• Fisheries and Aquatic Sciences
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• v.19 no.3
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• pp.14.1-14.10
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• 2016

Isoelectric solubilization/precipitation (ISP) processing allows selective, pH-induced water solubility of proteins with concurrent separation of lipids and removal of materials not intended for human consumption such as bone, scales, skin, etc. Recovered proteins retain functional properties and nutritional value. Four roe protein isolates (RPIs) from yellowfin tuna roe were prepared under different solubilization and precipitation condition (pH 11/4.5, pH 11/5.5, pH 12/4.5 and pH 12/5.5). RPIs contained 2.3-5.0 % moisture, 79.1-87.8 % protein, 5.6-7. 4 % lipid and 3.0-3.8 % ash. Protein content of RPI-1 and RPI-2 precipitated at pH 4.5 and 5.5 after alkaline solubilization at pH 11, was higher than those of RPI-3 and RPI-4 after alkaline solubilization at pH 12 (P < 0.05). Lipid content (5.6-7.4 %) of RPIs was lower than that of freeze-dried concentrate (10.6 %). And leucine and lysine of RPIs were the most abundant amino acids (8.8-9.4 and 8.5-8.9 g/100 g protein, respectively). S, Na, P, K as minerals were the major elements in RPIs. SDS-PAGE of RPIs showed bands at 100, 45, 25 and 15 K. Moisture and protein contents of process water as a 2'nd byproduct were 98.9-99.0 and 1.3-1.8 %, respectively. Therefore, yellowfin tuna roe isolate could be a promising source of valuable nutrients for human food and animal feeds.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.56 no.2
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• pp.162-173
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• 2023

Four roe protein isolates (RPIs) from olive flounder Paralichthys olivaceus roes (OFR) were recovered by isoelectric solubilization (pH 11 and 12) and precipitation (pH 4.5 and 5.5) and investigated for their food characteristics. RPIs contained 4.5-9.6% moisture, 64.1-69.5% protein, 16.1-19.8% lipid, and 1.0-3.9% ash. The protein yields of RPIs ranged from 50.1 to 56.8%, which was significantly different depending on the recovery conditions. A difference was observed in the SDS-PAGE protein band (25-100 kDa) between the alkaline solubilization at pH 11 (RPI-1 and 2) and pH 12 (RPI-3 and 4). The major amino acids of RPIs were Leu, Lys, Asp, Glu and Ala and major mineral components were sulfur, sodium, phosphorus, and magnesium, which were significantly different from OFR (P<0.05). Additionally, the lead and cadmium content was below the chemical hazard standard of the Korean food standards code. The Hunter color and whiteness of RPIs also showed significant differences according to the treatment conditions of the ISP process (P<0.05). This suggests that protein isolates recovered from olive flounder roes have high potential as nutritional supplements.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.57 no.1
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• pp.1-14
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• 2024

We investigated the functional properties and in vitro bioactivity of protein isolates (RPIs) recovered from olive flounder Paralichthys olivaceus roes by isoelectric solubilization/precipitation process, according to pH-shift treatments. The buffer capacity of RPIs was shown to be stronger in alkaline pH than in acidic pH. Water holding capacity of RPIs was in range of 4.5-5.2 g/g protein with no significant differences (P>0.05). The foaming capacity and emulsifying activity index of RPIs did not show any significant differences between RPI-1 (pH 11/4.5) and 3 (pH 12/4.5), however they were superior to RPI-2 (pH 11/5.5) and 4 (pH 12/5.5). The 2,2'-azino-bis-3-ethylbenzo-thiazoline-6-sulfonic acid radical scavenging activity of RPI-3 (2.5 mg protein/mL) was 102.4 ㎍/mL, and the angiotensin I converting enzyme inhibitory activity was 30.8%. Among the RPIs, RPI-3 was relatively superior in protein functional properties such as buffer capacity, foaming capacity, emulsification, and anti-oxidative activity. Therefore, we suggest that RPI prepared from olive flounder roes could serve as a potential food resource.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.50 no.6
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• pp.694-706
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• 2017

This study evaluated the protein recovery, functional properties and biological activity of isolate processed water (IPW) generated in the preparation of protein isolates from fish roes (BH, bastard halibut Paralichthys olivaceus; ST, skipjack tuna Katsuwonus pelamis; YT, yellowfin tuna Thunnus albacares) by an isoelectric solubilization and precipitation process. The IPWs contained 2.7-5.4 mg/mL of protein, and the protein losses were 8-21% (P<0.05). The form capacity of IPW-3 for BH and ST, and IPW-4 for YT was 155, 194, and 164%, respectively. The emulsifying activity index ($27-43m^2/g$) of the YT-IPWs was the strongest, followed by ST ($7-29m^2/g$) and BH ($10-19m^2/g$). The 2,2-diphenyl-1-picrylhydrazyl scavenging activities of IPW-1 and -3 were higher than those of IPW-2 and -4. The 2,2'-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid scavenging activity ($IC_{50}$, mg/mL) of IPW-2 and -4 was 0.03 mg/mL for BH, 0.04-0.08 mg/mL for ST, and 0.04-0.07 mg/mL for YT. BH IPW-3 had the strongest reducing power (0.41 mg/mL) and superoxide dismutase-like activity (1.68 mg/mL). The angiotensin-I converting enzyme inhibitory activity of IPW-3 was the highest for ST (1.52 mg/mL), followed by BH and YT. The common predominant amino acids in the IPWs were the essential amino acids Val, Leu, Lys, and Arg and the non-essential amino acids Ser, Glu, and Ala.