Article

Food Characteristics of Protein Isolates Recovered from Olive Flounder Paralichthys olivaceus Roe by Isoelectric Solubilization and Precipitation Process

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Abstract

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.

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... ㆍ ㆍ ㆍ ㆍ ㆍ ㆍ 2 화, 비타민 및 무기질소재와 같은 기능성 식품소재 (Galla et al., 2012b;Kim et al., 2016) 또는 단백질 및 지질추출소재 (Heu et al., 2006;Mahmoud et al., 2008)로서의 이용에 관한 연구 (Guerard et al., 2010;Kadam and Prabhasankar, 2010)를 통해 식품 또는 식품소재로 개발될 경우 그 가치는 5배 이상 증가할 것이라고 예상하였다 (Liu et al., 2015). 최근 수산가공 부산물의 식량자원화 또는 소재화를 위해, 고 영양원이면서 저 활용 식품자원인 어류 알의 식품기능성과 생 리활성에 대한 관심 또한 높아지고 있으나 (Intarasirisawat et al., 2014;Park et al., 2016;Cha et al., 2020;Yoon et al., 2020Yoon et al., , 2023Kang et al., 2023), 명태, 대구, 숭어, 가다랑어 등 일부의 어류 알만이 염장 발효식품인 알젓의 형태로 소비되고 있을 뿐, 대부분의 어류 알은 식품소재로 이용되지 못하고 있다. 이러한 일면에서 어류 알로부터 영양 강화를 위한 단백질 소 재로 이용하고자 하는 노력 (Yoon et al., 2019Cha et al., 2020;Kwon et al., 2022;Kang et al., 2023) (Galla et al., 2012b;Mohamed et al., 2012;Park et al., 2016), 특히 단백질 용해도(protein solubility)는 거품, 유화 및 겔 형성과 같은 식품단백질 기능성에 영향을 미치는 중요인자 이기도 하다 (Kristinsson and Rasco, 2000;Mohan et al., 2007;Azadian et al., 2012). ...
... 최근 수산가공 부산물의 식량자원화 또는 소재화를 위해, 고 영양원이면서 저 활용 식품자원인 어류 알의 식품기능성과 생 리활성에 대한 관심 또한 높아지고 있으나 (Intarasirisawat et al., 2014;Park et al., 2016;Cha et al., 2020;Yoon et al., 2020Yoon et al., , 2023Kang et al., 2023), 명태, 대구, 숭어, 가다랑어 등 일부의 어류 알만이 염장 발효식품인 알젓의 형태로 소비되고 있을 뿐, 대부분의 어류 알은 식품소재로 이용되지 못하고 있다. 이러한 일면에서 어류 알로부터 영양 강화를 위한 단백질 소 재로 이용하고자 하는 노력 (Yoon et al., 2019Cha et al., 2020;Kwon et al., 2022;Kang et al., 2023) (Galla et al., 2012b;Mohamed et al., 2012;Park et al., 2016), 특히 단백질 용해도(protein solubility)는 거품, 유화 및 겔 형성과 같은 식품단백질 기능성에 영향을 미치는 중요인자 이기도 하다 (Kristinsson and Rasco, 2000;Mohan et al., 2007;Azadian et al., 2012). 한편, 거품성(foaming capacity, FC) 및 거품안정성(foam stability, FS)은 식품의 신선감(refreshment), 부드러운 촉감(softening) 그리고 방향성분의 분산과 같은 독특 한 특성을 부여하며 (Mutilangi et al., 1996;Damodaran, 1997;Klompong et al., 2007), 그리고 유화능(emulsifying activity index, EAI)과 유화 안정성(emulsion stability index, ESI)은 water-oil 계면에서 단백질이 oil을 흡착하여 유화층의 형성 및 이를 유지시키는 능력을 말한다 (Karaca et al., 2011). ...
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The effects of different cooking methods (frying, boiling, baking, grilling, microwave cooking) on proximate composition and mineral contents of rainbow trout (Oncorhynchus mykiss Walbaum 1792) were determined. Mean moisture, protein, ash and fat contents of raw fish were 73.38±0.015, 19.8±0.035, 1.35±0.012 and 3.44±0.013%, respectively. The changes in dry matter, protein and ash contents were found to be significant for all cooking methods. The increase in fat content of fried samples was found to be significant but not those samples cooked by other methods. The Mg, P, Zn and Mn contents of fish cooked by almost all methods significantly decreased. The Na and K contents in microwave cooked samples increased, the Cu content increased in fried samples. Losses of mineral content in boiled fish were higher than those of fish cooked by other methods. On comparing the raw and cooked fish, the results indicated that cooking had considerable affect on the proximate composition and mineral contents. Baking and grilling were found to be the best cooking methods for healthy eating.
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The growing fishery industry needs to find new green-processes in order to provide a solution to the huge amount of wastes and by-products that such industrial activity produces. Currently, around a 40% of the total weight of the mackerel is considered a by-product, because just the fillets are used in the food market. ISP method has been revealed as a useful tool for protein recovering, however the yield of this process is traditionally lower than enzymatic methods. In present work, the use of sequential acid/alkaline extraction and alkaline extraction assisted by ultrasound, have been implemented in order to increase the yield of the process. It has been demonstrated that (i) sequential extraction is able to recover practically 100% of total protein, and (ii) applying ultrasound to alkaline extraction is possible to recover more than 95% of total protein from mackerel by-products. Extracted proteins were characterized according to their size, and the amino acid profile of final product was determined.
Article
Alcalase showed optimum activity against skipjack tuna (Katsuwonus pelamis) viscera at pH 10 and 65C. Enzyme concentration, reaction time and fish viscera/buffer ratio affected the degree of hydrolysis (DH) (P < 0.05). Hydrolysis with an enzyme level of 3% (w/w) for 20 min with fish viscera/buffer ratio of 1:2 (w/v) was found to be the optimum condition. Protein, lipid and ash content of freeze‐dried hydrolysate were 81.04, 6.78 and 12.01% dry weight basis, respectively. It was brownish yellow in color (L* = 62.46, a* = 1.44 and b* = 23.05). The hydrolysate contained a high amount of essential amino acids (43.13%) and had glutamic acid, methionine and aspartic acid as the dominant amino acids. Therefore, protein hydrolysate derived from skipjack tuna viscera could potentially serve as a good source of peptides and amino acids and the production of tuna waste protein hydrolysate has both ecological and economical advantage for the tuna industry. Practical Applications Efficient utilization of fish byproducts, especially viscera, is important for the economic viability of the aquatic food industry. Enzymatic hydrolysis is one of the most effective technologies for recovering value‐added proteins from fish viscera without losing their nutritional value. In this study, protein hydrolysate prepared from skipjack tuna viscera using Alcalase showed high protein content. Hence, it can be used in a wide range of food additives, diet nutrients and pharmaceutical agents.
Article
: Channel catfish muscle was subjected to 2 novel protein extraction and precipitation techniques using acid (pH 2.5) or alkaline (pH 11) pH and compared with surimi processing (3 wash cycles). Solubility of catfish proteins was found to be highest at pH 2.5 and 11, and at these pH levels, viscosity was found to be low enough to cause separation of proteins from insoluble materials via centrifugation. Both the acid-aided and alkali-aided processes led to higher recoveries (P < 0.05) of protein and larger reduction (P < 0.05) in lipids compared with surimi processing. The protein recovery could be increased even more with a modified version of the acid-aided and alkali-aided processes. There was no hydrolytic breakdown detected during low and high pH. The acid-aided process recovered more protein types than the alkali-aided process during isolelectric precipitation (pH 5.5), which indicated that it led to more protein denaturation and thus more aggregation at pH 5.5. The alkali-aided process had more soluble proteins (including heme proteins) at isoelectric precipitation than the acid-aided process, and the soluble proteins were of the same type as the soluble proteins for non-pH-treated catfish muscle at pH 5.5. This suggested the alkali-aided process led to less denaturation than the acid-aided process. Both acid-aided and alkali-aided processes recovered proteins of higher (P < 0.05) whiteness scores than surimi. The alkali-aided process recovered proteins of higher whiteness (P < 0.05) than the acid-aided process. The acid-aided process led to higher yellowness (P < 0.05) than the other 2 processes. All processes led to minimal levels of lipid oxidation as assessed by secondary oxidation products.
Article
The purpose of this study was to investigate and compare the physicochemical properties of fish protein isolate (FPI) produced from silver carp (Hypophthalmichthys molitrix), which is a relatively cheap fish with low consumption in Fars (a state of Iran). In this research, proteins were isolated using pH shifts method. Results showed that in terms of production efficiency, protein recovery, lipid reduction and functional properties such as water-holding capacity, emulsifying capacity, foaming capacity and water absorption, FPI was better than conventional surimi. The treated samples at pH = 2.5 represented better functional properties relative to other samples. The electrophoretic patterns demonstrated that acidic pH led to vanish high molecular weight protein bands because these proteins were converted to low molecular weight proteins, whereas basic pH caused the formation of high molecular weight proteins relative to myosin heavy chain. It seems that in basic pH, the proteins were linked together after denaturation and then aggregated. Overall, the results showed that physicochemical qualitative properties of FPI were better than those of conventional surimi.
Article
Proteins for foods, in addition to providing nutrition, should also possess specific functional properties that facilitate processing and serve as the basis of product performance. Functional properties of proteins for foods connote the physicochemical properties which govern the behavior of protein in foods. This general article collates the published information concerning the major functional properties of food proteins, e.g., solubility, binding properties, surfactant properties, viscogenic texturizing characteristics, etc. The effects of extraction and processing on functional properties and possible correlations between structure and function are discussed, in relation to practical performance in food systems. Modification of proteins to improve functional characteristics is briefly mentioned.
Article
Chicken-meat processing generates large quantities of by-products (backs, necks, etc.). Dark chicken-meat processing by-products present the lowest value and greatest challenge. Therefore, recovery of functional proteins from this source for inclusion in food products resembling those from light chicken-meat presents the greatest value addition and opportunity. Novel isoelectric solubilization/precipitation (ISP) was applied to model, dark chicken-meat processing by-products (skin-on bone-in chicken drumsticks) to recover muscle proteins. Thermal denaturation (endothermic transitions), gelation (elasticity, G′), and fundamental texture properties (shear stress and strain at mechanical fracture) of the ISP-recovered proteins were determined with differential scanning calorimetry (DSC), dynamic rheometer, and torsion test, respectively; and compared to boneless skinless chicken breast. Endothermic transition of myosin was not detected only when TiO2 was not added, while the ISP-recovered proteins with TiO2 showed small myosin peak and large actin peak. However, the level of TiO2 addition did not affect thermal transition/denaturation of the ISP-recovered proteins. The ISP-recovered proteins had a greater transition for actin compared to chicken breast, suggesting that ISP predisposes this protein to thermal denaturation. Similar to endothermic transitions, elasticity (G′) generally increased when TiO2 was added to the ISP-recovered proteins. Gels made of chicken breast had the highest (P
Article
Protein concentrates were prepared from underutilized mrigal (Cirrhinus mrigala) roe to produce value added by-products for food applications. Chemical composition and physicochemical properties of protein concentrates prepared from mrigal (Cirrhinus mrigala) roes were determined. The effects of pH and salt concentration on protein solubility were investigated. The protein content of the concentrates was found to be 75, and 91%, respectively for dehydrated and defatted powders. The maximum protein solubility was observed at pH 12, while minimum protein solubility was observed at pH 5, for both dehydrated and defatted protein concentrates. Salt concentration (0.1 to 1 M Nacl) significantly affected the solubility of protein concentrates. The mineral analysis revealed substantial amounts of iron and phosphorus. The emulsifying capacities of dehydrated and defatted protein concentrates were noted as 5.9, and 7.1 ml/g protein, respectively. SDS-PAGE analysis of fresh, dehydrated and defatted roe proteins has revealed the presence of major protein with a molecular weight (MW) of 97 kDa. Addition of defatted fish egg protein concentrate to pasta preparations had improved taste and texture. The results indicated that protein concentrates from underutilized mrigal fish egg may be useful for preparing protein rich food supplements.
Article
This study demonstrated feasibility of producing soluble protein powders from pink (PSP) and red (RSP) salmon heads. Differences were observed between physicochemical properties of the two protein powders, including nitrogen solubility, emulsion stability, and fat adsorption capacity. The flow and viscoelastic properties of the emulsions prepared with PSP and RSP were investigated using a parallel plate rheometer. The power law model and the Casson model were used to determine the flow behavior index (n), and consistency index (K) and yield stress. The emulsion containing PSP (PSPE) had a higher K value (8 Pa.s) than that (4.2 Pa.s) of the emulsion containing RSP (RSPE). Both PSPE and RSPE emulsions exhibited pseudoplastic behavior and viscoelastic characteristics. The G' (an elastic or storage modulus) and G" (a viscous or loss modulus) values for PSPE were higher than RSPE.
Article
The contents of Fe, Cu, Zn, Mn, K, Mg, Ca, Na, As and Cd in gutted Baltic herring (Clupea harengus membras), in Baltic herring fillets and in two commercial ready-to-eat products made of these were investigated. The fish was caught in 1996–1998 in the northern Baltic. The commercial products were fried fillets and fish burgers. The effects of industrial processing on the mineral composition were studied by collecting samples at several consecutive stages. In the gutted fish the levels of Mn, Ca and Cd were considerably higher than in the fillet mainly due to the bones. Significant differences were also observed in the contents of Mg, Na, Cu and Zn. In the burger process the bones and skin were removed which caused a decrease in the Zn and Ca levels. Ingredients such as salt, spices and flour as part of the formula increased Na and Mn contents in the ready-to-eat products. In the final products the Na content was about 6 times higher than that of the fresh fish.
Article
The proximate composition and mineral contents of blue crab (Callinectes sapidus) and swim crab (Portunus pelagicus), caught off the Gulf of Antalya, were investigated. The aim of this study was to demonstrate the nutritive value. Claw and body meat of these two species were analyzed. For both species there were no significant differences in the moisture, fat and ash contents of claw and body meats but protein contents of swim crab were significantly higher (P < 0.05) than those found in blue crab. Na, K, Ca, Zn and Cu values for blue crab and swim crab were not significantly different. There were no significant differences between Na, K, Mg, Zn, Fe, Mn and Cu contents of claw and body meats of the two species.
Article
There is a growing interest in adding value to the jumbo squid Dosidicus gigas fishery. This work describes two extraction procedures for processing muscle to obtain protein isolates with suitable functional properties. The effect on muscle protein solubility and protein recovery of combining freezing and grinding raw materials during storage was evaluated. Processes are based on extraction of protein at acid or alkaline pH and subsequent iso-electric precipitation. About 85% of the initial muscle protein was solubilized at pH 3 and 11. Regardless of the pH used for extraction, about 90% of the protein was obtained after precipitation at pH 5.5. The total yield from both procedures was 75%. Treatments during storage did not significantly affect solubility and yield of protein. Wastewater contained negligible amounts of protein and may be reused. Processing by acid and alkaline extraction are feasible alternatives for obtaining protein isolates either from fresh or frozen squid muscle, which is an important consideration when choosing the most appropriate and inexpensive method to scale up this technology.
Article
This study demonstrated the characteristics and gel properties of short-bodied mackerel (Rastrelliger brachysoma) surimi prepared by the conventional washing process and protein isolate prepared by alkaline solubilization process without and with prewashing. A decrease in Ca(2+)-ATPase activity (P < 0.05), with changes in the tryptophan fluorescence intensity of natural actomyosin, was observed in protein isolate from alkaline solubilization process. However, higher reactive sulfhydryl (SH) content was found in protein isolate, compared with that in conventional surimi (P < 0.05). Generally, the higher amounts of lipid and myoglobin in fish mince were removed by using the alkaline-aided process, compared with the conventional process (P < 0.05). Protein isolate from the alkaline solubilization process formed gels with higher breaking forces than conventional suirmi, especially with 2-step heating (40 degrees C, 30 min/90 degrees C, 20 min) (P < 0.05). The lowest expressible moisture was found in the gel of protein isolate prepared by alkaline solubilization process (P < 0.05). However, the highest whiteness was found in the conventional surimi gel prepared by 2-step heating (P < 0.05). Protein isolate prepared by the alkaline solubilization process yielded superior gels compared with the conventional surimi. Therefore, it can be concluded that the gelling properties of surimi or protein isolate are governed by the physicochemical properties of proteins and are affected by processing conditions.
Article
Textural properties of gels from Atlantic croaker surimi recovered by isoelectric precipitation, following acid (AC) or alkaline (AL) solubilization, were compared with that of conventionally washed (CW) surimi. Gel strengths were in the order of AL > AC > CW, with higher gel strength and deformability induced by microbial transglutaminase addition. None of the surimi treatments evidenced endogenous TGase activity. Salt (2% NaCl) addition had variable effects. Proteolysis was evident by sodium dodecyl sulfate-polyacrylamide gel electrophoresis in gels from all treatments when preincubated at 30 °C or 40 °C.
Article
Pacific whiting protein solubility was significantly affected as the pH shifted away from the isoelectric point (pH 5.5). The highest breaking force of gels was measured for fish proteins treated at pH 11, while high deformation values were obtained at pH 2 and 11. Sodium dodecylsulfate-polyacrylamide gel electrophoresis revealed that fish proteins were highly degraded by acid or alkali treatment. High activity of cathepsin B-like enzyme was detected from acid-aided fish proteins. Strong cathepsin L-like activity was found in fish proteins treated at pH 10.5, corresponding well to the lower breaking force and deformation. Disulfide bonds were thought to contribute to the high texture value of fish proteins treated at pH 11.
Article
Solubility of rockfish whole muscle and actomyosin was minimum at pH 5 and gradually increased as the pH was shifted to acidic or alkaline pH. Acidic and alkaline solubilization was followed by isoelectric precipitation induced degradation of myosin heavy chain, resulting in a protein band of about 120 kDa. Both myofibrillar and sarcoplasmic proteins underwent denaturation after acidic and alkaline treatment, exhibiting minimal solubility and absence of endothermic peaks. Acid- and alkali-treated muscle proteins readily aggregated upon heating, showing different dynamic rheological patterns compared with whole muscle and washed mince. Disulfide linkages occurred at a greater extent in gel prepared by alkaline solubilization, resulting in higher breaking force and deformation.
Article
Soluble protein powders were produced from pollock by-products and evaluated for their functional, nutritional and rheological properties. Soluble protein powders were made from pollock viscera (PVSP), viscera without liver (PVWLSP), heads (PHSP), frames (PFSP), trimmings (PTSP), and liver (PLSP) and had protein contents ranging from 65.0% to 78.9%. Yield of PVWLSP was higher than that of other pollock proteins powder and PTSP had the highest nitrogen solubility value (85.7%). Emulsion capacity and emulsion stability of the pollock protein powders ranged from 29% to 34.5% (mL of oil per 200 mg of protein) and 65.3% to 77.6%, respectively. Highest and lowest fat adsorption values were observed for PFSP (10.6 mL of oil per gram of protein) and PVSP (4.1 mL of oil per gram of protein), respectively. Fish protein powder samples were good sources in K, P, and Mg and amino acids. Emulsions made with pollock soluble protein powders exhibited viscoelastic characteristics.
Article
Bitter melon seeds are a rich source of protein. Optimum conditions for protein extraction from the seeds, determined using a response surface design, were at a pH 9.0 and 1.3 M NaCl. Soy protein isolate (SPI) was included for comparison. Surface hydrophobicity of bitter melon seed protein isolate (BMSPI) (690) was significantly higher than that of SPI (399). Electrophoretograms of BMSPI showed bands at 40 and 55 kDa, and at 22, 25, and 35 kDa in non-reducing and reducing buffers, respectively. BMSPI had most of the essential amino acids and hence could be considered as a high quality protein. BMSPI had a single denaturation temperature (113.1 °C) while SPI had two denaturation temperatures (78.0 and 94.8 °C). The proteins exhibited U-shaped curves with solubilities ranging from 62.0% to 67.5% for BMSPI and 86.7% to 90.1% for SPI at pH ⩾ 7.0. BMSPI had lower emulsifying activity (0.36 vs. 0.73), foaming capacity (39.6 vs. 61.0 ml), and foaming stability (21.5 vs. 25.5 min) than had SPI.
Article
a b s t r a c t Chemical compositions of roes from three tuna species including skipjack (Katsuwonous pelamis) (SJK), tongol (Thunnus tonggol) (TGL) and bonito (Euthynnus affinis) (BNO) were determined. Tuna roes con-tained 72.17–73.03% moisture, 18.16–20.15% protein, 3.29–5.68% lipid and 1.79–2.10% ash. Non-defatted and defatted roes from all species contained protein with a molecular weight of 97 kDa as the major com-ponent. Glutamic acid and glutamine were the most abundant amino acids (12.18–12.65 g/100 g pro-tein), while K, Na and P were the major elements in defatted-tuna roes. Crude lipids from tuna roes contained phospholipids as the major component (51.22–54.90% of total lipids) with high content of docosahexaenoic acid (C22:6 n-3) (20.53–26.19% of total lipids). Cholesterol contents of crude lipids from the roes of SJK, TGL and BNO were 172, 122 and 94 mg/100 g lipids, respectively. Therefore, tuna roe could be a promising source of valuable nutrients for human food and animal feeds.
Article
The recovery of myofibrillar protein from beef heart using nonthermal acidic solubilization was evaluated. Postmortem time, 3 or 24 h, did not affect protein solubility (p > 0.05). Protein solubility and yield were detrimentally affected by salt addition. Recovery of extracted protein (yield) was maximized with 0 mM NaCl (60.8 ± 3.9%). SDS-PAGE confirmed myosin solubilization below pH 5 and suggested reduced protein solubility below pH 2.5. Extracted protein from beef heart was significantly lower in fat, cholesterol, ash, and total collagen. In addition, the protein profile using a 7% SDS-Page gel consisted mainly of heavy chain myosin (36%), 150 kDa proteins (15%), and actin (21%).
Article
The solubility of protein components in salmon (Oncorhynchus keta) and sturgeon (Acipenser transmontanus) caviar in distilled water, 5% (w/v) NaCl, 70% (v/v) ethanol at 65C, and 0.2% (w/v) NaOH was determined. The salt soluble proteins were the predominant fraction and constituted 84.2% of the recovered protein in salmon and 86.1% in sturgeon samples. The two most prominent protein fractions (12.5% sodium dodecyl sulfate-polyacrylamide gel electrophoresis) for sturgeon caviar are most likely vitellin (96 kDa) and ovomucoid or phosvitin (28 kDa). For salmon roe, small proteins, possibly lysozyme or phosvitin (10 kDa), are also present.
Article
Excessive dietary intake of Na (i.e., NaCl) contributes to hypertension, which is a major risk factor for cardiovascular disease. Normally, NaOH and HCl are used to dissolve and precipitate, respectively, fish muscle proteins in isoelectric solubilization/precipitation (ISP), therefore contributing to increased Na content in the recovered fish protein isolates (FPI). Substitution of NaOH with KOH may decrease the Na content in FPI and, thus, allow development of reduced-Na seafood products. In this study, FPI was recovered with ISP using NaOH or KOH. In order to develop a nutraceutical seafood product, the FPI was extracted with NaCl or KCl-based salt substitute and subjected to cold- or heat-gelation. In addition, standard nutraceutical additives (ω-3 fatty acids-rich oil and dietary fiber) along with titanium dioxide (TiO(2)) were added to FPI. Color, texture, dynamic rheology, Na and K content, and lipid oxidation of the FPI gels were compared to commercial Alaska pollock surimi gels. FPI gels had greater (p < 0.05) whiteness, good color properties (L*a*b*), and generally better textural properties when compared to surimi gels. Although the ISP-recovered FPI and surimi developed similar final gel elasticity, the proteins in FPI and surimi had different gelation pattern. A reduction (p < 0.05) of Na content and simultaneous increase (p < 0.05) in K content of FPI gels was achieved by the substitution of NaOH with KOH during ISP and NaCl with the KCl-based salt substitute during formulation of the FPI paste. Although cooking and addition of NaCl during formulation of the FPI paste increased (p < 0.05) lipid oxidation in FPI gels, TBARS values were much below rancidity levels. These results indicate that KOH can replace NaOH to recover FPI from whole gutted fish for subsequent development of nutraceutical seafood products tailored for reduction of diet-driven cardiovascular disease.
Article
Albumin, globulin, glutelin and prolamin fractions were isolated from an Australian rice variety (cv. Langi) and characterised by yield, protein content and molecular weight profile using both capillary electrophoresis (SDS-CE) and sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). The influence of pre-extraction enzymatic hydrolysis of starch and heating to 70 °C was also investigated, as was the extraction of the glutelin fraction without prior removal of the albumin and globulin fractions. Pre-extraction treatment affected mainly the albumin fraction, increasing dry matter yield but reducing protein content. SDS-CE was able to separate the protein fractions over a wider molecular weight range than SDS-PAGE, and the peaks from SDS-CE showed slightly higher molecular weight compared to equivalent bands from SDS-PAGE. The glutelin fraction extracted without prior removal of albumin and globulin fractions had different characteristics compared to those obtained by conventional extraction methods. Pre-extraction hydrolysis of starch did not significantly affect the emulsifying, foaming and gelling properties of extracted protein. Although rice glutelin had poor solubility, emulsifying and foaming properties in aqueous systems, it had good gelling properties which could be important for food applications.
Article
Soluble spray dried protein powder (CRP) was made from catfish roe and its physical and nutritional properties were evaluated. An emulsion system (CRPE) was developed using CRP and rheological properties compared with two commercial mayonnaises (RME and RVE). CRP contained 67% protein, 4.5% moisture, 10% ash, and 18.3% fat. CRP had a high content of essential amino acids and desirable mineral contents. Nitrogen solubility, emulsion stability, and fat adsorption values for CRP were 64%, 85.1%, and 5.7 mL/g protein, respectively. CRP protein powder had several of proteins with molecular weights between 40 and 100kDA. Particle size of CRP ranged from 1.9 to 88 μm. The flow behavior index value for CRPE (0.14) was lower (P < 0.05) than RME (0.22) and RVE (0.21). CRPE (1.8) and RVE (2.1) had lower (P < 0.05) viscosity than RME (2.8). Viscoelastic characteristic of the CRP emulsion was greater than the RVE emulsion.
Article
Various physicochemical and biochemical properties were compared between raw mature and immature chinook salmon (Oncorhynchus tshawytscha) roe. The pH, osmolality and moisture content were lower for mature salmon roe but egg size, viscosity, protein, crude lipid and ash content values were all higher. Maturity had an impact on the profile of amino acids but not on fatty acids. Maturity affected mineral and trace elements with higher Ca, Co, Mg, P, S and lower Cu, Fe, Mn, Na, Zn found in mature salmon roe. Immature roes had more α- and total tocopherols but less γ- and δ-tocopherols. Soluble proteins from mature and immature roes were similar, but the profiles of membrane-bound proteins differed. Thus maturity will affect functional and physical properties during processing and consumption of chinook roes.
Article
The effects of different metal ions at various concentrations (0, 5, 25 ppm) on lipid oxidation, discolouration and physicochemical properties of muscle protein in cuttlefish (Sepia pharaonis) subjected to multiple freeze–thaw cycles, were investigated. Lipid oxidation of all treatments increased as the freeze–thaw cycle increased. However, the rate of the TBARS increases varied, depending on concentration, type and valency of the metal ion. Fe(II) induced lipid oxidation most effectively and its prooxidative effect was in a concentration-dependent manner. Cu(I), Cu(II) and Cd(II) showed negligible effects on lipid oxidation. The increased lipid oxidation of cuttlefish with added iron was coincidental with the increase in b* values (yellowness), especially with increasing freeze–thaw cycles. Cu(I) and Cu(II) altered cuttlefish protein sulfhydryl content and the protein solubility decreased with a concomitant increase in the disulfide bond content. The oxidative changes of proteins were observed only when a concentration of metal ions of 25 ppm was used. Those changes were more intense with increasing freeze–thaw cycles. The Ca2+, Mg2+, and Mg2+–Ca2+–ATPase activities of cuttlefish natural actomyosin decreased markedly in the presence of copper, whereas the Mg2+–EGTA–ATPase was increased. SDS-PAGE revealed that Cu(I) and Cu(II) induced the polymerization of muscle proteins stabilised by disulfide bond formation. However, Fe(II), Fe(III) and Cd(II) exhibited no pronounced effect on the oxidation of cuttlefish muscle proteins. Therefore, copper mainly caused the oxidation of protein, while iron induced lipid oxidation and the formation of a yellow colour in cuttlefish muscle, particularly with multiple freeze–thaw cycles.
Article
European perch (Perca fluviatilis) harvested from three lakes of Central Italy were studied in different seasonal periods of a year to evaluate their nutritional quality and some safety aspects related to the pollution of the aquatic environment. The lakes considered, located in the Latium region, differed with respect to their volcanic (Bolsena and Bracciano Lakes) or artificial (Salto Lake) origin. Fillets of fish caught in the three lakes were characterised by good protein (17–19%) and mineral contents and low lipid levels (0.6–1.2%) throughout the year. Total lipids were characterised by low cholesterol levels (41.9–74.7 mg/100 g) and high percentages of total n − 3 polyunsaturated fatty acids (27.7–33.8% of total fatty acids), in particular docosahexaenoic acid (14.2–25.3% of total fatty acids). The qualitative analysis of the stomach content of perch confirmed their predatory feeding behaviour. The chemical and nutritional profiles of perch from the three lakes were comparable except for rubidium and cesium levels, which were higher in the muscle tissues of perch from the volcanic lakes. These minerals may represent elements of traceability of the origin of fish. Low levels of organochlorine pesticides and polychlorinated biphenyls, well below the Italian and European action limits, were detected in the muscle tissue of perch from all three lakes.
Article
Rice endosperm protein was modified to enhance solubility and emulsifying properties by controlled enzymatic hydrolysis. The optimum degree of hydrolysis (DH) was determined for acid, neutral, and alkaline type proteases. Solubility and emulsifying properties of the hydrolysates were compared and correlated with DH and surface hydrophobicity. DH was positively associated with solubility of resulting protein hydrolysate regardless of the hydrolyzing enzyme, but enzyme specificity and DH interactively determined the emulsifying properties of the protein hydrolysate. The optimum DH was 6-10% for good emulsifying properties of rice protein, depending on enzyme specificity. High hydrophobic and sulfhydryl disulfide (SH-SS) interactions contributed to protein insolubility even at high DH. The exposure of buried hydrophobic regions of protein that accompanied high-temperature enzyme inactivation promoted aggregation and cross-linking of partially hydrolyzed proteins, thus decreasing the solubility and emulsifying properties of the resulting hydrolysate. Due to the highly insoluble nature of rice protein, surface hydrophobicity was not a reliable indicator for predicting protein solubility and emulsifying properties. Solubility and molecular flexibility are the essential factors in achieving good emulsifying properties of rice endosperm protein isolates.
Article
Using an improved method of gel electrophoresis, many hitherto unknown proteins have been found in bacteriophage T4 and some of these have been identified with specific gene products. Four major components of the head are cleaved during the process of assembly, apparently after the precursor proteins have assembled into some large intermediate structure.
Article
Functional, nutritional, and thermal properties of freeze-dried protein powders (FPP) from whole herring (WHP), herring body (HBP), herring head (HHP), herring gonad (HGP), and arrowtooth flounder fillets (AFP) were evaluated. The FPP samples have desirable nutritional and functional properties and contained 63-81.4% protein. All FPP samples had desirable essential amino acid profiles and mineral contents. The emulsifying and fat adsorption capacities of all FPP samples were higher than those of soy protein concentrate. The emulsifying stability of WHP was lower than that of egg albumin but greater than that of soy protein concentrate. Thermal stability of the FPP samples is in the following order: HGP > HBP > WHP > HHP > AFP.
Article
Proteins from herring (Clupea harengus) light muscle were extracted using acidic or alkaline solubilization; 92 and 89% of the initial muscle proteins were solubilized at pH 2.7 and 10.8, respectively, of which 96 and 94% were recovered during precipitation at pH 5.5. Consistency of the pH-adjusted muscle homogenates increased with increased raw material age and homogenization intensity; it declined following holding on ice. Some hydrolytic myofibrillar protein degradation occurred during cold storage of the acidified (pH 2.7) homogenates. With alkalized homogenates, hydrolysis was negligible. The total lipid content changed from 0.13 g/g of protein in the muscle to 0.04 g/g of protein in both the acid- and alkali-produced protein isolates. Corresponding values for the phospholipid content were from 0.037 to 0.02 g/g of proteins. Acid- and alkali-produced proteins made gels with equal strain and color. Stress values were equal or lower in acid- versus alkali-produced protein gels. When ice-stored raw material was used, strain and stress values of gels were reduced.