The cooling rate effect on the microstructure and rheological properties of blends of cocoa butter with vegetable oils

The elasticity (G′) and yield stress (σ¹) of blends of cocoa butter (CB) in vegetable oils (i.e., 30% CB/canola and 30% CB/soybean oil) crystallized at temperatures (T_Cr) between 9.5 °C and 13.5 °C and two cooling rates (1 °C/min and 5 °C/min) were determined, evaluating their relationship with parameters associated with the formation and structural organization of the crystal network [i.e., solid fat content (SFC), Avrami index, crystallization rate, fractal dimension (D)]. The results showed that T_Cr and cooling rate had a different effect for each blend on the three-dimensional organization of the crystal network, and on the proportion and size of β′ and β crystals. Thus, under low supercooling conditions at both cooling rates, the crystallized CB/canola oil blend was formed by a mixture of small β′ and large β crystals that provided high G′ and σ¹ at low SFC (i.e., 20.5–20.9%) and D (i.e., 1.66–1.72) values. The CB/soybean oil blend achieved similar G′ and σ¹ independent of cooling rate only at high supercooling. In this case, the crystal network was formed mainly by small β′ crystals with SFC (i.e., 25.4–26.3%) and D (i.e., 2.86–2.79) values higher (P < 0.05) than in the CB/canola oil blend at low supercooling.     

Influence of some bulk sweeteners on rheological properties of chocolate

Chocolates with reduced calories have become popular among consumers and manufacturers. One way of manufacturing chocolate with reduced calories is to replace sucrose with some alternatives. Effects of different bulk sweeteners (maltitol, isomalt, and xylitol) with different particle size intervals (PSI) (106-53, 53-38 and 38-20 μm) on rheological properties of molten chocolate were investigated. The best model that fit the rheological data was Herschel-Bulkley model. Maltitol resulted in similar rheological properties of chocolate compared to sucrose and thus can be a good alternative. Isomalt resulted in higher plastic viscosity while maltitol resulted in higher yield stress than others. As the particle size increased the plastic viscosity and the yield stress increased. The differences in rheological properties of chocolate with different bulk sweeteners were caused by differences in solid volume fraction and particle size distribution (PSD). A substitute with large particle size should be chosen to replace sucrose for improving rheological properties of chocolate, but the particle size should be small enough to obtain good sensory properties.     

Influence of lecithin–PGPR blends on the rheological properties of chocolate

Lecithin and polyglycerol polyricinoleate (PGPR) are common emulsifiers used in the manufacture of chocolate products. The effects of systematically varied blends of lecithin and PGPR added in a concentration up to 14 g/kg on the flow properties of melted dark and milk chocolate were determined by means of rotational rheometry. The results show that, independent of the total amount of the emulsifier, the yield stress of both dark and milk chocolate mass is most efficiently reduced by applying mixtures of approximately 30% lecithin and 70% PGPR. As regards total emulsifier concentrations between 4 and 6 g/kg, lowest viscosity values were found for lecithin–PGPR blends of 50:50 and 75:25 for dark chocolate and milk chocolate, respectively. The obtained results indicate that it is possible to tailor yield stress and viscosity of melted chocolate to specific requirements by the appropriate adjustment of both blending ratio and quantity of the emulsifiers.     

Shear rate and cooling modeling for the study of candelilla wax organogels’ rheological properties

The rheological properties evolution, during the organogelation by cooling of candelilla wax (CW) solution in safflower oil, was studied using computational fluid dynamics (CFD). A simulated storage modulus (G′) model agreed satisfactorily with experimental observations. The gelation of 3% CW solutions was done using static conditions during the whole process (90–5 °C), or by applying a shear rate (180, 300 and 600 s⁻¹) during cooling from 90 °C to 52 °C and then continuing the cooling under static conditions up to the final temperature (i.e. 5 °C). The proposed model predicts G′ evolution as a function of temperature, and considers the final torque (Γ_f) of the sheared stage as an inductor of molecular flow alignment. Predictions revealed that the final solid-like component (i.e. G′) increases as the shear rate increases up to a maximum for a shear rate of about 400 s⁻¹. Then, final G′ value diminishes gradually, probably due to the destruction of microstructures that generate the gelation. The model was validated by graphical methods and variance measures. The results demonstrate the potential of CFD to allow the development of a model linking process variables (i.e. cooling and shearing) and rheological properties. This model can be successfully applied for process control purposes and for the design of organogels with predefined properties.     

Effects of particle size distribution and composition on rheological properties of dark chocolate

Control of chocolate viscosity is vital to its quality and production cost, and directly influenced by solids particle size distribution (PSD) and composition. Effects of PSD and composition on rheological properties of molten dark chocolate were investigated by varying PSD [D₉₀ (90% finer than this size) of 18, 25, 35 and 50 μm], fat 25, 30 and 35% and lecithin (0.3 and 0.5%) using a shear rate-controlled rheometer. PSD, fat and lecithin content significantly affected all rheological parameters, with significant interaction among factors. Increasing particles size gave significant reductions in Casson plastic viscosity, Casson yield value, yield stress, apparent viscosity and thixotropy, with greatest effect with 25% fat and 0.3% lecithin, which reduced with increasing fat and lecithin contents. Statistical analysis revealed that fat exerts the greatest effect on the variability in all the rheological properties followed by PSD and lecithin. PSD, fat and lecithin could be manipulated to control dark chocolate rheology, influencing quality whilst reducing production cost.     

The influence of the structure of starch on its rheological properties

Some of the differences between various starches are considered and the mechanisms of gel formation are described.The requirements of many food situations are to thicken, clarify and change texture rather than to form gels—these require amylopectin starches.The importance of stabilisation of rheological properties is emphasised. These properties can be modified by other materials such as salt, fat, sugars, proteins and gums.     

The influence of additives on the rheological and sensory properties of nonfat yogurt

In this work, response surface methodology was applied to a study of the effects of the addition of skim milk powder and stabilizers on the apparent viscosity and sensory attributes of nonfat yogurt. The addition of stabilizers has been shown to produce a significant effect on sensory attributes, while high concentrations of xanthan and guar gum are seen to decrease the overall acceptability of the yogurt, with gelatin producing the higher apparent viscosity and consistency. The correlation among apparent viscosity, which is an instrumental measurement, and consistency, which is a sensory evaluation, was 0.72.     

Effects of monoglyceride content,cooling rate and shear on the rheological properties of olive oil/monoglyceride gel networks

Functionality of conventional fat spreads can be achieved without hydrogenation by the formation of stable network structures upon cooling of mixtures of monoglycerides (MGs) and vegetable oils from the melt. Such mixtures are healthy substitutes for margarine and butter. The effects of MG content, cooling rate and shear on the temperature ramp, mechanical spectra and hardness of olive oil/MG gel networks were investigated. A minimum MG volume fraction was necessary for formation of a gelled network, but this concentration was less than that needed for a space‐filling network structure. Onset of gel network or structure formation was indicated by a sudden divergence in value of the elastic modulus G′. The temperature at onset of structure formation, T_o, final G′ value and network hardness all increased with increase in MG content. High cooling rates led to low final G′ values but harder networks, and vice versa. Maximum gel network development occurred when moderate shear (about 300 s^?1) was applied at incipient gelation. Copyright © 2004 Society of Chemical Industry     

Crystallization and rheological properties of soya milk chocolate produced in a ball mill

The aim of this paper is to define the optimal conditions for the pre-crystallization of chocolate produced in a ball mill, that contains 20% soya milk. Chocolate mass and soya milk are refined in a ball mill employing three refining times (30, 60 and 90 min) and pre-crystallization temperatures (26, 28 and 30 °C).     

The influence of moisture content on the rheological properties of processed cheese spreads

Model processed cheese spreads were prepared from rennet casein, sunflower oil, water and a trisodium citrate/citric acid chelating salt system. The samples were cooked using a laboratory‐scale processed cheese cooker. The moisture content of the samples varied from 49.1 to 55.6%. The samples were characterized by dynamic rheology, rotational viscometry and fat particle size analysis. With increasing moisture content, the rheological behaviour of the samples changed from solid‐like (concentrated solution) to liquid‐like (dilute solution). The moduli decreased and the frequencies at which G′‐G′′ crossed over increased with increasing moisture content. Increasing moisture content resulted in an increase in pH and increase in the volume‐to‐surface diameter of the fat droplets. Rotational viscometry indicated that all the samples were shear thinning. The flow curves fitted a power law relationship (r² = 0.993). Thixotropic behaviour was displayed by all samples except those above 54% moisture. The shear stress at any particular shear rate increased with decreasing moisture content, indicating a stronger network structure in the low moisture samples.     

Impact of particle size distribution on rheological and textural properties of chocolate models with reduced fat content

ABSTRACT:  With an increasing consumption of lipids nowadays, decreasing the fat content in food products has become a trend. Chocolate is a fat-based suspension that contains about 30%wt fat. Reducing fat content causes an increase in the molten chocolate viscosity. This leads to 2 major issues: difficulties in the process and a loss of eating quality in the final product, reported to have poor in-mouth melting properties, remain hard, and difficult to swallow. Literature shows that optimizing the particle size distribution (PSD), that is, having one with an increased packing fraction, can decrease the viscosity of highly concentrated suspensions. This study focuses on the impact of the PSD and fat content on the rheological properties, melting behavior, and hardness of chocolate models (dispersions of sugar in fat). We show that optimizing the PSD while reducing the fat content to a critical amount (22%wt) can decrease the viscosity of the molten material and reduce the hardness of the crystallized chocolate models. Melting in the mouth, characterized by an in vitro collapse speed, is faster for the samples with an optimized PSD. The decrease in the viscosity by optimizing the PSD in systems with a constant fraction of medium phase is based on the decrease of interparticle contact, reducing the particle aggregates strength, and structure buildup during flow or meltdown. In its crystallized state, the particle network is less interconnected, providing less resistance to breakage and meltdown.     

The influence of acid type on self-assembly,rheological and textural properties of caseinomacropeptide

The influence of acid type (acetic, citric, lactic and hydrochloric acids) on caseinomacropeptide (CMP) self-assembly, rheological and textural properties was analysed. The acidulant selection had a large impact on self-assembly rate, gelation and the hardness of CMP gels. The highest self-assembly and gelation rates were for citric acid, followed by hydrochloric and lactic acids. CMP solutions did not gel when the pH was adjusted with acetic acid during the test period. Product development using CMP must be carefully designed from the point of view of gel properties. A product preparation with CMP gelled with lactic or acetic acids would not be recommended because these acids affect the rheological and textural properties of the gels.     

Effect of formulation and processing conditions on the rheological and textural properties of a semi-liquid syrup model

The effect of two hydrocolloids, the overall composition and stirring rate of a confectionery semi-liquid syrup model, were studied by means of the measure of rheological properties, instrumental texture evaluation and turbidity. A syrup model was made with sucrose, high fructose corn syrup, gum (dextran or carrageenan), citric acid and water. An experimental design based on Taguchi’s method was employed to evaluate the influence of sugar concentration, gum type, gum concentration, citric acid concentration and stirring rate. An analysis of variance was performed. From all evaluated properties (except turbidity), °Brix was the factor that showed the maximum influence, with higher values on textural properties (adhesive force, cohesive work and stringiness). The gum type had influence over viscosity, hardness, adhesive force and turbidity. The Newtonian behavior predominated in the syrups and viscosity of samples was affected by the variables studied. The mean values of viscosity, hardness and adhesive force for all samples with carrageenan were higher than those obtained with dextran (at both °Brix levels).     

Influence of conching temperature and some bulk sweeteners on physical and rheological properties of prebiotic milk chocolate containing inulin

Changes in food consumption habits and the developments set forth in the area of health and nutrition also change consumer expectations and demands. Sugar-free foodstuffs and products that have prebiotic activity are among the primary features of such expectations and demands. In the present study, the effects of substituting fine sugar with isomalt and maltitol in milk chocolate samples that contain inulin (9.0 % w/w), which is a substance with prebiotic activity, and the use of varying conching temperatures (CT) (50, 55 and 60 °C) in the sample preparation process on their physical (colour, hardness, water activity) and rheological properties were examined. Rheological data were obtained using the Herschel–Bulkley model which showed the best fitting for predicting rheology. It was determined that all properties included within the scope of the study are affected by the use of different bulk sweeteners or varying CT (P < 0.01). While colour properties, such as brightness (L*), hue angle (h°), water activity (aw) and rate index properties varied in a narrow range, it was determined that the yield stress and viscosity properties, which are among the important quality parameters of chocolate and can have determining effects on sensory properties, manifest variations within a broad range, depending on the CT and the bulk sweeteners used. It was concluded that maltitol is a more suitable fine sugar substitute in milk chocolates containing inulin.     

The optimization of the formulation for a chocolate cake containing inulin and yacon meal

The research aimed at determining, using surface response methodology, an optimal chocolate cake formulation when wheat flour was partially replaced with inulin and/or yacon meal. The yacon meal used in the formulation was prepared by using tuberous roots of yacon (Polymnia sonchifolia Poepp. & Endl.). The optimization indicated that a formulation with 20% of the wheat flour replaced with yacon meal, 153 mL of water and no inulin showed the best values for hardness (3.638 N), cohesiveness (0.691) and specific volume (1.86 cm³ g^?1). A formulation with 40% of the wheat flour replaced with yacon meal, 6% replaced with inulin and containing 126 mL of water showed similar values to the optimized formulation for the three responses mentioned earlier but, in addition, it had a greater content of fructooligosaccharides and inulin. Consequently, both formulations may give useful functional foods with physical parameters comparable with the control formulation.     

Tentative hierarchization of the influence of milk properties and technological practices on rheological properties of Abondance cheese

An attempt at classifying the influence of different characteristics of milk and cheesemaking on the rheological properties of Abondance cheese is presented. Abondance is a traditional farmhouse French hard cheese with protected denomination of origin (PDO). Thirty-nine cheeses made from unpasteurized cows' milk were sampled. Spline partial least squares regression was used to relate milk properties and cheesemaking practices to rheological properties of the six-month-old cheeses. These properties were the deformability modulus and the strain and stress at fracture measured by compression. Milk properties and technological practices had overall the same degree of relationship with the rheological properties investigated: plasminogen-derived activity in milk and mineral-protein equilibrium, on the one hand, and brining and resting, on the other hand. However, acidification kinetics and 1-d pH, which result from both milk properties and technological practices, showed the strongest relationships with rheological characteristics. Factors that were most appropriate for modelling Abondance rheological properties are discussed.