Effect of heating temperature and sodium chloride concentration on ultrastructure and texture of gels made from giant squid (Dosidicus gigas) with addition of starch,l-carrageenan and egg white

This paper seeks to compare the ultrastructure of gels made from frozen muscle of giant squid (Dosidicus gigas) at various temperatures with a number of different rheological parameters, with reference to a variety of added ingredients (non-muscle proteins and hydrocolloids) and to NaCl concentration. Interesting data on gel rheological properties were found where formulae containedl-carrageenan, starch and egg white, with a low salt concentration (1.5%). This seems to be because carrageenan forms an independent network which supports the principal structure formed by the fish protein; starch is incorporated into the network and retains water; and egg white forms a supplementary network which helps to improve rheological properties.     

Food product models developed to evaluate starch as a food ingredient

Three highly reproducible food models have been developed to evaluate rheological and functional properties of starches. The food models are dutch vla, dressing, and white sauce, and they vary in pH, serving temperature, oil content, and content of other functional ingredients than starch (milk proteins, whole egg, carrageenan). The viscous properties were calculated in a controlled stress rheometer, and the power law index, n, and the consistency index, K, was calculated. The viscoelastic properties at small deformations were measured by oscillating viscometry. Also a spreadability analysis was performed. The rheological data for the three food models were analysed by use of a principal component analysis (PCA), which enabled an evaluation of the functionality of the models and visualisation of the correlation to the concentration of starch. The rheological parameters all varied significantly with starch concentration in dutch vla. In dressing and white sauce most of the rheological parameters depended on the starch concentration. In addition, it was found that results from the empirical rheological method (USDA consistometer) correlate well with fundamental rheological parameters. Syneresis was measured for a period of time up to 15 days. The degree of syneresis of dressing was highly dependent on starch concentration, while the syneresis of the white sauce was dependent on time but not on starch concentration. The dutch vla showed no syneresis at all.     

蛋清蛋白对豌豆淀粉凝胶化及凝胶特性的影响

为探究蛋清蛋白对豌豆淀粉凝胶化及凝胶特性的影响。分别以0%、3%、6%、9%和12%的蛋清蛋白替代豌豆淀粉,研究蛋清蛋白对豌豆淀粉糊化特性、热特性、静态流变、动态流变、凝胶质构及水分子状态的影响。结果表明：蛋清蛋白以浓度依赖的方式影响豌豆淀粉的糊化特性,峰值黏度、谷值黏度、崩解值、最终黏度、回生值均随蛋清蛋白添加量增加而降低,而糊化温度则升高。蛋清蛋白对豌豆淀粉凝胶化温度影响不显著,但降低了淀粉的凝胶化焓值。添加不同量蛋清蛋白的豌豆淀粉糊均表现为假塑性流体特征,Herchel-Bulkley模型能够很好地拟合其静态流变行为,稠度指数和屈服应力均随蛋清蛋白添加量增加而降低。添加蛋清蛋白降低了豌豆淀粉糊体系的黏弹性及凝胶的硬度、强度和可塑性。蛋清蛋白对豌豆淀粉凝胶中自由水含量影响不显著,但使结合水含量增加而不可流动束缚水含量降低。     

Effect of soapwort extract on physical and sensory properties of sponge cakes and rheological properties of sponge cake batters

Soapwort extract yields relatively stable, soap-like foam in aqueous solution because of its saponin content. The objective of this study was to utilise the advantage of the high foam forming capacity of soapwort extract in the production of sponge cakes. Egg white proteins were partially replaced with soapwort extract in the sponge cake formulation. The effects of soapwort extract addition on the rheological and physical properties of cake batters and on the physical and sensory properties of sponge cakes were determined. Replacing egg white proteins with soapwort extract, up to 75% by weight, did not have any significant influence on the specific gravity of batters (p > 0.05). Addition of soapwort extract into the cake mixture did not influence the flow behaviour indices (n) of cake batters nor the consistency indices (K) of cake batters. In general, replacing egg white proteins with soapwort extracts (up to 75% by weight) did not alter physical properties of sponge cakes. Replacing egg white proteins with soapwort extract had no unfavourable influence on the sensory properties of sponge cakes. Indeed, sponge cakes formulated with soapwort extract (by replacing egg white proteins by 50% and 75% on weight basis) received significantly higher chewiness scores than did control cakes (p < 0.05). This study showed that egg white proteins could be partially replaced with soapwort extract in the formulation of sponge cakes.     

Enzymatic modifications of pea protein and its application in protein-cassava and corn starch gels

The interactions between starch and proteins during processing influence pasting and rheological properties of starch and produce modifications on starch gel structure. Enzymatic modifications have been proposed for overcoming the limitations of using proteins as food ingredients. This work aimed to study the impact of native and enzymatically modified pea proteins on the properties of protein-starch (from cassava or corn) gels. Pea protein isolate (PPI) was incubated with endopeptidase (AL) or microbial transglutaminase (TG). Pasting profile, rheological behaviour and water retention capacity of protein-starch gels were analyzed. Protein (native and enzymatically modified) incorporation increased the viscosity of both corn and cassava starches during gel preparation. However, the hydrolyzed protein reduced drastically the increment of viscosity of protein-starch gels. The addition of PPI led to corn starch network that shifted from an elastic-like nature to a more viscous-like, whereas the opposite effect was observed in cassava gel network. TG- and AL-treated proteins led to a decrease of both G′ and G″ moduli of protein-starch gels, and AL-treated proteins showed the highest decrease on these parameters. Hydrolyzed proteins also favoured the syneresis of the protein-corn starch gel, whereas crosslinked proteins tended to reduce it. Enzymatic modifications of pea proteins affected significantly pasting and rheological properties of protein-starch gels.     

Effect of non-starch polysaccharides on the in vitro digestibility and rheological properties of rice starch gel

The starch digestibility and rheological properties of gels were evaluated in the presence of three non-starch polysaccharides (agar, xanthan gum and konjac glucomannan) with rice starch. Each polysaccharide was added to 30% (w/w) rice starch suspension at defined concentrations and starch gels were prepared. The extent of starch gel digestibility was determined by an in vitro method and rheological properties by a dynamic oscillatory test and a compression test. The added polysaccharides suppressed starch hydrolysis in the gels compared with the control, and a concentration dependency of this suppressive effect was observed. Adding agar and xanthan gum increased the storage shear modulus (G′) of starch gels, while adding konjac glucomannan decreased G′ values. The results indicate that the suppressive effect of non-starch polysaccharides on starch digestibility appears to be not only due to the rigidity of the gel, but also the interaction between starch and non-starch polysaccharides.     

Rheological and baking characteristics of batter and bread prepared from pregelatinised cassava starch and sorghum and modified using microbial transglutaminase

The effect of different concentrations (0, 0.5, 1 and 1.5 U/g) of microbial transglutaminase (MTG) on the creep-recovery properties of gluten-free batter prepared from pregelatinised cassava starch, sorghum and egg white was investigated. The test conducted in the rheometer had an instant loading of 80 Pa for 60 s and recovery of 0 Pa for 140 s. Increasing MTG concentration decreased the batters’ resistance to deformation and compliances but increased zero shear viscosity and elastic recovery. Changes in batter rheological properties were insignificant (P > 0.05) at MTG concentrations beyond 0.5 U/g. Crumb properties of gluten-free bread baked from the batter revealed that increasing MTG concentration increased (P < 0.05) crumb firmness and chewiness, whereas increasing incubation time decreased (P < 0.05) crumb cohesiveness, chewiness and resilience. There were no significant interaction effects (P > 0.05) between enzyme concentration and incubation time.     

不同打发状态蛋清泡沫及其凝胶特性的比较

蛋清具有良好的起泡性和凝胶性,其在充气食品中具有难以取代的地位。为研究不同状态蛋清泡沫凝胶的理化性质,该文在室温条件下以恒定搅拌速率（980 r/min）制备了不同打发状态（打发时间为0、50、70和90 s）的蛋清泡沫,并测定了蛋清泡沫的理化特性。随后将不同打发时间的蛋清泡沫加热固化,制备了蛋清泡沫凝胶,通过显微观察、色度、质构和流变分析考察了蛋清泡沫凝胶的特性。实验结果表明,在恒定的搅拌速率下蛋清泡沫的气泡状态会随打发时间的变化而变化。适当延长打发时间,有利于形成比重较低的（0.16～0.17）、具有高起泡性和泡沫稳定性的固态泡沫。打发70 s的蛋清泡沫（蛋清泡沫呈小弯钩状,比重为0.165）稳定性最佳,且经加热固化后,该蛋清泡沫凝胶的亮度（L*=90.28）显著升高,硬度（27.69 g）和弹性（0.78 mm）显著降低（P<0.05）,凝胶性质优良。结果揭示了蛋清泡沫的流变学性质能显著影响蛋清泡沫及其凝胶的性能,为蛋清泡沫在充气食品中的应用提供了理论参考。     

Rheological properties of instant fried noodle dough as affected by some ingredients

An experiment was set up to investigate the influence of ingredients such as moisture, gum and starch on the rheological properties of instant fried noodle dough. The noodle dough was formulated using a mixture of wheat flour (100%), 0–0.3% guar gum, 0–7.5% starch and 30–42% moisture. The rheological properties of noodle dough were influenced by the ingredients and their interactions. Increasing moisture content decreased Young's modulus (E) of dough samples. Addition of gum to dough at a lower moisture content of 30% increased E, decreased the energy at break (EB) and increased the storage modulus (G′) values. Interactions of starch and gum influenced changes in the rheological parameters at higher moisture contents. Increasing starch content in noodle dough with a lower gum concentration increased EB to a point beyond which further increase in starch concentration decreased EB. Gum and starch improved the binding and mechanical network in the dough. Insufficient water in the dough apparently reduced cohesion in the dough whereas excess water reduced the functionality of gum and starch. Copyright © 2005 Society of Chemical Industry     

Comparison of the effect of hydrodynamic and acoustic cavitations on functional,rheological and structural properties of egg white proteins

The impacts of hydrodynamic cavitation (HC) (orifice plate-2 mm) and acoustic cavitation/ultrasound (US) (probe sonicator- 50% amplitude; 20 kHz frequency) on the functional (foaming, gelling, emulsifying), physicochemical (solubility), rheological and structural properties of egg white proteins (EWP) were evaluated. The egg white solutions were treated for 5, 10 and 15 min for both HC and US. The results suggested that HC-treated samples had higher impact on physiochemical and functional properties when compared to US-treated samples. The best foaming, emulsifying and gelling property was obtained for HC-treated samples (15 min treatment time). Both cavitation treatments exhibited shear thinning behavior, among which US-treated samples had the lowest viscosity. HC-treatment applied for 15 min provided the highest in vitro digestibility (75.51 ± 0.126%) among all the samples. The FTIR spectra of EWP exhibited similar backbone structure for all the samples, while the secondary structure obtained from deconvolution of Amide-I peak differed significantly. Moreover, for product development with EWP, HC -treated samples were more appropriate in gelling and emulsifying applications, which can ensure quality products with higher in vitro digestibility. Overall, this study indicated that HC treatment (for 15 min) improved the functional, rheological, and structural properties of EWP.     

Rheological properties of angel food cake made with pH unfolded and refolded egg albumen

Angel food cake was made using egg albumen subjected to the pH-induced unfolded and refolded treatment. The effect of treatment on the rheological properties of angel food cake was investigated. Egg albumen solutions were prepared and pH was adjusted to 1.5, 4.5, 8.5 or 12.5 and then held 60 min to unfold the proteins. After holding, the solutions were readjusted to pH 4.5 or 8.5, and held for 45 min to partially refold the proteins. Egg white foam with sucrose was whipped and flour and the rest of sucrose were folded into the foam. The foam batter was heated in a TA Instrument AR 2000 controlled stress rheometer equipped in a parallel geometry. Samples were heated from 21 °C to 150 °C at a rate of 8.5 °C per min and then cooled down to 21 °C to bake the angel food cake. At 21 °C, oscillatory stress sweep was performed. There was no relationship between the G′ value of angel cake batter and its G′ value at 150 °C. Changes in rheological properties of batters and angel food cakes using different combinations of ingredients were studied. The pH unfolding and refolding procedure led to more rigid final products compared to the controls with egg albumen samples not subjected to pH treatment. Adding sucrose to the flour increased the starch gelation temperature up to 82 °C. Higher protein concentrations resulted in better foams in the cake batter, but the batter made with an intermediate protein concentration produced the most rigid angel food cake. Adding egg albumin did not change gelation temperature of the starch. It appears that incorporation of flour with the egg white foam, leads to about a ten times decrease in the strength of the foam, and a decrease in the gelatinization process of starch after adding sugar, are crucial in forming of an angel food cake texture.     

Effects of enzymatic modification of soybean protein on the pasting and rheological profile of starch–protein systems

Reformulation of traditional food systems to introduce new ingredients may change their structure and perceived texture. Interactions between proteins and starch during processing can markedly influence starch gel network structure and rheological profile. The present work aimed to study the effects of soybean protein and the products of enzymatic modification on the pasting and rheological profile of corn and cassava starch. The behavior of those protein‐enriched gels during storage was also assessed. Soybean protein isolate (SPI) was incubated with endopeptidase (AL) or food grade microbial transglutaminase (TG). Pasting and rheological behavior, water retention capacity, and structure of protein– and hydrolyzed protein–starch gels were analyzed. Protein incorporation increased the viscosity of starch suspension during and after heating. SPI‐modified proteins increased peak viscosity. Only the structural modifications brought by TG on SPI increased the final viscosity during starch pasting and the storage modulus (G′). This modulus (G′) of the gelled systems decreased with the addition of AL‐treated protein isolate. Light and fluorescence microscopy showed that SPI formed a continuous phase, like a network, in the gelled system. Different network structures and rheological properties can be obtained when SPI are modified by protease and TG enzymes, which may be very useful for designing new food products.     

Comparative assessment of textural properties and microstructure of composite gels prepared from gelatine or gellan with maize starch and/or egg white

Single component gels (SCG) were formed from gelatine, gellan, maize starch or egg white, while binary composite gel (BCG) and ternary composite gel (TCG) were formed by mixing gelatine or gellan with maize starch and/or egg white. Each type of SCG exhibited distinct textural and microstructure characteristics. Gelatine‐SCG was the softest to hold but has the strongest and the most elastic network compared with other SCG. The effects of gelatine or gellan proportions on the textural properties of composite gels were investigated using mixture design experiments. Gelatine and gellan yielded composite gels that showed different textural behaviours and microstructure. All BCG and TCG blends showed antagonistic effects; the composite gels were softer and weaker as compared to the SCG. Gelatine‐BCG and TCG were comparatively stronger than those of gellan due to their different gelling mechanisms, in which the former had yielded a denser network structures as compared to the latter.     

Noodle quality affected by different cereal starches

To investigate the effects of starch characteristics on the quality of noodle making, white salted noodles (WSN) made from reconstituted flours, in which the wheat starch was substituted by different cereal starches, including waxy and non-waxy rice starches, waxy wheat starch and waxy corn starch, were prepared. The rheological properties of raw WSN were mainly influenced by the size of starch granules, where the small starch granules, such as for rice starches, exhibited high amounts of water absorption during dough preparation and a dense packing of starch granules inside a thin gluten-strand network. The rheological properties of cooked WSN were mainly dominated by the amylose content and fine structure of the amylopectin, which resulted in the differences in water absorption and cooking time required for cooked WSN.     

Rheological and thermal effects of galactomannan addition to acorn starch paste

Effect of galactomannans (guar gum and locust bean gum) at different concentrations on rheological and thermal properties of acorn starch pastes was examined. Steady and dynamic shear rheological tests indicated that the magnitudes of consistency index (K), apparent viscosity (η_a,100), Casson yield stress (σ_oc), dynamic moduli (G′, G″), and complex viscosity (η∗) of acorn starch-galactomannan mixtures were much higher than those of the control (0 g/100 g gum concentration), and that these values also increased with an increase in gum concentration. At temperatures ranging from 25 to 70 °C, the effect of temperature on η_a,100 was well described by the Arrhenius equation. In addition, DSC studies showed that the presence of galactomannans resulted in an increase in the transition temperatures (T_o, T_p, and T_c) and a decrease of the gelatinization enthalpy (ΔH). In general, these results suggest that the presence of galactomannans in acorn starch modifies the rheological and thermal properties, but that these modifications are dependent on the gum type and gum concentration.     

Heat-induced Changes in Angel Food Cakes Containing Egg-white Protein or Whey Protein Isolate

ABSTRACT: Angel food cakes made from egg white or whey protein foams were compared. Cakes were evaluated based on final volume, dynamic volume change, and rheological transitions during baking. Cake expansion during baking was a function of protein concentration regardless of protein type. Cakes containing whey proteins had a lower ability to prevent collapse once starch gelatinization started during baking. Heat-treating whey proteins or adding xanthan gum increases cake volume, but not to the extent of egg-white proteins. Cakes containing egg-white proteins became more elastic at 60 to 85 °C than those containing whey proteins, indicating physical differences in the heat-set protein foam network associated with protein type.     

Rheological studies on commercial egg white using creep and compression measurements

The gel properties of commercial egg white (EW) with high gelling ability were compared with those of standard type using creep and compression measurements. The effects of heating time, temperature, and protein concentration on gel properties were investigated at pH 7.5. The experimental creep curves were analyzed using four elements of the Maxwell–Voigt model. The difference in rheological properties of the two types of EW was reflected in the values of elastic modulus and viscosity. The experimental stress–strain curves for all EW gels were fitted using the BST equation with high accuracy. This equation contained two fitting parameters, i.e. Young's modulus and the elasticity parameter n_BST. The elasticity parameter n_BST characterized non-linear elastic behavior for large deformation. At 80°C, n_BST of both types of EW gels did not change with increasing heating time. However, n_BST decreased with increasing temperature in a range of 70–85°C.     

Wheat batter physical properties as influenced by starch/flour types and egg contents

Batter liquid–solid phase interactions can play a critical role in determining the functionality, including adherence, appearance and texture of end use coated product. Batter chemical composition is a key factor affecting batter characteristics. The effect of substituting wheat flour with fractions of rice flour, native corn starch, modified waxy corn starch, tapioca starch and lupine flour ranging from 26 to 56% of the solid phase and egg levels ranging from 6 to 35% of the liquid phase on the rheological properties of batter systems was studied. Results indicated that lupine flour had the greatest water holding capacity (WHC) ranging from 93.9 to 119.3% of various lupine flour percent to egg levels used. Flow behaviour index of batter flour treatments ranged from 0.91 to 1.87; values that were significantly (P?<?0.05) greater than a 100% control wheat flour. Consistency coefficient of treatments ranged from 0.01 to 0.37 mPa sⁿ; values that were significantly lower than wheat flour (i.e., 5 mPa sⁿ). Egg level used in this study had minimal effect on treatment rheological properties. The changes in WHC and viscoelastic properties of treatments were attributed to changes in protein and fibre contents and structure as a result of replacing wheat flour with starch/flour. Protein–starch–lipid matrix formation and variation in water absorption kinetics of treatments most probably wrought batter functionality. The increase in pasting properties with the increase in starch/flour contribution suggested an increased contribution of starch in forming a net effect of batter treatments pasting viscosities. Results of this study provide vital information for the potential use of starch types to enhance the rheological properties of coating applications including adhesion and water holding capacity of substituted batter treatment.     

糖类对蛋清蛋白凝胶强度的影响

为改善蛋清蛋白凝胶的加工特性,探讨了不同种类与不同浓度糖类对蛋清蛋白凝胶强度的影响。选择并固定适宜的蛋清蛋白凝胶制备条件,在制备前加入不同浓度的糖类,形成凝胶后运用物性仪测定其强度。结果表明,结冷胶、黄原胶和阿拉伯树胶均在胶类-蛋清蛋白凝胶体系发生相变的浓度点使体系强度有明显的变化;蔗糖在实验浓度范围内对体系的凝胶强度没有明显的作用;麦芽糖对蛋清蛋白凝胶的作用显著,在低浓度可以增强蛋清蛋白凝胶强度而在高浓度可以降低蛋清蛋白凝胶强度;玉米淀粉也在一定浓度可显著提高蛋清蛋白凝胶的强度。结果说明,以糖类作为添加剂改善蛋清蛋白的凝胶强度时,应充分考虑所加入的糖类种类及浓度。      

Thermophysical and rheological properties of liquid egg white and yolk during thermal pasteurization of intact eggs

Thermophysical properties of eggs was studied in a temperature range of 5–60 °C, which could be used to optimize the thermal processing. The effective thermal conductivity of egg white was predicted by Krischer model (f_λ = 0.20), and for egg yolk, parallel model was in good agreement with the experimental data. Power law and Herschel–Bulkley models were used to describe rheological behavior of egg yolk and white, respectively. The differential scanning calorimeter showed that denaturation of white protein starts at 60 °C. Surface heat transfer coefficient increased with increasing temperature. Density decreased during thermal process and was in a good agreement with the predictive models, based on the chemical component.