Gel‐forming properties of surimi produced from bigeye snapper,Priacanthus tayenus and P macracanthus,stored in ice

The influence of iced storage of two species of bigeye snapper, Priacanthus tayenus and P macracanthus, on the gel‐forming ability of the resulting surimi was investigated. Upon iced storage, whole fish underwent deterioration faster than beheaded/eviscerated fish. Total volatile base and trimethylamine contents of whole fish were higher than those of beheaded/eviscerated fish, particularly after 9 days of storage (P < 0.05). P macracanthus muscle was more susceptible to proteolytic degradation than P tayenus muscle. Ca²⁺‐ATPase activity decreased as the storage time increased (P < 0.05), indicating the denaturation of myosin. A marked decrease in Ca²⁺‐ATPase activity was found in whole fish kept for more than 6 days in ice (P < 0.05). Breaking force and deformation of surimi gels from both species decreased, with a concomitant decrease in whiteness, as the storage time increased (P < 0.05). Beheading and evisceration of fish retarded the deterioration. However, the gel‐forming ability of surimi produced from both species decreased continuously throughout iced storage (P < 0.05), probably owing to the denaturation and degradation of myofibrillar proteins. © 2002 Society of Chemical Industry     

Autolysis of goatfish (Mulloidichthysmartinicus) mince: Characterisation and effect of washing and skin inclusion

Autolysis of goatfish mince and washed mince incubated at different temperatures (30–70 °C) was investigated. The highest autolytic activity was generally observed in mince and washed mince at 60 °C as evidenced by the highest trichloroacetic acid (TCA) soluble peptide content and the greatest disappearance of myosin heavy chains (MHCs). Autolysis of both mince and washed mince was maximised at pH 4, and lower autolytic activity was observed at pH 7. trans-epoxysuccinyl-l-leucyl-amido (4-guanidino) butane (E-64) showed the greatest inhibition of autolysis at pH 4, showing that at least one cysteine protease was active in goatfish muscle. Nevertheless, soybean trypsin inhibitor effectively inhibited the autolysis at neutral pH (pH 7), suggesting that goatfish muscle also contained at least one serine protease. Generally, autolysis of mince was more pronounced than that of washed mince, indicating that washing could lower the autolytic activity of mince. In the presence of skin, a higher autolysis was obtained with the goatfish mince. Therefore, both sarcoplasmic and myofibril-associated proteases in muscle as well as the contamination of skin likely contributed to the degradation of muscle proteins of goatfish.     

Extraction and characterisation of pepsin‐solubilised collagens from the skin of bigeye snapper (Priacanthus tayenus and Priacanthus macracanthus)

BACKGROUND: Fish collagen has been paid increasing attention as an alternative to the mammalian counterpart owing to the abundance of fish skin as a processing by‐product. Generally, the low yield of collagen extracted using the typical acid solubilisation process has led to the use of mammalian pepsin as an aid for increasing the yield. Alternatively, fish pepsin, especially from tuna stomach, can be used for the extraction of pepsin‐solubilised collagen (PSC). Therefore the objective of this study was to extract and characterise PSC from the skin of bigeye snapper, a fish widely used for surimi production in Thailand. RESULTS: PSCs from the skin of two species of bigeye snapper, Priacanthus tayenus and Priacanthus macracanthus, were extracted with the aid of tongol tuna (Thunnus tonggol) pepsin and porcine pepsin. PSCs from the skin of both species extracted using porcine pepsin had a higher content of β‐chain but a lower content of α‐chains compared with those extracted using tuna pepsin. All PSCs contained glycine as the major amino acid and had an imino acid (proline and hydroxyproline) content of 189–193 residues per 1000 residues. Transition temperatures of PSCs were in the range 30.6–31.3 °C. Fourier transform infrared spectra revealed some differences in molecular order between PSCs extracted using porcine pepsin and tuna pepsin. Nevertheless, the triple‐helical structure of PSCs was not affected by pepsin digestion. Zeta potential analysis indicated that PSCs from P. tayens and P. macracanthus possessed zero net charge at pH 7.15–7.46 and 5.97–6.44 respectively. CONCLUSION: Tongol tuna pepsin could be used as a replacement for mammalian pepsin in PSC extraction. However, a slight difference in PSC properties was found. Copyright © 2009 Society of Chemical Industry     

Effect of microbial transglutaminase on rheological properties of oxidised and non‐oxidised natural actomyosin from two species of bigeye snapper

The contribution of microbial transglutaminase (MTGase) to the thermal gelation of non‐oxidised and oxidised natural actomyosin (NAM) from two species of bigeye snapper was studied by dynamic rheological testing. Under two‐step heating, the addition of MTGase increased the gel‐forming ability of both species. During setting at 40 °C, Priacanthus macracanthus NAM seemed to show higher reactivity to MTGase than P tayenus NAM, resulting in a higher rate and magnitude of G′ development. An increase in final G′ of NAM from P macracanthus and P tayenus by 13.7–24 and 6.6–10.8 times respectively was observed compared with NAM alone. Iron‐catalysed oxidation substantially decreased the gel‐forming ability of P tayenus NAM but enhanced that of P macracanthus NAM. However, oxidation decreased the reactivity of both NAM types to added MTGase. The results suggested that the native NAM structure was essential for MTGase to maximise the setting response. The gel‐forming ability and setting response of denatured NAM were partially recovered by the addition of MTGase. © 2002 Society of Chemical Industry     

Transglutaminase-mediated setting in bigeye snapper Surimi

Effect of setting induced by endogenous transglutaminase (TGase) in two species of bigeye snapper, Priacanthus tayenus and Priacanthus macracanthus, on gel properties and protein cross-linking was investigated. Setting at either 25 or 40 °C, prior to heating at 90 °C resulted in the increase in both breaking force and deformation of surimi from both species, particularly when setting time increased (P<0.05). A decrease in solubility of surimi gels in a mixture of sodium dodecyl-sulfate, urea and β-mercaptoethanol suggested increased formation of non-disulfide covalent bonding which coincided with increased gel strength and the decrease in myosin heavy chain (MHC) polypeptide. The optimum conditions for setting of surimi sol was found to be 40 °C for 2 h for P. tayenus and 25 °C for 3 h for P. macracanthus. Assayed by monodancylcadaverine (MDC)-incorporation method, TGase from P. tayenus and P. macracanthus exhibited an optimum temperature at 40 and 25 °C, respectively. In addition, the breaking force and deformation of surimi from both species increased markedly with the addition of calcium chloride, while they decreased considerably in the presence of EDTA, N-methylmaleimide and ammonium chloride. The results confirmed that endogenous transglutaminase played an important role in gel enhancement of surimi from both species of bigeye snapper.     

Gel-forming ability of small scale mud carp (Cirrhiana microlepis) unwashed and washed mince as related to endogenous proteinases and transglutaminase activities

Gel-forming ability of small scale mud carp (Cirrhiana microlepis) mince and washed mince was investigated with respect to their proteinase and transglutaminase (TGase) activities. Proteinases in sarcoplasmic fluid showed the optimum activity at 65 °C and pH 9, whereas autolytic activity was maximum at 70 °C and pH 10, indicating the presence of heat-stable alkaline proteinases. When mince was washed with three volumes of water twice, TGase and proteinases were mainly removed in the first washing cycle, resulting in a decreased autolytic activity of washed mince. Breaking force of the single washed mince gels was greater than the twice washed mince and the unwashed mince gels (p<0.05). Pre-incubation of mince pastes at 40 °C for 1 h prior to cooking (90 °C/30 min) increased breaking force of all samples, particularly the single washed mince (p<0.05). This coincided with an increase of higher molecular weight polymers observed on SDS-PAGE. Washing did not completely eliminate proteinases as it was evident by an increased trichloroacetic acid (TCA)-soluble oligopeptides of washed gels pre-incubated at 55 °C. Whiteness values of washed mince gels were greater than that of mince gels.     

Heat-activated proteolysis in lizardfish (Saurida tumbil) muscle

Autolysis of lizardfish mince and washed mince during heating at elevated temperatures was studied. Higher degradation of myosin heavy chain (MHC) was generally observed in mince, compared to washed mince. The highest autolysis was observed at 65 and 60 °C for mince and washed mince, respectively. Autolysis was extended as the incubation time increased by the result of the decrease in MHC band intensity on SDS-PAGE and the increase in TCA-soluble peptides. Autolysis of washed mince was markedly inhibited by E-64 and soybean trypsin inhibitor, suggesting that myofibril-associated proteinases were both cysteine and serine proteinases. Sarcoplasmic proteinase was characterized to be heat-activated alkaline proteinase, which had the optimal pH and temperature of 8.0 and 65 °C, respectively. The preteinase was inhibited by E-64 and activated by reducing agents, which was one of the characteristics of cysteine proteinase. Therefore, endogenous sarcoplasmic and myofibril-associated proteinases play an important role in degradation of myofibrillar proteins of lizardfish during heat-induced gelation, which results in gel weakening.     

Cross-linking activity of sarcoplasmic fraction from bigeye snapper (Priacanthus tayenus) muscle

Addition of sarcoplasmic fraction from bigeye snapper (Priacanthus tayenus) into natural actomyosin in combination with setting at 40°C resulted in the cross-linking of myosin heavy chain (MHC). Higher amount of sarcoplasmic fraction and extended setting time resulted in a higher cross-linking, indicating the presence of endogenous transglutaminase (TGase) in bigeye snapper muscle. TGase activity was activated by calcium ion and reducing agents (β-mercaptoethanol and dithiotreitol), but was inhibited by N-ethylmaleimide (NEM), NH₄Cl and EDTA. TGase in the sarcoplasmic fraction was not stable when heated at temperature above 40°C, particularly with an increasing heating time. TGase was stable at pH ranging from 5.0 to 7.0, in which more than 70% activity was retained. Therefore, sarcoplasmic fraction possessed a cross-linking activity caused by TGase and its recovery for further uses should be considered.     

Isolation and characterization of collagen from bigeye snapper (Priacanthus macracanthus) skin

Acid‐solubilized collagen (ASC) and pepsin‐solubilized collagen (PSC) were isolated from the skin of bigeye snapper (Priacanthus macracanthus) with yields of 64 and 11 g kg^?1 wet weight, respectively. Both ASC and PSC were characterized as type I collagens with no disulfide bonds. Peptide maps of ASC and PSC digested by V8 protease and lysyl endopeptidase showed some differences in peptide patterns and were totally different from those of calf skin collagen. The maximum solubility was observed at pH 4 and 5 for ASC and PSC, respectively. A sharp decrease in solubility of both collagens in acetic acid was found with NaCl concentration above 30 g l^?1. Thermal transitions of ASC and PSC in deionized water were observed with T_max of 30.37 and 30.87 °C, respectively, and were lowered in the presence of acetic acid (0.05 mol kg^?1 solution). Therefore, ASC was a major fraction in bigeye snapper skin and it exhibited some different characteristics to PSC. Copyright © 2005 Society of Chemical Industry     

Autolysis and the endogenous proteinases characterised in beardless barb (Anematichthys apogon) muscle

Beardless barb is a common fish species used in fermentation of fish paste Ka-pi-plaa. Autolytic profile of beardless barb muscle showed the maximum autolysis was at 50 °C, at both acidic and alkaline pH values. With augmentation concentration of NaCl, autolytic activity slightly decreased. Endogenous proteinases isolated from fish muscle in crude extract forms were also characterised. The acidic proteinases had optimum activity at pH 3.0 and 50°C, and they showed higher proteolytic activity than the alkaline proteinases which were optimally active at pH 9.0 and 50 °C. Proteinases in peak at pH 3.0 were inhibited by pepstatin A, but those in peak at pH 9.0 were highly inhibited by PMSF, TLCK and soybean trypsin inhibitor, suggesting that both aspartic and serine proteinases were existed in beardless barb muscle. The proteinases were stable in pH range of 2.0-5.0 but unstable at the temperatures higher than 40 °C. NaCl suppressed the proteolytic activity, ATP activated the proteinase activity, while CaCl₂, MgCl₂ and CoCl₂ exhibited no influence on the activity. The results implied that cathepsin D is the predominant proteinase responsible for autolysis in beardless barb. The findings were useful to improve the processing and qualities of Ka-pi-plaa product using beardless barb as raw material.     

Effects of washing with oxidising agents on the gel-forming ability and physicochemical properties of surimi produced from bigeye snapper (Priacanthus tayenus)

The effects of washing with hydrogen peroxide (H₂O₂) and sodium hypochlorite (NaOCl) solutions on the gel-forming ability and physicochemical properties of surimi produced from bigeye snapper (Priacanthus tayenus), stored in ice for up to 14 days, were investigated. Generally, pH and the trichloroacetic acid (TCA)-soluble peptide content of washed mince varied, depending on the type of oxidizing agent and storage time of the fish. With increasing time of storage, the pHs of water- and H₂O₂-washed mince were lower than that of NaOCl-washed mince (P < 0.05). However, no differences in the TCA-soluble peptide contents of the resulting mince washed with any media were observed (P > 0.05). Washing with 20 ppm NaOCl resulted in the highest increase in both the breaking force and the deformation of mince from fish stored in ice for all the times studied (P < 0.05). Natural actomyosin (NAM) extracted from NaOCl-washed mince had higher surface hydrophobicity and disulfide bond (SS) content than that of water-washed mince (P < 0.05). With no effect on Ca²⁺-, Mg²⁺-, or Mg²⁺–Ca²⁺-ATPase activities, NaOCl washing resulted in an increase in Mg²⁺–EGTA-ATPase activity of NAM (P < 0.05). The results suggested that washing mince with the appropriate type and concentration of oxidizing agent can improve the gelling ability of surimi, particularly from low quality fish.     

Characterization of ginger proteases and their potential as a rennin replacement

BACKGROUND: Ginger rhizome (Zingiber officinale Roscoe) contains ginger proteases and has proteolytic activity. Ginger proteases have been used for tenderizing meat but rarely for milk clotting. The purpose of this study was to purify ginger proteases and to research their biochemical characteristics. RESULTS: The milk clotting activity (MCA) and proteolytic activity (PA) of the proteases was stable after storage at 4 °C for 24 h. The MCA and PA of fresh ginger juice with 0.2% L ‐ascorbic acid remained stable for 6 days at 4 °C. When under storage at ?80 °C for 2 months, the MCA and PA of the fresh ginger juice and acetone precipitate were still high. Two peaks with protease activity were purified from a DEAE FF ion‐exchange column; the specific activity (units mg^?1 protein) of the MCA (MCSA) and PA (PSA) for the first peak was significantly higher than the second peak (P < 0.05). The protease activity of the ginger proteases was significantly inhibited by E‐64, leupeptin, and iodoacetic acid. Zymography results showed that two protease fractions purified from ginger juice with 62 and 82 kDa had a higher PA against α‐ and β‐casein than against κ‐casein. CONCLUSION: The ascorbic acid addition significantly stabilized the MCA and PA of ginger proteases. The protease inhibition test suggested that ginger proteases belonged to the cysteine type. The biochemical characteristics of ginger protease described in this paper can provide useful information for making new milk curd products. Copyright © 2009 Society of Chemical Industry     

Thermal Denaturation of Hake (Merluccius hubbsi) Myofibrillar Proteins. A Differential Scanning Calorimetric and Electrophoretic Study

Denaturation of hake (Merluccius hubbsi) proteins was studied with DSC by monitoring T_max of transitions and denaturation enthalpies. Whole muscle free of connective tissue showed two transitions (T_max 46.5°C and 75.3°C), and ΔH of 4.27 cal/g. The exudative sarcoplasmic fraction showed three transitions (T_max 45.2°C, 59.0°C and 75.5°C) and ΔH of 3.92 cal/g. The sarcoplasmic proteins from whole hake muscle contributed to both denaturation peaks. Muscle depleted of sarcoplasmic proteins by chloride extraction showed a higher thermal sensitivity and a diminished denaturation enthalpy on the second transition. This suggested an additional effect of chloride upon actin in addition to sarcoplasmic protein extraction. pH had an effect upon the native conformation of thick filament proteins, specifically myosin.     

Autolysis of Squid Mantle Muscle Protein as Affected by Storage Conditions and Inhibitors

Autolysis of squid mantle muscle was investigated under various conditions using muscle homogenate as a model system. Cleavage of myosin into heavy and light meromyosin was prominent during autolysis. Storage conditions such as NaCl concentration and temperature affected not only the rate of autolysis but also the products formed. Conditions for maximal autolysis were: NaCl concentration 0.3M, pH 7 and temperature 40°C. Autolysis was well inhibited by ethylenediaminetetra acetic acid and Na-pyrophosphate at <25°C and by phenyhnethylsulfonyl fluoride and chymotrypsin inhibitor extracted from potato tuber at >35°C suggesting two different types of proteinases were involved.     

Proteolytic Activity in Muscle from Atlantic Salmon (Salmo salar)

The maximum proteolytic activity appeared in the neutral to slightly alkaline pH range. Heat-stable alkaline proteases were detected. Optimal activity was found at pH 8 and 65°C. The activity dropped off markedly below 60°C and above 70°C. Preincubation of the muscle-extract for about 10 min at 65°C stimulated the activity. Salmon muscle was especially susceptible to proteolytic degradation at elevated temperatures. No notable differences were detected in proteolytic activities of Atlantic salmon in the feeding stage (superior quality) and in the sexually mature stage.     

Effects of Alkali and Acid Solubilization on Gelation Characteristics of Rockfish Muscle Proteins

ABSTRACT: 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.     

Non-binding property of cathepsin L to myosin

Disodium pyrophosphate at 10 mM concentration, was effective in dissociating myosin and actin from actomyosin in walleye pollock (Theragra chalcogramma) surimi and red bulleye (Priacanthus macracanthus) surimi. After Sepharose 2B gel filtration, cathepsin L contained in the actomyosin was obviously non-binding to myosin. Actomyosin from carp (Cyprinus carpio) muscle was not dissociated in pyrophosphate solution in the absence of MgCl₂ and it was successfully dissociated by 10 mM pyrophosphate in the presence of 2 mM MgCl₂. Cathepsin L in carp actomyosin was shown to be much more complicated than that in the above two surimis. After Sepharose 2B gel filtration, there were two activity peaks of cathepsin L in carp, one almost corresponding with actomyosin, the other obviously separated from actomyosin. Both of the peaks were non-binding to myosin.     

Characteristics of gelatin from the skins of bigeye snapper, Priacanthus tayenus and Priacanthus macracanthus

Gelatins extracted from the skins containing fine scales of two species of bigeye snapper, Priacanthus tayenus (GT) and Priacanthus macracanthus (GM), were characterised. Both gelatins had the protein as the major component with high content of imino acids (proline & hydroxyproline) (186.29–187.42 mg/g). GT and GM contained calcium at levels of 6.53 and 2.92 g/kg, respectively. Both gelatins contained α1 and α2 chains as the predominant components and some degradation peptides. The absorption bands of both gelatins in Fourier transform infrared (FTIR) spectra were mainly situated in the amide band region (amide I and amide II). GT and GM had a relative solubility greater than 90% in the wide pH ranges (1–10). The bloom strength of GM (254.10 g) was higher than that of GT (227.73 g) (P < 0.05), but was slightly lower than that of commercial bovine gelatin (293.22 g) (P < 0.05). Finer gel structure with smaller strands and voids was observed in GM gel, in comparison with that observed in GT counterpart.     

Autolysis of Pacific white shrimp (Litopenaeus vannamei) meat: characterization and the effects of protein additives

ABSTRACT:  Autolytic activity of Pacific white shrimp ( Litopenaeus vannamei ) mince in the absence and in the presence of 2.5%NaCl was investigated. Pacific white shrimp mince exhibited the maximum autolytic activity at 35 and 40 °C in the absence and in the presence of 2.5%NaCl, respectively, as evidenced by the highest TCA-soluble peptide content and the greatest disappearance of myosin heavy chain (MHC). The autolysis was more pronounced in the acidic pH values, followed by alkaline pH ranges. Pepstatin A showed the highest inhibition toward autolysis in the acidic condition, revealing that aspartic proteinase was dominant in shrimp muscle. Nevertheless, soybean trypsin inhibitor effectively inhibited the autolysis at neutral and alkaline pH values, suggesting that serine proteinase was present in shrimp mince but contributed to autolysis at a lower extent in shrimp meat. Autolysis in shrimp meat could be inhibited partially by all protein additives, including bovine plasma protein (BPP), egg white (EW), and whey protein concentrate (WPC). The inhibition of autolysis increased when the level of protein additives increased with the concomitant increase in band intensity of MHC retained. WPC and BPP in the range of 2% to 3% exhibited the highest inhibition toward autolysis of shrimp mince.     

Impact of lecithin incorporation on gel properties of bigeye snapper (Priacanthus tayenus) surimi

Gelling characteristics of bigeye snapper (Priacanthus tayenus) surimi functionalised by lecithin at different concentrations were investigated. Lecithin at ≤1 g 100 g⁻¹ had no impact on breaking force and deformation (P > 0.05). Expressible drip tended to decrease with increasing lecithin level up to 1 g 100 g⁻¹. Lecithin at 1–3 g 100 g⁻¹ improved the whiteness (P < 0.05). Jointed clusters were formed in the gel microstructure with 1 g 100 g⁻¹ lecithin. Gel without and with 1 g 100 g⁻¹ lecithin had the same texture profile and likeness scores (texture, odour and flavour) (P > 0.05). Peroxide value, TBARS content and rancid odour score of gels were changed considerably during refrigerated storage (4 °C/polyethylene bag) for 15 days but lower values of all indices were noticeable in gel with lecithin. Therefore, lecithin at 1 g 100 g⁻¹ was the optimum concentration for stabilising the texture, improving the water holding capacity, whitening the colour and retarding the lipid oxidation of bigeye snapper surimi gel.