Quality Characteristics of Dark Muscle from Yellowfin Tuna Thunnus Albacares to Its Potential Application in the Food Industry

Food and Nutrition Sciences, 2011, 2, 22-30 doi:10.4236/fns.2011.21003 Published Online January 2011 (http://www.SciRP.org/journal/fns) Quality Characteristics of Dark Muscle from Yellowfin Tuna Thunnus albacares to Its Potential Application in the Food Industry Elena Sánchez-Zapata1, Mahassine Amensour2, Rosa Oliver1, Evangélica Fuentes-Zaragoza1, Casilda Navarro1, Juana Fernández-López1, Esther Sendra1, Estrella Sayas1, José Angel Pérez-Alvarez1 1Agro-food Department–IPOA, Universidad Miguel Hernández, Ctra, Orihuela, Alicante, Spain; 2Biology Department, Science Fac- ulty, Abdelmalek Essaâdi University, Tetouan, Morocco. Email: [email protected] Received September 30th, 2010; revised November 16th, 2010; accepted November 24th. ABSTRACT Dark muscle from yellowfin tuna is an important edible fish by-product. However, it has a low commercial value, and it is underutilized. The present study was conducted to establish the characteristic of this by-product. Myoglobin concentration in tuna dark muscle is high (9650.12 mg/kg). Total iron in tuna muscle was 32.11 mg/kg, higher than other animal foods like veal or pork, and heme iron concentration was 23.56 mg/kg (73.38% of the total iron), indicating a high bioavailability of heme iron in dark muscle from yellowfin tuna, which is a nutritional advantage. As for the technological properties, yellowfin tuna dark muscle had a water holding capacity of 8.37 g water/g and oil holding capacity of 8.11 g oil/g. This indicates that tuna dark muscle has possible applications to elaborate products, such as emulsion- ated foods or cooked products, so its industrialization is possible. Keywords: Dark Muscle, Tuna Fish, Haemopigments, Myoglobin, Heme Iron, Physicochemical Properties 1. Introduction This would cause serious disposal and pollution prob- lems, especially in developing countries. These wastes, Yellowfin tuna Thunnus albacares is an intensely ex- which represent an environmental problem to the fishing ploited fish. Large quantities of yellowfin tuna are com- industry, constitute an important source of proteins. Tra- mercially used in canned and dry-salted products, like cured tuna loin (a typical product from Spanish Southeast, ditionally, this material is transformed into fish flour to called “mojama”) [1] and as sashimi, a delicate-tasting animal feed. Nevertheless, novel processing methods are raw fish product popular in Korea and Japan. The use of required to convert fish by-products into more profitable yellowfin tuna as sashimi is increasing in several other and marketable products [6,7]. In other cases the fish wa- countries, with an annual worldwide production of 3,400,000 stes have been use to produce collagen, chondroitin sul- MT [2]. Yellowfin tuna industrialization is increasing phate and gelatine which have indirect environmental fishery by-products. The amount of by-products pro- benefits [5]. duced during fish processing can be as high as 75% of Fish muscle consists of light and dark muscle, the dark the total weight of fish [3,4]. Some of the by-products are muscle is a band of dark tissue that lies beneath the skin used to produce fish sauces and food products such as throughout the body. In tuna, dark muscle is also located dry-salted roe, also could be used in animal feed, but near the backbone. Although generally the relationship much of it is discarded and is a source of environmental between light and dark muscle varies with the fish active- contamination. The amount of hazardous waste produced ity, fatty fish contains higher proportion of dark muscle, from fish processing has tended to increase annually [3]. reaching values up to 48% [8], like in yellowfin tuna. Optimal utilisation of fishery by-products is becoming This is because the fatty fish are migratory species, so increasingly important [5]. Large quantities of protein- they need more fat, glycogen and myoglobin for their rich fish processing by-products are discarded as waste, long journeys. There are many differences in the chemi- without any attempt to recover the essential nutrients. cal composition of the two types of fish muscle, but the Copyright © 2011 SciRes. FNS Quality Characteristics of Dark Muscle from Yellowfin Tuna Thunnus albacares to Its 23 Potential Application in the Food Industry most important are the high fat and heamopigments con- 2.3. Technological Properties tent in dark muscle. Consequently, the higher lipid con- 2.3.1. Physicochemical Analysis tents, less stable proteins, greater concentrations of heme The pH was measured using a pH-meter (Mod. pH/Ion proteins, lower ultimate pH values, higher concentrations 510, Eutech Instruments Pte Ltd., Singapore) by AOAC of sarcoplasmic proteins of dark muscle have been sug- method 14.022 [15]. Water activity (A ) was determined gested to contribute to the difficulties in its industrializa- w in a Novasina Thermoconstanter Sprint TH-500 (Pfäf- tion and making high-quality products from raw material fikon, Switzerland) at 24.9℃. The CIELAB color space containing high contents of dark muscle. Because of this was selected for color determination. Color measures it is considered as a by-product of the tuna industry [4-9]. were made using a spectrophotometer Minolta CM-2600d Yellowfin tuna dark muscle (“sangacho” in Spanish) is (Minolta Camera Co. Osaka, Japan), with D as illumi- not commonly used by the canned and dry-salted tuna 65 nant and an observer angle of 10˚. Low reflectance glass fish industry [10], being a by-product for these industries. (Minolta CR-A51/1829-752) was placed between the sa- However, the characteristics of yellowfin tuna dark mus- mples and the equipment. The CIELAB coordinates stud- cle (DM) that make it not acceptable for these industries ied were: Lightness (L*), co-ordinate red/green (a*) and (strong dark color and highly susceptible to lipid oxida- co-ordinate yellow/blue (b*) [16]. tion speeding up its deterioration) [11] could give it a high nutritive value, even higher than that of light muscle. 2.3.2. Functional Properties Fish dark muscle contains many n-3 polyunsaturated fa- Water-holding capacity (WHC) and oil-holding capacity tty acids (n-3 PUFA) such as icosapentaenoic acid (EPA: (OHC) were determined according to El Khalifa et al. C20:5n-3) and docosahexaenoic acid (DHA:C22:6n-3). [17]. For the water holding capacity (WHC), 1 g of sam- These fatty acids have various bioactive functions, such ple was placed in previously weighted centrifuge tubes, as anti-cancer activity, recovery from heart failure, atte- and 14 mL of water was added. For the oil holding ca- nuation of cerebrovascular disease, and anti-arterioscl- pacity (OHC), 14 mL of sunflower oil was added. Both erosis action [12]. Dark muscle is also a high source of samples were stirred in a tube stirrer and kept at rest for 30 iron which is an essential mineral. When it is as heme min at room temperature before being centrifuged at 5,000 iron is several times more absorbable than non heme iron × g for 25 min. The excess of water or oil was removed by present in other foods [13]. tube inversion over tissue paper. The difference between Several methods have been successfully applied to the sample’s weight before and after water or oil absorp- preserve fish and to extend the shelf life of fish products tion was taken as the amount of water or oil absorbed. but none has been tested to use in DM [14]. The aim of WHC was expressed as g of water held per g of sample, this paper was to characterize (chemical, physicochemi- and OHC was expressed as g of oil held per g of sample. cal and microbiologically) the yellowfin tuna dark mus- Water adsorption capacity (WAdC) and water absorption cle to determine their possible industrialization and thus capacity (WAbC) were determined according to Vázq- exploit by-products from the tuna industry. uez-Ovando et al. [18]. Water absorption capacity (WAbC) 2. Materials and Methods is indicative of a structure’s aptitude to spontaneously absorb water when placed in contact with a constantly 2.1. Raw Material moist surface or when immersed in water, while the water adsorption capacity (WA C) is the ability of a struc- The raw material (frozen tuna dark muscle) was obtained d ture to spontaneously adsorb water when exposed to an from a local fish manufacturer. It had been rapidly frozen atmosphere of constant relative humidity. It is initially a at –40℃ and then stored at –18℃ for 1 month. It was surface phenomenon but, at higher hydration levels, ab- transported to the pilot plant facilities of the IPOA Res- sorption can occur inside the structure, leading to swell- earch Group, at the Universidad Miguel Hernández (Ori- ing and eventual solubilization [18]. WA C was ex- huela, Alicante, Spain) in refrigerated conditions (4℃). d pressed as g of water adsorbed per g of sample, and Tuna dark muscle was thawed before each analysis in WA C was expressed as g of water absorbed per g of chill storage (4℃) over night. b sample. Emulsifying activity (EA) and emulsion stability 2.2. Proximate Composition (ES) were evaluated according to Chau et al., [19] with slight modifications. 100 mL of 2% (w/v) sample susp- For all chemical analysis, samples were grounded in an ension in water was homogenized at 11000 rpm for 30 s electric mini food chopper Moulinex 390 (Moulinex, Paris, at room temperature, using a homogenizer IKA T-25. France). Moisture, ash, protein and fat content were de- 100 mL of sunflower oil was then added and homoge- termined by AOAC methods 24.003, 24.009, 24.027 and nized for another 1 min. The emulsions were centrifuged 24.005, respectively [15]. Copyright © 2011 SciRes. FNS 24 Quality Characteristics of Dark Muscle from Yellowfin Tuna Thunnus albacares to Its Potential Application in the Food Industry in 10 mL graduated centrifuged tubes at 1200 g for 5 min, De Man, Rogosa, Sharpe (MRS) broth for lactic acid ba- and the volume of the emulsion left was measured.

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