Chemical composition of protein concentrate prepared from Yellowfin tuna Thunnus albacares roe by cook-dried process
© Lee et al. 2016
Received: 20 March 2016
Accepted: 1 April 2016
Published: 10 May 2016
Roe is the term used to describe fish eggs (oocytes) gathered in skeins and is one of the most valuable food products from fishery sources. Thus, means of processing are required to convert the underutilized yellowfin tuna roes (YTR) into more marketable and acceptable forms as protein concentrate. Roe protein concentrates (RPCs) were prepared by cooking condition (boil-dried concentrate, BDC and steam-dried concentrate, SDC, respectively) and un-cooking condition (freeze-dried concentrate, FDC) from yellowfin tuna roe. The yield of RPCs was in the range from 22.2 to 25.3 g/100 g of roe. RPCs contained protein (72.3–77.3 %), moisture (4.3–5.6 %), lipid (10.6–11.3 %) and ash (4.3–5.7 %) as the major constituents. The prominent amino acids of RPCs were aspartic acid, 8.7–9.2, glutamic acid, 13.1–13.2, and leucine, 8.5–8.6 g/100 g of protein. Major differences were not observed in each of the amino acid. K, S, Na, and P as minerals were the major elements in RPCs. No difference noted in sodium dodecyl sulfate polyacrylamide gel electrophoresis protein band (15–100 K) possibly representing partial hydrolysis of myosin. Therefore, RPCs from YTR could be use potential protein ingredient for human food and animal feeds.
KeywordsProtein concentrate Roe Yellowfin tuna Chemical composition Cook-dried process
Yellowfin tuna Thunnus albacares is a large tuna species found in the Pacific, Indian and Atlantic oceans. It is an important component of tuna fisheries worldwide and is one of the major target species for the tuna fishery in the major oceans, and popularly catched marine fish with annual availability of 44,013 t on overseas fishery in Korea during 2013 (Ministry of Ocean and Fisheries 2014). It is used extensively in raw cuisine such as sushi and sashimi. Byproducts such as scales, heads, skin, fat, visceral, and roe are generated increasingly and discarded as waste, without any attempt to recover the essential nutrients (Chalamaiah et al. 2010). Among by-products, roes are highly nutritious material rich in essential fatty acids and amino acids (Heu et al. 2006; Narsing Rao et al. 2012b). Fish roes are produced in large quantities during the spawning seasons, which constitute about 1–3 % of the weight of fish (Chalamaiah et al. 2013; Klomklao et al. 2013; Intarasirisawat et al. 2011). Currently roe obtained from fish such as salmon, cod, and pollock have a potential commercial market, especially they have a higher demand in Asian countries (Sathivel et al. 2009). Yellowfin tuna roe is an abundant and underutilized byproduct that can be used as a unique protein source (Heu et al. 2006). The roe can be used to recover protein that may be converted into a higher value food ingredient suitable for use as an emulsifier in food and feed systems (Sathivel et al. 2009).
Protein concentrates are widely used as ingredients in food industry because of their high nutritional quality, functional properties, high protein level and low content of antinutritional factors (Cordero-de-los-Santos et al. 2005). Using fish proteins in powder form presents some advantages since they do not require special storage conditions and they can also easily be used as an ingredient in foods (Pires et al. 2012). Drying preserves fish by inactivation enzymes and removing the moisture necessary for bacterial and mold growth (Bellagha et al. 2002; Bala and Mondol 2001; Duan et al. 2004). Recently, protein concentrate preparation have been reported for different protein sources such as roe of Channa striatus and Lates calcarifer (Narsing Rao et al. 2012a), byproducts of Alaska pollock (Sathivel and Bechtel 2006), mrigal egg (Chalamaiah et al. 2013) and roes of hake and ling (Rodrigo et al. 1998).
Before the drying process, boiling and steaming of fish improve their digestibility, enhances palatability, and provide a safe eating by killing harmful bacteria, other micro-organisms and parasites. Thus, means of processing are required to convert the underutilized yellowfin tuna roes into more marketable and acceptable forms as protein concentrate. There is no information about protein concentrate by cook-dried process. The objectives of this study were to investigate chemical characteristic for protein concentrate from yellowfin tuna roe prepared by cook-dried process and to identify possibility on utilization of 2’nd byproduct. Hence, we expected that full utilization for fish roe concentrate will be possible by reducing the 2’nd byproduct wastage and environmental pollution.
Yellowfin tuna Thunnus albacares roe was obtained from Dongwon F&B Co., Ltd. (Changwon, Korea). Roe was stored at −70 °C in sealed polyethylene bags, and transferred to the laboratory. Frozen roe was partially thawed for 24 h at 4 °C and then cut into small pieces with an approximate thickness of 1.5–3 cm and minced with food grinder (SFM-555SP, Shinil Industrial Co., Ltd., Seoul Korea). Minced roe was frozen at −20 °C until used.
Sodium dodecyl sulfate (SDS) and glycine were purchased from Bio Basic Inc., (Ontario, Canada). Coomassie Brilliant Blue R-250 was purchased from Bio-Rad Laboratories (Hercules, CA, USA). Bovine serum albumin (BSA), β-Mercaptoethanol (β-ME), egg white, glycerol, N,N,N′,N′-tetramethyl ethylene diamine (TEMED), sodium carbonate, sodium hydroxide, sodium L-tatarate, and potassium hydroxide were purchased from Sigma-Aldrich Co., Ltd. (St. Louis, MO, USA). Copper (II) sulfate pentahydrate was purchased from Yakuri Pure Chemicals Co., Ltd. (Kyoto, Japan). Bromophenol blue and Folin-Ciocalteu’s reagent were purchased Junsei Chemical Co., Ltd. (Tokyo, Japan). All reagents used analytical grade.
Preparation of roe protein concentrates (RPCs)
The proximate composition was determined according to the AOAC method (AOAC 1995). Moisture content was determined by placing accurately weighed 0.2 g of sample into an aluminum pan. Sample was dried in a forced-air convection oven (WFO-700, EYELA, Tokyo, Japan) at 105 °C until a constant weight was reached. The ash content was determined by charring approximately 0.1 g of sample in a ceramic crucible over a hot plate and then heating in a muffle furnace (Thermolyne 10500 furnace, a subsidiary of Sybron Co., Dubuque, IA, USA) at 550 °C until a constant final weight for ash was achieved. The total crude protein (nitrogen x 6.25) content of samples was determined using the semi-micro Kjeldahl method. Protein concentration of cooking process drips was determined by the method of Lowry et al. (1951) using bovine serum albumin as a standard. Total lipid content was determined according to the Soxhlet extraction method. 5 g of sample was extracted with dimethyl ether and performed for 30 min at a drip rate of 10 mL/min. Total lipid content was determined on a gravimetric basis and expressed as percent.
Total amino acid
Total amino acid analysis was conducted according to AOAC method (AOAC 1995). The sample (20 mg) was hydrolyzed with 2 mL of 6 N HCl at 110 °C for 24 h in heating block (HF21, Yamoto Science Co, Tokyo, Japan) and filtered out using vacuum filtrator (ASPIRATOR A-3S, EYELA, Tokyo, Japan). Amino acids were quantified using the amino acid analyzer (Biochrom 30, Biochrom Ltd., Cambridge, United Kingdom) employing sodium citrate buffers (pH 2.2) as step gradients. The data are reported as g of amino acid per 100 g of protein. Asparagine is converted to aspartic acid and glutamine to glutamate during acid hydrolysis, so the reported values for these amino acids (Asp and Glu) represent the sum of the respective amine and amino acid in the proteins.
Analysis of iron (Fe), copper (Cu), manganese (Mn), cadmium (Cd), nickel (Ni), lead (Pb), zinc (Zn), chromium (Cr), magnesium (Mg), sodium (Na), phosphorus (P), potassium (K), calcium (Ca), and sulfur (S) contents in sample was carried out using the inductively coupled plasma optical emission spectrophotometry (OPTIMA 4300 DV, Perkin Elmer, Shelton, Conn., USA). Briefly, teflon digestion vessel was washed overnight in a solution of 2 % nitric acid (v/v) prior to use.
Sample was dissolved in 10 mL of 70 % nitric acid. The mixture was heated on the hot plate until digestion was completed. The digested samples were added in 5 mL of 2 % nitric acid and filtered using filter paper (Advantec No. 2, Toyo Roshi Kaisha, Ltd., Tokyo, Japan). Sample was massed up to 100 mL with 2 % nitric acid in a volumetric flask. Sample was run in triplicate. The concentration of mineral was calculated and expressed as mg/100 g sample.
The molecular weight distribution of YTR and RPCs was observed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS–PAGE). It was performed according to the method of Laemmli (1970). Briefly, 10 mg of sample was solubilized in 1 mL of 8 M urea solution containing 2 % β-mercaptoethanol and 2 % sodium dodecyl sulfate (SDS) solution. Protein solution was mixed at 4:1 (v/v) ratio with the SDS-PAGE sample treatment buffer (62.5 mM Tris–HCl (pH 6.8), 2 % SDS (w/v), 10 % glycerol, 2 % β-mercaptoethanol and 0.002 % bromophenol blue) and boiled at 100 °C for 3 min. The sample (20 μg protein) was loaded on the 10 % Mini-PROTEAN® TGX™ Precast gel (Bio-Rad Lab., Inc., Hercules, CA, USA) and subjected to electrophoresis at a constant current of 10 mA per gel using a Mini-PROTEANⓇ tetra cell (Bio-Rad Lab., Inc., Hercules, CA, USA).
Electrophoresed gel was stained in 0.125 % Coomassie brilliant blue R-250 and destained in 25 % methanol and 10 % acetic acid until background was clear. Molecular weight of protein bands was estimated using Precision Plus Protein™ standards (10–250 K, Bio-Rad Lab., Inc., Hercules, CA, USA).
All experiments were conducted in triplicates. The average and standard deviation were calculated. Data were analyzed using analysis of variance (ANOVA) procedure by means of the statistical software of SPSS 12.0 KO (SPSS Inc., Chicago, IL, USA). The mean comparison was made using the Duncan’s multiple range test (P < 0.05).
Results and discussions
Proximate composition of yellowfin tuna roe (YTR) and roe protein concentrates (RPCs) prepared by cook-dried process
Protein yield2) (g)
77.3 ± 0.1
18.2 ± 0.0
2.4 ± 0.1
1.5 ± 0.2
4.3 ± 0.1ab
72.3 ± 0.4c
10.6 ± 0.1a
5.7 ± 0.5a
4.8 ± 0.1a
77.3 ± 1.4b
11.3 ± 0.5a
5.0 ± 0.9a
5.6 ± 1.0a
76.0 ± 1.9b
10.6 ± 0.3a
4.3 ± 0.2a
3.0 ± 0.6b
81.4 ± 0.5a
Moisture and protein content of process drips obtained from yellowfin tuna roe during cook-dried process
Volume (mL/100 g roe)
Total protein (mg)
92.0 ± 0.1a
5.8 ± 0.0a
90.5 ± 0.7b
6.4 ± 0.5a
Total amino acid
Total amino acid composition (g/100 g protein, %) of yellowfin tuna roe (YTR) and roe protein concentrates (RPCs) prepared by cook-dried process
Protein content (%)
Hydrophobic amino acid
RPCs had essential amino acid/non-essential amino acid ratio in range of 1.00–1.06. From this result, essential amino acid/non-essential amino acid ratio of PRCs was lower than that (1.10) of egg white, but it was similar to the value reported Heu et al. (2006) for yellowfin tuna roe. Lysine is often considered a first limiting amino acid for cereal food. Therefore, it needs to be emphasized that the RPCs had a higher content of lysine (8.5 %) than egg white (8.2 %) (P < 0.05). The lysine content of RPCs was 8.5 % which was higher than that reported for Channa (6.94 %) and Lates (6.86 %) roe protein concentrate (Narsing Rao et al. 2012a).
YTR and RPCs had hydrophobic amino acids ranged from 45.0 to 46.6 %. Hydrophobicity plays an important positive role in determining emulsifying properties (Chalamaiah et al. 2013). FitzGerald and O’Cuinn (2006) reported that bitterness of protein hydrolysate is associated with the release of peptides containing hydrophobic amino acid residues. Thus, RPCs could possibly be a dietary protein supplement to poorly balanced dietary proteins exhibiting to low bitterness.
Mineral contents (mg/100 g sample) of yellowfin tuna roe (YTR) and roe protein concentrates (RPCs) prepared by cook-dried process
456.0 ± 2.0c
1179.9 ± 8.3a
761.6 ± 67.4b
758.9 ± 200.3b
787.0 ± 13.2b
992.3 ± 92.6b
858.2 ± 10.3c
818.1 ± 141.8bc
1341.3 ± 1.2a
167.0 ± 1.0d
376.2 ± 2.1b
287.2 ± 17.5c
268.3 ± 55.5c
1015.8 ± 8.8a
437.0 ± 3.0a
257.7 ± 2.8b
223.4 ± 13.4c
208.5 ± 35.2c
92.5 ± 0.4d
29.0 ± 0.0c
66.8 ± 0.4a
70.6 ± 2.5a
59.1 ± 7.7a
8.0 ± 0.0c
45.0 ± 0.3b
49.9 ± 0.4a
48.4 ± 3.5a
11.0 ± 0.0c
33.5 ± 0.3b
58.6 ± 12.2a
32.3 ± 3.7b
65.2 ± 0.6a
9.8 ± 0.1b
12.9 ± 0.2b
9.7 ± 0.8ab
0.6 ± 0.0a
0.1 ± 0.0a
0.2 ± 0.0b
0.1 ± 0.0b
0.0 ± 0.0b
0.5 ± 0.0a
0.5 ± 0.1a
0.4 ± 0.1a
0.1 ± 0.0b
0.2 ± 0.1a
0.1 ± 0.0a
0.3 ± 0.1a
0.0 ± 0.0a
0.1 ± 0.0a
0.1 ± 0.0a
0.1 ± 0.0a
0.0 ± 0.0b
0.1 ± 0.0a
0.2 ± 0.1a
0.2 ± 0.1a
0.1 ± 0.0a
0.0 ± 0.0a
0.1 ± 0.1a
0.0 ± 0.0a
0.0 ± 0.0a
L*, a* and b* color values and whiteness of concentrates (FDC, BDC and SDC) by cook-dried process
59.2 ± 0.1a
55.7 ± 3.7b
55.4 ± 1.9b
6.5 ± 0.1a
5.2 ± 0.6b
5.3 ± 0.4b
18.6 ± 0.0a
17.8 ± 0.1b
17.4 ± 0.1c
42.3 ± 0.1a
45.0 ± 3.4a
45.1 ± 1.8a
54.7 ± 0.1a
52.0 ± 3.5a
51.8 ± 1.8a
Fish roe, a by-product in fishery industry, can be utilized as a low cost source of protein for value addition. Production of roe protein concentrate from yellowfin tuna roe is a simple and economical process. This study demonstrated that is feasible to produce concentrates from yellowfin tuna roe by cook-dried process. The roe protein concentrates were found to be rich in protein with essential amino acid. Fish roe protein concentrates may potentially serve as a good source of protein with desirable functional properties. Therefore, these protein concentrates could be used as protein supplements and functional ingredients in human diets.
This research was supported by Basic Science Research Program through the National Research Foundation of Korea(NRF) funded by the Ministry of Education(NRF-2014R1A1A4A01008620).
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