The influence of caseins on the rheology of ι-carrageenan gels

Heat-Induced Changes in κ-Carrageenan-Containing Chocolate-Flavoured Milk Protein Concentrate Suspensions under Controlled Shearing

Milk protein dispersions containing added cocoa powder (1.5% (w/w)) and sucrose (7% (w/w)) and varying levels of κ-carrageenan (0.01, 0.03, or 0.05% w/w) were subjected to combined heat treatment (90 °C/5 min or 121 °C/2.6 min) and shear (100 or 1000 s-1) to investigate the heat stability of milk proteins. The application of shear led to a notable reduction in non-sedimentable proteins, resulting in an increase in the average particle size and apparent viscosity of the dispersions, particularly at high concentrations of k-carrageenan and elevated temperatures. This indicates that shear forces induced prominent protein aggregation, especially at higher κ-carrageenan concentrations. This aggregation was primarily attributed to the destabilisation of micelles and presence of loosely bound caseins within the κ-carrageenan network, which exhibited increased susceptibility to aggregation as collision frequencies increased due to shear.

Using the mixture design approach to predict the rheological properties of low-calorie dairy desserts containing gum tragacanth exuded by three Iranian Astragalus species

In this study, the flow behavior and creep parameters of saffron desserts containing gum tragacanth combinations of three species were modeled by the mixture design approach. Flow behavior and creep-recovery experiments were performed and models were predicted for apparent viscosity, consistency index, flow index, instantaneous compliance, and viscoelastic compliance. Five representative samples regarding the range of apparent viscosity at the shear rate of 50 s^-1 were subjected to sensory evaluation. According to rheological measurements, the addition of GT species of A. gossypinus led to the production of a dessert with a strong structure. Then, two samples with the highest consistency index and the lowest creep parameters were compared with two commercial saffron desserts. The results revealed that the overall acceptance of the two selected samples [containing 4% (w/w) A. gossypinus or 2.66% (w/w) A. gossypinus and 1.33% (w/w) A. fluccosus] was similar to those of the two commercial samples.

Characterization of intrinsic material properties of a model lipoproteic emulsion gel by oscillatory and creep compliance rheometry

The effects of varying formulation and processing parameters on rheological properties in a model lipid/protein-based emulsion gel were studied. Heat-set model lipoproteic emulsion gels were prepared with varying levels of protein, lipid, and NaCl contents and high pressure homogenization treatments. Small deformation oscillatory rheometry, creep compliance, and pore size analysis experiments were used to characterize intrinsic structural properties, matrix interactions, and microstructure. Creep compliance behavior of the gel system was successfully modeled by a four-component Burgers model. Shear storage and loss moduli and Newtonian viscosity increased while instantaneous compliance, retarded compliance, and pore size decreased with increasing protein or fat content or homogenization pressure. The data obtained in this study provide information on factors affecting protein network structure and strength, properties may be useful for creating desirable attributes in lipid/protein-based foods with a further optimization process.

PRACTICAL APPLICATIONS

This research evaluates the effects of formulation and processing factors on the properties of a protein/fat-based food system. These properties may be related to sodium mobility and salty taste perception. This research provides information on strategies that can be used to control factors influencing the physical properties of protein/fat-based food systems targeting sodium reduction.

Effects of Fat Reduction and Curd Dipping Temperature on Viscoelasticity, Texture and Appearance of Gaziantep Cheese

The effects of varying fat content (from 13.5 to 50.4% w/w) and curd dipping temperatures (75, 85 and 95°C) on changes in viscoelastic properties, texture and appearance of Gaziantep cheese were examined. Viscoelastic properties of cheeses were studied using creep and recovery tests. Creep measurements showed that fat reduction from 50.4% (w/w) to 13.5% (w/w) decreased viscoelasticity while dipping into hot whey increased that of low-fat cheeses. Textural characteristics (hardness, gumminess, cohesiveness, springiness) were determined by texture profile analysis (TPA). Hardness, gumminess, cohesiveness and springiness values increased with decreasing fat content (P < 0.05). The application of curd dipping also increased hardness, gumminess, cohesiveness and springiness. Textural parameters were correlated with each others, except cohesiveness. Fat in dry matter correlated only with hardness and springiness, however curd dipping process correlated with all TPA parameters considered in this study. Colour of the cheese samples was affected by fat content as L value and b value decreased with decreasing fat content (P < 0.05). The decrease in curd dipping temperature increased the L value (P < 0.05) and decreased the b value.

Gelation of iota-carrageenan and micellar casein mixtures under high hydrostatic pressure

Effects of high-pressure treatment (HPT) on the rheological parameters and gelation of iota-carrageenan (iota-Car) and mixtures of micellar casein (MC) and iota-Car have been investigated under neutral pH conditions. It was established that HPT showed no significant effect, in the presence or absence of ionic calcium, with or without initial thermal processing, on the rheology or gelation/melting temperatures of the pure iota-Car solution. However, in mixed systems containing varying concentrations of iota-Car (up to 1 wt %) and MC (up to 8 wt %), considerable changes were detected. At the higher molar ratios of MC to iota-Car, and especially at the higher pressures, the dispersions were not thermoreversible in gelation, presumably due to the strong interactions of disrupted casein micelles with iota-Car molecules, as well as due to the formation of a dominant proteinaceous network at higher concentrations of MC. The associative protein-polysaccharide interactions in these systems are highly dependent on the ionic calcium content.

Heat-induced gels of egg white/ovalbumins from five avian species: thermal aggregation, molecular forces involved, and rheological properties

Product processing (heating, pH change, etc.) usually alters protein structure, improves rheological properties, and gives a unique texture to foods. The thermal aggregation and structural properties of ovalbumins from five avian species were studied at different pH values by polyacrylamide gel electrophoresis (PAGE) and determinations of sulfhydryl group content and surface hydrophobicity. The results showed that sulfhydryl group content changed insignificantly in heat-denatured ovalbumins other than hen ovalbumin (pH-independent), and surface hydrophobicity markedly increased (pH-dependent) after heating, with a significant difference among species. Furthermore, it was demonstrated that the hydrophobic interaction and sulfhydryl-disulfide interchange reaction were necessary in the aggregation and cross-linking of gel networks. Creep tests were also used to characterize the gel network structures of various egg white/ovalbumins upon heating. The viscoelastic behavior of the ovalbumins of all species was dependent on pH values, and changed significantly with the phylogeny of these species. With increases in pH value (7.0-8.5), the heat-induced gels of ovalbumins gradually changed from turbid to translucent, the instantaneous modulus (E(0)) increased slightly and reached a nearly constant value, and the Newtonian modulus (etaN) increased significantly in each sample. The heated egg white from these five avian species also formed highly viscoelastic gels, with a good correlation of viscoelastic behavior between ovalbumin and egg white in corresponding species.

A viscoelasticity index for cheese meltability evaluation

A device especially designed for uniaxial creep test was used in this study. Cheddar cheeses of different fat content were used. To study the linear viscoelastic response of the cheese, temperature of 40 degrees C and stress of 1119.5 Pa were chosen. Tests were carried out at cheese ages of 1, 3, 6, and 12 wk after production date. A six-element Kelvin model was used to model the creep data. Instantaneous slope of the creep curve was defined as the viscoelasticity index. The results showed that the viscoelasticity index based on viscoelastic parameters could be used for predicting cheese meltability. From the analysis of variance test, it was evident that that the viscoelasticity index can be used to distinguish the meltability of Cheddar cheeses of different ages and fat levels.