pH Induced Aggregation and Weak Gel Formation of Whey Protein Polymers

Whey protein polymers were formed by heating (80 °C) a 4% (w/v) whey protein (WP) isolate dispersion at pH 8.0 for 15, 25, 35, 45, or 53 min. Dispersions were adjusted to pH 6.0, 6.5, 7.0, 7.5, or 8.0 after heating and the rheological properties were determined. Viscosity increased with increased heating time and decreased pH. At pH 7.0 and 7.5, high-viscosity dispersions with pseudoplastic and thixotropic flow behavior were formed, while weak gels were formed at pH 6.0 and 6.5. The storage (elastic) and loss (viscous) moduli of pH-induced gels increased when temperature was increased from 7 °C to 25 °C, suggesting that hydrophobic forces are responsible for gelation. Key Words: weak-gels, whey proteins, polymers, gelation, functionality     

Effect of protein concentration, pH, lactose content and pasteurization on thermal gelation of acid caprine whey protein concentrates

The influence of pH (4.5-6.5), sodium chloride content (125-375 mM), calcium chloride content (10-30 mM), protein concentration (70-90 g/l) and lactose content on the gel hardness of goat whey protein concentrate (GWPC) in relation to the origin of the acid whey (raw or pasteurized milk) was studied using a factorial design. Gels were obtained after heat treatment (90 degrees C, 30 min). Gel hardness was measured using texture analyser. Only protein concentration and pH were found to have a statistically significant effect on the gel hardness. An increase in the protein concentration resulted in an increase in the gel hardness. GWPC containing 800g/kg protein formed gels with a hardness maximum at the pHi, whereas GWPC containing 300 g/kg protein did not form true gels. Whey from pasteurized milk formed softer gels than whey from raw milk. A high lactose content (approximately 360 g/kg) also reduced the gelation performance of GWPC.     

Effects of milk heat treatment and solvent composition on physicochemical and selected functional characteristics of milk protein concentrate

Milk protein concentrate (MPC) powders (～81% protein) were made from skim milk that was heat treated at 72°C for 15 s (LHMPC) or 85°C for 30 s (MHMPC). The MPC powder was manufactured by ultrafiltration and diafiltration of skim milk at 50°C followed by spray drying. The MPC dispersions (4.02% true protein) were prepared by reconstituting the LHMPC and MHMPC powders in distilled water (LHMPC_w and MHMPC_w, respectively) or milk permeate (LHMPC_p and MHMPC_p, respectively). Increasing milk heat treatment increased the level of whey protein denaturation (from ～5 to 47% of total whey protein) and reduced the concentrations of serum protein, serum calcium, and ionic calcium. These changes were paralleled by impaired rennet-induced coagulability of the MHMPC_w and MHMPC_p dispersions and a reduction in the pH of maximum heat stability of MHMPC_p from pH 6.9 to 6.8. For both the LHMPC and MHMPC dispersions, the use of permeate instead of water enhanced ethanol stability at pH 6.6 to 7.0, impaired rennet gelation, and changed the heat coagulation time and pH profile from type A to type B. Increasing the severity of milk heat treatment during MPC manufacture and the use of permeate instead of water led to significant reductions in the viscosity of stirred yogurt prepared by starter-induced acidification of the MPC dispersions. The current study clearly highlights how the functionality of protein dispersions prepared by reconstitution of high-protein MPC powders may be modulated by the heat treatment of the skim milk during manufacture of the MPC and the composition of the solvent used for reconstitution.     

Influence of milk pre-heating conditions on casein–whey protein interactions and skim milk concentrate viscosity

The viscosity of concentrates (50–55% total solids) prepared from skim milk heated (5 min at 80 or 90 °C) at pH 6.5 and 6.7 was examined. The extent of heat-induced whey protein denaturation increased with increasing temperature and pH. More denatured whey protein and κ-casein were found in the serum phase of milk heated at higher pH. The viscosity of milk concentrates increased considerably with increasing pH at concentration and increasing heating temperature, whereas the distribution of denatured whey proteins and κ-casein between the serum and micellar phase only marginally influenced concentrate viscosity. Skim milk concentrate viscosity thus appears to be governed primarily by volume fraction and interactions of particles, which are governed primarily by concentration factor, the extent of whey protein denaturation and pH. Control and optimization of these factors can facilitate control over skim milk concentrate viscosity and energy efficiency in spray-drying.     

Mixtures of whey protein microgels and soluble aggregates as building blocks to control rheology and structure of acid induced cold-set gels

Whey proteins (WP) today offer an extremely high potential for innovative development of functional and nutritious food products. Acid cold-set gels present an interesting approach of gelation at low temperature upon acidification of preformed whey protein (WP) aggregates. In the present work, we aimed to demonstrate how structure and rheological properties of acid gels can be controlled by combining two types of WP aggregates with different structural and chemical properties. Whey protein microgels (WPM) and soluble aggregates (WPSA) were generated upon heating WP isolate in specific pH conditions and temperature, leading to Z-average hydrodynamic diameters close to 270 nm for WPM and 100 nm for WPSA. Mixtures of WPM and WPSA were prepared at different weight ratios ranging from 100% WPM to 100% WPSA. The total protein concentration was set to 4 or 8%wt. Acidification was performed at 40 °C by addition of 1%wt glucono-δ-lactone (GDL). Gelation was followed using turbidimetry and small deformation rheology as function of pH. Microstructures of the gel were investigated at different length scales using various microscopy techniques (CLSM, SEM, AFM). When the WPM/WPSA ratio decreased, the pH of gelation and the gel strength increased because of the different structure and chemical reactivity of the two types of WP aggregates. The final pH had a strong impact on the structure of the gels. When final pH decreased below pH 4.3, a structure change was suggested by turbidimetry measurements. This resulted in a non self-supporting gel or in a decrease of gel strength. For pH above 4.3, self supporting gel were obtained. The rheological properties of the gel could therefore be modulated depending on the properties of the building blocks used (WPM versus WPSA). Interestingly, the gel microstructures observed for WPM/WPSA mixtures or WPM were comparable to those of acidified skimmed milk gels ranging from coarse structures with clumps of aggregates or to homogeneous fine networks (WPSA only) that have been described for WP gels obtained upon direct heating at various pH.     

Rheological properties of milk gels formed by a combination of rennet and glucono-delta-lactone

The effects of heat treatment of milk, and a range of rennet and glucono-delta-lactone (GDL) concentrations on the rheological properties, at small and large deformation, of milk gels were investigated. Gels were made from reconstituted skim milk at 30 degrees C, with two levels each of rennet and GDL. Together with controls this gave a total of sixteen gelation conditions, eight for unheated and eight for heated milk. Acid gels made from unheated milks had low storage moduli (G') of < 20 Pa. Heating milks at 80 degrees C for 30 min resulted in a large increase in the G' value of acid gels. Rennet-induced gels made from unheated milk had G' values in the range approximately 80-190 Pa. However, heat treatment severely impaired rennet coagulation: no gel was formed at low rennet levels and only a very weak gel was formed at high levels. In gels made with a combination of rennet and GDL unusual rheological behaviour was observed. After gelation, G' initially increased rapidly but then remained steady or even decreased, and at long ageing times G' values increased moderately or remained low. The loss tangent (tan delta) of acid gels made from heated milk increased after gelation to attain a maximum at pH approximately 5.1 but no maximum was observed in gels made from unheated milk. Gels made by a combination of rennet and GDL also exhibited a maximum in tan delta, indicating increased relaxation behaviour of the protein-protein bonds. We suggest that this maximum in tan delta was caused by a loosening of the intermolecular forces in casein particles caused by solubilization of colloidal calcium phosphate. We also suggest that in combination gels made from unheated milk a low value for the fracture stress and a high tan delta during gelation indicated an increased susceptibility of the network to excessive large scale rearrangements. In contrast. combination gels made from heated milk formed firmer gels crosslinked by denatured whey proteins and underwent fewer large scale rearrangements.     

Influence of skimmed milk concentrate replacement by dry dairy products in a low fat set‐type yoghurt model system. I: Use of whey protein concentrates,milk protein concentrates and skimmed milk powder

Ten commercial samples of dry dairy products used for protein fortification in a low fat yoghurt model system at industrial scale were studied. The products employed were whey protein concentratres, milk protein concentrates, skimmed milk concentrates and skimmed milk powder which originated from different countries. The gross chemical composition of these dried products were determined, including polyacrylamide gel electrophoresis (SDS‐PAGE) and isoelectric focusing of the proteins, and minerals such as Na, Ca, K and Mg. Yoghurts were formulated using a skim milk concentrated as a milk base enriched with different dry dairy products up to a 43 g kg⁻¹ protein content. Replacement percentage of skim milk concentrated by dry dairy products in the mix was between 1.49 and 3.77%. Yoghurts enriched with milk protein concentrates did not show significantly different viscosity (35.12 Pa s) and syneresis index (591.4 g kg⁻¹) than the two control yoghurts obtained only from skimmed milk concentrates (35.6 Pa s and 565.7 g kg⁻¹) and skimmed milk powder (32.77 Pa s and 551.5 g kg⁻¹), respectively. Yoghurt fortified with the whey protein concentrates, however, was less firm (22.59 Pa s) and had less syneresis index (216 g kg⁻¹) than control yoghurts. Therefore, whey protein concentrates may be useful for drinking yoghurt production. © 1999 Society of Chemical Industry     

Influence of heat treatment of goat milk on casein micelle size,rheological and textural properties of acid gels and set type yoghurts

Acid gels and yoghurts were made from goat milk that was heated at 72°C/30 s, 85°C/5 min, and 95°C/5 min, followed by acidification with starter culture at 43C until pH 4.6. The rheological and textural properties of acid gels and yoghurts were analyzed using dynamic low amplitude oscillatory rheology and back extrusion texture analysis, respectively. The effect of goat milk heat treatment on the mean casein micelle diameter and protein profile was also determined by dynamic light scattering and SDS PAGE electrophoresis, respectively. The shortest gelation and fermentation time was recorded for yoghurt prepared from milk heated at 85°C/5 min. Also, the pH of gelation, the storage moduli (G′) and yield stress were higher for this yoghurt, compared with the other two. Textural properties of goat milk yoghurts such as firmness and consistency were strongly affected by milk heat treatment, and the highest values were recorded for yoghurt produced from milk preheated at 85°C/5 min, as well. The largest casein micelles were measured after 85°C/5 min treatment and their size decreased at higher temperature, despite higher denaturation of whey proteins at the most intense heat regime, indicating the structure changes that influence on the acid gelation.     

Rheological properties of acid gels prepared from heated milk fortified with whey protein mixtures containing the A,B and C variants of β-lactoglobulin

The effect of fortification of reconstituted skim milk with different levels of a whey protein mixture containing a 1:2 ratio of α-lactalbumin (α-la) and different genetic variants of β-lactoglobulin (β-LG) on the rheological properties of acid milk gels, formed by acidification with glucono-δ-lactone, was investigated. Milk samples were either unheated or heated at 80°C for 30 min before acidification. Acid gels prepared from unheated skim milk had very low G′ values, long gelation times and low gelation pH. Samples prepared from heated milk had markedly higher G′ values, a reduced gelation time and an increased gelation pH. The addition of increasing levels of whey protein mixtures containing β-LG B or β-LG C to the milk prior to heating and acidification caused an almost linear increase in the G′. In contrast, whey protein mixtures containing β-LG A caused a progressive increase in the G′ with added protein levels up to about 0.7% (w/w) but little further change at higher addition levels. A mixture of the A and B variants of β-LG gave an intermediate behaviour between those of the A and B variants. In all samples, the G′ value at 5°C was approximately twice that at 30°C so that the relative differences as a result of the β-LG genetic variants were similar for the two temperatures.     

Formation of soluble protein complexes and yoghurt properties influenced by the addition of whey protein concentrate

The effects of whey protein concentrate (WPC) on the formation of soluble protein complexes and yoghurt texture were evaluated. Skim milk (SM) and skim milk enriched with 1% WPC (SM + 1%WPC) or 2% WPC (SM + 2%WPC) were left unheated or heated and then made into yoghurt gels. Yoghurt prepared from heated SM + 2%WPC had significantly higher storage modulus, water holding capacity and firmness values and a denser microstructure than those prepared only from skim milk. Electrophoretic analysis of the milk showed that the level of β-lactoglobulin and κ-casein in the serum phase increased with increasing WPC concentration, indicating that the content of disulfide-linked β-lactoglobulin and κ-casein was higher in SM + 2%WPC than in SM, suggesting that more soluble protein complexes had been formed. Consequently, yoghurt prepared from heated SM enriched with WPC may have more bonds and more protein complexes in the protein network than yoghurt prepared only from SM, thus resulting in firmer gels.Practical applicationsYoghurt, one of the most popular fermented milk products, is of high economic importance to the dairy industry worldwide. In particular, high-protein yoghurt, such as Greek-style or set-type yoghurt, has been driving its ongoing popularity over recent years. In current industrial production of high-protein yoghurt, protein fortification and heat treatment of milk are two of the most important processing parameters affecting yoghurt texture. Whey protein concentrate has been added to milk to reduce whey separation and to increase the firmness of the yoghurt. From a technological point of view, the interaction of the denatured whey proteins with casein micelles or with κ-casein in the serum phases is regarded as responsible for obtaining a good yoghurt structure. The present research has shown that it is possible to produce yoghurt with a range of textural properties by precisely controlling the rate of whey protein fortification during its manufacture. Therefore, this study provides a better understanding of the effect of WPC fortification and aims to extend this insight for the production of good-quality yoghurt.     

Compositional and functional properties of buttermilk: a comparison between sweet, sour, and whey buttermilk

Buttermilk is a dairy ingredient widely used in the food industry because of its emulsifying capacity and its positive impact on flavor. Commercial buttermilk is sweet buttermilk, a by-product from churning sweet cream into butter. However, other sources of buttermilk exist, including cultured and whey buttermilk obtained from churning of cultured cream and whey cream, respectively. The compositional and functional properties (protein solubility, viscosity, emulsifying and foaming properties) of sweet, sour, and whey buttermilk were determined at different pH levels and compared with those of skim milk and whey. Composition of sweet and cultured buttermilk was similar to skim milk, and composition of whey buttermilk was similar to whey, with the exception of fat content, which was higher in buttermilk than in skim milk or whey (6 to 20% vs. 0.3 to 0.4%). Functional properties of whey buttermilk were independent of pH, whereas sweet and cultured buttermilk exhibited lower protein solubility and emulsifying properties as well as a higher viscosity at low pH (pH ≤ 5). Sweet, sour, and whey buttermilks showed higher emulsifying properties and lower foaming capacity than milk and whey because of the presence of milk fat globule membrane components. Furthermore, among the various buttermilks, whey buttermilk was the one showing the highest emulsifying properties and the lowest foaming capacity. This could be due to a higher ratio of phospholipids to protein in whey buttermilk compared with cultured or sweet buttermilk. Whey buttermilk appears to be a promising and unique ingredient in the formulation of low pH foods.     

Acid gelation properties of fibrillated model milk protein concentrate dispersions

Whey proteins in milk are globular proteins that can be converted into fibrils to enhance functional properties such gelation, emulsification, and foaming. A model fibrillated milk protein concentrate (MPC) was developed by mixing micellar casein concentrate (MCC) with fibrillated milk whey proteins. Similarly, a control model MPC was obtained by mixing MCC with milk whey proteins. The resulting fibrillated model MPC and control model MPC contained 5% protein and a ratio of casein to whey proteins similar to milk. The objective of the current study was to understand the rheological characteristics of fibrillated and control model MPC during acid gelation, using Förster resonance energy transfer (FRET) to assess small amplitude oscillation and casein–whey protein interaction. The results from the FRET index images showed greater interactions between caseins and whey proteins in fibrillated model MPC compared with the moderate and uniform interactions in control model MPC gels. Rheological study showed that the maximum storage modulus of acid gel of fibrillated model MPC was 546.9 ± 15.5 Pa, which was significantly higher than acid gel made from control model MPC (336.9 ± 11.3 Pa), indicating that fibrillated model MPC produced a firmer gel. Therefore, it can be concluded that acid gel produced from fibrillated model MPC was stronger than control model MPC. Selective fibrillation of the whey protein fraction in MPC can be used to improve gelation characteristics of acid gel type products.     

Incorporating whey proteins into mozzarella cheese

A study was conducted to improve the yield of cheese and make reduced fat cheese by incorporating whey proteins. Whey protein dispersions were prepared by heating whey at 95°C and pH 4.6, then removing excess serum and homogenizing part of the whey protein. Cheeses were made from standardized milk and standardized milk with homogenized and non-homogenized protein dispersions. Cheeses were also made from standardized milk, reduced fat milk and reduced fat milk with homogenized protein. Adding whey proteins improved the yield, but lowered the retention of fat. Homogenization of whey proteins improved fat retention and yield. The dry matter increase was due to increased solids-non-fat. Reduced fat cheese gave lower yields, which were partially offset by adding homogenized whey proteins. Physical and sensory properties of reduced fat cheeses made with homogenized whey proteins were similar to the control.     

Utilizing whey protein isolate and polysaccharide complexes to stabilize aerated dairy gels

Heated soluble complexes of whey protein isolate (WPI) with polysaccharides may be used to modify the properties of aerated dairy gels, which could be formulated into novel-textured high-protein desserts. The objective of this study was to determine the effect of polysaccharide charge density and concentration within a WPI-polysaccharide complex on the physical properties of aerated gels. Three polysaccharides having different degrees of charge density were chosen: low-methoxyl pectin, high-methoxyl type D pectin, and guar gum. Heated complexes were prepared by heating the mixed dispersions (8% protein, 0 to 1% polysaccharide) at pH 7. To form aerated gels, 2% glucono-δ-lactone was added to the dispersions of skim milk powder and heated complex and foam was generated by whipping with a handheld frother. The foam set into a gel as the glucono-δ-lactone acidified to a final pH of 4.5. The aerated gels were evaluated for overrun, drainage, gel strength, and viscoelastic properties. Without heated complexes, stable aerated gels could not be formed. Overrun of aerated gel decreased (up to 73%) as polysaccharide concentration increased from 0.105 to 0.315% due to increased viscosity, which limited air incorporation. A negative relationship was found between percent drainage and dispersion viscosity. However, plotting of drainage against dispersion viscosity separated by polysaccharide type revealed that drainage decreased most in samples with high-charge-density, low-methoxyl pectin followed by those with low-charge-density, high-methoxyl type D pectin. Aerated gels with guar gum (no charge) did not show improvement to stability. Rheological results showed no significant difference in gelation time among samples; therefore, stronger interactions between WPI and high-charge-density polysaccharide were likely responsible for increased stability. Stable dairy aerated gels can be created from WPI-polysaccharide complexes. High-charge-density polysaccharides, at concentrations that provide adequate viscosity, are needed to achieve stability while also maintaining dispersion overrun capabilities.     

Manufacture of acid gels from skim milk using high-pressure homogenization

The effect of high-pressure homogenization (HPH) alone or in combination with a thermal treatment (TT) was investigated for the manufacture of acid gels from skim milk. Raw skim milk was subjected to HPH (0 to 350 MPa) or a TT (90°C, 5 min), or both, in the following processing combinations: 1) HPH, 2) HPH followed by TT, 3) TT followed by HPH, 4) TT, and 5) raw milk (control). After treatments, L* (lightness) values were measured, and then skim milk was acidified with 3% glucono-δ-lactone and rheological properties (G′ and gelation time), and whey holding capacity was evaluated. Treatments in which HPH and TT were combined showed greater L* values than those in which just HPH was applied. In all treatments, the L* values decreased as the pressure was increased up to 300 MPa with little change afterward. Gelation times were lower when HPH was combined with TT compared with the acid skim milk gels that were just pressure treated. The final G′ in gels obtained from skim milk subjected to the combined process (HPH and TT) was greater and pressure-dependent compared with all other gels. A maximum G′ (∼320 Pa) was observed with skim milk subjected to a combination of thermal processing before or after HPH at 350 MPa. Acid gels obtained from HPH milk at 350 MPa showed a linear decrease in whey holding capacity over time, retaining 20% more whey after centrifugation for 25 min compared with samples treated at lower pressures and all other treatments. Our results suggest that HPH in combination with TT can be used to improve the rheological properties and stability of yogurt, thus decreasing the need for additives.     

Effect of pH adjustment at heating on the rheological properties of acid skim milk gels with added potato starch

The rheological properties of acid skim milk gels, prepared from milk with added potato starch and pH adjusted (pH 6.5–7.1) prior to heat treatment and acidification, were investigated. The storage modulus, G′, of the final acid gels was increased by heating the milk at higher pH and further increased by adding starch. The effect of pH at heating and addition of starch appeared to be additive and independent of each other up to a starch addition level of 1%. Above this starch level, the pH at heating had a lesser effect. This may have been due to the increased viscosity of the aqueous phase as a result of starch gelatinization or to direct contributions of the starch to the gel network structure. Confocal microscopy showed that milk proteins developed fewer but broader protein clusters at higher pH than at lower pH. Starch addition resulted in an increased density of the protein network.     

Rheological properties of rennet gels containing milk protein concentrates

Different milk protein concentrates (MPC), with protein concentrations of 56, 70, and 90%, were dispersed in water under different treatments (hydration, shear, heat, and overnight storage at 4°C), as well as in a combination of all the treatments in a factorial design. The particle size distribution of the dispersions was then measured to determine the optimal conditions for the dispersion. Heating at 60°C for 30 min with 5 min of shear was chosen as the best condition to dissolve MPC powders. The samples were also characterized for composition, presence of protein aggregates, and ratio of calcium to protein. The total calcium present in MPC increased with increasing concentration of protein; however, the total calcium-to-protein ratio was lower in MPC90 than in MPC56 and MPC70. The level of whey protein denaturation, the presence of κ-casein-whey protein aggregates in the supernatant after centrifugation, and the amount of caseins dissociated from the micelle increased as the protein concentration in the powder increased. The total amount of casein macropeptide released was lower in samples from powders with a higher protein concentration than for MPC56 or the skim milk control. The gelation behavior of reconstituted MPC was tested in systems dispersed in water (5% protein) as well as in systems dispersed in skim milk (6% protein). The gelation time of MPC dispersions was considerably lower and the gel modulus was higher than those of reconstituted skim milk with the same protein concentration. When MPC dispersions were dialyzed against skim milk, a significant decrease in the gelation time and modulus were shown, with a complete loss of gelling functionality in MPC90 dispersed in water. This demonstrated that the ionic equilibrium was key to the functionality of MPC.     

Gelation of casein-whey mixtures: effects of heating whey proteins alone or in the presence of casein micelles.

The aim of the present work was to investigate the role of whey protein denaturation on the acid induced gelation of casein. This was studied by determining the effect of whey protein denaturation both in the presence and absence of casein micelles. The study showed that milk gelation kinetics and gel properties are greatly influenced by the heat treatment sequence. When the whey proteins are denatured separately and subsequently added to casein micelles, acid-induced gelation occurs more rapidly and leads to gels with a more particulated microstructure than gels made from co-heated systems. The gels resulting from heat-treatment of a mixture of pre-denatured whey protein with casein micelles are heterogeneous in nature due to particulates formed from casein micelles which are complexed with denatured whey proteins and also from separate whey protein aggregates. Whey proteins thus offer an opportunity not only to control casein gelation but also to control the level of syneresis, which can occur.     

Effects of added whey protein aggregates on textural and microstructural properties of acidified milk model systems

Non-fat milk model systems containing 5% total protein were investigated with addition of micro- or nanoparticulated whey protein at two levels of casein (2.5% and 3.5%, w/w). The systems were subjected to homogenisation (20 MPa), heat treatment (90 °C for 5 min) and chemical (glucono-delta-lactone) acidification to pH 4.6 and characterised in terms of denaturation degree of whey protein, particle size, textural properties, rheology and microstructure. The model systems with nanoparticulated whey protein exhibited significant larger particle size after heating and provided acid gels with higher firmness and viscosity, faster gelation and lower syneresis and a denser microstructure. In contrast, microparticulated whey protein appeared to only weakly interact with other proteins present and resulted in a protein network with low connectivity in the resulting gels. Increasing the casein/whey protein ratio did not decrease the gel strength in the acidified milk model systems with added whey protein aggregates.     

Small and large deformation rheology and microstructure of κ-carrageenan gels containing commercial milk protein products

The rheological behaviour of commercial milk protein/κ-carrageenan mixtures in aqueous solutions was studied at neutral pH. Four milk protein ingredients; skim milk powder, milk protein concentrate, sodium caseinate, and whey protein isolate were considered. As seen by confocal laser microscopy, mixtures of κ-carrageenan with skim milk powder, milk protein concentrate, and sodium caseinate showed phase separation, but no phase separation was observed in mixtures containing whey protein isolate. For κ-carrageenan concentrations up to 0.5 wt%, the viscosity of the mixtures at low shear rates increased markedly in the case of skim milk powder and milk protein concentrate addition, but did not change by the addition of sodium caseinate or whey protein isolate. For κ-carrageenan concentrations from 1 to 2.5 wt%, small and large deformation rheological measurements, performed on the milk protein/κ-carrageenan gels, showed that skim milk powder, milk protein concentrate or sodium caseinate markedly improved the strength of the resulting gels, but whey protein isolate had no effect on the gel stength.