Vegetable hydrocolloids are biopolymers with high molecular weight, soluble or suspendable in water. They are important in meat processing primarily because of: their capability of binding large amounts of water and ease of forming lasting gels.
Frequently they have properties facilitating emulsification, dispersing, filling, and forming protective coats. They are widely used in manufacturing perishable finely minced deli meats, smoked meats, canned meats, and patés.
All hydrocolloids are polymers of high molecular weight determining their functional properties. Molecules are linear with side chains, their shape, however, may change in an aqueous solution. Internal bindings or presence of charges in groups may contribute to the molecules’ coiling into spiral forms (helixes) or forming long chain formations, which has a significant effect on such properties as viscosity and stability of solutions.
Key properties of hydrocolloids include dispersibility and solubility, as well as viscosity and gelification. Very often, due to large molecular size, hydrocolloids are difficult to disperse in water because the hydration process progresses rapidly and internally non-hydrated clots form easily, or a difficult to disperse gelification in the surface layer occurs. According to the definition, hydrocolloids are soluble in water and polar solvent, but they vary significantly in terms of solubility degree and optimum temperature of this process.
Carrageenans and hybrid carrageenans
Carrageenan is one of the most frequently used hydrocolloids in meat technology. Depending on the number of sulphate groups in polysaccharide chain and their location, carrageenans can be divided into five types, i.e. kappa (κ), iota (ι), lambda (λ), mi (μ), nu (ν), and in food industry the first three types are of greatest and deciding importance. The chain forming carrageenan’s structure is not homogenous but repetitive units corresponding to basic structure of disaccharides can be distinguished there.
Carrageenans are soluble in water giving solutions of high viscosity. This property results from their non-branched, linear structure and polyelectric nature. Mutual repulsion between many negatively charged ester groups of sulphuric acid, placed along the polymer chain, makes the molecules dispersed in the solution which is caused by carrageenan's hydrophilic groups being surrounded with water molecules. Multifractional carrageenans obtained from sea algae Gigartina, Chondrus spp,. and Eucheuma spp. belonging to the Rodophyceae class are very interesting. They are built of appropriately selected fractions of carrageenans, mainly kappa, iota, and lambda types, owing to which they form hard, plastic, stable gels. Standardisation of the obtained blends of various carrageenan fractions using potassium chloride, sodium chloride, sugars ensures constantly high gel strength. Hybrid carrageenans show an extremely high affinity to meat proteins, having a synergetic effect with other functional additives such as animal and soy proteins, starches, gums, and fibres commonly used in processing. They are versatile and offer many methods of application. They may be added while chopping, mixing and as an ingredient of curing brines, both injection and immersion brines. In thixotropic (pseudoplastic) solutions, they have a limited sedimentation and reduce deposition of other brine ingredients such as proteins, starches etc. on injector filters. Hybrid carrageenans in vacuum-packed and MAP products significantly reduce the quantities of free brine deposits. They form a stable gel even during high-temperature heat processing, thanks to which they may used in the manufacture of sterilised canned meats. They are also an excellent additive to cooked sausages and high-yield formed deli meats. When used in smoked meats, they ensure high final productivities. In meat industry, hydrocolloids are used to improve juiciness, consistency, and productivity of finished products. When added in small amounts, they have a high water-binding capability which allows reduction of losses during heat processing, while improving the consistency of the finished product.
Alginates and alginate blends
Of natural hydrocolloids used in food manufacturing, alginates are a very numerous group (E 400, E 401, E 402, E 403, E 404, E 405). Alginates are obtained from brown algae, especially from Macrocystis pyrifera reaching up to 60m in length. In Europe, Ascophyllum nodosum and Laminaria hyperborea are raw materials for production of alginates. In their native plants, these compounds form a water-binding structure which prevents their desiccation when exposed to air, e.g. during low tide. Chemical properties of alginates offer great possibilities of shaping the food products gelification process. In chemical terms, alginates are salts or esters of alginic acid, which is a polymer of guluronic and mannuronic acids, with various shares of these two components. In neutral solutions, they are nearly entirely dissociated into molecules with negative charges and have viscosity-increasing property. pH reduction lifts the electrostatic repulsion forces, molecule chains draw nearer to each other and tend to gelify.
Alginic acid is a linear copolymer built of two units: D-mannuronic acid and L-guluronic acid. In a molecule of alginic acid, there are alternating blocks made of many homologous monomers of D-mannuronic or L-guluronic acid, called M or G blocks. In the presence of calcium ions or other bivalent cations of similar size (e.g. Ba+2, Sr+2), alginic acid gellifies. Then, the macromolecules of alginic acid are ordered into a configuration consisting in dimerisation of units in blocks made up of L-guluronic units. Two neighbouring chains of the acid form a coordinated structure in which the space between dimers is filled in by a calcium ion which binds carboxylic groups and negatively charged oxygen atoms of hydroxy groups. Geometry of fitting of calcium ions into the spatial structure of acid macromolecules resembles an egg box structure. As gelification triggered by calcium ions occurs in blocks made of G units, the number of these blocks, their length, and alternating order with M blocks define properties of gels obtained from alginic acids of various origin. Alginates may be used as thickeners for sauces, stabilisers, and as a film-forming agent in coating deli meats and fish products. To manufacture deli meats without casings, sodium alginate is usually used. Moreover, alginates can bind water without concerns about syneresis. Alginate addition in foods ranges from 0.1% to 1.5%. Owing to relatively quick gelification induced by calcium ions, sodium alginate found application also in manufacturing of restructured food - as a binding agent for small pieces of meat (slaughter animals, poultry, fish). Unique gelification system gives the resulting gels high thermal stability.
Starches and modified starches
Addition of starch is aimed at increasing water binding, stabilisation of the batter, limitation of thermal losses, and thus increasing product yield. Such effects are obtained owing to the starch’s ability to expand in hot water and form solutions of high viscosity resulting from starch gelation. Gelation of starch, viscosity of solutions, and characteristics of starch gels depend not only on the quantitative ratio of amylose to amylopectin, heat processing temperature, but also from the type and quantity of other ingredients present in a given nutritional system (e.g. fat, emulsifiers).
Very poor solubility in cold water, lack of emulsifying properties, forming opaque gels excludes or significantly reduces the use of this ingredient in the manufacture of smoked meats, pasteurised or sterilised canned meats, patés. Use of starch is on the other hand attractive with regard to cooked sausages, popular in our country. It should be remembered, though, that the larger the addition of starch, the greater the reduction of palatability and deterioration of texture typical for meat products. Susceptibility of native starch to retrogradation, manifested as an adverse syneresis, should also be taken into consideration. Retrogradation is catalysed by mechanical and thermal operations, and in particular the freezing and defrosting processes, so commonly used in food processing, storage, and distribution. Nevertheless, because of general availability and affordable price, native starches are one of the most common raw materials and fillers used in food processing.
Modified starches are starch preparations with significantly enhanced functional properties. Starch can be modified using physical, chemical, and enzymatic methods. Chemical modifications offer the greatest possibilities in obtaining high-functionality starches. Products with the desired functional properties can be obtained by using various modification treatments, such as depolymerisation with acids, salts, and alkali, treatment with oxygenating substances, replacement with esterifying and etherifying agents, intermolecular netting, and modifications with a simultaneous use of two or more methods. Most products obtained this way are not classified as added ingredients but as additives marked with the E symbol.