The rheological properties of exudates from cured porcine muscle: effects of added carrageenans and whey protein concentrate/carrageenan blends

Meat exudates were collected from massaged cured porcine M semimembranosis using a model massaging unit. Exudates were used to observe changes in gelation properties of test exudates containing carrageenans and whey protein concentrate (WPC) and carrageenan blends. Three carrageenan powders iota (ι ), kappa (κ), as well as a kappa/locust bean gum mix, were assessed at a 1% residual level, both individually and as blends. WPCs assessed included high gelling A‐35, B‐75 and C 55% protein β‐lactoglobulin powders, as well as a regular 76% protein, WPC D. All WPCs were incorporated at a 2% residual powder level in the final meat. Treatment and control meat samples and resulting exudates were prepared in duplicate with analysis performed in triplicate. The viscoelastic properties of control and test meat exudate samples (n=6) were analysed using control stress rheology in oscillatory mode. All exudates were heated from 20 to 80°C at 1°C min⁻¹ , and subsequently cooled after 30 min back down to 20°C at 1°C min⁻¹. Combinations of high gelling WPCs, especially β‐lactoglobulin together with iota and kappa‐carrageenans A and B, were found to increase storage modules G′ (Pa) values when compared with control values. Significant (p<0.05) synergies were observed on blending high gelling WPCs with carrageenans A and B. © 1999 Society of Chemical Industry     

The rheological properties of exudates from cured porcine muscle: effects of added non‐meat proteins

Meat exudates were collected from massaged cured porcine M semimembranosus using a model massaging unit. Exudates were used to observe changes in gelation properties due to the incorporation of commercially available non‐meat proteins. These included: soya isolate (90%), sodium (Na) caseinate (85%) and high gelling whey protein concentrates (WPCs, A‐35%, B‐75% and C‐β‐lactoglobulin (55%), as well as a regular 76% protein, WPC D. Compositional analysis ( n=6) showed that incorporation of non‐meat proteins significantly (P<0.05) increased the protein concentration of test exudates in all cases compared to controls. The viscoelastic properties of control and test meat exudate samples (n=6) were analysed using control stress rheology in oscillatory mode. All exudates were heated from 20 to 80°C at 1°C min⁻¹, and subsequently cooled after 30 min back down to 20°C at 1°C min ⁻¹. Addition of WPCs at a 1, 2 and 3% residual powder level and soya isolate at a 1% residual level, resulted in increased storage modulus G′ (Pa) values compared with controls. A 1% residual level of Na caseinate was detrimental to meat exudate gelation, resulting in lower final G′ (Pa) values than those observed for the control. © 1999 Society of Chemical Industry     

Dynamic rheological properties and bread‐making qualities of wheat gluten: effects of urea and dithiothreitol

Controlled stress rheometry differentiated glutens from the cultivars under study into ‘extra‐strong’, strong and weak on the basis of their elastic and viscous moduli measured in the linear domain. The mechanical spectra of different glutens revealed no qualitative differences, but exhibited large quantitative differences in the magnitude of the dynamic measurements, ie elastic modulus, G′, viscous modulus, G″, and loss tangent, tanδ. Both covalent and non‐covalent interactions appeared to contribute to these differences. However, disulfide cross‐links proved to be especially important determinants of differences in the elastic characteristics of the glutens. The present study indicated that dynamic rheological parameters of glutens were related to their bread‐making performance, as evidenced by the significant correlations between the dynamic moduli of the glutens and loaf volume. Copyright © 2004 Society of Chemical Industry     

Influence of tragacanth gum exudates from specie of Astragalus gossypinus on rheological and physical properties of whey protein isolate stabilised emulsions

The aim of this work was to investigate the effects of Iranian tragacanth gum (Astragalus gossypinus) (0.5, 1 wt.%), Whey protein isolate (WPI) (2, 4 wt.%) and acid oleic‐phase volume fraction (5, 10% v/v) on droplet size distribution, creaming index and rheological properties of emulsions with various compositions. Rheological investigations showed that both loss and storage modules increased with gum and oil contents. However, the viscoelastic behaviour was mainly governed by the gum concentration. Delta degree (storage and loss modules ratio) increased with frequency indicated that liquid like viscose behaviour dominates over solid like elastic behaviour. The shear‐thinning behaviour of all dispersions was successfully modelled with power law and Ellis models and Ellis model was founded as the better model to describe the flow behaviour of dispersions. Droplet size distribution was measured by light scattering; microscopic observations revealed a flocculated system. Increase in gum, WPI and oil contents resulted in decrease in creaming index of emulsions with dominant effect of gum concentration.     

The effects of low salt concentrations on the mechanism of adhesion between two pieces of pork semimembranosus muscle following tumbling and cooking

The aim of this research was to gain deeper insight into the effect of salt content on the adhesion between pieces of semimembranosus pork muscle bound by a tumbling exudate gel. Hydrophobic site number, free thiol and carbonyl content were measured in tumbling exudate and meat protein to evaluate the protein–protein interactions involved in the adhesion process. Proteins were far more oxidized in exudate than in meat, and under our experimental conditions, salt content increased protein bonding in the exudate but not in the meat. Breaking stress increased between non-salted meat and 0.8%-salted meat but did not depend on the protein physicochemical properties of the tumbling exudate. Modifying the meat surface by tumbling alone, tumbling and salting, or scarification had no effect on breaking stress. It is suggested that the break between the meat pieces occurred between the tumbling exudate and the meat surface due to weaker chemical bonds at this location.     

Textural properties of a model aqueous phase in low fat products. Part 2: Alginate/caseinate blends and three-component systems

Summary The second paper in this series completes the investigation of the textural properties of alginate, starch and caseinate preparations. Thus mixtures of alginate and caseinate show liquid-like properties up to 200 p.p.m. Ca²⁺. At higher levels of the counterion, alginate gels form a continuous matrix which supports the liquid-like caseinate inclusions. Caseinate acts mainly as a sequestrant for calcium ions. In the absence of added counterions, the ternary system is characterized by a weak starchy network which supports the liquid alginate and caseinate phases. Addition of Ca²⁺ produces a plethora of textures governed mainly by the alginate phase and the sequestering influence of caseinate. Intelligent manipulation of polymeric composition and levels of calcium resulted in binary systems of caseinate/starch, alginate/starch and caseinate/alginate capable of reproducing the texture of ternary mixtures, thus offering attractive alternatives to the commercial aqueous phases. In conclusion, it is demonstrated that basic understanding of ingredients and their properties in mixtures leads to purposeful formulation of products.     

Rheological,thermal and sensory properties of whey protein concentrate/pectin‐fortified mashed potatoes made from dehydrated flakes

The effect of different amounts of whey protein concentrate (50–150 g kg^?1), low and high methoxyl pectin (5–15 g kg^?1) on the rheological, thermal, structural properties and sensory quality of mashed potatoes prepared from dried mashed potatoes flakes was investigated. The response surface technique was used to analyse the effects of whey protein concentrate and pectin simultaneously on the consistency index, flow behaviour index, apparent viscosity and Casson plastic viscosity. Both whey protein concentrate and pectin decreased the consistency of the mashed potatoes weakening its structure in all concentrations assayed. Results suggest that whey protein concentrate interacts with high methoxyl pectin through non‐covalent interactions. Based on the sensory evaluation results, up to 100 g kg^?1 whey protein concentrate with 15 g kg^?1 of low methoxyl pectin and 15 g kg^?1 of high methxyl pectin could be incorporated to dried mashed potatoes flakes without losing significantly the sensory quality of the product.     

Myofibrillar protein from different muscle fiber types: Implications of biochemical and functional properties in meat processing∗

Texture, moisture retention, and tenderness of processed muscle foods are influenced by the functionality of myofibrillar protein. Recent studies have revealed large variations in processing quality between red and white muscle groups that can be attributed to differences in the functional properties of myofibrillar protein associated with the type of fiber. Myofibrillar proteins from fast‐ and slow‐twitch fibers exhibit different biochemical and rheological characteristics and form gels with distinctly different viscoelastic properties and microstructures. The existence and wide distribution of the numerous myosin isoforms in different muscle and fiber types contribute to the various functional behaviors of myofibrillar protein. The different sensitivities of fast and slow myofibrillar proteins to pH, ionic environment, temperature, and other external factors have been well documented and illustrate the importance of adjusting meat processing conditions, according to fiber type profile to achieve maximum protein functionalities, and hence, uniform quality of the final muscle foods.     

Three sulphated polysaccharides isolated from the mucilage of mud snail, Bullacta exarata philippi: Characterization and antitumour activity

Three sulphated polysaccharides, coded as BEMPA, BEMPB₁, BEMPB₂, were extracted from the mucilage of mud snail of Bullacta exarata and purified by DEAE-cellulose ion-exchange and size-exclusion chromatography. Structural analysis of purified polysaccharides by chemical and biochemical methods revealed BEMPA was a high (1→3,4)-linked mannose-containing polysaccharide with molecular weight of 22,977 Da. BEMPB₁, with molecular weight of 64,117 Da, was a high (1→3)-linked arabinose-containing polysaccharide. BEMPB₂ was mainly composed of (1→3,4)-linked mannose with molecular weight of 47,507 Da. The comparison between sulphated polysaccharides and their desulphated products showed that sulphate substitutions of BEMPB₁ were deduced to be at the C-3 of (1→4)-linked mannose, while sulphate substitutions of BEMPA and BEMPB₂ were at C-4 of (1→3)-linked mannose. Furthermore, BEMPA exhibited highest inhibitory effects on growth of B-16 melanoma cells, and IC₅₀ were 31.1 μg/mL.     

Emulsifying properties of ovalbumin in mixtures with sulphated polysaccharides: effects of pH,ionic strength,heat and high‐pressure treatment

The influence of sulphated polysaccharides (dextran sulphate (DS), ι‐carrageenan (ι‐CAR) and κ‐carrageenan (κ‐CAR)) on the emulsifying properties of ovalbumin (OVA) has been investigated over a range of pressures and temperatures. Oil‐in‐water emulsions (10 g l⁻¹ protein, 200 ml l⁻¹ n‐tetradecane, pH 6.2) prepared with heat‐treated (80 °C for 10 min) mixtures of OVA + DS (1:0.25 by weight) had increased creaming stability but unchanged average droplet size compared to those made with untreated OVA and OVA + DS. Emulsions made with pressure‐processed (600 MPa for 20 min) OVA + DS (1:0.25 or 1:0.5 by weight) mixtures had the best emulsifying efficiency and stability. Under similar experimental conditions, replacement of DS with either ι‐ or κ‐CAR gave emulsions with larger droplets and more rapid serum separation, probably owing to depletion flocculation. High‐pressure treatment (600 MPa) of the OVA and mixed biopolymer solutions at pH 6.2 in the presence of salt (>0.04 M ) led to unstable emulsions, and so the protective effect of DS was lost. High‐pressure treatment (600 MPa) of emulsions prepared with native OVA or OVA + DS mixtures induced significant levels of flocculation, as indicated by changes in the average droplet size and creaming behaviour. © 2000 Society of Chemical Industry     

超声对蔗糖共溶质场中大豆分离蛋白/魔芋胶共混体系流变及凝胶性质的影响

以大豆分离蛋白/魔芋胶(10.0%/0.3%)共混溶液体系为研究对象,研究了超声处理(0、10、20 min,475 W)及添加蔗糖共溶质(0%、10%、20%)对溶胶-凝胶转变过程流变性质及凝胶化速度(v_g)的影响,并分析了质构及微观结构的变化趋势。结果表明:未经超声处理时,随蔗糖共溶质浓度增加,可显著提升共混体系黏弹模量(G′)、凝胶化速率、硬度及黏附性(P0.05);未添加蔗糖条件下超声处理明显弱化了共混体系的v_g及G′,并降低了硬度及黏附性,伴随微观结构发生团块状聚集化;超声可抑制蔗糖共溶质提高共混体系凝胶强度的作用。     

Enrichment of stirred yogurt with soluble dietary fiber from Pachyrhizus erosus L. Urban: Effect on syneresis, microstructure and rheological properties

Yam soluble fiber (YSF) extracted from Pachyrhizus erosus was added (1 g per 100 mL) to a stirred yogurt (SY_YSF). Its syneresis and microstructure properties were evaluated and compared to those of a stirred yogurt (SY_C) without added YSF. The SY_C yogurt exhibited a more compact casein micelle aggregates network than that of the SY_YSF yogurt which was more open, relaxed and covered with fibrous structures attributed to the YSF components. The rheological analysis showed that the SY_YSF yogurt had lower storage modulus (G′) and loss modulus (G″) values in the linear viscoelastic region than the SY_C yogurt, but its flow behavior was characterized by a lower flow index (n), higher consistency index (k), and higher yield stress (τ₀) than the SY_C yogurt. Incorporation of the YSF reduced significantly the syneresis and produced a more acceptable mouthfeel in the SY_YSF yogurt in comparison to the SY_C yogurt, indicating the viability of the process to obtain a commercial product.     

超声辅助酶解对龙头鱼蛋白肽理化性质及风味特性的影响

目的:解决龙头鱼酶解蛋白肽鲜味低、苦味重、风味不良等问题。方法:利用超声辅助酶解法制备龙头鱼蛋白肽,以木瓜蛋白酶作为催化剂,研究不同超声功率(0,120,240,480,600 W)条件下龙头鱼蛋白肽粒径、水解度、可溶性多肽含量、相对分子质量分布、游离氨基酸含量以及电子舌风味信号的变化,进而探究不同超声强度对龙头鱼蛋白肽结构及风味特性的影响。结果:超声强度360 W、超声时间1 h,水浴温度55℃以及水浴时间4 h的条件下,蛋白质水解度达到19.29%,可溶性多肽含量为0.57 mg/mL,超声辅助显著降低了龙头鱼蛋白肽的粒径和相对分子质量,相对分子质量<3 000的组分占比从67%增加至82%。此外,龙头鱼蛋白肽中,苦味氨基酸占主要地位,其次是甜味和鲜味氨基酸。超声辅助酶解蛋白肽中鲜味游离氨基酸含量的增幅最大,因此,超声辅助酶解通过增加鲜味氨基酸的含量降低了龙头鱼蛋白肽的苦味。结论:超声辅助可以提高龙头鱼蛋白的酶解作用,进而改善龙头鱼多肽的理化性质及风味特性。