Hydrocolloids_tee

**__Food Hydroco__****__lloid: Gums and stabilizers__** ====Gums, or hydrocolloids, are mainly long-chain, straight or branched polysaccharides that contain hydroxyl groups than can bond to water molecules. (Gelatin, a polymer of amino acids linked with peptide bonds, is also often described as a gum since it functions in a similar manner.) ====

** Gum's viscosity & hydration rate **

 * ====chain length, or degree of polymerization (DP)====
 * ====molecular weight (MW)====
 * ====degree of substitution (DS)====
 * ====types of substitution====
 * ====even vs uneven substitution====

- Longer molecules tend to produce higher viscosities and take longer to hydrate than shorter ones.
====- A highly branched molecule takes up less space than a straight one with the same molecular weight, and therefore provides less viscosity. ==== ====- The more substitution, the more the chains are held apart from each other. Because this prevents them from forming hydrogen bonds, they hydrate more quickly. ==== ====- Guar gum vs. locust bean gum -> both gums are galactomannans, but LBG is cold water insoluble (highly uneven substituted), guar gum is cold water soluble (even substituted). ====

====In general, gums are used to influence texture and mouthfeel, as well as water-binding and stabilization of crystallization properties of ice cream and confectionery products. We can get a variety of different textures - from just a mouthfeel texture like you'll see in a diet soft drink, to a firm, hard gel used in confectionery products. Some actually form a gel, while others act as thickeners. ====

====**Gum arabic ** comes commercially from the //Acacia senegal// tree. It is used as an emulsifier, thickener and flavor encapsulator. Gum arabic contains small amounts of protein surrounded by beta-1,3-linked galactose units. It is very water-soluble, compatible with high solids and provides low viscosity. ====


====**Agar-agar** is a polysaccharide derived from various species of red algae such as //Sphaerococcus, Euchema// and //Gelidium//, and contains sulfated galactose monomers. Agar forms gels at approximately 35°C, but once formed, does not melt below 85°C. ====

====**Guar gum** is derived from the seed bean plant //Cyamopsis tetragonolobus//. This long-chain, linear molecule of beta-1,4-D-galactomannans with alpha-1,6-linked D-galactose has a molecular weight of approximately 1,000,000. Guar gum is a cold-water-soluble polysaccharide, and it hydrates easily to produce solutions with a high viscosity at low concentrations. The molecules exhibit interfacial binding which makes them true emulsifiers. Guar has viscosity synergism when combined with xanthan. ====

====**Locust bean gum**, from //Ceratonia siliqua//, is a branched beta-1,4-D-galactomannan with a high molecular weight. This non-ionic polymer is only partially soluble in cold water; to fully hydrate, it must be heated. It works synergistically with kappa-carrageenan to form a rigid gel. ====


====**Konjac**, a beta-1,4-glucomannan, is derived from the roots of the elephant yam (//Amorphophallus konjac//). It has a molecular weight of 200,000 to 2,000,000. It swells at room temperature, but shear and heat increase the hydration rate. It is considered a pseudoplastic viscosifier, and yields thermally irreversible gels, when set with alkali or heat, that are stable at pH 3 to 9. ====


====<span style="font-family: 'Times New Roman','serif'; font-size: 16.6667px;">**Alginates** are extracted from brown seaweed or kelp. Alginate is made up of the five-carbon polymers mannuronic acid and gluronic acid. In the presence of calcium ions, it forms thermally irreversible gels. The reaction can easily be varied to control speed of set and degree of setting. Alginate gels are heat-resistant and can be prepared at very low solids. ====

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====<span style="font-family: 'Times New Roman','serif'; font-size: 16.6667px;">**Carrageenans** are linear sulfated galactans obtained from red seaweeds (//Rhodophyceae//), but since the carrageenan molecule has up to 1,000 galactose residues, it has many structures. These are usually defined as one of three main types: kappa, iota or lambda. Mu, nu and xi fractions have also been identified. These types have different gelling properties and protein reactivities, although they are stable over a wide pH range. Kappa carrageenans produce strong, rigid gels, especially in the presence of potassium ions, while gels made with iota are weaker, with less tendency toward syneresis. Although lambda carrageenans do not gel in water, they interact strongly with proteins to produce a pseudoplastic thickener. ====

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====<span style="font-family: 'Times New Roman','serif'; font-size: 16.6667px;">**Pectin** is commercially extracted from citrus peels and apple pomace. It consists mainly of galacturonic acid and galacturonic acid methyl ester units that form linear chains. It is normally classified according to its degree of esterification - a pectin with at least 50% DE or greater is a high-methoxy (HM) pectin, while one below a DE of 50% is a low-methoxy (LM) pectin. The two types possess different properties; for example, low-methoxy pectin requires calcium to gel. ====

====**<span style="font-family: 'Arial','sans-serif';"> - **<span style="font-family: 'Arial','sans-serif';">DE <50%, form thermally reversible gel in the presence of divalent cations, Ca2+ ions at low pH ====

====<span style="font-family: 'Times New Roman','serif'; font-size: 16.6667px;">**Xanthan gum** is a polysaccharide produced by //Xanthomonas campestris// bacteria. Xanthan gum develops a weak structure in water, which creates high-viscosity solutions at low concentration. The viscosity remains fairly constant from 0°C to 100°C. It is pseudoplastic over broad shear rate and concentration ranges, but imparts a stringy texture. Xanthan has excellent solubility and stability under acidic and alkaline conditions and in the presence of salts, and resists common enzymes. Guar and xanthan show viscosity synergy, and when combined with tara or locust bean gum, xanthan can form thermoreversible gels above certain concentrations. ====

====<span style="font-family: 'Times New Roman','serif'; font-size: 16.6667px;">**Gellan gum** is a gel-forming polysaccharide derived from //Pseudomonas elodea//. These gels are clear, heat stable, and set quickly with minimal refrigeration. ====

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====<span style="font-family: 'Times New Roman','serif'; font-size: 16.6667px;">**Cellulose** is the most common polysaccharide, a polymer of glucose molecules linked by beta-1,4 linkages, and is the starting material for cellulosic gums. ====

====<span style="font-family: 'Times New Roman','serif'; font-size: 16.6667px;">**Microcrystalline cellulose (MCC)** provides a high degree of thixotropy, which results from the large number of colloidal microcrystalline particles formed by hydrolyzing cellulose. The network establishes a weak gel structure with a measurable yield point that is broken down by shear. Upon removal of shear, the gel structure re-establishes. MCCs are heat- and freeze/thaw stable, and stable from pH 4 to 11. ====

====<span style="font-family: 'Times New Roman','serif'; font-size: 16.6667px;">**Carboxymethylcellulose (CMC) gum**, or cellulose gum, is a sodium salt derived from purified cellulose. The long, negatively charged molecules produce a stable thickener that can also help stabilize protein against precipitation. CMCs form viscosity synergies with guar. ====

====<span style="font-family: 'Times New Roman','serif'; font-size: 16.6667px;">**Methylcellulose (MC) and hydroxypropyl methylcellulose (HPMC)** are cellulosic gums with methyl ether and/or hydroxypropyl groups. The molecules are soluble in cold water, but also exhibit a unique reversible thermal gelation effect, forming a gel with the application of heat. ====

====<span style="font-family: 'Times New Roman','serif'; font-size: 16.6667px;">**Gelatin** is a high-molecular-weight polypeptide derived from collagen from animal connective tissues. Gelatin is not a polysaccharide, rather a mixture of peptides used as a gelling, thickening and stabilizing agent. ====

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> ====<span style="font-family: 'Times New Roman','serif'; font-size: 16.6667px;">Gums are generally used in the range of 0.05% to 1.00%, while starches are usually in the 0.75% to 10.0% range. The higher concentration of starches tends to encapsulate or capture flavor molecules more readily than gums. ==== > ====<span style="font-family: 'Times New Roman','serif'; font-size: 16.6667px;">Agar is a very unique product. It gels at 35°C, but guess when it melts - 85°C. Very few gums do this. When you want a gel that is heat-reversible, but will not melt at high-temperature conditions, agar can be used. This might be of value in applications such as icings and confectionery products ==== <span style="font-family: Arial,Helvetica,sans-serif;">
 * 1) ====Gums vs Starches====
 * 1) ====Cellulosic gums are thermal gellation.====
 * 2) ====Gelatin melts at around body temperature (<span style="font-family: 'Times New Roman','serif'; font-size: 16.6667px;">35°C ) -> melt-in-mouth special properties====
 * 3) ====Xanthan gum is stable at wide pH range, acid tolerant.====