The term `hydrocolloids’ is commonly used to describe a range of polysaccharides and proteins that are nowadays widely used in a variety of industrial sectors to perform several functions including thickening and gelling aqueous solutions, stabilizing foams, emulsions and dispersions, inhibiting ice and sugar crystal formation and the controlled release of flavors, etc.
Proteins have emulsification and foaming properties. Polysaccharides are used as a water-holding tool, and some hydrocolloids are used as emulsifying agents, e.g., gum Arabic and gelatin.
Food Hydrocolloids
High-molecular-weight hydrophilic biopolymers that can control microstructure, texture, flavor, and shelf-life. Many polysaccharides are extracted from plants, seaweeds, microbial sources (agar, carrageen, xanthan), and gums (gellan, guar, acacia gum) and modified starch or cellulose (chemically or enzymatically).
Stabilizer: Maintains the homogeneous dispersion of two or more immiscible substances in a food.
Thickener: Increases the viscosity of the continuous phase. The size and structure of these large molecules (polysaccharides) create viscosity at fairly low concentrations (usually less than 1%)
Gelling agent: Forms a network gel by chain-chain, chain-solvent crosslinks
Locust Bean gum (LBG): Locust bean gum is milled from the locust bean, also known as the carob bean. It is a branched polysaccharide. The building blocks are α-D-galactopranose, β-D-mannoopranose.
Guar Gum: Guar gum is a galactomannan polysaccharide extracted from guar beans that has thickening and stabilizing properties useful in food, feed, and industrial applications. The building blocks are α-D-galactopranose, β-D-mannoopranose.
Application of LBG and Guar gum
Fat mimetic, ice crystal and viscosity control in ice cream. Speeds up coagulation, Improved moisture binding and texture in cream cheese.
Carrageenan
Carrageenan is a natural carbohydrate (polysaccharide) obtained from edible red seaweeds.
Interactions with proteins
- k-Carrageenan stabilizes milk k-casein products due to its charge interaction with the casein micelles (~200 nm diameter); their incorporation into the network prevents whey separation.
- k-Carrageenan’s ability to complex with milk proteins leads to the formation of a weak thixotropic gel structure which will suspend cocoa in chocolate milk at 0.02% and form milk gels, such as flans, at 0.20%.
- K-carrageenan is also used as a binder in cooked meats, to firm sausages, and as a thickener in toothpaste and puddings.
Xanthan Gum
Xanthan gum is an extracellular polysaccharide secreted by the micro-organism Xanthomonas campestris. Xanthan gum is soluble in cold water and solutions exhibit highly pseudoplastic flow. Its viscosity has excellent stability over a wide pH and temperature range and the polysaccharide is resistant to enzymatic degradation. Xanthan gum exhibits a synergistic interaction with galactomannans such as guar gum and locust bean gum (LBG) and the glucomannan konjac mannan. This results in enhanced viscosity with guar gum and soft, elastic thermally reversible gels with LBG and konjac mannan. Blends of xanthan gum, carrageenan, and galactomannans are excellent stabilizers for a range of frozen and chilled dairy products such as ice cream, sherbet, sour cream, sterile whipping cream, and recombined milk. These economical blends are available pre-prepared to provide optimal viscosity, long-term stability, improved heat transfer during processing, and heat shock protection.
Microcrystalline cellulose (MCC):
Microcrystalline cellulose (MCC) has been used for over 40 years to provide physical stability and texture modification in a wide variety of food applications.
MCC crystals do not dissolve in water, but the colloidal form hydrates to form thixotropic gels that can stabilize foams, replace fat, and control ice-crystal growth.
Heat Stability–MCC is stable during heat processing, including baking, retorting, UHT processing and microwave heating with minimal loss in viscosity.
Shorten Textures–shorten textures or add body without creating a gummy or pasty texture →cleaner mouthfeel and excellent flavor release.
Replace Fats and Oils –mimics the flow behavior of oil emulsions.
Control Ice Crystal Growth-the 3-dimensional matrix of colloidal MCC and the surface area of the microcrystals retards ice crystals’ growth during freeze/thaw cycles. Generally effective in maintaining the three-phase system of water/fat/air.
Opacity-insoluble cellulose crystallites act as opacifiers and can add whiteness to products.
Starch
No other single food ingredient compares with starch in terms of sheer versatility of application in the food industry. Second only to cellulose in natural abundance, this polymeric carbohydrate was designed by nature as a plant energy reserve. Man, however, has extended the use of starch far beyond this original design. Modifications – physical, chemical, or biochemical -mean that numerous highly functional derivatives have enabled the evolution of new processing technologies and market trends.
Starch selection will be influenced not only by the process requirements but also by the product characteristics. Typically, 1±3% starch is used for pouring consistencies, 3±4% for medium viscosity, and 4±6% for thick, spoonable textures. Gelled textures, as in cheese analogs, are achievable with some converted starches or high amylose starches. Gelled dairy desserts will also use other hydrocolloids, notably carrageenans, in combination with starch to create the desired textures.
Pectin
Pectins belong to the group of hetero-polysaccharides and are present in all plant primary cell walls. Depending on the molecular composition there are different types of pectin characterizing themselves, particularly by different gelling mechanisms.
Pectin can have two distinct functions in dairy products and dairy analogs such as those prepared from soya. High-ester pectins can act as protein dispersion stabilizers at reduced pH. Typical examples include yogurt drinks, milk/fruit juice drinks, acidified whey drinks and acidified soy drinks. Low ester pectins behave quite differently and can be used to gel neutral milk desserts or as texturizers in more acid products (e.g., stirred yogurt) by interaction with calcium and milk proteins.
Reference:
Phillips, G.O. and Williams, P.A. eds., 2009. Handbook of hydrocolloids. Elsevier.
