Colloids and Colloidal Systems in Human Health and Nutrition

Abstract

A material system in which one kind of matter, usually in the form of fine particles, is distributed more or less evenly throughout another is called dispersion. The term colloid is usually applied either to a particle of matter falling within a specified size range, or to a colloidal system, which is a combination of particles and a containing medium, i.e., a dispersion. In this essay, colloid will refer to particles only and colloidal system to the dispersion. A colloidal system may consist of one kind of colloid or a combination of solid, liquid or gas colloids dispersed in the medium. Essentially, particle size distinguishes colloidal systems from other material systems, such as suspensions and solutions (suspensions have larger particles and solutions have smaller). Classification of dispersions In 1925, H Freundlich classified dispersions into three basic categories: true solutions, colloidal solutions, and emulsions/ suspensions. There were four parameters for categorizing dispersion: (1) particle size; (2) Brownian movement (movement of suspended particles resulting from the impact of molecules of the medium); (3) ability to pass through ordinary filter paper; and (4) level of solubility. Freundlich's success in categorizing dispersions was somewhat limited due to the laboratory equipment available at that time. As a result, he and his contemporaries had to calculate the size of the particles. The table below identifies these categories of solutions (Figure 1). Half a century later, the Russian scientist SS Voyutsky wrote his book on colloidal chemistry, and his findings [1]. Particle size was still of major importance in distinguishing systems from one another, but although the range of particle sizes in the diagram is the same as that originally calculated, the difference is that the emulsion/suspension level is divided into the micro heterogeneous level (next up from colloidal) and the coarsely dispersed system. Voyutsky's term for a true solution is the more accurate molecularly dispersed system, in which particles tend to be below 1 nanometer (nm). Though particle size is critical in making distinctions among systems, exact points of transition between the various degrees of dispersion cannot be established. Rather, there is continuity much like the colour transitions in a rainbow. Even so, colloidal systems are quite different from micro-heterogeneous ones, which do not have the very large total surface area of colloids. Abstract Colloids and colloidal systems are essential to life. They are extremely useful, even indispensable, in many commercial and industrial situations as well. They function in everybody cell, in the blood, and in all body fluids, especially the intercellular fluids, formerly known as "humours." Therefore, increased understanding of colloids and their attendant phenomena, as well as the application of their operating principles, to enhance human health considerably is discussed in this article. Colloidal science is relatively young, however, and the number of qualified experts is few compared to other areas of science. In addition, most study in colloids has been confined to industrial processes. Having found use in agriculture, the concrete industry, horticulture, the floral industry, mining, electroplating and cosmetics, to name a few, colloids may have specific application in almost every form of human endeavour. Each of the few general areas just mentioned can be broken down into extensive subdivisions as discussed in this article. Figure 1: The differences between suspensions, solutions and colloidal solutions.