thermal treatment, as well as the pH of the meat. Our study showed, as well as the literature data, that African catfish meat has a good nutritional value [
22,
23,
24], thus it can replace raw materials and animal products in the human diet. Additionally, the results did not show significant differences in the basic chemical composition or the energy values of heteroclarias and
C. gariepinus meat. Toko et al. [
25] did not show significant differences in the protein content between the meat of African catfish and
H. longifilis; however, they recorded a higher fat content in
H. longifilis meat, which was particularly evident at high stocking density. We found about 17% protein and 4% fat in
C. gariepinus meat, which means that fish of this species can be classified as medium-fat [
26]. This was also confirmed by the results obtained for this species (16.8–17.42% of protein, and 5.3–5.7% of fat) by Rosa et al. [
22], Chwastowska-Siwiecka et al. [
5], and Chwastowska-Siwiecka et al. [
27]. However, the content of protein (17%) and fat (3%, low-fat species) in the heteroclarias meat was respectively higher and lower than that observed by Olaniyi et al. [
24] in the meat of
H. bidorsalis (66.8% crude protein—approx. 14.9% protein in d.m., and 21.5% ether extract—approx. 4.8% lipids in d.m.). In addition to protein and fat, the nutritional value of the raw material is also determined by the quality of the fat (fatty acid profile). Our study showed that the fat of
C. gariepinus and heteroclarias fillets had a high content of MUFA (48.4–49.9%) and similar share of SFA (22.2–25.9%) and PUFA (25.6–27.8%), but the fat of the hybrid fillet was more saturated and had a lower content of n − 6 and n − 9 fatty acids. In both of the fish groups, the fat was characterized by a comparable amount of n − 3 FA (including the sum of EPA and DHA), but the fat of heteroclarias had significantly higher DHA content. This essential unsaturated fatty acid is responsible for reducing the risk of cancer and cardiovascular disease [
28,
29,
30], and is particularly beneficial in the nutrition of pregnant women and children due to its beneficial effect on development and the nervous system, among others [
31]. A similar share of three FA fractions (SFA, MUFA, PUFA) in African catfish meat was shown by Abouel-Yazeed [
32]. According to Rosa et al. [
22], it was found that the content of SFA and PUFA in
C. gariepinus was higher (approx. 32.7 and 36.3%, respectively), and MUFA was lower (approx. 30.9%) than that found in our work. These differences in protein and fat content and in the fatty acid profile may result from different fish farming conditions (feed composition) and fish weight in compared experiments. Rosa et al. [
22] conducted research on fish weighing approx. 2052 g, whereas individuals in our study weighed approx. 1100 g, and as is also described in the literature, with the age (weight) of animals, the fat content increases, and the protein content in their body decreases [
33], and the fatty acid profile changes [
34]. On the other hand, the type of feed determines the content of protein and fat and its quality in the body of fish [
34,
35], especially the content and type of lipid component in feed [
4,
36,
37,
38]. The study showed that the fat of both fish groups has a high health value due to higher than recommended by nutritionists [
39,
40] ratios, PUFA:SFA > 0.45 (1.0–1.3 in our study), n − 6:n − 3 < 4 (2.7–3.1 in our study), index of atherogenicity IA < 1.0 (0.25–0.30 in our study), index of thrombogenicity IT < 0.5 (0.37–0.45 in our study), and high h:H ratio (3.64–4.42 in our study). These quality parameters of fat were found in catfish fillets. Similarly, the high nutritional value of catfish fat has been confirmed by Abouel-Yazeed [
32].
In the sensory assessment, hybrid meat received better notes than African catfish, which, according to literature data, is characterized by high sensory attractiveness, including tenderness, which is a consequence of the low content of connective tissue proteins in the meat of this species [
5], at a level of approx. 3% of total protein [
41]. In our research, we showed that heteroclarias had a less tender, but easier to chew, meat, and therefore, it was better digested, especially compared to meat from slaughter animals [
42]. We observed low-level gaping in both fish groups, as confirmed by the preserved fillet structure—clearly visible muscle fibers surrounded by endomysium. The gaping phenomenon is caused by damage to the fish meat structure at the fiber and myocommata attachments level, which causes the formation of slits or holes in the fillet surface [
20]. Kiessling et al. [
21] suggest that fish with many small fibers would have a relatively larger amount of connective tissue, which would prevent the fillet from gaping. Hence, smaller muscle fibers that have been observed in hybrid muscles may be responsible for the slightly smaller gaping of the heteroclarias fillets. On the other hand, smaller heteroclarias muscle fibers may also indicate a greater degree of packing of their muscle structure, which, in turn, resulted in significantly higher hardness and insignificantly higher chewiness of hybrid meat. Variation in muscle structures is an important determinant of texture and other flesh quality characteristics [
20]. Fish with smaller average cross-sectional area have a higher sensory firmness [
20,
43,
44]. A higher muscle fiber density was positively and significantly correlated with textural properties (hardness, springiness, cohesiveness, and chewiness) of sea bass (
Dicentrarchus labrax) meat [
45], as well as with a lower amount of fat and “oiliness score” in Atlantic salmon (
Salmo salar) muscles [
46], which is consistent with our results. However, meat texture does not depend exclusively on its structure properties. According to the literature [
21,
47], texture is strongly affected by the chemical composition of meat (amount protein, fat), as well as type, structure, and functional properties of proteins. Our study showed that the greater hardness of heteroclarias meat resulted from the higher content of protein, lower content of fat, and higher saturation of fat. Similarly, Saavedara et al. [
38] found a correlation between a lower amount of fat in meat and higher hardness. Fish lipids and lipid-derived aroma compounds, which are produced by the enzymatic oxidation of the polyunsaturated fatty acids present in fish, are responsible for the typical fish taste and smell [
47]. Although our study showed differences in the content of PUFA, no significant differences were found between palatability parameters of
C. gariepinus and heteroclarias meat. The meat of fish from both groups was characterized by a low intensity of fish smell and taste, and a low intensity of taste deviations (geosmine taste), which makes this raw material attractive to consumers who are reluctant to consume fish due to its taste and flavor. However, Olaniyi et al. [
24] showed that hybrid meat in comparison to parental species (
C. gariepinus,
H. bidorsalis) had poorer sensory acceptability. These differences in sensory evaluation of hybrid meat in both experiments are probably the result of using other species of the catfish family, or another feed composition used in the nutrition for their production.
In the technological assessment of raw materials, parameters such as color, pH, and WHC (water holding capacity) are used. Compared to
C. gariepinus, heteroclarias meat had a lighter color, as evidenced by greater brightness (L*) and whiteness index (WI), as well as lower a* and b* parameters. The color of meat is determined by, among others, its pH—lighter muscles have higher pH values than darker muscles [
48]. We also found this relationship between pH and meat color in our work, whereas Kralik et al. [
49] and Saláková et al. [
50] determined a negative correlation between pH and L*. Meat pH is a parameter that determines weight loss during storage and processing, as well as the texture of the meat [
41]. We have shown in studies that a higher pH of hybrid meat was responsible for higher hardness and chewiness, as well as lower cooking losses compared to African catfish meat. A similar relationship between pH and drip loss was obtained by Kralik et al. [
44], and a relationship between pH and texture parameters was shown by Periago et al. [
45].
When choosing and purchasing fish, consumers are guided mainly by their price and nutritional value, as well as by species. They do not take into account the sex of the fish because they are not able to assess whether the fish, which they most often buy in the form of a fillet, is male or female. In our research, we showed that sex significantly affected the amount of protein and fat in the meat, as well as fat quality, meat color (L*, WI, a*, and c), size and shape of fibers, sensory perception of connective tissue and chewiness, and the energy value of the meat. However, this factor did not affect carcass and fillets yields, dry matter, ash and pH, cooking loss, endomysium thickness, TPA parameters, and most of the sensory traits. Moreover, [
19] did not show the effect of
C. gariepinus sex on the performance of edible parts (carcass and fillet yields), although in males, they found a significantly higher proportion of head and fins, whereas in females—guts (due to the greater weight of gonads). In turn, Chwastowska-Siwiecka et al. [
27] showed significant differences between males and females in thermal loss, shear force value, and color parameters of their meat. Biró et al. [
51] found significant differences between the two sexes in the n-3 PUFA, resulting in a higher n − 3/n − 6 ratio in the male fillets of Nile tilapia. Akpinar et al. [
52] showed a significantly higher share of SFA, MUFA, and n − 3 PUFA (including EPA) in female fillets than male fillets of
Salmo trutta macrostigma. The available literature lacks information on the effect of fish sex on the culinary and processing quality of their meat. This biological factor also determines the quality of raw fish material, and can probably be the reason for differences in the consumer assessment of the quality of fish fillets of the same species.