Hydrocolloids serve a variety of functions. In foods which have had value added the functionality may be complicated by the other ingredients. The listing of gums, does not cover all food gums available to the food processor and preparer. Genetic and processing improvements are constantly being made. Additionally, further sources are being investigated. It is likely that there may be a additional hydrocolloids developed from trees, plants and seaweed. However, it is more likely that innovations and development of additional hydrocolloids will be obtained from microbes. It is because of the latter that the food industry is more likely to talk about the use of hydrocolloids; however, one needs to be aware that, historically, vegetable gums are a significant category of these hydrocolloids.

There are many different sugars involved in the primary hydrocolloids used in foods. It should be remembered that many hydrocolloids themselves are polysaccharides. There may be other constituents removed during extract of a exudate, seed or seaweed. It is of interest to note that Gum Arabic, although considered to be a polysaccharide, may have amino acids at the peripheral of the branched structure with a greater proportion located within the core of the exudate structure. One should thus recognize that the functionality of the gums may be determined by proteoglycans rather than that of pure polysaccharidse. Other gums may also have amino acids. Further work in this area needs to be done.

Basically, these hydrocolloids are water-soluble. Because of this water-solubility, they improve mouthfeel and pourability, extend shelf-life, encapsulate flavors, emulsify beverages, build viscosity, retain moisture, and provide elasticity and freeze-thaw stability. By definition, hydrocolloids, to various degrees, are water-soluble, and will hydrate and increase viscosity. Selecting the appropriate hydrocolloids requires not only an understanding of the physical properties of the hydrocolloids but also an understanding of the foods themselves. The important differences are exhibited in the other properties and functions. It is difficult to ascribe defined exact characteristics and functions to the broad class of gums' indicated in this module. The properties of the gums expressed in food are effected by many factors such as: orientation and molecular association, orientation, water-binding and swelling, concentration, particle size, degree of dispersion, and interaction with other gums. For example, carraggeenan has several chemical structures which gives slightly different functional properties. The individual characteristics of carrageenan and locust bean gum may be enhanced beyond the sum of each due to the synergism and interaction of these two gums. This is particularly evident in chocolate milk or a frozen dairy product.

How does the food processor and preparer go about selecting the appropriate hydrocolloid?

To some extent one can generally indicate the gum to select for a product based on its characteristics. It is critical to have a concept and understanding of characteristics to do this, however, a more precise and accurate selection can be made by contacting a manufacturer.

Applications are many. Part of the reason, this is so the properties given off by the tremendous properties many 1% low little flavor little color. However, the selection process and subsequent application is critical to understanding the interaction of hydrocolloids, food ingredients and the ultimate food product. One of the processes for gaining this understanding is to work through applications available on this web site.

Classes of Hydrocolloids:

Water-Soluble Hydrocolloids

• agar: agar is a polysaccharide found in the cell walls of some red algae and is unusual in containing sulfated galactose monomers. It requires nothing but extraction and purification to become agar, but is sometimes chemically modified into agarose for special applications. Agar: gracilaria or gelidium, is the queen of gelling agents
• hydrocolloid: a substance with particles of colloidal size that is greatly attracted to water and absorbs it readily; colloidal materials such as vegetable gums, that bind water and have thickening and/or gelling properties; large molecules, such as those that make up vegetable gums, that form colloidal dispersions, hold water, and often serve as thickeners and stabilizers in processed foods.
• methyl ester of galacturonic acid: ester is the chemical word used to describe the linkage between an organic acid group (-cooh) and an alcohol group (-oh); in this case, the alcohol is methanol (which contains only one carbon atom) and the acid is galacturonic acid
• microcrystalline cellulose: is a gum which is the nonfibrous form of cellulose, being an alpha cellulose. It is dispersible in water but not soluble, requiring considerable energy to disperse and hydrate. In this form it is used in dry applications such as tableting, capsules, and shredded cheese where it functions as a nonnutritive filler, binder, flow aid, and anti caking agent.
• plant exudates: materials that ooze out of certain plants; some that ooze from certain tree trunks and branches are gums
• polydextrose: a bulking agent made from an 89:10:1 mixture of glucose, sorbitol, and citric acid; in body metabolism it yields one kilocalorie per gram; often used with nonnutritive sweeteners in manufactured foods; is a condensation polymer of dextrose with minor amounts of sorbitol and citric acid; it contains only 1 kilocalorie per gram.
• polymer: a giant molecule formed from smaller molecules that are chemically linked together.
• vegetable gums: polysaccharide substances that are derived from plants, including seaweed and various shrubs or trees, have the ability to hold water, and often acid as thickeners, stabilizers, or gelling agents in various food products; for example, algin, carrageenan, and gum arabic
• xanthan gum: A polysaccharide gum produced on a commercial basis from the fermentation of corn sugar by the bacterium Xanthomonas campestris. The United States Agriculture Department has asked for the3 use of xanthan gum as a necessary ingredient in packaging meat and poultry products. It is now used to thicken, suspend, emulsify, and stabilize water-based foods, such as dairy products and salad dressings.