Thermally Induced Interactions and Gelation of Combined Myofibrillar Protein from White and Red Broiler Muscles

The gelling properties of broiler myofibrillar protein were studied by determining protein-protein interactions during heating. Breast and leg salt-soluble protein (SSP) showed 1–3 transitions in protein-protein interactions within pH 5.5–6.5. The maximum transition temperatures of leg SSP decreased when leg SSP was mixed with breast SSP. The combined breast/leg myofibrils formed stronger gels than leg myofibrils alone at pH ≥ 6.0, and stronger gels than breast myofibrils alone at pH < 6.0. The results suggest that interactions existed between breast and leg myofibrillar proteins, and the transitions in these interactions were useful for predicting gel strength of the combined breast/ leg myofibrils.     

Capillary electrophoresis for bovine and ostrich meat characterisation

The objective of this study was to characterise, compare and quantify the water soluble protein (WSP) and salt soluble protein (SSP) fractions from bovine and ostrich muscle by using sodium dodecyl sulphate polymer-filled capillary gel electrophoresis (CE-SDS). Samples were raw ostrich leg and eye round beef collected 24 and 48 h, respectively, after sacrifice from local slaughter houses. WSP were extracted with cold double distilled deionized water and SSP with 0.6 M NaCl/0.01 M phosphate buffer pH 6 with 0.5% polyphosphates. Separation of WSP and SSP extracts was achieved by CE-SDS. Quantitative data for individual proteins was generated by constructing a calibration curve using bovine serum albumin (BSA) as a standard. The WSP profiles showed differences for bovine and ostrich meat, both qualitatively and quantitatively and could be employed for species differentiation. Quantitative data derived for WSP and SSP from bovine and ostrich muscle showed significant differences among individual proteins. A comparison of protein profiles form ostrich and bovine meat should be useful for meat species differentiation and muscle characterisation for establishing relations to meat quality.     

Changes in texture qualities and pectin characteristics of fermented minced pepper during natural and inoculated fermentation process

Texture qualities and pectin characteristics in fermented minced pepper (FMP) prepared by natural fermentation (NF) and inoculated fermentation (IF) were analysed during fermentation. The results showed variation in texture qualities and pectin characteristics was similar during NF and IF process. The hardness, cell wall material, sodium carbonate-soluble pectin (SSP) and chelate-soluble pectin (CSP) content, and CSP esterification degree decreased, while water-soluble pectin (WSP) content significantly (P < 0.05) increased after fermentation. The rhamnose (Rha) molar ratio in three pectins increased, but arabinose (Ara) and galactose (Gal) molar ratios in most pectins decreased after fermentation. Changes in Ara/Gal and (Gal + Ara)/Rha ratios represented the backbone and branched chains of rhamnogalacturonan-I in three pectins depolymerised during fermentation. The decrease of molecular weight (M_w) in CSP was more obvious than that in WSP and SSP, and it was extensively depolymerised into low-M_w pectin after fermentation. Pearson's correlation analysis showed FMP hardness was extremely (P < 0.01) positively correlated with CSP content and significantly (P < 0.05) positively correlated with SSP content and CSP M_w. Hence, CSP was the main pectin to affect texture compared with WSP and SSP, and its characteristics played a crucial role for regulating FMP texture during NF and IF process.     

Functional Properties of Myofibrillar Proteins from Cold-Shortened and Thaw-Rigor Bovine Muscles

Prerigor bovine sternomandibularis muscles were stored at 15, 0 and ?29°C to examine cold-shortening and thaw-rigor effects on myofibrillar protein extractability and gelation properties of myofibrils and salt-soluble protein (SSP). Frozen muscle that underwent severe contraction at thawing showed greater protein extractability (35%) than muscles stored at 0 and 15°C (27% extractability). Of the three tempered muscles, thaw-rigor muscle produced the strongest myofibril gel and cold-shortened muscle formed the most elastic SSP gel as determined by dynamic shear and penetration measurements. However, thermally induced changes in gel viscoelastic moduli for all protein samples followed similar patterns. Results indicated that physicochemical changes accompanying muscle contraction affected protein network formation during gelation.     

Changes in Protein Solubility and Gelation Properties of Chicken Myofibrils during Storage

The effect of storage on protein solubility and heat-induced gelation properties of chicken hen breast and leg myofibrils was investigated. Myofibrils suspended in 0.6M NaCl, pH 6.0, showed increasing protein solubility, viscosity, gel strength and water holding capacity with storage at 4°C. However, the effect of storage was most dramatic only during the initial 10 hr for all of the parameters studied. The relative distribution of the proteins comprising the salt soluble protein (SSP) extract changed during storage. Although storage had little effect on breast SSP, it was detrimental to leg SSP gelation. Breast myofibril suspensions, for all storage times, contained a greater amount of SSP and had better gelation properties than leg myofibril suspensions.     

Physico‐chemical and functional properties of proteins from green mussel (Perna viridis) during ice storage

The effect of ice storage on the properties of proteins from green mussel (Perna viridis) has been investigated. Ice storage of green mussel for a period of 19 days revealed a marginal increase in moisture and decrease in total nitrogen content. There was significant reduction (P < 0.05) in non‐protein nitrogen content and calcium activated adenosine triphosphatase enzyme activity. The solubility of the total proteins in high ionic strength buffer decreased marginally. The ice storage of green mussel had a significant effect on association‐dissociation/denaturation phenomenon of proteins as revealed by gel filtration profile, reduced viscosity values and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS‐PAGE) pattern. The dynamic viscoelastic behaviour of green mussel meat in the temperature range of 30–90 °C revealed higher storage modulus (G′) values at a later part of ice storage. The emulsion capacity of green mussel did not show significant variation (P < 0.05) during ice storage. Copyright © 2006 Society of Chemical Industry     

Sarcoplasmic proteins influence water-holding capacity of pork myofibrils

Water-holding capacity (WHC) is one of the main pork quality characteristics. The objective of this study was to determine the influence of (denaturation of) sarcoplasmic proteins on WHC. Myofibrils extracted from red, firm, non-exudative (‘normal’) and PSE (pale, soft, exudative) pork longissimus muscle were combined with sarcoplasmic extracts (with or without proteins) from PSE and normal pork longissimus samples. Weight increase of myofibrils (mg increase mg⁻¹ myofibrillar protein) was used as a measure of WHC. When combined with protein-containing sarcoplasmic extract from normal pork, WHC of myofibrils from PSE (2.6 mg mg⁻¹) and normal (2.8 mg mg⁻¹) pork was higher (P < 0.05) than when combined with sarcoplasmic extract from PSE meat (1.3 mg mg⁻¹ for PSE and 1.9 mg mg⁻¹ for normal myofibrils). Protein-free sarcoplasmic extracts were prepared by heating the extracts for 30 min at 80 °C. WHC of myofibrils combined with protein-free sarcoplasmic extract from PSE and normal pork was not significantly different. WHC of myofibrils combined with protein-free extract was lower than WHC of myofibrils combined with protein-containing extract. Ionic strength or pH could not explain the observed differences. It was concluded that sarcoplasmic proteins do influence WHC. The mechanism of this influence still needs to be determined. © 1999 Society of Chemical Industry     

Effects of rice residue on physicochemical properties of silver carp surimi gels

The objective of this study was to determine the effects of rice residue on the physicochemical properties of silver carp surimi gels. The whiteness of gels was slightly decreased when rice residue was added. Breaking force and deformation of gels were significantly decreased with more than 1% rice residue addition (p < 0.05). The trends of storage modulus, tan δ, and interactions demonstrated a negative effect of rice residue (more than 1%) on gel network. The addition of rice residue reduced the interactions in surimi gel network, such as hydrophobic interaction. The sodium dodecyl sulfate–polyacrylamide gel electrophoresis indicated that there was little interaction between rice proteins and myofibrillar proteins. Rice residue deteriorated the freeze-thaw stability of surimi gels. Therefore, rice residue could be an inactive filler in the gel network unless it was less than 1%.     

Proteins Associated with Thermally Induced Gelation of Turkey Breast Meat

ABSTRACT:  Principal component analysis was performed on turkey breast muscle that originated from a pool of genetically distinct turkeys by separating the salt-soluble from the salt-insoluble proteins. The salt-soluble proteins (SSP) formed thermally induced meat gels and the viscoelastic properties of the gels were analyzed. The storage modulus (G') at 80 °C of thermally induced gels derived from the SSPs ranged from 3 to 400 Pa. Each protein fraction was analyzed using 5% to 20% sodium dodecyl sulfate polyacrylamide gel electrophoresis. Reverse stepwise regression analysis of the electrophoretic fingerprints of the protein fractions showed that G' at 80 °C was associated with the 2 protein bands from the salt-soluble fraction ( R ²= 0.87, P < 0.01) and 1 protein from the salt-insoluble fraction ( R ²= 0.27, P < 0.05). Primary sequence analysis identified one of the SSPs positively associated with G' at 80 °C as α-tropomyosin and the other SSP negatively associated with G' at 80 °C as pyruvate kinase. The salt-insoluble protein identified as triose phosphate isomerase was negatively associated with G' at 80 °C. These findings are unique in that they show that proteins other than myosin and actin participate in the mechanisms of forming thermally induced meat gels.     

Heat-induced gelation properties of chicken breast muscle salt soluble proteins when mixed with β-lactoglobulin or an α-lactalbumin enriched protein fraction

The heat-induced gelation properties of mixed protein systems containing chicken breast muscle salt-soluble proteins (SSP) and β-lactoglobulin (β-lg) or SSP and an α-lactalbumin-enriched fraction (α-la) in 0.6 M NaCl, pH 6.5, were investigated using dynamic rheology. At 70 °C, SSP had greater storage modulus (G') values than mixtures containing SSP/α-lg. However, at 90 °C, mixtures containing 80:20 and 60:40 SSP: β-lg had higher G' values than SSP alone, indicating that denaturation of β-lg directly or indirectly facilitates the formation of a more rigid gel structure. On subsequent cooling to 20 °C, the extent of structure formation, as reflected by G' values, was greater for SSP than for mixtures containing SSP/β-lg, which suggests that the denatured β-lg is unable to interact with the SSP during cooling. Mixtures containing SSP and an α-la-enriched fraction had lower G' values than SSP at 90 °C and on subsequent cooling to 20 °C, which reflects the poor gelling properties of α-la. A fibrous network was observed when the microstructure of the SSP and 40:60 SSP: α-la gels were examined using scanning electron microscopy, while aggregated networks were seen in the β-lg and 40:60 SSP: β-lg gels. No significant differences (p > 0.05) were observed between the water holding capacity (WHC) of SSP and SSP/β-lg gels. Gels formed from a mixture of SSP and the α-la-enriched fraction had lower WHC than the SSP gels. The myosin heavy chain was a major contributor to gel structure formation in all mixed gel systems.     

Changes in functional properties of common carp (Cyprinus carpio) myofibrillar protein as affected by ultrasound-assisted freezing

Ultrasound-assisted freezing (UF) has proven to be a method that can effectively increase the freezing rate of frozen food and improve its quality. The functional properties of myofibrillar proteins (MP) are important factors that affect the further processing quality of meat products. At present, the effect of UF on the functional properties of frozen MP is not yet clear. Therefore, in the present study, changes in the functional properties (emulsifying and gel properties) of MP in common carps (Cyprinus carpio) frozen with UF at different power levels were investigated. The results revealed that, compared with immersion freezing (IF), UF at 175 W (UF-175) effectively inhibited the decrease in protein solubility, absolute Zeta potential, emulsion activity index, storage modulus (G'), and loss modulus (G'') caused by freezing. UF-175 sample had lower protein turbidity, and smaller protein particle size than any other frozen samples (P < 0.05), which suggested that UF-175 inhibited protein aggregation induced by freezing. In addition, shorter T₂₁ and T₂₂ relaxation times were obtained in UF-175 sample than other frozen samples, indicating that UF-175 reduced the mobility of immobilized and free water. Accordingly, UF-175 sample had higher gel strength and water holding capacity than other frozen samples (P < 0.05). A denser and more uniform gel network structure was also found in UF-175 sample than other frozen samples. In general, improved functional properties of common carp MP can be achieved by optimal UF.     

Effect of laccase and transglutaminase on the textural and water-binding properties of cooked chicken breast meat gels

The effects of laccase and transglutaminase (TG) on the firmness and weight loss of cooked chicken meat homogenate gels were investigated at laboratory scale. The salt, trisodium pyrophosphate and meat contents were also used as variables. Laccase decreased firmness and increased weight loss of phosphate-free, low-meat (65%) and low-salt (1%) gels, although it modified myosin and troponin T and reacted with isolated myofibrils. By applying both low-salt (1%) and low-phosphate (0.17%) amounts, gel firmness decreased and weight loss increased (p<0.05) greatly. A high dosage of TG significantly improved (p<0.05) the strength of phosphate-free, low-meat and low-salt homogenate gels compared to the corresponding no-enzyme controls. TG improved gel firmness of the low-meat homogenate to the level of the homogenate containing 75% meat. Weight loss was increased significantly (p<0.05) in all cases when the high-TG dosage was used. Enzymes were not capable of improving either texture or water-holding capacity in the low-salt–low-phosphate system. The firmness and cooking loss of the chicken meat products containing different amounts of meat, salt and TG were investigated at pilot scale. Under the conditions and dosages used, TG was capable of improving (p<0.05) firmness of the products without a significant reduction in water-holding capacity.     

SDS-PAGE Conditions for Detection of Titin and Nebulin in Tender and Tough Bovine Muscles

Purified myofibrils were prepared from infraspinatus (tender) and rhomboideus (tough) muscles at 7 days postmortem and examined for myofibrillar/cytoskeleta1 protein degradation by using sodium dodecyl sulfate polyactylamide gel electrophoresis (SDS-PAGE). Four acrylamide/bisacrylamide ratios (37:1, 50:1, 75:l and 100:1) and two SDS-PAGE gel buffers (Tris-HCl, pH 8.0 and 8.9) were used to determine the optimum conditions for detection of titin and nebulin. Titin was degraded to a greater extent in myofibrils from the infraspinatus than in myofibrils from the rhomboideus. Very little nebulin was detected in either muscle. Use of acrylamide/bisacrylamide ratio of 37:1 and a gel buffer of pH 8.0 provided the most optimum conditions for detecting differences in the resolution of titin, nebulin and their apparent degradation products.     

Dependence of microbial transglutaminase on meat type in myofibrillar proteins cross-linking

The objectives of this study were to determine the factors that cause differences in the improvements of gel strength and ε(γ-glutamyl)lysine (G-L) content in chicken and beef (Japanese black cattle) myofibrillar proteins after adding microbial transglutaminase (MTG). As the amount of MTG added increased, the breaking strength increased progressively (p < 0.01) in chicken and beef samples, with the exception of chicken samples treated at 40 °C. The values of elasticity in the chicken samples were lower than those of the beef samples (p < 0.01). Surprisingly, the elasticity level, ε(γ-glutamyl)lysine contents and myosin heavy chain (MHC) band sizes of chicken and beef at all levels of MTG were significantly different (p < 0.01). The results of this study suggest that MTG activity was affected by MTG inhibitors; that MTG develops the texture of myofibrils differently in different species. However, the activity is limited and inconstant among meat proteins, as suggested by the data collected from the chicken samples. As a result, when the transferable amino acid residues are depleted (cross-linked) by MTG activity, the function of MTG will be insignificant. The correlation between MTG and different sources of meat protein is quite unstable but it is strong, which was observed when chicken and beef responded differently to MTG because their chemical and physiological properties were different. The remarkable rate of formation of cross-linked proteins and the discrepancy between the expected and observed amount of dipeptide raises the possibility that there are enzymes capable of reversing the reaction induced by transglutaminase in chicken and beef myofibrils. In summary, our results suggest that access of MTG to chicken and beef myofibrils is different because it depends on physiological (muscles and their fibre types), biological (substrates) and biochemical (inhibitors and amino acids) variables.     

Functional properties of pH-shifted protein isolates from bigeye snapper (Priacanthus tayenus) head by-product

The functional properties of pH-shifted protein isolates from bigeye snapper head were evaluated. Alkaline isolate showed a superior salt-solubility and gel forming ability to acid counterpart as indicated by a regular gel structure (i.e., imaged by scanning electron microscope) with higher gel strength and lower expressible drip (p < 0.05). Acid isolate exhibited higher surface hydrophobicity (p < 0.05) and thereby improved interfacial properties. Emulsifying activity index of acid isolate was lower than commercial whey protein and egg-white (p < 0.05) but its emulsion stability was better (p < 0.05). Both protein isolates had lower foamability than commercial proteins but their foam stability was not different (p > 0.05).     

POSTMORTEM CHANGES IN MYOFIBRILLAR PROTEINS OF GOAT SKELETAL MUSCLES

Postmortem changes at 5C in myofibrillar proteins of longissimus dorsi (LD), biceps femoris (BF), semimembranosus (SM) and semitendinosus (ST) muscles and myofibrillar structure of LD muscle of goat were investigated. Muscle samples were immediately collected after killing, and from carcasses stored at 5C for 3, 6, 9, 12 and 20 days. The sodium dodecyl sulfate‐polyacrylamide gel electrophoresis of myofibrils indicated the appearance of a 30 kDa component, depending on the type of the muscles. A new 55 kDa component appeared in BF and SM muscles during postmortem. Titin I and nebulin also disappeared during storage. The disappearance of titin 1 and nebulin and the appearance of a 30 kDa component were confirmed by Western blot analysis. The Transmission Electron Microscopy studies showed that after 3 days postmortem, Z‐disks stayed unaltered. After 6 days postmortem, a little ultrastructural alteration was observed, and at 12 days postmortem a considerable degradation of Z‐disk ultrastructure was shown. The Z‐disk degradation, which results in the fragmentation of myofibrils and the appearance of 30 kDa components, is the major change observed in goat skeletal muscles during postmortem.     

Effect of ice storage on the functional properties of pink perch and oil sardine meat

Ice storage of dressed pink perch (Nemipterus japonicus) and Indian oil sardine (Sardinella longiceps) for 16 and 20 days, respectively, resulted in a decrease in emulsifying capacity (EC), protein solubility (PS), relative viscosity (RV) of salt‐soluble proteins (SSP) and water‐soluble proteins (WSP), water binding capacity (WBC) in terms of absorbed moisture in water (AM_w), absorbed moisture in brine lpar;AM_b), retained moisture in water (RM_w) and retained moisture in brine (RM_b), WSP and SSP, and increase in cook loss (CL). Decrease in protein solubility influenced the EC, RV, CL and WBC in both the species of fish. Significant (P<0.05) correlations existed among various functional properties analysed, in both the fishes during the ice storage. © 1999 Society of Chemical Industry     

A novel method for total protein analysis of protein mixtures using enzyme hydrolysis and derivatisation with o-phthaldialdehyde – Application to dairy products

A novel approach to analysis of proteins in dairy products was demonstrated using enzyme hydrolysis followed by derivatisation with o-phthaldialdehyde (OPA) and fluorescence detection. Unlike the response of other dye-binding methods, enzyme hydrolysis significantly eliminated dependence of the fluorescence intensity upon protein primary sequence and, compared with chemical hydrolysis, was achieved under relatively mild conditions. Enzyme hydrolysis and OPA-derivatisation steps were successfully automated using a flow-injection manifold, with a method coefficient of repeatability <6%. The enzyme-OPA (eOPA) method was applied to analysis of total (TP) and serum-soluble proteins (SSP, proteins soluble at pH 4.6) in reference standards spanning two decades of protein concentration. Method accuracy was very good for analysis of TP and acceptable for analysis of SSP. Discrepancies between the eOPA and standard methods for SSP were explained by sample preparation and not analytical factors. The eOPA method may be suitable for automation into a portable or miniaturised device.     

HEAT-INDUCED GELATION OF MYOSIN IN THE PRESENCE OF ACTIN

ABSTRACT The rabbit muscle contractile proteins, myosin, actin and reconstituted actomyosin were mixed in 0.1–1.0 M KCl, 20 mM buffers, pH 5.0–8.0, and were tested quantitatively for thermally induced gelation properties by measuring the rigidity (shear modulus) of the system at 20–70°. Scanning electronmicroscopy (SEM) was also used to study the structure of the gels formed by gelation of myosin in the presence of F-actin. Under the standard condition, i.e. at 0.6 M KCl, pH 6.0 and 65°, decrease of the myosin/actin mole ratio to about 1.5–2.0 in the reconstituted acto-myosin system resulted in substantial augmentation of the rigidity of the gel formed. Further decreases in the myosin ratio relative to F-actin reduced the rigidity value of the gel to close to the level of myosin alone. Gel-formability of the reconstituted actomyosin was maximal at pH 5.5–6.0 and between 0.5 and 0.8 M KCl and decreased considerably at other pH values and KCl concentrations. The SEM studies revealed progressive changes in three dimensional ordering as actin concentration in the actomyosin varied. These were in concordance with the results of gel strength.     

Immunomodulatory properties of selectively processed prawn protein fractions assessed using human peripheral blood mononuclear cells

Prawn muscles were treated with acetic acid and high-pressure processing (600 MPa) separately to analyse their antigenicity and immunogenicity. The protein fractions were separated and isolated using preparative HPLC, and their antigenicity was analysed using Immunoglobulin G (IgG) ELISA kit. Out of thirty-nine protein fractions, only four (A10, A11, B10 and C9) were detected with antigenic potentials. The immunogenicity of these protein fractions was analysed using human PBMCs, and supernatants were collected at multiple times from 0 to 144 h. The treated fractions (B10 and C9) analysed using Immunoglobulin E (IgE) ELISA kit showed significantly (P < 0.05) lower pro- and anti-inflammatory cytokine production compared with control (A10). The allergenic fractions were characterised using an LC/MS/MS, which identified nine proteins. Among these, six proteins (tropomyosin, arginine kinase, haemocyanin, enolase, vitellogenin and 14-3-3 zeta) have been established as allergenic in prawn muscle and ovaries. Other three proteins (beta-1,3-glucan-binding protein, translationally controlled tumour protein and farnesoic acid O-methyltransferase short isoform protein) identified in this study need further investigation for their immunogenic properties.