Comparison of Proximate, Fatty Acid and Amino Acid Compositions of Various Types of Fish Roes

Abstract

Proximate compositions, amino acid compositions and fatty acid compositions of fish roe have been measured and compared. Glutamic acid, aspartic acid, lysine, and serine have been the major amino acids. However, Imperial-type caviar has also included higher amounts of tryptophan (p < 0.05). Essential /Nonessential (E/NE) ratio has been found to be between 0.93 - 1.23, and n3/n6 ratio has been found to be 2.56–8.06. Major fatty acids were C16:0, C18:1 n9c, C16:1 n7, C20:5n3, and C22:6 n3. Fish roes contain high amount of lipids and energy, however, they are also rich sources of unsaturated fatty acids, proteins and amino acids.

Keywords:

• Fish roe
• Caviar
• Proximate composition
• Fatty acids
• Amino acids

INTRODUCTION

The word roe refers to the gonads of fish, which are considered as a high-price-flavor in international and domestic markets.[1] They are consumed for the special dinners and invitations all over the world.[2] Several types of roes from different fish species are marketed as shelf-stable products. The most widely recognized and valuable caviar is made from sturgeon harvested from the Caspian Sea.[2] Sturgeon caviar is exported from Iran to Turkey, England, France, Greece, Japan, Australia and Scandinavia.[3] More than 20 species (Huso sp. and Acipenser sp.) of sturgeon are harvested in order to obtain caviar. Beluga, Osetra, and Imperial are the popular black caviars and Beluga is usually regarded as the best among those.[4]

In the U.S. only sturgeon caviar can be labeled as “caviar.” Caviar from other species must be identified with a qualifying term that includes the common name of the marine animal for use. For instance, roe of salmon must be labeled as “salmon caviar,” and the majority of salmon caviar is produced from Oncorhynchus sp. and Salmo sp. Red salmon roe is one of the most important trade products of Japan.[5] Eggs from salmonid fish are much larger than sturgeon roe namely the eggs range might be from 4 to 7 mm diameter.[2]

Mullet (Mugil cephalus) roe, another type of fish caviar, is also consumed as a salted product. Dried mullet roe has a unique chewy mouth feel and a yellowish red color.[2] The two main principles of the processing of fish roe are salting and draining.[3–7] However, processing of mullet roe has some different characteristics than the others. The process to produce mullet roe involves coating the roe with salt for 4 to 5 h, removing the salt and compressing the roe during the curing process, and lastly air drying the product and waxing.[6,8]

Composition of fish roe depends on the type of roe and the method of processing.[9,10] They are regarded as high quality foods since they include important amounts of protein and amino acids. The lipid from fish roe products has presented as a useful food source for maintaining human health.[11] It is known that, fish roes contain eicosapentaenoic acid (C20:5n-3) and docosahexaenoic acid (C22:6n-3),[2,12,13] and they play an important role in the prevention and treatment of cardiovascular diseases.[14]

Despite the importance of these products in international commerce, there is relatively little technical information available about their chemical composition, product quality, and food safety attributes.[2] The aim of this study was to estimate and compare the proximate, amino acid and fatty acid compositions of different types of fish roes.

MATERIALS AND METHODS

Three different types of imported (from Iran) black caviar (Beluga, Imperial, and Osetra); red salmon roe and waxed mullet roe (100 g each) are obtained from three different shops in Old Bazaar, which is a very important place for the caviar trade in Istanbul. Beluga, Osetra, and Imperial caviars were the roes of Huso huso, Acipenser gueldenstaedti and Acipenser persicus, respectively. Beluga caviar was 0.30 ± 0.01 mm in diameter and 0.02 ± 0.01g in weight, osetria was 0.27 ± 0.02 mm and 0.01 ± 0.06 g, and imperial was 0.29 ± 0.05 mm and 0.22 ± 0.07 g, respectively. The diameter of salmon roe (Salmo trutta labrax) was 0.70 ± 0.08 mm, and its weight was 0.87 ± 0.05 g. The weight of waxed mullet (Mugil cephalus) gonad was 349.70 ± 1.12 g.

Sampling was carried out between January-May 2005. Protein, ash, lipid, moisture, amino acid, and fatty acid analyses of these samples have been performed, and the carbohydrate and energy values have been calculated. Five repetitions were carried out for the proximate analyses while amino acid and fatty acid analyses duplicated.

Kjeldahl method has been used for the determination of crude protein content of fish roes.[15] Samples with H₂SO₄ and catalyst has been heated to 420°C for 20 min using Velp DK 6 heating digester (Velp Scientifica, Italy). Velp UDK 140 Distillation (Velp Scientifica, Italy) unit has been used for the treatment with NaOH and boric acid; the amount of nitrogen has been estimated by the titration with HCl. Coefficient has been estimated to be 6.25.

For the determination of lipid content; homogenized sample has been well mixed with solvent (petroleum ether-acetone). This mixture centrifuged and upper layer, which contains solvent and lipid, has been taken to a flask. Solvent has been evaporated at 60°C by Buchi rotavapor R 2–3000 (Labortechnic, Switzerland), then flask has been kept at 105°C (FN 500 Nüve, Turkey) for 3 h, chilled in a desiccator for 3 h, and then it has been weighed. The fat content has been calculated from the weight of material held in the flask.[16] Moisture content has been determined considering the weight difference of the sample after and before drying. A thin layer of the homogenized sample has been weighted and dried at 105°C (FN 500 Nüve, Turkey) to constant weight.[17] Samples have been weighted after and before burning in oven (MF 100 Nuve, Turkey) at 550°C to estimate ash content.[18]

Carbohydrate content has been calculated by the difference between 100 and the sum of the crude protein, lipid, moisture and ash. Energy values of the samples has been also calculated and expressed as Kj/100 g.[19] Factors were used 5.65 for protein, 9.50 for fat and 3.90 for carbohydrates. For the estimation of amino acid composition; sample has been prepared prior to hydrolysis. Performic acid oxidation has been performed to oxidize cystine and methionine to cysteic acid and methionine sulfone. Sodium metabisulfite has been added to decompose performic acid. Amino acids have been hydrolyzed by 6M HCl, hydrolysates have been diluted with sodium citrate buffer or neutralized, pH has been adjusted to 2.20, and amino acids have been separated by high pressure liquid chromatography (HPLC). Aglient 1100 HPLC (Palo Alto, CA, USA) equipped with Aglient Zorbax SB-C18 4.6 × 75 mm column and Aglient 1100 G1314A UV detector (Palo Alto, CA, USA) has been used. Wave length has been 338 nm for primer amino acids and 262 nm for secondary amino acids.[20]

Fatty acid composition has been studied and results have been expressed as area percent (%). 0,150 g of the sample has been mixed with 5 ml methanolic NaOH (0,5 N) in a flask equipped with a glass cooler and boiled for 15 min in a water bath. 5 ml of BF₃ has been added to this mixture, boiled for 5 min, and boiled again for 1 min after adding heptane (2–5 ml). Upper layer has been taken to a tube, mixed with crystal anhydrous Na₂SO₄ and injected to Thermoquest Trace GC.[21] Chromatograph equipped with a flame ionization detector, and SP-2330 (Supelco, Sigma-aldirch) fused silica capillary column (30 m. –0.25 mm ID- 0.20 μm film) has been used. Oven temperature has been 120°C for 2 min and 220°C for 8 min. The injector and detector temperatures have been 240°C and 250°C, respectively. Air rate has been 350 ml/min., helium has been used for make up (30 ml/min.), range has been 1, carrier rate has been 0.5 ml/min., split ratio has been 1/150 and sample injection has been 0.5 μl. Sigma (Code: 189–19) lipid standard (Fatty Acid Methyl Ester mixtures) has been used. For the comparison of the data; differences have been studied at p < 0.05 level and measurements have been subjected to t-test.[22]

RESULTS AND DISCUSSION

In this study; protein contents of Beluga, Imperial, and Osetra caviars have been determined as 24.7 g/100 g roe; 24.2 g/100 g roe; 24.0 g/100 g roe, respectively. Similarly, protein contents of Beluga and Osetra were reported as 21.6 g/100 g roe and 24.5 g/100 g roe by Rehbein.[23] In this study, the highest and lowest protein contents (p < 0.05) have been estimated for waxed mullet roe (27.3 g/100 g roe) and for Osetra-type caviar (24.0 g/100 g roe). Protein content of fish roe is higher than that of fish meat. It is known that fish meat generally contains protein of 17–20 g/100 g fish,[24] while caviar contains between 25.40–26.90 g/100 g roe.[25] Protein content of salmon roe has been estimated as 26.8 g/100 g roe, and it has been 27.3 g/100 g roe for mullet roes. These values have been reported as 25.0–27.0 g/100 g roe[9,10] and 28.7 g/100 g roe[10] in the literature, respectively.

Fish roes contain significant amount of lipids. It has been reported as 15.5 g/100 g roe in black caviars.[25] In this study, lipid content has been measured as 15.9 g/100 g roe, 14.7 g/100 g roe, and 14.6 g/100 g roe (p > 0.05) for different types of black caviar (Beluga, Imperial, and Osetra, respectively). Similarly; lipid content has been reported to be 17.4 g/100 g roe for Beluga and 16.1 g/100 g roe for Osetra-type caviars.[23]

In various studies lipid content of red salmon roe has been reported as 14.0–15.0 g/100 g roe,[9,10] and it has been estimated as 12.7 g/100 g roe in our study. Lipid content of waxed mullet roe was significantly higher (p < 0.05) than the others as it was shown in Table 1. Moisture content is generally reported as 75–80 g/100 g for fish, 80–82 g/100 g for lean fish meat,[26] and it is considerably higher than that of the fish roe. The average content of moisture for black caviar was suggested as 47.00 g/100 g roe in the literature,[25] and it's amount was determined as 48.4 g/100 g roe for Beluga, 51.5 g/100 g roe for Imperial, and 52.0 g/100 g roe for and Osetra-type caviars (p > 0.05). In this study, moisture content of red salmon roe has been measured as 45.1 g/100 g roe, while it has been mentioned as 53.0 g/100 g roe and 57.6 g/100 g roe [9,10] in various studies. Due to the processing procedure (heavily salted, pressed, and waxed), moisture content of waxed mullet roe (21.2 g/100 g fish) has been significantly lower (p < 0.05) than that of the other roes. In a similar study, the moisture content of waxed mullet roe has been reported as 23.6 g/100 g roe.[27]

Table 1 Proximate composition and energy value of fish roes

	Beluga-type caviar	Imperial-type caviar	Osetra-type caviar	Red salmon roe	Waxed mullet roe
Protein (g/100g roe)	24.7 ± 0.3^ab	24.2 ± 1.3^ab	24.0 ± 2.9^a	26.8 ± 1.8^ab	27.3 ± 1.5^b
Lipid(g/100g roe)	15.9 ± 2.0^a	14.7 ± 0.5^a	14.6 ± 2.4^a	12.7 ± 0.5^a	36.8 ± 3.9^b
Moisture(g/100g roe)	48.4 ± 2.2^ab	51.5 ± 0.5^b	52.0 ± 0.8^b	45.1 ± 2.3^a	21.2 ± 5.8^c
Ash(g/100g roe)	4.1 ± 1.0^a	4.2 ± 0.1^a	4.8 ± 1.62^ab	7.1 ± 0.2^bc	8.3 ± 2.3^c
Carbohydrate (g/100g roe)	6.9 ± 1.4^a	5.4 ± 0.6^a	4.6 ± 1.94^a	8.3 ± 1.2^a	6.5 ± 3.4^a
Energy(Kj/100 g)	1327 ± 2.0^a	1244 ± 2.9^a	1224 ± 2.0^a	1273 ± 2.9^a	2212 ± 2.0^b
Different letters in the same row show significant differences among samples (p < 0.05).

In this study, content of ash has been between 4.1–4.8 g/100 g roe for black caviars, and 7.1 g/100g roe for red salmon roes. Amount of ash has been reported as 7.0% in the literature similar to our results.[28,29] It has been determined that; waxed mullet roes contain significantly higher (p < 0.05) amount of ash than black caviars. The ash content of salted mullet roe has been determined as 7.2 g/100 g roe and this value has been measured as 10.1 g/100 g roe after waxing by Şengör et al.[27] Therefore, it has been mentioned that ash content increase after waxing.

Carbohydrate content of the samples has been between 4.6–8.3 g/100 g roes in this study. Carbohydrate composition of caviar has been reported as 5.4–8.1 g/100 g roe in the literature, [25] and it has been well correlated with the results of present study. As it is presented in Table 1, fish roes contain high amounts of energy. There is not an important difference between black caviar types (p ? 0.05). However, energy value of waxed mullet roe is about 200 Kcal/100 g higher due to its content of lipid, and it is significantly different (p < 0.05) the others.

Aspartic acid was one of the major amino acids determined in fish roe in this study. It's amount was between 2958–3348 mg/100 g roe for black caviars in our study, and is reported as 2290 mg/100g roe in the literature.[25] Aspartic acid has been determined as 3133 mg/100 g roe for mullet roes in our study, while it has been reported as higher than 7000 mg/100 g roe.[10,30] These differences from the literature may be related with the species, age, diet, and habitat of the fish, but it is clear that aspartic acid is the one of the main amino acids for fish roes.

Glutamic acid is the other important amino acid for fish roes and its content is reported as 3770 mg/100 g roe [25] in the literature. Its highest value is estimated for red salmon roe (4953 mg/100g roe) and it is clear that the content of glutamic acid is important for fish roes. Glutamic acid and aspartic acid has been reported as the major components for fish roes,[10] and it has been confirmed by our study as it was shown in Table 2. It has also been determined that, fish roe contain considerable serine and its amount might be different in various types of black caviar (p < 0.05). For black caviars, the average content of serine has been reported to be 2000 mg/100 g roe by Souci et al.[25]

Table 2 Amino Acid composition of fish roes

	Beluga-type caviar (mg/100g)	Imperial-type caviar (mg/100g)	Osetra-type caviar (mg/100g)	Red salmon roe (mg/100g)	Waxed mullet roe (mg/100g)
Aspartic acid	2958 ± 9.1^a	3011 ± 117.2^ab	3348 ± 111.2^c	3269 ± 16.7^c	3133 ± 29.5^b
Glutamic acid	4797 ± 20.6^ac	4530 ± 317.3^a	4854 ± 34.0^bc	4953 ± 40.7^bc	4881 ± 84.6^bc
Asparagin	47 ± 4.2^a	277 ± 24.5^b	75 ± 2.6^c	65 ± 3.8^ac	50 ± 2.6^a
Serine	2328 ± 12.8^a	1008 ± 15.5^b	3010 ± 12.5^c	2677 ± 18.5^d	2538 ± 120.7^e
Histidine∗	36 ± 5.5^a	272 ± 13.5^b	105 ± 4.2^c	58 ± 3.8^d	71 ± 8.5^d
Glicyne	235 ± 6.0^a	239 ± 20.6^a	285 ± 7.0^b	346 ± 6.7^c	240 ± 7.6^a
Treonine∗	333 ± 6.2^ad	315 ± 28.0^a	380 ± 4.0^bd	471 ± 7.5^c	361 ± 34.4^d
Arginine∗	245 ± 4.0^a	1047 ± 112.1^b	310 ± 13.3^ac	354 ± 4.7^c	235 ± 16.4^a
Alanine	163 ± 11.1^a	301 ± 38.2^b	814 ± 12.0^c	221 ± 6.0^ad	282 ± 64.1^bd
Trosine	442 ± 5.9^a	815 ± 32.5^b	150 ± 6.9^c	690 ± 3.5^d	457 ± 53.2^a
Cystine	432 ± 3.0^a	242 ± 17.4^b	160 ± 24.0^c	669 ± 16.7^d	446 ± 32.9^a
Valine∗	2904 ± 46.1^a	681 ± 107.3^b	3296 ± 19.3^c	3165 ± 83.8^c	3258 ± 193.4^c
Metionine∗	2730 ± 45.0^a	2721 ± 135.7^a	2560 ± 66.4^b	395 ± 17.6^c	3038 ± 110.9^c
Tryptophan∗	368 ± 4.0^a	5274 ± 103.4^b	180 ± 7.1^c	434 ± 5.6^a	142 ± 8.0^c
Phenylalanine∗	341 ± 2.1^a	114 ± 14.0^b	227 ± 5.9^c	494 ± 2.9^d	339 ± 34.3^a
İsoleucine∗	360 ± 2.0^a	258 ± 33.2^b	163 ± 8.6^c	485 ± 6.6^d	299 ± 7.5^e
Leucine∗	317 ± 3.6^ab	285 ± 24.0^b	367 ± 9.5^c	455 ± 44.7^d	329 ± 14.3^ac
Lysine∗	4029 ± 580.6^a	2647 ± 216.3^b	5595 ± 30.0^c	6213 ± 3.8^d	5180 ± 183.6^c
Hydroxiproline	271 ± 2.5^a	293 ± 17.1^b	220 ± 1.2^c	397 ± 11.1^d	191 ± 6.0^e
Proline	138 ± 4.0^a	307 ± 14.0^b	65 ± 4.2^c	231 ± 10.8^d	91 ± 3.1^e
E/NE	0.99	1.23	1.00	0.93	1.08
∗Essential amino acids. Different letters in the same row show significant differences among samples (p < 0.05).

Valine and methionine are the other two important amino acids for fish roes, however the amount of valine was lower (p < 0.05) than the others for Imperial-type caviars. It has also been seen that, Imperial-type black caviars contain significant (p < 0.05) amount of tryptophan.

Lysine is one of the major amino acids, and its content has been the highest for salmon roes (p < 0.05) similar to the literature.[10] Souci et al.[25] reports the lysine content of black caviar to be 2070 mg/100 g roe, and it has been estimated as 4029 mg/100 g roe, 2647 mg/100 g roe, and 5595 mg/100 g roe (p < 0.05) for Beluga, Imperial, and Osetra-type caviars, respectively, as it is shown in Table 2.

Kaitaranta and Reino [31] reported that, fatty acid profiles in various fish roes are very similar though differences exist in the relative amounts of individual components. As it is shown in Table 3; C16:0 one of the other important fatty acids for fish roes; and black caviars include higher amounts (p < 0.05) of this fatty acid than red salmon roe and waxed mullet roe. C16:1n7 has also been estimated for fish roes and its amount is especially higher (p < 0.05) for waxed mullet roes than the others. Similarly higher amount of this fatty acid (18.12%) is reported for mullet roes in the literature.[30]

Table 3 Fatty Acid composition of fish roes

	Beluga-typecaviar (%)	Imperial-type caviar (%)	Osetra-type caviar (%)	Red Salmon Roe (%)	Waxed mullet roe (%)
C12:0	—	—	—	0.08 ± 0.0	—
C13:0	—	—	—	0.03 ± 0.0	—
C14:0	0.69 ± 0.17^a	1.28 ± 0.51^b	0.78 ± 0.18^a	4.18 ± 0.29^c	1.52 ± 0.13^b
C15:0	0.46 ± 0.06^a	0.33 ± 0.09^b	0.51 ± 0.01^a	0.46 ± 0.02^a	0.19 ± 0.03^d
C16:0	19.83 ± 0.49^a	20.28 ± 0.45^a	19.72 ± 1.33^a	9.81 ± 0.56^b	2.79 ± 0.93^c
C17:0	0.33 ± 0.26^a	0.34 ± 0.07^a	0.41 ± 0.32^a	0.58 ± 0.02^a	0.36 ± 0.26^a
C18:0	1.83 ± 0.14^ab	2.13 ± 0.43^a	1.58 ± 0.23^b	2.05 ± 0.11a^b	0.98 ± 0.36^c
C20:0	0.06 ± 0.00^a	0.10 ± 0.03^a	0.09 ± 0.04^a	0.19 ± 0.02^a	0.56 ± 0.23^b
C21:0	0.16 ± 0.04^a	0.93 ± 0.08^a	0.14 ± 0.03^a	—	0.18 ± 0.17^a
C22:0	0.05 ± 0.00^a	0.04 ± 0.01^a	0.05 ± 0.03^a	0.09 ± 0.03^ab	0.14 ± 0.04^b
C23:0	0.07 ± 0.02^a	0.02 ± 0.04^b	0.09 ± 0.04^a	0.01 ± 0.01^b	1.07 ± 0.62^c
C24:0	0.02 ± 0.03^a	—	—	—	3.47 ± 3.40^b
TOTAL SFA	23.50	25.45	23.37	17.48	11.26
C14:1	0.26 ± 0.33^a	0.07 ± 0.02^a	0.07 ± 0.04^a	0.12 ± 0.01^a	0.11 ± 0.02^a
C15:1 n5	0.26 ± 0.17^a	0.13 ± 0.06^a	0.25 ± 0.19^a	0.08 ± 0.02^a	0.10 ± 0.04^a
C16:1 n7	7.43 ± 0.28^ac	5.81 ± 1.71^a	8.69 ± 0.44^c	6.74 ± 0.18^ac	24.25 ± 2.59^d
C17:1n7	1.00 ± 0.29^ab	0.66 ± 0.19^ac	1.29 ± 1.18^b	0.61 ± 0.02^c	1.12 ± 0.25^b
C18:1n9t	0.36 ± 0.07^a	0.30 ± 0.03^a	0.74 ± 0.35^b	0.15 ± 0.03^a	0.36 ± 0.09^a
C18:1n9c	36.22 ± 2.58^a	30.97 ± 2.78^b	29.26 ± 6.01^b	14.86 ± 0.45^c	8.41 ± 1.62^d
C20:1n9	0.67 ± 0.14^ac	1.33 ± 0.47^b	0.53 ± 0.05^c	1.03 ± 0.03^ab	0.37 ± 0.16^c
C22:1n9	0.13 ± 0.03^a	0.41 ± 0.25^a	0.28 ± 0.28^a	0.76 ± 0.02^b	0.25 ± 0.13^a
C24:1n9	0.17 ± 0.23^a	0.24 ± 0.17^a	0.14 ± 0.18^a	0.11 ± 0.11^a	0.63 ± 0.79^a
TOTAL MUFA	46.50	39.95	41.25	24.46	35.60
C18:2n6t	0.20 ± 0.10^a	0.17 ± 0.20^b	0.14 ± 0.07^a	0.19 ± 0.02^a	0.22 ± 0.15^a
C18:2n6c	1.10 ± 0.09^a	1.10 ± 0.09^a	1.36 ± 0.43^ba	2.38 ± 0.48^c	1.85 ± 0.53^bc
C18:3n6 g	0.21 ± 0.03^ab	0.14 ± 0.04^ac	0.25 ± 0.01^b	0.10 ± 0.01^c	0.25 ± 0.08^b
C18:3n3 a	0.76 ± 0.23^a	0.59 ± 0.11^a	0.68 ± 0.24^a	1.60 ± 0.07^b	0.82 ± 0.04^a
C20:2n6	0.34 ± 0.09^a	0.31 ± 0.08^a	0.44 ± 0.08^a	0.55 ± 0.43^a	0.48 ± 0.37^a
C20:4n6	0.06 ± 0.02^a	0.24 ± 0.36^b	0.03 ± 0.05^a	—	—
C22:2 n6	1.99 ± 0.32^ab	1.62 ± 0.41 ^ac	2.81 ± 0.75^b	0.83 ± 0.02^c	1.89 ± 0.59^a
C20:5n3	2.89 ± 0.06^a	5.37 ± 2.14^b	4.43 ± 1.54^ab	17.87 ± 0.66^c	6.08 ± 1.15^b
C22:6n3	8.45 ± 1.61^ab	10.50 ± 1.19^a	7.79 ± 1.67^b	12.21 ± 1.78^c	9.36 ± 0.80^ab
TOTAL PUFA	16.00	21.04	17.93	36.73	20.95
Total n3	12.10	16.46	12.90	32.68	16.26
Total n6	3.90	4.58	5.03	4.05	4.69
n3/n6	3.10	3.59	2.56	8.06	3.47
—: Not Determined; SFA: saturated fatty acids; MUFA: monounsaturated fatty acids; PUFA: polyunsaturated fatty acids. Different letters in the same row show significant differences among samples (p < 0.05).

Fatty acid composition is also studied and C18:1 n9c is determined as one of the most important fatty acids found in fish roes (Table 3). Black caviar contain considerably higher (p < 0.05) amount of this fatty acid than that of the others. In the literature, the amount of C18:1 n9c is reported as 30.97% for catfish roes similar to our findings.[32] The lowest (p < 0.05) level of this fatty acid was estimated for waxed mullet roe in our study.

Docosahexaenoic acid (22:6n3, DHA) content of the samples has been estimated as 8.45%, 10.50% and 7.79% for black caviars; 13.21% for red salmon roe and 9.36% for waxed mullet roe in our study. It has been reported as 8.04% for channel catfish roe.[32] Another important fatty acid is eicosapentaenoic acid (20:5n3, EPA), and it is significantly higher in salmon roes (p < 0.05) than the other types of fish roe. This fatty acid is also determined in ripe roes of some marine fish.[13] It has been reported that, in general fish accumulate essential polyunsaturated fatty acids (PUFA), such as eicosapentaenoic (EPA) and docosahexaenoic (DHA), in their muscle tissue, then transfer them into gonads. Therefore, roe of Siberian grayling had 3 to 4 times higher poly unsaturated fatty acids (PUFA) contents, than had that of the muscle tissue.[33] Similar to our results, the main fatty acids of fish roe products has been presented as 16:0, 18:1n-9c, 20:5n-3, and 22:6n-3.[11] In this study, the n3-type fatty acids have been higher in all samples compared to the n6-types, and this result has been well correlated with the literature.[34]

CONCLUSION

Fish roes could have a favorable E/NE ratio (0.93–1.23), and they may be considered as a food source of high-quality protein. They contain significantly higher (p < 0.05) amount of unsaturated fatty acids (MUFA and PUFA) than saturated fatty acids (SFA) and therefore a valid alternative for normal diets. Fish roes may be considered as one of the high quality foods for human nutrition, and the result of this study may be of value to scientists studying on nutrition and seafoods.

ACKNOWLEDGMENTS

This work was supported by the Research Found of Istanbul University. Project Number: T-105/11112002.

Notes

15. Association of Official Analytical Chemists. Official Methods of Analysis, 928.08. Nitrogen in meat. Kjeldahl Method. Meat and meat products; Soderberg, D.L., Chap. Ed. In Official methods of analysis of AOAC international, 16^th ed., 4^th Rev., Vol II.; Cunniff, P., Ed.; AOAC: Gaithersburg, MD, Chap. 39, 1998; 5–6.

16. Laves, S. Amtliche Sammlung von Untersuchungsuerfahren nach Veterinârinstitut fîir Fishe und Fischwaren. Cuxhaven, Bestimmung des Gesamt fettge halts in Fish und Fishwaren Verfahren Sprinzipien zentrifuge Methode, 2002.

17. Association of Official Analytical Chemists. Official Methods of Analysis, Official method 950.46. Moisture in Meat. Meat and Meat Products. Soderberg, D.L., Chap. Ed. In Official methods of analysis of AOAC international; 16^th ed., 4^th Rev., Vol II.; Cunniff, P., Ed.; AOAC: Gaithersburg, MD, Chap. 39, 1998; 1.

18. Association of Official Analytical Chemists. Official Methods of Analysis, Official method 938.08. Ash of Seafood, Fish and Other Marine Products. Hungerford, J.M., Chap. Ed. In Official methods of analysis of AOAC international. Sixteenth Edt. 4^th Rev. Vol II. Cunniff, P. Ed. AOAC: Gaithersburg, MD, Chap. 35, 1998, 6.