Additives for Appearance, Consistency, and Stability
Additives added to food in order to consolidate the structure and ensure desired physical characteristics such as appearance, consistency, and long-term stability are classified as thickeners, emulsifiers, gelling agents and humectants.
Thickeners are substances that increase the viscosity of a foodstuff (Regulation UE 1333/2008), control moisture and confer structure to food. Among them, there are substances that have always been used in foods, such as pectin, agar, starch, and gelatin. Until the 1990s, gelatin was one of the most favorite hydrocolloids, but the situation changed dramatically with the discovery of bovine spongiform encephalopathy (BSE, also called mad cow disease).
Thickeners can be grouped in different ways:
- • Based on the source of the raw material (extracts from seaweed, gums obtained from seeds, fermentation products or exudates of plants, of animal origin such as gelatin)
- • Based on their function (thickeners, stabilizers, or gelling agents)
Besides favoring the compactness of some food preparations, since thickeners are allowed to replace some caloric macronutrients such as starches, sugars, and fats retaining water, they are widely used in “light food” preparations.
In recent years, the use of hydrocolloids has been proposed for nutritional and nutra- ceutical purposes. Some of them, such as guar gum, are used as sources of soluble fiber while others are supposed to bring specific benefits to human health (e.g., in weight loss programs).
• Viscosity is, probably, the main function of thickeners. The property to absorb or to bind water, swelling, and making more dense and creamy food preparations allows to maintain the desired rheological characteristics of the product even reducing or completely eliminating fats and oils.
The most used hydrocolloids are modified starch, xanthan gum, sodium carboxym- ethyl cellulose, methylcellulose, and hydroxymethylcellulose, galactomannans (guar gum, locust bean gum, tara gum), konjac mannan.
- • Stability—hydrocolloids have the property of stabilizing the emulsions preventing the separation of two phases in the frozen food and controlling the formation of ice crystals—for example, in ice cream, where carrageenan, locust bean gum and/or guar gum are often used.
- • Suspension—the separation and sedimentation of insoluble particles, when present in a food preparation, must be reduced to a minimum. Some hydrocolloids, such as xanthan gum, are able to create three-dimensional structures that help to maintain such particles in suspension.
- • Gelification—the property of forming gels and solidifying a liquid is one of the thickener's key functions in food products. Carrageenan is used for the preparation of milk gels. Other classic gelling agents are agar, pectin, and gelatin. Some types of alginates form gels with calcium ions, while xanthan gum and locust bean gum form gels together and not individually. Some of them, such as methylcellulose and hydroxy- propylmethylcellulose, form reversible gels only if heated.
A number of materials used in food manufacture may fulfill more than one function. Typical examples are some of the complex carbohydrates otherwise known both as soluble fibers and as effective stabilizing and thickening agents. In normal subjects, some soluble dietary fiber may have a beneficial cholesterol-lowering effect, a fact highlighted by manufacturers of foods naturally high in soluble fiber. In non-insulin- dependent diabetics fed with soluble fibers, an additional postprandial reduction in blood glucose is observed. However, these beneficial effects are dose dependent. An alternative approach relies on the use of polysaccharide gums such as guar, pectin, sodium alginate, and konjac glucomannan incorporated at appropriated doses in everyday consumer products such as bread or cereal.
New trends of use are: 
- • Stellar: This is a microparticulated cornstarch gel used in pastries, snack foods, frost- ings, and fillings, cheese products, margarines, meat products, salad dressings, and other selected products (Anonymous, 1991; Frye and Setser, 1993). The water is bound sufficiently so that migration from the cake to the filling is slowed and staling is retarded. The small, intact starch granules duplicate the mouthfeel sensation of fat. The particle aggregates are 3-5 pm in diameter, slightly larger than the protein-based fat replacer products, but approximately of the same size as the fat crystals they are designed to replace. The microparticulate character is required to maintain the smooth, creamy texture. If the product is heated sufficiently to completely gelatinize and disperse the starch (105°C), much of the fat substitute or mimetic functionality is permanently lost. Applications include low-fat margarines, salad dressings, soups, confectionery products, baked goods, frostings, fillings, and selected dairy and meat products.
- • Fiber-based products include gums, celluloses, hemicelluloses, pectins, p-glucans, and lignins. They are isolated from a wide variety of sources, including cereals, fruits, legumes, nuts, and vegetables gums. They are employed at low concentrations (0.1%- 0.5%) to form gels that increase product viscosity. Agar, alginate, gum arabic, carrageenan, konjac, guar gum, high and low methoxy pectin, xanthan gum, and cellulose derivatives can all potentially be used to this purpose.
-  Alternatives to milk proteins in cheese analogs: There are preparations based onpotato starch, which are capable of reproducing the functional characteristics of milkproteins and to confer the structure and to emulsify the fats. Semi-hard cheese andsliced cheese can be obtained. Suitable for vegans. • Fat replacers—Xanthan gum, guar gum, gum arabic, alginates, cellulose hydrolysis products, hydroxypropyl cellulose, starch hydrolysis products (n < 50), karayagum, and pectins are suitable oligo/polisaccharide materials to be esterifiedwith fatty acids. Preparation may involve direct esterification or transesterification, with metal (sodium methoxide, potassium hydroxide, titanium isopropox-ide, or tetraalkoxide) catalyzed transesterification preferred due to the charringof saccharides that can occur during direct esterification (Mahungu et al.,2002).