Preparation, food colloids

Most food products and food preparations are colloids. They are typically multicomponent and multiphase systems consisting of colloidal species of different kinds, shapes, and sizes and different phases. Ice cream, for example, is a combination of emulsions, foams, particles, and gels since it consists of a frozen aqueous phase containing fat droplets, ice crystals, and very small air pockets (microvoids). Salad dressing, special sauce, and the like are complicated emulsions and may contain small surfactant clusters known as micelles (Chapter 8). The dimensions of the particles in these entities usually cover a rather broad spectrum, ranging from nanometers (typical micellar units) to micrometers (emulsion droplets) or millimeters (foams). Food products may also contain macromolecules (such as proteins) and gels formed from other food particles aggregated by adsorbed protein molecules. The texture (how a food feels to touch or in the mouth) depends on the structure of the food. 

Weiss, J., Kobow, K., and Muschiolik, G. 2004. Preparation of microgel particles using membrane emulsification. Abstracts of Food Colloids, Harrogate, U.K., B-34. 

Spray drying has been used to prepare pharmaceutical products from solid meat by-products such as liver, intestine and stomach. The solid material is first ground and then homogenised in a colloidal mill (Masters, 1991) prior to spray drying. This technology could be adapted to prepare food ingredients from solid offals, trimmings and MSM. 

Many texibiwks on tlie physicochemical properties of colloidal suspensions mention the pharmaceutical held as one in which colloids hnd industrial and technological applications (see, e g.. Refs. 1-3). Together with, perhaps, inks, food colloid., and paints, pharmaceutical suspensions are designed to be used in most cases not by specialists but rather by people who only need to know proper directions for use, and quick and efficient therapeutic effects. This means that in their formulation there are involved factors that are not normally considered when colloid scientists prepare their suspensions. For in.stance. pharmaceutical suspensions... 

Carotenoids are also present in animal products such as eggs, lobsters, greyflsh, and various types of hsh. In higher plants, they occur in photosynthetic tissues and choloroplasts where their color is masked by that of the more predominant green chlorophyll. The best known are P-carotene and lycopene but others are also used as food colorants a-carotene, y-carotene, bixin, norbixin, capsanthin, lycopene, and P-apo-8 -carotenal, the ethyl ester of P-apo-8-carotenic acid. These are Upid-soluble compounds, but the chemical industry manufactures water-dispersible preparations by formulating coUoid suspensions by emulsifying the carotenoids or by dispersing them in appropriate colloids. ... 

The structures of four of the synthetic carotenoids (beta-carotene, canthaxanthin, beta-apo-8 -carotenol, beta-apo-8 -carotenoic acid) are shown in Fig. 8.2. By virtue of their conjugated double bond structure, they are susceptible to oxidation but formulations with antioxidants were developed to minimize oxidation. Carotenoids are classified as oil soluble but most foods require water soluble colorants thus three approaches were used to provide water dispersible preparations. These included formulation of colloidal suspensions, emulsification of oily solutions, and dispersion in suitable colloids. The Hoffman-LaRoche firm pioneered the development of synthetic carotenoid colorants and they obviously chose candidates with better technological properties. For example, the red canthaxanthin is similar in color to lycopene but much more stable. Carotenoid colorants are appropriate for a wide variety of foods.10 Regulations differ in other countries but the only synthetic carotenoids allowed in foods in the US are beta-carotene, canthaxanthin, and beta-8-carotenol. 

The U.S. Food and Drug Administration has clamped down on colloidal-silver preparations, banning the sale of any such product that claims to deliver health benefits. Unfortunately,... 

Although colloids may be undesirable components in industrial systems, particularly as waste or by-products and, in nature, in the forms of fog and mist, they are desirable in many technologically important processes such as mineral beneficiation and the preparation of ceramics, polymers, composite materials, paper, foods, textiles, photographic materials, drugs, cosmetics, and detergents. The remainder of this chapter specifies some applications for colloidal solids, liquids, and gases and illustrates how colloids can affect many technologically important systems. 

The applications of colloid solutions are not restricted to paints and clay. They are also to be found in inks, mineral suspensions, pulp and paper making, pharmaceuticals, cosmetic preparations, photographic films, foams, soaps, micelles, polymer solutions and in many biological systems, for example within the cell. Many food products can be considered colloidal systems. For example, milk is an interesting mixture containing over 100 proteins, mainly large casein and whey proteins [6,7]. 

Sorption of various gases (02, N2, C02, and He) on wheat flour, soybean flour, potato starch, and wheat starch has been investigated in order to study the effect of those gases on the functional properties of processed food products. Results indicate that such properties improved only after flour and starch were treated with chlorine.455,456 The adsorptivity of various gases by starch has been reexamined.457 Liquid ammonia quickly forms a gelatinous paste with starch.458 Tomasik et al.459 attempted to prepare inclusion complexes of starch with colloidal sulfur. A key result was that inclusion inside the starch matrix was only possible in small amounts because of the large relative size of the sulfur micelles. 

Colloid mills are used to grind and disperse solids in hquids and to prepare emulsions. They operate on the principle of high-speed fluid shear to grind the feed material. Another application is in the manufacture of lubricating greases by dispersion of calcium stearate in hydrocarbon oils. In the paint industry, colloid mills are used to incorporate pigments in liquid vehicles. In the food industry, the mills are used to make purees, sauces, ointments, creams, lotions, and other products. 

Colloidal, aqueous dispersions of microcrystalline cellulose can be prepared by boiling cotton linters for 15 minutes with 2.5 N hydrochloric acid, followed by subjecting the resulting (level-off D.P.) cellulose to vigorous mechanical agitation. The microcrystals ( Avicel ), which are thereby freed from their fibrous packed structure, have been put to a variety of uses in the production of food gels and structural materials. ... 

We wish to thank the following companies for their generous financial support of the symposium Hewlett-Packard-Genenchem The Upjohn Company EMC Marine Colloids Division Perkin-Elmer Corporation Eldex Laboratories, Inc. and Pharmacia, Inc. Additional financial support was provided by the Divisions of Agricultural and Food Chemistry and Analytical Chemistry of the American Chemical Society. We also greatly appreciate the assistance provided by members of the Electrophoresis Society of America. Finally, we wish to thank Janice Olson and Dorothy Olson for their assistance in preparing the symposium and this book. 

Naturally, there are wide variations in the requirements of any specific colloidal function. For example, starch is employed as a thickening agent to provide a smooth creamy texture to the following products gravy, cream soups, sauces, chop suey, Harvard beets, salad dressings, prepared mustard, cream pie fillings, fruit pie fillings, pork and beans, cream-style corn, and baby foods. 

USE In the preparation of jellies and similar food products Owens e< ot, Factors Influencing Gelation with Pectin in Advances in Chemistry Scries, Natural Plant Hydra colloids (A.C.S., Washington, 1954) pp 10-15. 

The preparation of microcrystalline cellulose by acid hydrolysis of native and regenerated fibers has been studied extensively (3) and developed into a commercial process by Battista et ah (4). The resulting products are used as aqueous gels with high water-bonding capacity, inert food and drug additives, viscosity regulators, and stabilizers in colloidal... 

Patel, A.R., Heussen, P.C.M., Hazekamp, J., Dorst, E., Velikov, K.P., 2012. Quercetin loaded biopoly-meric colloidal particles prepared by simultaneous precipitation of quercetin with hydrophobic protein in aqueous medium. Food Chem. 133, 423-429. 

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