Buckwheat and Millet Affect Thermal,Rheological, and Gelling Properties of Wheat Flour

Buckwheat (BF) and millet (MF) are recommended as healthy foods due to their unique chemical composition and health benefits. This study investigated the thermal and rheological properties of BF‐WF (wheat flour) and MF‐WF flour blends at various ratios (0:100 to 100:0). Increasing BF or MF concentration led to higher cold paste viscosity and setback viscosity of pasting properties gel adhesiveness, storage modulus (G′) and loss modulus (G″) of dynamic oscillatory rheology, and yield stress (σ₀) of flow curve of WF. BF and MF addition decreased peak viscosity and breakdown of pasting, gel hardness, swelling volume, and consistency coefficient (K) of flow curve of WF. Thermal properties of the blends appeared additive of that of individual flour. Nonadditive effects were observed for some property changes in the mixtures, and indicated interactions between flour components. This may provide a physicochemical basis for using BF and MF in formulating novel healthy products.     

RHEOLOGICAL PROPERTIES OF RENNET-INDUCED GELS DURING THE COAGULATION AND CUTTING PROCESS: IMPACT OF PROCESSING CONDITIONS

The effects of gelation temperature (GT), pH, milk solids nonfat (MSNF) content and aging time on the small and large deformation rheological properties of rennet‐induced skim milk gels were studied. Small amplitude oscillatory rheometry (SAOR) was used to study gel formation. A constant shear rate was applied to gels of various ages to try to simulate the cutting process used in cheese vats. Second‐order polynomial models successfully predicted (R² ≥ 0.83) the relationship between processing parameters and rheological properties of gels. The processing parameters – gelation pH, GT and MSNF – had a significant effect on the rheological properties of rennet‐induced gels. The type and the nature of bonds in these networks and the time scale of applied deformation affected the rheological properties of rennet gels. As time after rennet addition increased, storage modulus, loss modulus and yield stress values increased. This resulted from an increase in the number and strength of bonds with time. The yield strain decreased with time probably because of rearrangements in the network making the gel shorter/brittle in texture. When the impact of the time scale of the applied deformation was compared between the small (storage modulus as a function of frequency) and large (yield stress as a function of constant shear rate) deformation properties of rennet‐induced gels, similar power law exponents were obtained. This similarity presumably reflects the type and relaxation behavior of bonds in this casein network. These results identify the impact of several important processing variables on both the small and the large deformation rheological properties of rennet‐induced gels, which could be useful in identifying gelation properties that improve cheese yield.     

驴乳的系统流变学性质研究

目的:研究不同温度对驴乳流变学性质的影响。方法:选取测试温度为4、20、36、50℃,测试其流动性、触变性、动态粘弹性,并采用流变学模型进行拟合分析。结果:驴乳为非牛顿流体,表现出剪切稀化行为;流动曲线服从Carreau模型,随温度升高,其黏度越小,触变测试中形成的滞后环面积变小;并且在粘弹性测试中4℃的储能模量G'表现出最大值,储能模量G'和损耗模量G″对温度的依赖性较大;4~50℃测量温度范围内驴乳黏度随温度增加逐渐减小。结论:驴乳的流变性对温度的依赖性较大。     

Quality of dried white salted noodles affected by microbial transglutaminase

To examine the potential application of microbial transglutaminase (MTGase) in oriental noodle making, the effects of various MTGase addition levels on the rheological, textural and structural properties of noodles were investigated using good quality (‘Red Bicycle’) and poor quality (‘Sandow’) wheat flours. Addition of MTGase at 5–20 g kg^?1 levels, but not at 1 g kg^?1 level, to the two different wheat flours decreased rapid visco‐analyser (RVA) parameters of hot paste viscosity and final viscosity while increasing breakdown. For fresh white salted noodle dough sheets, the storage modulus (G′) and loss modulus (G″) increased significantly at 1 g kg^?1 MTGase addition for both types of flour, but there was no clear trend with higher levels of MTGase. For dried white salted noodles, textural parameters (tensile force, hardness and gumminess) generally increased, cooking loss was little affected and the yield of the cooked noodle was significantly decreased by MTGase. Color was slightly adversely affected. Scanning electron microscopy (SEM) results indicated that physical properties of dry noodles were improved through the formation of cross‐links [ε‐(γ‐glutamyl)lysine] by MTGase. Copyright © 2005 Society of Chemical Industry     

DYNAMIC AND STEADY-STATE RHEOLOGY OF AUSTRALIAN HONEYS AT SUBZERO TEMPERATURES

The rheology of 10 Australian honeys was investigated at temperatures ?15C to 0C by a strain‐controlled rheometer. The honeys exhibited Newtonian behavior irrespective of the temperature, and follow the Cox–Merz rule. G″/G′ and ω are quadratically related, and the crossover frequencies for liquid to solid transformation and relaxation times were obtained. The composition of the honeys correlates well (r² > 0.83) with the viscosity, and with 247 data sets (Australian and Greek honeys), the following equation was obtained: The viscosity of the honeys showed a strong dependence on temperature, and four models were examined to describe this. The models gave good fits (r ² > 0.95), but better fits were obtained for the WLF model using T_g of the honeys and µ_g= 10¹¹ Pa.s. The WLF model with its “universal values” poorly predicted the viscosity, and the implications of the measured rheological behaviors of the honeys in their processing and handling are discussed.     

冷榨菜籽油的流变特性

以3种不同芥酸含量的油菜籽为原料,通过低温压榨获得冷榨菜籽油(cold-pressed rapeseed oils,CROs),分析其静态和动态流变特性以及特征指标,同时采用Bingham模型对其流体行为进行拟合。结果表明：在剪切速率为0.1～200s-1条件下,CROs呈剪切变稀的假塑性流体;当剪切速率大于5s-1时,CROs表现为牛顿流体行为;温度是影响CROs流变性质的重要因素,CROs的黏度、损耗模量(GO`)和塑性稠度系数(ηp)随着温度升高而降低,但是温度变化对CROs的贮能模量(GO`)影响较小;另外CROs的黏度和GO`随芥酸含量增加而提高,而且ηp值与芥酸含量成正相关。     

不同品种花生蛋白流变特性的研究

对8种花生蛋白的流变特性进行了探讨。静态流变特性测定结果表明,8种花生蛋白的流变模型为幂率模型,均为非牛顿流体。在同样的流动方式下,忠毅9616的黏度最大,花育16次之,其他几种变化无明显差别。动态流变特性测定结果表明,随着温度的升高,不同品种花生蛋白的贮藏模量、损失模量以及损失系数均呈现出不同的变化趋势。其中,忠毅9616品种蛋白的贮藏模量最大,红珍珠次之,花育16最小;红珍珠、奇山208、的损失模量高于其他几种,花育16最低;忠毅9616的损失系数最小,奇山208最大。     

Applicability of time-temperature superposition principle: Dynamic rheology of mung bean starch blended with sodium chloride and sucrose - Part 2

Dynamic rheological characteristics of mung bean starch individually and blending with sodium chloride (5-10%) and sucrose (5-10%) in aqueous medium were studied isothermally (70-95 °C). The elastic modulus (G′) of each dispersion was significantly higher than viscous modulus (G″) and showed a predominant solid-like property. Each ingredient affected the rheological behavior differently. Incorporation of sugar increased the gel rigidity, whereas sodium chloride-starch blend lowered the gel strength as function of concentration. The empirical principle of time-temperature superposition (TTS) was examined to bring experimental dynamic rheological data at various temperatures together into single master curves at a reference temperature of 80 °C. The complex viscosity (η^∗) master curve was obtained for the blends with slight deviation. The elastic modulus superposition (G′-ω) has been found to fail in the studied temperature regime. The failure of TTS was believed to be happened due to complex starch-additive-water matrix formation, temperature response of individual components and phase change during gelatinization of starch.     

Rheological behavior of concentrated yogurt (Labneh)

In this paper, the rheological behavior of concentrated yogurt (Labneh) is presented. The rheological behavior of Labneh was measured using a rotational viscometer in a temperature range of 5‐55°C. The tested Labneh exhibited shear‐thinning and thixotropic behaviors. The power law model expressed as τ = mγ ⁿ was found to be the most appropriate for the rheological model of Labneh. The effects of temperature on power law parameters were determined. The parameter (m) significantly decreased with increasing temperature, while the parameter (n) slightly increased with temperature. It was also found that the Weltmann's model described well the relationship between the apparent viscosity of Labneh and the shearing time. The activation energy of flow was nearly constant for all samples tested and not affected by the shear rate.     

Modeling changes in rheological properties of potatoes during storage under constant and variable conditions

The changes in rheological properties of potatoes stored at 5, 15, 25 °C and variable (fluctuating) temperature for 16 or 26 weeks were evaluated in terms of elasticity and viscosity parameters using axial compression and creep tests. Cylindrical test specimens (15 mm diameter and 30 mm long) were used. A third-degree polynomial best fitted the force-deformation curves in axial compression test (R²=0.98-0.99) whereas a four-element (Burgers) mechanical model adequately described the creep response of potatoes (R²=0.95-0.99). The tangent modulus of elasticity in axial compression and elasticity and viscosity parameters in creep tests in general decreased significantly (P<0.05) with increase in storage time both under constant and variable storage conditions. The changes in rheological properties of potatoes stored under constant storage condition were sufficiently described by a modified exponential model (R²=0.89-0.96) except for the viscosity parameter of the Maxwell component of the four-element model. The logarithm of degradation rate constant, k, and the constant, n, were linearly related to storage temperature. For the variable storage condition, a bulk mean temperature (T_bm) was calculated to account for a series combination of storage time and temperature to which the potatoes were subjected. The changes in rheological properties due to variable storage temperature were then described as a function of T_bm and storage time, t_s, using stepwise multiple regression. The result indicated that except the viscosity parameter of the Maxwell component of the four-element model, it was possible to describe the changes in rheological properties as a function of T_bm and t_s (R²=0.84-0.99).     

Physicochemical,Rheological, and Thermal Properties of Six Types of Honey from Various Floral Origins in Tunisia

The present study was undertaken to determine the physicochemical, rheological, and thermal properties of six types of Tunisian honey samples from various floral origins (eucalyptus, orange, thyme, mint, rosemary, and horehound). All the honey samples exhibited non-Newtonian behavior at a shear rate ranging between 0.01 and 500 s^–1, with the highest levels of viscosity (µ) being observed for thyme, followed by eucalyptus, rosemary, mint, orange, and horehound honeys, respectively. The effect of temperature on the dynamic viscosity of the samples followed an Arrhenius-like pattern, with activation energy values ranging from 21.23 to 34.91 kJ/mol. The results from oscillatory rheology analysis also revealed that the loss modulus predominated over the storage one in the whole frequency range. As determined by differential scanning calorimetry, the glass transition (T_g) and melting temperatures of the Tunisian honey samples varied between –41.55 and –47.06 °C and between 197.9 and 221.1°C depending on their sugar compositions, respectively.     

湿热处理对大米淀粉流变特性的影响

本文通过测定湿热处理前后大米淀粉的流变学特性,旨在研究湿热处理对大米淀粉稳态流变、动态流变及温度流变学行为的变化.结果表明,湿热处理后大米淀粉均呈现剪切稀化的现象,且湿热处理增强了大米淀粉的凝胶强度;在动态流变测定中发现,所有大米淀粉样品的弹性模量(G′)都大于黏性模量(G〃),且湿热处理后大米淀粉的弹性模量(G′)和...     

Rheological Properties of Rice Starch Dispersions in Dimethyl Sulfoxide

The steady and dynamic shear rheological properties of rice starches dispersed in dimethyl sulfoxide (DMSO) solution (90% DMSO‐10% water) were evaluated at various concentrations (7, 8, 9 and 10%, w/w). Rice starch dispersions in DMSO solution at 25°C showed a shear‐thinning flow behavior (n=0.44–0.60) and their consistency index (K) and apparent viscosity (η_a,100) increased with the increase in concentration. The apparent viscosity over the temperature range of 25–70°C obeyed the Arrhenius temperature relationship, indicating that the magnitudes of activation energy (E_a) were in the range of 11.7–12.7 kJ/mol. The Carreau model provided better fit on the shear rate‐apparent viscosity data than the Cross model. Dynamic frequency sweep test showed that both storage modulus (G′) and loss modulus (G′′) of rice starch dispersions increased with the increase in concentration. G′′ showed a higher dependence on frequency (ω) compared to G′ due to the higher G′′ slopes. All rice starch dispersions showed the plateau of G′ at high frequencies. Intrinsic viscosity of rice starch dispersions in DMSO was 104.1 mL/g.     

Rheological properties of polysaccharides from Pholiota nameko with different temperature extraction: Concentration,pH, temperature,and saltion

Cold and hot water extracted polysaccharides (CW-PNPs and HW-PNPs) were isolated from Pholiota nameko. The rheological properties of PNPs were investigated by steady shear and oscillatory rheological measurements. The PNPs exhibited typical non-Newtonian and shear-thinning behavior, which are affected by PNP concentration, temperature, pH value, salt ion, and concentration. Specifically, the apparent viscosity of the two PNPs solutions at concentration of 1% (w/w) was shown as HW-PNPs > CW-PNPs. The apparent viscosity of PNPs decreases under acidic and alkaline conditions and when the temperature rises; K⁺ and Na⁺ cause the apparent viscosity of CW-PNPs to decrease, while Ca²⁺ and Al³⁺ are opposite. The addition of four different salt ions all caused the apparent viscosity of the HW-PNPs to decrease. The results of dynamic rheological experiments show that G′ and G″ showed slightly frequency dependency with G′ exceeding G″ throughout the accessible range of frequency for CW-PNPs and HW-PNPs.     

Temperature Dependency of Steady, Dynamic, and Creep-Recovery Rheological Properties of Ice Cream Mix

In this study, effect of processing temperature (5, 15, 25, and 35 °C) on the steady, dynamic, and creep recovery rheological properties of the ice cream mix (ICM) was investigated. It was found that processing temperature significantly affected all rheological parameters of the ICM sample. The flow behavior of the ICM sample was fitted to the Ostwald de Waele model. The magnitude of storage modulus (G′) was higher than that of loss modulus (G″) indicating that ICM sample had weak gel-like structure. Modified Cox–Merz rules were satisfactorily applied to the ICM sample to observe relationship between steady and dynamic shear properties. Additionally, Burger model was used to characterize the viscoelastic properties of the ICM sample. The gel strength (S) value was also calculated, and a decrease was observed with the increase of temperature. Arrhenius equation satisfactorily described the temperature dependency of the rheological parameters such as apparent viscosity at 50 s^?1 (η ₅₀), consistency coefficient (K), the instantaneous shear modulus of the Maxwell unit (G ₀), permanent deformation (J _∞ ), and S values that may be predicted by using established equations depending on the temperature. The increase in processing temperature caused a decrease in resistance of the mixture subjected to the deformation, which is very important for production of high quality ice cream.     

On solid-like rheological behaviors of globular protein solutions

Dynamic viscoelastic and steady flow properties of β-lactoglobulin, bovine serum albumin, ovalbumin, and α-lactalbumin aqueous solutions were investigated at 20°C. When a sinusoidal strain in the linear viscoelastic region was applied, the solutions of the globular proteins except for α-lactalbumin showed typical solid-like rheological behavior: the storage modulus G′ was always larger than the loss modulus G″ in the entire frequency range examined (0.1–100 rad/s). Under a steady shear flow, strong shear thinning behavior was observed with increasing shear rate from 0.001 to 800 s⁻¹, for the globular proteins except for α-lactalbumin. The values of the steady shear viscosity η were lower than those of the dynamic shear viscosity η* at a comparable time scale of observation, violating the Cox–Merz rule, and thus suggesting that a solid-like structure in a globular protein solution was susceptible to a steady shear strain. During isothermal gelation of the protein colloids at 70°C, no crossover between G′ and G″ was observed so that the gelation point was judged by an abrupt increase in the modulus or a sudden decrease in tanδ.     

Viscoelastic properties of caseinmacropeptide isolated from cow,ewe and goat cheese whey

Caseinmacropeptide (CMP) is a C‐terminal glycopeptide released from κ‐casein by the action of chymosin during cheese‐making. It is recognised as a bioactive peptide and is thought to be an ingredient with a potential use in functional foods. CMP occurs in sweet cheese whey and whey protein concentrate (WPC). Its composition is variable and depends on the particular whey source and the fractionation technology employed in the isolation. There were no significant (P < 0.05) differences in the relative apparent viscosities between species of CMPs (cow, ewe and goat). Analyses at different pH (2, 4, 7, 10), ionic strength (0, 0.2, 0.4 and 0.7 as NaCl molarity) and protein concentration (50, 100 and 200 g kg^?1) at temperatures from 10 to 90 °C carried out found pH 7 and high protein concentration (200 g kg^?1) conditions to be the best for CMP solutions to keep low and constant relative viscosity values with increasing temperature up to 75 °C. The viscoelastic properties–storage modulus, loss modulus and phase angle–of the different CMPs and WPC solutions were determined. Heat‐induced rheological changes in CMP solutions occurred at moderate temperatures (40–50 °C) with no appreciable differences in viscosity. Gelation took place significantly (P < 0.05) earlier in goat CMP (41 °C), followed by cow CMP (44 °C), ewe CMP (47 °C) and WPC (56 °C). Heating at 90 °C showed that WPC required significantly (P < 0.05) longer times to form gels (>5 min) than the CMPs (<5 min). WPC gels had higher (>20°) phase angle than CMP (<20°), which could be associated with untidy structures, limiting elastic properties of the gel. Copyright © 2006 Society of Chemical Industry     

Physical Properties and Oxidation Rates of Unrefined Menhaden Oil (Brevoortia patronus)

ABSTRACT: Unrefined menhaden oil was evaluated for thermal and rheological properties and its temperature-dependent viscosity and lipid oxidation rate were determined. Peroxide value, free fatty acids, density, specific gravity, water activity, moisture content, and enthalpy of the unrefined menhaden oil were 5.70 meq/kg, 3.80%, 0.93 g/mL, 0.93%, 0.52%, 0.15%, and 20.2 kJ/kg, respectively. The melting point range of unrefined menhaden oil was found to be −69.5 to 27.21 °C. The menhaden oil exhibited non-Newtonian fluid behavior at lower temperatures (5 to 25 °C), while it behaved like a Newtonian fluid at 30 °C. The oil apparent viscosity at 5 °C (0.22 Pa.s) was significantly higher (P < 0.05) than that at 30 °C (0.033 Pa.s). The average magnitude of activation energy for viscosity of the unrefined menhaden oil was 50.37 kJ/mol. The predicted apparent viscosity agreed (R²= 0.9837) satisfactorily with the experimental apparent viscosity. The minimal lipid oxidation rate of the oil was found at 25 and 35 °C for 6 h, higher lipid oxidation rates were observed when the oil was heated for 6 h at 45 to 85 °C. The rate of lipid oxidation for unrefined menhaden oil was temperature dependent (R²= 0.9425). This study showed that the magnitude of the apparent viscosity and oxidation rate of the unrefined menhaden oil was greatly influenced by temperature.     

Effect of temperature on dynamic and steady-state shear rheological properties of siriguela (Spondias purpurea L.) pulp

The present work has evaluated the dynamic and steady-state shear rheological properties of siriguela (Spondias purpurea) pulp as function of temperature (0-80 °C), as well as the applicability of the Cox-Merz rule. The product flow behavior could be well described by the Herschel-Bulkley’s model (R² > 0.98), whose parameters were modeled as function of temperature (R² > 0.91). The product has shown a weak gel behavior, with storage modulus higher than loss modulus in the evaluated frequency range. The storage and loss modules could be well described by a power function of the oscillatory frequency (R² > 0.93), whose parameters were modeled as function of temperature (R² > 0.97). Moreover, a power modified Cox-Merz rule could describe the rheological properties of S. purpurea pulp (R² > 0.96). The obtained data are potentially useful for future studies on food properties and process design.     

Structural and rheological properties of potato starch affected by degree of substitution by octenyl succinic anhydride

The objective of the present study was to investigate the structural and rheological properties of octenyl succinic anhydrate (OSA) modified potato starch. Potato starch was modified with different concentrations of OSA (0, 1, 3, and 5%, v/v). X-ray results suggested that OSA modification did not disrupt the crystallinity of the native starch, and esterification occurs primarily in the amorphous regions. The use of ¹H-NMR spectra confirmed the presence of methyl protons in substituted OSA groups, which interacted with the starch molecules. In steady shear rheological analysis, OSA modified starch pastes showed a pronounced shear thinning behavior (n = 0.47–0.54). The consistency index (K) and yield stress (σ_oc) values of OSA modified starch pastes were significantly lower than those of the native starch. Dynamic shear rheological tests indicated that OSA modified starch pastes had weak gel-like behavior with storage moduli (G’) higher than loss moduli (G’’). OSA potato starch pastes were more viscous as compared to the native potato starch paste, as evidenced by their higher tan δ values.