Effect of Washing and Sodium Chloride on Mechanical Properties of Fish Muscle Gels

Excellent gels, as measured by fold test, were prepared from three species of fish without washing if NaCl were added. Dependent on species, excellent to adequate gels could be prepared from fish muscle without NaCl, provided that the minced tissue was washed prior to gel formation. Red hake formed an excellent gel, cod formed a good gel, and flounder formed a fair gel in the absence of NaCl, as judged by fold scores of 5, 4, and 3, respectively.     

Salt-Induced, Low-Temperature Setting of Antarctic Fish Muscle Proteins

Freshly prepared salted pastes (2.5%, w/w NaCl) of muscle tissue of the Antarctic fishes Pagothenia borchgrevinki (white muscle) and Dissostichus mawsoni (red and white muscle) rapidly formed cold-set gels. Set times were minutes rather than the hours required to cold-set salted pastes of fish from cold- temperate waters. Cold-setting was related to habitat temperature and the stability of fish muscle myosin, the protein responsible for gel formation.     

Contribution of Retained Organ Tissues to the Alkaline Protease Content of Mechanically Separated Atlantic Croaker (Micropogon undulatus)

The greater texture breakdown observed in gel-type products prepared from mechanically separated tissue as opposed to manually separated tissue can to some extent be attributed to the significantly higher protease activity measured in mechanically separated tissue. Failure to thoroughly wash eviscerated fish prior to mincing appears to result in the retention of tissue from internal organs as evidenced by a concommitant increase in protease activity in the minced tissue. Alkaline protease activity in croaker kidney and liver is several thousand fold higher than in skeletal muscle. Addition of kidney and liver tissue to deboned tissue from thoroughly washed fish results in increased protease activity and degradation of the fish tissue upon comminuting and cooking at 60°C. Isoelectric focusing provided evidence that the increased alkaline protease activity observed in mechanically separated fish tissue resulted to some degree from retention of kidney tissue in the fish mince. Isolation of Ca⁺⁺-dependent protease fractions from liver also implicated contamination from this source as an additional contribution to the total protease activity of minced fish.     

Anti-oxidant activity of added tea catechins on lipid oxidation of raw minced red meat, poultry and fish muscle

The comparative anti-oxidative effects of added tea catechins (TC) and α-tocopherol to raw minced red meat (beef and pork), poultry (chicken, duck and ostrich) and fish (whiting and mackerel) muscle on susceptibility to lipid oxidation were investigated during 10 days of refrigerated (4 °C) display. Fresh meats, poultry and fish, purchased from a local market, were trimmed to remove bones, skin and surface fat and minced through a 4 mm plate. The minced muscle of each species was treated with either the addition of 300 mg TC kg^–1 minced muscle (TC300) or 300 mg α-tocopherol kg^–1 minced muscle (VE300). Minced muscle without any additives served as control (C). Oxidative stability (TBARS) was measured at 3-day intervals. Total lipids, fatty acid composition, total iron and haem iron from minced muscle for each species were also analysed. The susceptibility of untreated minced muscle to lipid oxidation was in the decreasing order: mackerel > beef > duck > ostrich > pork ≥ chicken > whiting. This may be because of the different content of total fat, iron and fatty acid composition between species. The TC300 significantly ( P  < 0.05) reduced lipid oxidation compared with controls for all seven species as shown by lower TBARS values. The anti-oxidant potential of TC was two to fourfold greater than that of α-tocopherol at the same concentration and this potential was species dependent. The VE300 showed limited capacity in inhibiting lipid oxidation for pork, chicken, duck and whiting. The results obtained show that TCs are powerful natural antioxidants when used in minced muscle food.     

OCCURRENCE OF TRANSGLUTAMINASE IN GREY MULLET (MUGIL CEPHALUS) MUSCLE AND IT'S EFFECT ON MINCED FISH PRODUCT

The gel strength of the minced fish product made from the unwashed mullet mince was found higher than that of the washed product. Transglutaminase (TGase) was found in the water soluble fraction of mullet muscle. It's optimal temperature was at 30C to 35C and the optimal pH was 7.5 to 7.7. Increased setting time at 30C, increased the gel strength of the minced fish product produced from the unwashed mullet mince. p-Chloromercuribenzoate (PCMB), an inhibitor to TGase was added to the mullet mince up to 2.0 mM, the mince was set at 35C and then heated to 85C. The gel strength of the product was inversely correlated to the PCMB concentration, Y₁= - 0.45X + 1.66 (r = 0.95). Studies of setting of the mullet mince at temperatures ranging 20 to 60C indicated that maximal gel strength was obtained at 35C, coinciding with the optimal temperature of TGase. Meat from 21.5 monthold grey mullet produced a minced product of higher gel strength than those produced from younger fish, although the muscle TGase activities were not significantly different.     

Antioxidative effect of added tea catechins on susceptibility of cooked red meat,poultry and fish patties to lipid oxidation

The comparative antioxidant activity of added tea catechins on susceptibility of cooked and overwrapped red meat (beef and pork), poultry (chicken, duck and ostrich) and fish (whiting and mackerel) to lipid oxidation was investigated. Fresh meats, poultry and fish, purchased from a local market, were trimmed to remove bones, skin and visible fat and minced through a 4-mm plate. The minced muscle from each species was treated with either 1% NaCl (S), 300 mg tea catechins kg⁻¹ minced muscle (TC) or 1% NaCl plus 300 mg tea catechins kg⁻¹ minced muscle (TCS). Control minced muscle samples (C) contained neither NaCl nor tea catechins. Patties (50 g), prepared from treated and untreated minced muscle, were cooked until the core temperature reached 75°C, cooled down to room temperature and held in a refrigerated (4°C) and illuminated (616 lux) display cabinet for 10 days. Oxidative stability (TBARS) was measured at 3-day intervals. The susceptibility of cooked patties to lipid oxidation was closely related to lipid content, concentration of unsaturated fatty acids and presence of iron in different species. Addition of NaCl to raw minced muscle significantly (P<0.05) promoted lipid oxidation for cooked patties regardless of species sources. Tea catechins added at a level of 300 mg kg⁻¹ minced muscle significantly (P<0.01) inhibited the pro-oxidation caused by NaCl and controlled lipid oxidation for all cooked muscle patties examined. Tea catechins at concentrations greater than 300 mg kg⁻¹ were necessary to reduce oxidation for mackerel patties containing high levels of lipids and unsaturated fatty acids. The high affinity of tea catechins for the lipid bilayers of muscle and the radical scavenging abilities of tea catechins may be possible mechanisms to explain the oxidative stability in cooked muscle foods.     

捶打时间对牛肉凝胶品质的影响研究

为探究捶打工艺对牛肉凝胶品质的影响,以打浆工艺制作的牛肉凝胶为对照组,通过测定不同捶打时间的牛肉凝胶色差、肌原纤维蛋白氧化程度、蒸煮损失率、脂肪渗出率、质构特性,并测定牛肉凝胶的肉糜粒径、蛋白质二级结构及微观结构的变化,了解捶打时间对牛肉凝胶品质的影响机理。结果表明,捶打时间在15~40 min之间时,随着捶打时间延长,肉糜L*值与W值先降后升,a*值和b*值先升后降;肌原纤维蛋白氧化程度不断增加,总巯基不断减少,羰基值及溴酚蓝结合量不断增加;蒸煮损失率与脂肪渗出率先减少后增加;凝胶质构中硬度、咀嚼性逐渐增加,弹性、内聚性与回复性先增加后减少,以30 min为分界点,捶打30 min以内凝胶品质呈上升趋势,超过30 min呈下降趋势。30 min前凝胶品质上升原因为肉糜粒径减小及蛋白质二级结构β-折叠增多;30 min后凝胶品质下降原因为蛋白质氧化程度加深及凝胶微观结构的改变。试验结果表明传统捶打方式能提高肉糜品质,但过度捶打会引起肉糜品质劣变。     

EFFECT OF SETTING CONDITIONS USING MICROBIAL TRANSGLUTAMINASE DURING OBTENTION OF BEEF GELS

Microbial transglutaminase (MTG) is a food additive widely used to improve the mechanical properties of beef, poultry and fish gels. The aim of this study was to determine the effect of incubation temperature on the mechanical properties of restructured beef gels treated with MTG. The restructured beef gels were obtained by adding 0.0% (untreated) or 0.3% MTG. Three incubation temperatures (40, 50 or 60C) for 30 min were used, followed by cooking at 90C for 15 min. Control samples without incubation were also prepared. Changes in the mechanical properties (texture profile analysis and puncture test), color attributes, expressible water and cooking loss were determined. Results indicated that the maximum mechanical properties can be obtained by incubating beef pastes at 50C for 30 min with minimal effect on color, expressible water and cooking loss when 0.3% of MTG is added.

PRACTICAL APPLICATIONS

Meat and poultry are considered nonsetting proteins, and consequently, an incubating treatment to allow optimal cross-linking has not been considered, and the products are usually obtained by direct cooking. Our results showed that beef gels containing 0.3% of microbial transglutaminase incubated at 50C showed higher mechanical properties than control gels without incubation. These results could be useful to improve the mechanical properties of beef gels.     

TEXTURE PROFILE ANALYSIS AND COMPOSITION OF A MINCED CATFISH PRODUCT1

Texture Profile Analysis of minced catfish products indicated that minced proteins from the belly flap meat have excellent functional properties to form gels or restructured products. Belly flap meat is considered a low‐value trimming, with about 16.9% protein and 11.2% total lipid. Washing of minced catfish trimmings increased the moisture content from 71.5% to 77.9% while reducing mechanical hardness (19.1 N to 11.9 N), chewiness index (14.2 N to 8.83 N) and shear energy (0.82 J to 0.51 J). No significant changes were found in cohesiveness, resilience, and springiness of the minced fish after washing or the addition of 3.3% (v/w) of 4% starch solution. Washing of minced fish reduced the total lipid content from 9.82% to 4.39%. Overall, washed minced channel catfish belly flap meat had functional characteristics that enabled its proteins to be formed and restructured. Products made from minced catfish had acceptable textural characteristics.     

Strength of Gels Prepared from Washed and Unwashed Minces of Hoki (Macruronus novaezelandiae) Stored in Ice

Washed and unwashed fish minces were prepared from hoki that had been stored in ice. Gels were formed from the minces, cooked at both 60°C and 90°C and assessed by puncture, torsion and a folding test method. The strength of the gels decreased as the fish were stored. However, after 10 days, the strength of gels made from hoki minces still compared favorably with gels made from other commercial fish species without storage. This suggests that manufacture of hoki surimi on-shore may be practical. Fish freshness as evaluated by sensory methods was closely related to the K value and gel strength. Hence K values might provide the basis of a raw material quality control system for an on-shore surimi plant.     

RELATIONSHIPS BETWEEN BINDING QUALITY OF MEAT AND MYOFIBRILLAR PROTEINS V. Effect of 'Setting' and Pyrophosphate on Rheological Properties of Heated Minced-Meat Gel

‘Setting’ was observed in minced hen meat stored with 3.5% wt/wt added NaCl. When gels were made from the ‘set’ sol the breaking energy was greatly increased and the relaxation modulus was characterized by a wide ‘quasi-equilibrium’ region. The effect of added pyrophosphate on the rheological properties of the gel prepared at pH 6.0 from ground ‘set’ sol was very similar to that previously observed for ATP in gels prepared at pH 6.0 from ‘unset’ sols. When pyrophosphate or ATP were added at pH 7.0 to the ‘unset’ minced meat sol, the strain at the breaking point and the ratio of the equilibrium to the instantaneous modulus of the heated gel were increased. A comparison with previous results from a model system suggests that pyrophosphate brings about a change in gel structure by dissociating ‘myosin B’ into myosin A and F-actin.     

Testing caffeic acid as a natural antioxidant in functional fish-fibre restructured products

The antioxidant effectiveness of caffeic acid addition to minced fish muscle with or without wheat dietary fibre added was studied. Wheat dietary fibre showed a significant prooxidant effect on minced fish muscle during chilled storage that was significantly inhibited in presence of 100 mg/kg caffeic acid. In samples containing caffeic acid and wheat dietary fibre, lipid oxidation was completely inhibited after 10 days. Results obtained from the instrumental texture profile analysis showed that the inclusion of wheat dietary fibre with or without caffeic acid lowered the texture profile analysis parameters. Caffeic acid did not render any changes on the water binding capacity. These results prove that caffeic acid can be successfully used as a natural antioxidant in wheat dietary fibre minced fish restructured products.     

Cholesterol and lipid oxidation in raw and pan‐fried minced beef stored under aerobic packaging

BACKGROUND: The type of packaging atmosphere has been reported as a technological factor that consistently affects the quality of lipid fraction in meat. Oxidation of cholesterol and lipids was evaluated before and after pan frying in commercial refrigerated minced beef stored under aerobic atmosphere for 1 and 8 days. RESULTS: In raw beef, cholesterol and lipid oxidation developed at a slow rate. Cholesterol oxidation products (COPs) did not significantly vary (～8 µg COPs g^?1 of fat) over 8 days, while in the same period thiobarbituric acid reactive substances (TBARS) less than doubled (from 0.7 to 1.2 malondialdehyde equivalents kg^?1 of muscle). Pan frying did not influence the oxidative degree in the fresh product but consistently catalyzed cholesterol oxidation in stored beef. A significant increase was assessed in beef at the end of storage: from 8.6 to 30.0 µg COPs g^?1 of fat in raw and cooked beef, respectively. CONCLUSION: Aerobic packaging did not appear as a pro‐oxidant factor in fresh minced beef with a good oxidative quality during a short period of refrigerated storage. Copyright © 2010 Society of Chemical Industry     

Gelling properties of surimi as affected by the particle size of fish bone

The effects of adding fish bone with two different particle sizes (micro and nano) on Alaska pollock surimi gels prepared by two heating procedures were investigated. Heating procedures (with or without setting) resulted in significantly different gel texture values. The addition of nano-scaled fish bone (NFB) (up to 1 g/100 g) effectively increased gel breaking force and penetration distance while micro-scaled fish bone (MFB) did not. Endogenous transglutaminase (TGase) activity of surimi paste increased obviously as the concentration of NFB increased, indicating calcium ions readily released from NFB and assisting gel formation through TGase-induced covalent bonds. With MFB, TGase activity increased slightly, but not significantly. Scanning electron microscopy (SEM) results revealed NFB was capable of being imbedded in the gel matrices without disrupting the myofibrillar gel network. Surimi with MFB formed a discontinuous and porous network with pores near the size of MFB. Lightness (L*) and whiteness (L*-3b*) of NFB gels were higher than those of MFB.     

EFFECT OF MgCl2/SODIUM PYROPHOSPHATE ON CHICKEN BREAST MUSCLE MYOSIN SOLUBILIZATION AND GELATION

Sodium chloride (0.29 M) at pH 7 solubilized about 24% of the myosin of washed, minced chicken breast muscle. At a similar pH, 0.2 M sodium chloride in the presence of 10 mM sodiumpyrophosphate and 10 mM magnesium chloride solubilized almost 60% of the myosin. In spite of the greater solubility of myosin under the latter conditions, when gels were prepared with these concentrations of salt at pH 7, the gels without the sodium pyrophosphate and magnesium chloride were slightly superior in both stress (39.3 kPa vs 28.3 kPa) and true strain (2.3 vs 2.0) values. Gels made at a lower pH (6.1–6.5) made much poorer gels. This was true whether the low pH was obtained naturally in the preparation of the sample or re‐adjusted after bringing the mince to a neutral pH. It appears that conditions of pH and salt content that cause solubilization of myosin at more dilute conditions does not contribute to gel quality, but the neutral pH is an important factor for obtaining good gels at ionic strengths <0.3.     

Changes in Electrophoretic Patterns of Gadoid and Non-gadoid Fish Muscle during Frozen Storage

Sodium dodecyl sulfate polyacrylamidc gel electrophoresis of fish muscle during frozen storage showed that a crosslinked protein of 280,000 daltons formed with gadoids, whereas this band did not occur with non-gadoid fish species. For cod, 20 days at -7°C are needed for the crosslink to appear, whereas for whiting only 3 days arc needed. Formaldehyde (FA) may be responsible for the crosslinking. Adding ascorbic acid to cod mince prior to freezing accelerated dimcthylamine and FA formation during frozen storage and accelerated the formation of the crosslinked protein, while leaving cod fillets on ice for 10 days prior to freezing, reduced the Instron hardness and the crosslinked protein did not appear with 50 days of frozen storage at -7°C.     

Thermal Gelation of Myofibrils from Pork, Beef, Fish, Chicken and Turkey

Myofibril gels with 5, 7, or 10% protein and 2% NaCl were prepared from pork, beef, fish, chicken and turkey muscles using a heating rate of 0.7°C/min and pH 6.0 to compare the thermal gelation properties of myofibrillar protein from different species. The force required to rupture gel (Pf), force required to move plunger through gel (Fp), viscosity index (Ni), and elasticity (Ea) increased and cooking loss decreased with increasing protein contents. Myofibrils of chicken breast and thigh had lower and fish and turkey thigh had higher cooking loss at protein contents of 7% or 10%.     

SUITABILITY OF THE WARNER-BRATZLER SHEAR FOR TEXTURAL MEASUREMENTS OF FISH PROTEIN GELS

Protein gels were prepared without added NaCl, from the minced, washed, dewatered flesh of red hake and flounder. Similar gels were prepared from red hake with added NaCl. Gel strength was measured by means of the Warner-Bratzler shear, Fold Test, and Instron UTM. Flounder gels had the highest moduli of deformability values while red hake (with NaCl) had the lowest. Instron percent recovery values were inversely related to these results. The red hake (with NaCl) gel was the most elastic (greatest percent recovery) and the flounder gel was the least elastic. The highest Warner-Bratzler shear force values were recorded for flounder gels while the lowest were recorded for red hake (with NaCl) gels. Fold Test scores were 4.6 – 4.7) for both red hake gels, and low (2.7) for flounder gels. The Warner-Bratzler shear was very highly correlated with Instron deformability measurements and highly correlated with percent recovery. It was not significantly correlated with Fold Test scores. Fold Test scores correlated very highly with both Instron values.     

Effects of adding fish gelatin on Alaska pollock surimi gels

Fish gelatin is a food additive obtained after hydrolysis of collagen from fish skin. The importance of fish gelatin as a food additive is increasing due to its increased commercial availability. Surimi is washed minced fish meat used as the raw material for seafood analogs like crabmeat substitutes. The most important attributes of surimi are gelling and whiteness. The objective of this work was to determine the effect of using fish gelatin as an additive in surimi to improve the mechanical and functional properties of gels. Surimi gels were prepared by mixing grade A or FA surimi (Alaska pollock) with salt (20 g/kg w/w) and commercial fish gelatin at 0 (control), 5, 7.5, 10, or 15 g/kg (w/w) previously dissolved in water (200 mL/kg surimi). The solubilized paste was incubated at 40 °C for 30 min followed by cooking at 90 °C for 15 min. Changes in mechanical properties (torsion test), a functional property (expressible water content) and color attributes of surimi gels were measured. Grade FA surimi gels containing 7.5–15 g/kg of fish gelatin showed an improved expressible moisture. However, gelatin added at 15 g/kg showed a disruptive effect detrimental to the mechanical properties. Color parameters were modified slightly. Whiteness attribute as affected by increasing the fish gelatin was instrumentally detected but not observed by sensory panelists. Gelatin did not change the overall color attributes and all gels remained in the grayish region. These results indicated that fish gelatin did not have an advantage for using as a functional additive in Alaska pollock surimi grades A or FA. However, it can be used at up to 10 g/kg without a negative effect on the mechanical properties.     

Ultrastructural and rheological changes during the gelation of giant squid (Dosidicus gigas) muscle

The giant squid or dosidicus (Dosidicus gigas) is normally shipped frozen from the coasts of America. During the period prior to freezing-when conditions are not always optimum-and during frozen storage, the functional capacity of the muscle proteins declines, rendering the material useless for certain processes such as conversion to gel. This paper examines the reasons for the lack of a good gel-forming capacity as measured both rheologically (breaking force, breaking deformation and gel strength) and in terms of ultrastructure (scanning microscopy). The study was carried out at four different temperatures known to be critical for fish muscle protein gel formation, and at two salt concentrations. At 35°C the structure was spongier in gels made with 1.5% NaCl, although a true gel was still not formed, as shown by rheological measurements. Above 30°C, the ultrastructure became more cellular, particularly in samples made with 2.5% NaCl, at which concentration gel strength values were higher. However, at neither salt concentration nor at any of the experimental temperatures was the mesh as spongy as in other fish gels reported in the literature. The values of rheological analysis and folding test were correspondingly low.