Rheological Properties of Mozzarella Cheese Filled with Dairy, Egg, Soy Proteins, and Gelatin

The Rheological behavior of mozzarella cheese filled with various proteins (whey protein, caseinate, egg white, soy protein isolate, gelatin) incorporated was determined by uniaxial compression at 10°C and the effect of temperature (10°C?60°C) by dynamic measurement. Mozzarella cheese with whey protein, caseinate, egg white, and soy protein isolate showed significant water retention during heating. Among the proteins, soy protein isolate induced the strongest gel network structure with mozzarella cheese. All proteins altered the viscoelastic properties of mozzarella cheese.     

Effect of soy protein isolate on gel properties of Alaska pollock and common carp surimi at different setting conditions

The effects of soy protein isolate (SPI) on the gel properties of different grade Alaska pollock and common carp surimi at different setting conditions were evaluated and compared. Breaking force and distance of gels decreased with increasing SPI concentrations in direct cook (85 °C for 30 min) and in cook after setting at 30 °C for 60 min conditions. The effect of SPI on gel strength of common carp surimi was less than in Alaska pollock surimi. The breaking force obtained for addition of 10% SPI to Alaska pollock surimi was higher than for surimi alone when cooked after incubation at 50 °C for 60 min. Addition of SPI decreased the whiteness and increased the yellowness of the gel. The gel structure showed that the addition of SPI modified the microstructure of the fish protein gel, thus resulting in surimi with different gelling properties. Copyright © 2004 Society of Chemical Industry     

Gel‐forming ability of surimi from grass carp (Ctenopharyngodon idellus): influence of heat treatment and soy protein isolate

The effects of setting conditions and soy protein isolate (SPI) on textural properties of surimi produced from grass carp were investigated. Effects of setting temperature, setting time and protein concentration on the breaking force and distance were evaluated and compared utilizing response surface methodology. Models for breaking force and breaking distance of grass carp surimi were established. Protein concentration was the major factor affecting the gel strength of grass carp surimi. Breaking force and distance of grass carp surimi gels decreased with increase of protein ratio from SPI at 30 °C and 40 °C for 60 min setting and heating at 85 °C for 30 min, but the breaking force obtained for addition of 100 g kg^?1 SPI protein to grass carp surimi was higher than that for surimi alone at 60 °C for 60 min incubation and heating at 85 °C for 30 min. Copyright © 2005 Society of Chemical Industry     

Interactions and gel strength of mixed myofibrillar with soy protein, 7S globulin and enzyme-hydrolyzed soy proteins

The mixed protein gels were prepared adding soy protein isolate (SPI), 7S globulin, enzyme-hydrolyzed soy proteins, 10- to 100-kDa ultrafiltration fraction and 0.5- to 10-kDa ultrafiltration fraction to myofibril protein isolate (MPI) gels, and five chemical interactions namely nonspecific associations, ionic bonds, hydrogen bonds, hydrophobic interactions and disulfide bonds in these gels were investigated by means of determining gel solubility within 20–75 °C. Furthermore, correlations between gel strength and different chemical interactions were evaluated statistically by Pearson’s correlation test. The gels with 0.5- to 10-kDa fraction presented the biggest gel strength below 60 °C, and the gels with SPI had better gel strength above 65 °C. At different endpoint temperatures, nonspecific associations decreased in order of MPI mixed with 0.5- to 10-kDa fraction, 10- to 100-kDa fraction, enzyme-hydrolyzed soy proteins, 7S globulin and SPI. Gels with ultrafiltration fractions had higher ionic bonds. Hydrogen bonds fluctuated in small scale below 55 °C and reduced at higher temperature. Hydrophobic interactions increased to maximum before decreasing slowly as the temperature went on. In short, both hydrophobic interactions and ionic bonds had significantly positive correlation with gel strength for mixed gels with enzyme-hydrolyzed soy proteins, whereas for the other four mixed gels, it was hydrophobic interactions and nonspecific associations.     

Preparation of Cooked Egg White, Egg Yolk, and Whole Egg Gels for Scanning Electron Microscopy

Cooked egg white, egg yolk, and whole egg gels, fixed with glutaraldehyde or unfixed, were frozen at - 35°C or at - 95°C and freeze-dried. Alternatively, unfrozen gels fixed with glutaraldehyde, os-mium-thiocarbohydrazide-osmium, or osmium-tannic acid-uranyl acetate were dehydrated in ethanol and critical point-dried from carbon dioxide. Egg yolk and whole egg gels were defatted. Freeze-dried and critical point-dried gels were examined by scanning electron microscopy. Freezing and freeze-drying introduced artifacts due to ice crystal damage, with egg white gels distorted most, and egg yolk gels distorted least. Gels fixed only by glutaraldehyde shrank by 50% during critical point drying. Further fixation by osmium tetroxide and uranyl acetate stabilized gels against shrinkage. Removal of fat from egg yolk and whole egg was essential for observation of protein matrices.     

Effect of soy protein substitution for sodium caseinate on the transglutaminate-induced cold and thermal gelation of myofibrillar protein

The influence of soy protein isolate (SPI) substitution for sodium caseinate (SC) on the properties of cold-set (4 °C) and heat-induced gels of pork myofibrillar protein (MP) incubated with microbial transglutaminase (TG) was investigated. The strength of cold-set MP–SC gels (formed in 0.45 M, NaCl, 50 mM phosphate buffer, pH 6.25) increased with time of TG incubation, but those gels with more than 66% SPI substituted for SC had a >26% reduced strength (P < 0.05). Upon cooking, both incubated and non-incubated protein sols were quickly transformed into highly elastic gels, showing up to 6000 Pa in storage modulus (G′) at the final temperature (72 °C). However, no differences (P < 0.05) in G′ were observed between heated samples with SPI and SC. Myosin heavy chain, casein and soy proteins gradually disappeared with TG incubation, contributing to MP gel network formation. Both cold-set and heat-induced gels had a compact protein matrix, attributable to protein cross-linking by TG.     

Using modified soy protein to enhance foaming of egg white protein

BACKGROUND: It is well known that the foaming properties of egg white protein are significantly reduced when a small amount of yolk is mixed in the white. To improve foaming properties of yolk‐contaminated egg white protein, soy protein isolate (SPI) and egg proteins were modified to make basic proteins, and effects of these modified proteins on egg white foaming were evaluated in a model and an angel cake system. RESULTS: SPI and egg yolk proteins were modified to have an isoelectric point of 10, and sonication was used to increase protein dispersibility after the ethyl esterification reaction. However, only the addition of sonicated and modified SPI (SMSPI) showed improvement of foaming in the 5% egg protein model system with 0.4% yolk addition. SMSPI was then used in making angel food cake to examine whether the cake performance reduction due to yolk contamination of the white would be restored by such alkaline protein. Cake performance was improved when cream of tartar was used together with SMSPI. CONCLUSION: Basic soy protein can be made and used to improve egg white foaming properties and cake performance. Copyright © 2012 Society of Chemical Industry     

On the temperature reversibility of the viscoelasticity of acid-induced sodium caseinate emulsion gels

Viscoelastic properties of acid-induced sodium caseinate emulsion gels have been investigated using a controlled shear stress rheometer. Gelation was introduced by addition of acidulant glucono-δ-lactone (GDL) at three different temperatures (5, 25 and 45°C). It was found that the gelation temperature has a significant effect on the rate of gelation and on the dynamic moduli of the emulsion gels. The rheology of these emulsion gels was investigated over the temperature range 5–45°C. The viscoelasticity of the emulsion gel prepared at 45°C was temperature reversible, suggesting that the temperature change only affects the strength of physical bonding within the network and not the gel microstructure. In contrast, the temperature-dependent viscoelasticity of the emulsion gel prepared at 5°C exhibited a highly irreversible character. This implies significant structural reorganization of the network during the heating stage from 5°C. Analogous temperature irreversibility has been observed in emulsion electrophoretic mobility measurements and in solution surface tension measurements of the corresponding caseinate systems at pH values near the isoelectric point of the protein.     

Physical Properties of Mixed Dairy Food Proteins

Foods may contain more than one type of protein, and food formulators sometimes combine different proteins for desired synergistic textural benefits. Egg albumin, fish protein isolate, or soy protein isolate were blended with calcium caseinate or whey protein isolate and mixed in water adjusted to pH 2.5, 6.8, and 9.0 at 25 or 60°C. The effect of pH and temperature on solubility, viscosity, and the structure of the resulting gels were determined. The viscosity at the most soluble concentration at 25°C were: egg albumin (175.2 mPa.s/35 wt%), fish protein isolate (2207.4 mPa.s/30 wt%), soy protein isolate (2531.5 mPa.s/10 wt%), calcium caseinate (1115.8 mPa.s/15 wt%), and whey protein isolate (161.2 mPa.s/35%). In mixed protein systems viscosity values were reduced. The values for calcium caseinate or whey protein isolate with egg albumin, at the protein level of 15 g/100 g were: calcium caseinate/egg albumin (10:5 wt%) 535.1 mPa.s and whey protein isolate/egg albumin (10:5 wt%) 8.7 mPa.s. Microscopy imaging revealed changes in protein aggregation clusters during heating of calcium caseinate, egg albumin, and whey protein isolate. Egg albumin acted synergistically to increase viscosity, while fish protein isolate acted antagonistically to reduce viscosity. This knowledge is useful to manufacturers who may seek to enhance food texture by blending different proteins.     

Ability of various proteins to form thermostable gels with propylene glycol alginate

Propylene glycol alginate forms gels with proteins in alkaline conditions (pH 9.3 to 10.5). The ability of gelatin, casein, soya isolate, whey protein concentrate, egg albumin and bovine serum albumin to form ‘protein-alginate’ gels was investigated. Conditions were varied so as to alter the structures of the protein and observe the effect on gel formation. These conditions include changing pH, heat, the action of nitrous acid, SDS, mercaptoethanol, hydrogen bond breakers and changing concentration of the protein. The extent of gel formation was indicated by its rigidity modulus. The tertiary structure of the protein appears to be a very important factor in the gel formation. The gels are readily brought down to pH values more suitable for foods, and are stable to heating at 95°C and to freeze-thawing.     

三种添加物对鱼肉猪肉复合凝胶品质的影响

研究了三种外源添加物(大豆蛋白、液体蛋清、转谷氨酰胺酶)对鱼肉猪肉复合凝胶品质的影响。结果表明,添加大豆蛋白和液体蛋清均可提高复合凝胶的破断强度和凝胶强度;添加液体蛋清还可提高复合凝胶的明度L*和白度W,而添加大豆蛋白则会降低明度L*和白度W。添加转谷氨酰胺酶可显著提高复合凝胶的凝胶强度,且鱼肉加盐斩拌后加入转谷氨酰胺酶、再斩拌,然后加入猪肉或者鱼肉、猪肉加盐混合斩拌后再加入转谷氨酰胺酶,两种效果较好。      

Heat-Induced Aggregation of Egg White Proteins as Studied by Vertical Flat-Sheet Polyacrylamide Gel Electrophoresis

Heat-induced aggregation of proteins in egg white was investigated by a vertical flat-sheet polyacrylamide gel electrophoretic method. The fractional and step-wise aggregation of egg white proteins was caused by heating. Even with a heating time of 120 min, ovalbumin and globulins Al and A2 failed to aggregate in egg white (pH 7 and 9) at 70°C, and ovotransferrin and ovomucoid also did not aggregate in egg white at 60°C (pH 9) and 76°C (pH 7 and 9), respectively. The ovoinhibitor was much more unstable than ovomucoid under heat-treatment, and the time dependency of heat-induced aggregation of flavoprotein was greater than those of the other proteins in egg white.     

Interaction of Myosin-Albumin and Myosin-Fibrinogen to Form Protein Gels

Myosin, fibrinogen, albumin, myosin-fibrinogen and myosin-albumin gels were formed by heating in pH 6.0 phosphate buffer at two heating rates. Gel strength was measured with an annular pump and soluble protein was determined. Myosin and fibrinogen interacted to form a gel which was stronger than the sum of the gel strengths for the two individual proteins. The strength of myosin-fibrinogen gels formed at 50°C was not affected by heating method; however, the strength of gels developed between 55°C and 70°C was related to heating method. Myosin and albumin did not interact to form a gel matrix until 80°C where sufficient thermal alteration of albumin had occurred.     

UNIAXIAL COMPRESSION OF GELS MADE FROM PROTEIN AND K-CARRAGEENAN

Investigations of gels (18% total solids) made from pea protein isolates (PPI) or soy protein isolate (SPI) with differing amounts of _K-carrageenan added showed that the gel strength increased with the concentration of _K-carrageenan. When the concentration of_K-carrageenan exceeded 0.4%, gels made with PPI were stronger and more stiff than equivalent gels made with SPI. Addition of _K-carrageenan stabilized gels made with PPI towards variations in brittleness (indicated by strain at fracture) with pH. This was not the case when SPI was used. Preheating (75C, 2 min) suspensions containing protein isolates and _K-carrageenan before gel formation increased the strength and stiffness of the final gels, most pronounced when SPI was used. Addition of NaCl (0.5–2%) reduced strength and stiffness of gels, whereas CaCl₂ had no influence on gel properties. Mixtures of PPI and SPI proved to be weaker and more brittle than gels made from only SPI of PPI. Results indicate that using proteins of different origin can cause differences in gel structure.     

Rheological and microstructural changes in gels made from high and low quality sardine mince with added egg white during frozen storage

 This paper examines the influence of freezing temperature (–40°C or –18°C) and frozen storage temperature (–18°C or –12°C) on gels made from two different sardine minces (M1, high functional quality; M2, low functional quality), with the addition of egg white as a gel enhancing ingredient. To characterize the washed mince, proximate analyses and protein functionality were determined. Freezing at either –40°C or –18°C caused no drastic changes in gel structure. Throughout the course of frozen storage of all samples, a decrease in the water holding capacity (WHC) was detected, along with an increase in the amount of protein soluble in 8 M urea. At 90 days the gels frozen at –40°C exhibited numerous ice micro-crystals; however, they did not affect the external appearance of the gel and had hardly any effect on gel strength, shear strength, hardness, cohesiveness or elasticity. On the other hand, at 90 days the gels frozen at –18°C and stored at either temperature exhibited large, macroscopically visible ice crystals. In these samples, gel strength and shear strength increased while hardness decreased. No definite changes attributable to mince quality were detected during frozen storage. Received: 23 June 1997     

Correlation of the Rheological Behavior of Egg Albumen to Temperature, pH, and NaCl Concentration

Rheological parameters of viscosity, gel strength, and elasticity were determined on heat-set egg albumen gels over various treatment combinations ranging from 65-90°C, pH 6.4-9.6, and NaCl concentrations of 0.0-0.1M added NaCl. Maximum viscosity was measured at a treatment combination of 77.5°C, pH 8.00, and 0.1M NaCl. Elasticity and gel strength were highest in gels with a treatment combination of 85.2°C, pH 9.0, and 0.08M NaCl. Temperature had the greatest effect on all three rheological parameters. Gels heated above 80°C were of unusual character, exhibiting syneresis and shrinkage.     

Effect of non-meat proteins on hydration and textural properties of pork meat gels enhanced with microbial transglutaminase

The combined effect of incorporation of four non-muscle proteins, NMP (blood plasma, BP; sodium caseinate, SC; soy protein isolate, SPI; gelatin, G) at 2 g/100 g levels on hydration and textural characteristics of pork gels processed without or with 0.6 g/100 g microbial transglutaminase preparation (MTG) was investigated. Addition of SC and BP most favourably affected hydration properties and thermal stability, yielding lower cooking loss and expressible moisture for pork gels. Interactions between NMP and MTG were observed. Improvement of gel strength by addition of transglutaminase was observed for treatments containing SC and BP but not G nor soy isolate. Of the four proteins tested SC was found to be a superior substrate for MTG in enhancing textural properties of a gelled meat system. None of the tested ingredients was able to yield gel cohesiveness equivalent to the control containing 8% muscle proteins. Results of this study indicate a potential for using MTG to improve or modify the functional and textural properties of investigated food proteins (SC and BP in particular) in comminuted meat products.     

Protein Components Precipitated from Egg White by Removal of Salt

A precipitate that formed in egg white at low ionic strength affected the transparency of heat-induced gels prepared at pH 2-4 and low ionic strength. The precipitate solubilized with SDS solution containing 2-mercaptoethanol and urea included major proteins of the egg white, as shown by SDS-polyacrylamide gel electrophoresis. The bands of ovalbumin, conalbumin and other protein were smaller when the precipitate was washed with water, but lysozyme and ovomacroglobulin probably remained in the precipitate fraction. It seemed that ovalbumin, conalbumin, and other proteins co-precipitated with these two kinds of proteins. Lysozyme added to the supernatant of egg white after dialysis, did not appear to produce turbidity upon heating at pH 2.5, but whole egg white was converted to a turbid gel upon being heated at this pH.     

Gel Point of Whey and Egg Proteins Using Dynamic Rheological Data

The gel point temperatures of coagulation type proteins and gelation type proteins were determined by extrapolating the rapidly rising phase of the storage modulus G’back to the temperature axis. The gelation onset. temperatures of the concentration-independent proteins oval-bumin, ovotransferrin, and BSA were 81°C, 62°C, and 75°, respectively, Gelation of whey protein isolate and egg white gels, both concentration-dependent, was presumably due to disulfide bonds formed by the interactions of the concentration-independent proteins: α-lac-talbumin and β-lactoglobulin, and ovalbumin and ovotransferrin, respectively. Moreover, the incipient gel temperature of whey proteins decreased when the concentration of whey proteins increased.     

RHEOLOGY OF ACID-INDUCED SODIUM CASEINATE STABILIZED EMULSION GELS

The storage modulus G', loss modulus G", and phase angle δ of acidinduced sodium caseinate emulsion gels were measured at 25C for a certain period of time after the addition of glucono-δ-lactone (GDL). Comparison between pure protein gels and emulsion gels revealed that the presence of emulsion droplets greatly enhanced the gel strength. Acidification by mixing an emulsion with a GDL solution caused immediate gelation but the emulsion gel had similar mechanical properties to the gel formed by direct addition of GDL granules. The viscoelasticity of the gel was strongly related to the pH value of the system. There was no evidence for a three-dimensional network when the pH value was higher than 5.8 or lower than 3.2. The largest storage and loss moduli were observed for gels formed at pH values near the isoelectric point of sodium caseinate (pH 4.6). Rheological differences for gels made at different pH values became distinguishable at low frequencies, where a much smaller phase angle was determined for a gel made at a pH value below the isoelectric point. Partial recovery of the three-dimensional gel network was observed for disrupted gels formed at a pH near the isoelectric point.