Food Hydrocolloids: Structures, Properties, and Functions

---

Physiological Aspects of Food Hydrocolloids D.

Includes bibliographical references and index. View online Borrow Buy Freely available Show 0 more links Related resource Table of contents only at http: Set up My libraries How do I set up "My libraries"? These 2 locations in All: Open to the public. This single location in New South Wales: This single location in Victoria: None of your libraries hold this item. Tags What are tags? Public Private login e. Add a tag Cancel Be the first to add a tag for this edition. Lists What are lists? Login to add to list. Be the first to add this to a list.

Comments and reviews What are comments? The important gums that find application in food as gelling agents include alginate, pectin, carrageenan, gellan, gelatin, agar, modified starch, methyl cellulose and hydroxypropylmethyl cellulose. The formation of gel involves the association of randomly dispersed polymer segments in dispersion in such a way so as to form a three-dimensional network that contains solvent in the interstices. The gelation process is essentially the formation of these junction zones Oakenfull The physical arrangement of these junction zones within the network can be affected by various parameters like temperature, presence of ions and inherent structure of hydrocolloid.

For the gelation of hydrocolloids, the three main mechanisms proposed are ionotropic gelation, cold-set gelation and heat-set gelation Burey et al. Ionotropic gelation occurs via cross-linking of hydrocolloid chains with ions, typically a cation mediated gelation process of negatively charged polysaccharides.

Examples of such systems are alginate, carrageenan and pectin Draget ; Imeson ; May Ionotropic gelation is carried out by either diffusion setting or internal gelation. Agar and gelatin form gel by this mechanism Glicksman Heat set gels require the application of heat to gel eg, curdlan, konjac glucomannan, methyl cellulose, starch and globular proteins. It is usually only where heat setting is required in foods eg, the use of starch in sauces. Junction zones play a very important role in the gelling process of hydrocolloids de Vries They also markedly influence the characteristics and functional behaviour of a particular gel.

The number of molecules that form a junction zone is an important gel property determinant. During gelatin, junction zones are formed by three molecules through hydrogen bonding. More the number of molecules in the junction zone, more rigid will be the gel. The number of junction zones and number of molecules in the junction zones and the flexibility of the interrupting segments are important for the characteristics of a set gel. The thermal behaviour of gels also differs because of the junction zones. Gelatin melts at much lower temperature because the junction zones are only bound by weak hydrogen bonds.

On the other hand, it is possible to make alginate gels that do not melt on boiling because of the strength of calcium bridges in the junction zones. One of the major factors influencing the strength of junction zones is their length. Calcium bridging is cooperative, i. Solvent quality is also another important factor. Hydrogen bonds in high methoxy pectin gels can only be formed if the water activity is sufficiently reduced by addition of sugar. In addition to having knowledge of the factors that affect gel formation by hydrocolloids, it is also necessary to characterize the gels formed by them.

Microstructural and rheological characterizations are generally done and are often followed by sensory evaluation. Rheological characterization of gels involves characterizing a gel on the basis of various parameters like modulus of elasticity, yield stress, shear modulus, storage and loss modulus, complex viscosity, gel strength and compliance.

These parameters are usually determined by conducting tests like compression test, dynamic oscillatory rheometry, creep and texture profile analysis, etc. Not only the measurement but also studying the influence of gel forming conditions on the attributes and characteristics forms an indispensable part of the study on gels.

There was a problem providing the content you requested

These studies, in turn, help in the formulation of food products, wherein hydrocolloids are incorporated as gelling agents. Addition of sucrose results in an increase of true rupture stress in all these gels. However, addition of aspartame at low concentration does not affect the textural compression parameters. In addition, the main factors determining the gel sweetness are related with mechanical properties of gel like gel strength, rupture stress, rupture strain and particularly with the amount of deformation required to break the network and with its resistance to deformation Bayarri et al.

Besides, co-solutes like sucrose, concentration of hydrocolloid, shear rate and temperature are also important variables that influence the rheological status of hydrocolloid gels Marcotte et al. The non-gelling agents eg, xanthan and guar gum , and gelling agents carrageenan and locust bean gum are commonly combined to achieve increased viscosity or superior properties of food gels, such as higher elasticity Nussinovitch The blending of different polysaccharides offers an alternative route to the development of new textures.

The major interest lies in the development of synergistic mixtures with improved or induced gelation. Both xanthan and galactomannans do not form gels when used singly. But together, they form gels because of synergistic interactions. The mixture of xanthan and galactomannan is one of the oldest and most extensively studied synergistic gelling systems.

Xanthan shows quite spectacular synergistic interactions with other non-gelling polysaccharides of galactomannan family leading to increase in viscosity Casas and Garcia-Ochoa and gel formation Rodriguez-Hernandez and Tecante The distinction between increased viscosity and gelation lies on the mannose-galactose ratio of the galactomannan Morris At higher concentrations, soft and elastic gels are formed with locust bean gum LBG.

The interaction of xanthan gum with galactomannan is dependent on the ratio of the mixture, pH and ionic environment. Optimum gum ratios are Generally, the synergistic interaction with galactomannans is at its maximum in deionised water at neutral pH and it gets reduced at high salt concentrations and low pH Sworn Xanthan possesses a synergistic interaction with konjac glucomannan KGM during gel formation. Their synergism produces thermoreversible physical gels at neutral pH. Best synergism is obtained when konjac to xanthan ratio is Kappa-carrageenan is a gelling agent, the synergistic interactions of which, with other hydrocolloids have been exploited in several food formulations.

The maximum interaction, and hence, peak rupture gel strength occurs at ratios between These polymer combinations are used in large quantities in cooked meats and in gelled pet foods. The selection of a particular hydrocolloid to be used in a specific food product depends on the characteristics of gelling agent. For example, alginate can form gels without prior heating because sodium alginate is cold water soluble and these cold-formed gels are heat stable.

This makes alginate a preferred gelling agent for re-structured foods and for cold-prepared instant bakery custard that are bake-stable de Vries The rapid setting behaviour of alginate gels is also important in restructured foods that are diffusion-set Draget Alginates as gel forming agents find applications in restructured fruits and vegetables, restructured fish and meat, puddings and desserts, cold prepared bakery creams, fruit preparations and bakery jam Onsoyen In icings and toppings, fruit pie fillings and table jellies alginates are used but they are incompatible with milk, except in the presence of calcium sequestrants.

Carrageenan is a hydrocolloid that finds maximum application in dairy desserts like puddings, milk shakes, ice cream and chocolate milk because of its ability to form gels in milk at much lower concentrations compared to any other gelling agent Puvanenthiran et al. Use of carrageenan in tofu soybean curd significantly decreases the hardness of tofu when calcium sulphate and calcium acetate are used. The other important application of carrageenan is in injected meat, in which only carrageenans can be dispersed in brine without too high viscosity and simultaneous gel formation when the ham has been cooked de Vries Because of the clarity of carrageenan gel and high gelling temperature, it is valued in the preparation of cake glazes and water dessert gels.

In addition, the firm and quick setting behaviour of carrageenan gels is made use of in processed cheese systems Thomas Synergistic carrageenan-locust bean gum combinations are being used in table jellies and low sugar, low-acid fruit gels, in which carrageenan has the advantage over pectin that it dissolves well in sugar solutions, whereas pectin has to be pre-dissolved in water.

Commercial pectin finds maximum applications in jams and jellies. Pectins are the most preferred gelling agents for acidic fruit gels because of being acid stable.

Account Options

To overcome the limitation of high methoxyl pectin, low methoxyl pectins both commercial and amidated types are used in the preparation of reduced sugar jams and jellies. Low methoxyl pectins are also used for the production of glazes in bakery industries. Other applications of pectin include desserts, both water gels and milk based gels. Milk and milk products can easily be gelled with low methoxyl pectin because they contain calcium; milk desserts and gelled or thickened milk products like yoghurts can be prepared.

Gelatin exhibits a wide range of functional properties. It can be used as a gelling agent in jellied confectionery Jones Gelatin gels melt at relatively low temperature melt-in mouth , and they are slow-setting; all these features make gelatin the preferred gelling agent in yoghurt products, low-fat spreads and sugar confectionery.

Marshmallow, an aerated gelled confectionery, uses gelatin as gelling agent for its elasticity and clarity; clarity of gelatin is also the main reason for its use in table jellies de Vries Gelatin has also been used in flavoured gelled milk desserts, either alone or in combination with carrageenan, and also in dessert creams. In dessert creams, it is used to achieve a smooth gel texture Poppe The food applications of agar are in the areas like bakery products, confectionery, Japanese desserts and confections, meat, fish and poultry products, dairy products, ice cream, peanut butter and beverages.

The high melting point of agar gels is improved by the addition of salts. Agar is used in baked goods where it is superior to carrageenans and far superior to gelatin. Agar is also widely used as a gelling agent in jelly confections including traditional Japanese food items and confections like Yokan, Mitsumame, Tokoroten etc Uzuhashi and Nishinari Agar is also used at levels of 0. Gellan gum is unique in the spectrum of gelling agents used in food applications.

Rapid setting behaviour, low use level, sparkling clarity of the gel and good flavour release are some of the attributes that make gellan as a preferred gelling agent for food products Valli and Miskiel It is also used in bakery fillings as partial starch replacement to increase flavour release, in water based dessert gels because of its good clarity and adequate thermal stability. Deacylated gellan gum is used to improve moisture retention, flavour release and storage stability in puddings and to reduce syneresis Sworn The fluid like behaviour of gellan gum at low concentrations Sworn et al.

Gellan gum also acts as a very good stabiliser in reconstituted vegetable juice Liang et al. Characterisation of gels forms an essential part in the study of thickened dispersions and gels formed by various hydrocolloid gelling agents.

Account Options

Characterisation may involve rheological characterization, structural characterization, microscopic characterization and molecular characterization employing different instruments like viscometers, rheometers, texture measuring systems, differential scanning calorimeters, scanning electron microscope, atomic force microscope, NMR and NIR. Among these, rheological characterisation of sample is most important and generally performed practice since it correlates to the textural attributes of the product, which, in turn, determines its sensory characteristics and consumer acceptability.

In rheological terms, thickened dispersions and gels are viscoelastic materials. They simultaneously exhibit some of the elastic properties of an ideal solid and some of the flow properties of an ideal liquid. Various parameters like apparent viscosity, shear stress, modulus of elasticity, yield stress, shear modulus, storage and loss modulus, complex viscosity and loss angle are used to describe the characteristic rheological behaviour of these food systems.

The rheological behaviour of food products involving hydrocolloids has been studied extensively in both time and frequency domains, using small stress and strain regimes. However, during processing, manufacture and consumption of foods, these systems are subjected to large deformations.

These two types of tests give complementary information that does not necessarily correlate. Small deformation testing generally investigates viscoelastic parameters. These moduli values are independent of the geometry of both the measuring system and the gel sample; consequently these are invaluable for comparing the elasticity of gelling systems.

Large deformation tests, on the other hand, are used to measure shear stress, yield stress, apparent viscosity, strain and failure properties of the product. In general, the rheological test methods for the assessment of gel characteristics can be grouped into three types namely, fundamental, imitative and empirical. Each has certain advantages and a few limitations. Fundamental small deformation tests involve dynamic oscillatory rheometry, creep test and stress relaxation test. In dynamic oscillatory rheometry, the sample is subjected to an oscillatory stress-strain of frequency.

These parameters are very important for the rheological characterization of gels. Its value is given by the formula. Another important test is the creep test. Gel, being a viscoelastic material, responds to the creep test with a nonlinear strain. The important property measured during creep test is the ratio of strain to stress as a function of time, and is referred to as the creep compliance.

It describes how compliant a material is; the greater the compliance, the easier it is to deform the material. Stress relaxation is another important study in the rheology of food. If a gel sample is deformed by a fixed strain and held there over a long time interval, the stress required to maintain this constant strain will gradually decrease due to relaxation of the sample.

The sample under testing will only partially recover its original geometry. The relaxation modulus is an important rheological property measured during stress relaxation. It is the ratio of the measured stress to the applied initial strain. These parameters are usually determined by constant speed experiments such as uniaxial compression and uniaxial tension performed on texture measuring systems. Compression test and tensile tests are generally performed in this study. Compression or penetration tests constitute the basis of many small-deformation empirical tests used to measure gel strength.

The most common parameter used to measure gel quality is gel strength. The choice of instrument for gel measurement will depend on whether a single-point or multi-parameter analysis.

Hydrocolloids as thickening and gelling agents in food: a critical review

It is governed by factors like high-speed data acquisition, precision and accuracy of results. Large-deformation empirical tests are used to measure another parameter of gels known as rupture strength i. The single point measurements, often based on rupture tests, are not representative of the overall mechanical behaviour of gels.

A much more comprehensive understanding of gel texture is obtained by analysis of the force-deformation curve generated by compressing a gel sample using a texture measuring system.

This instrumental technique is known as texture profile analysis. It is a technique based on compression of free-standing gels twice in succession and is capable of providing both fundamental and empirical data on the mechanical properties of gels. It has the advantage of providing data at both low and high strains allowing gels to be characterised by multiple parameters. The flowable materials like thin and thick dispersions are conventionally examined employing a viscometer or rheometer.

Introduction

Generally, the shear rate-stress data are collected over a wide range along with the measurement of apparent viscosity, yield stress, zero-shear and high-shear viscosities. A number of available rheological models are used to calculate model parameters like consistency index and flow behaviour index and these parameters help in the characterisation of the samples.

Food Hydrocolloids: Structures, Properties, and Functions - Google Книги

As an important food additive, hydrocolloids are finding increasing applications in several food products as thickening and gelling agents. The thickening effects are mainly provided by carboxymethyl cellulose, methyl cellulose and hydroxypropylmethyl cellulose, guar gum, locust bean gum, tara gum, konjac maanan, gum tragacanth, gum ghatti and gum Arabic.

The frequently used gelling agents include modified starch, agar, carrageenans, pectins, gellan gum, alginates and methyl and hydroxypropylmethyl celluloses. The role of each hydrocolloid in food formulations and product development has been discussed along with examples and methods of characterisation to indicate the increasing use of hydrocolloids as an important food additive.

National Center for Biotechnology Information , U. J Food Sci Technol. Published online Nov 6. Dipjyoti Saha and Suvendu Bhattacharya. Author information Article notes Copyright and License information Disclaimer. Revised Jan 27; Accepted Feb 2. This article has been cited by other articles in PMC. Abstract Hydrocolloids are widely used in many food formulations to improve quality attributes and shelf-life. Hydrocolloids, Thickening, Gelling, Rheology. Thickening agents Hydrocolloids are frequently used in several foods for thickening. Hydrocolloid as a thickener Properties Application in food products Reference Xanthan Highly shear thinning; maintains viscosity in the presence of electrolytes, high temperature and wide pH ranges Soups and gravies, ketcups, instant beverages, desserts, toppings and fillings Urlacher and Dalbe , Sahin and Ozdemir Carboxymethyl cellulose CMC High viscosity but is reduced by adding electrolytes and at low pH Salad dressings, gravies, fruit pie fillings, ketchup Koocheki et al.

Open in a separate window. Hydrocolloid as a gelling agent Characteristics Application in food Reference Modified starch Thermally irreversible opaque gels formed on cooling Dairy desserts Verbeken et al. Process of thickening The application of a hydrocolloid depends on the knowledge and understanding of the process of thickening—an important role of any hydrocolloid. Gels and gelling agents Gels may also be defined as a form of matter intermediate between solid and liquid and show mechanical rigidity Aguilera Process of gelling The formation of gel involves the association of randomly dispersed polymer segments in dispersion in such a way so as to form a three-dimensional network that contains solvent in the interstices.

Role of junction zones in gelling Junction zones play a very important role in the gelling process of hydrocolloids de Vries Applications of hydrocolloids as gelling agents The selection of a particular hydrocolloid to be used in a specific food product depends on the characteristics of gelling agent.

Rheology of thickeners and gels Characterisation of gels forms an essential part in the study of thickened dispersions and gels formed by various hydrocolloid gelling agents. Fundamental methods Fundamental small deformation tests involve dynamic oscillatory rheometry, creep test and stress relaxation test. Empirical methods Compression or penetration tests constitute the basis of many small-deformation empirical tests used to measure gel strength.

Imitative methods The single point measurements, often based on rupture tests, are not representative of the overall mechanical behaviour of gels. Conclusions As an important food additive, hydrocolloids are finding increasing applications in several food products as thickening and gelling agents. Effect of carrageenan on yield and properties of tofu.

Melt-in-the-mouth gels from mixtures of xanthan and konjac glucomannan under acidic conditions—a rheological and calorimetric study of the mechanism of synergistic gelation.

• When 1+1=1: That Impossible Connection
• Storie di Fantasmi per il Dopocena (Told After Supper) (Radici) (Italian Edition)
• Whats Eating....YOU?
• From the Secret Files of J. Edgar Hoover
• Child Health & Development: General Practice: The Integrative Approach Series