SURFACTANTS: BASICS AND VERSATILITY IN FOOD INDUSTRIES

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About Authors:
Dr.Rakesh K. Sharma
M.Sc., M.Phil., Ph.D.
Assistant Professor, Applied Chemistry Department,
Faculty of Technology & Engineering,
The M. S. University of Baroda,
Vadodara, Gujarat, India.
rksharmamsu@gmail.com

Abstract
Surfactant, as an abbreviation of “surface active agent”, is an organic compound that is amphiphilic comprising both hydrophilic groups(commonly referred to as “polar heads”) and hydrophobic groups(“nonpolar tails”). Based on the electron charges of the polar head parts, surfactants are classified as anionic, cationic, nonionic, zwitterionic. Many other pecular class of compounds also categorized in the types of gemini, cyclodextrin based, polymeric surfactants etc. Due to their some interesting properties such as nontoxicity, higher rate of biodegradability, high foaming capacity and optimal activity at extreme conditions like temperatures, pH and salinity, surfactants have been increasingly attracting the attention of the scientific and industrial community. Biocompatible, biodegradable, and/or nontoxic emulsion-based formulations of surfactants have great potential for applications in the food preparation and processing. Basics of surfactants and mainly there way of utility as food emulsifiers in food industries is thoroughly discussed.

REFERENCE ID: PHARMATUTOR-ART-2117

PharmaTutor (ISSN: 2347 - 7881)

Volume 2, Issue 3

Received On: 17/01/2014; Accepted On: 24/01/2014; Published On: 05/03/2014

How to cite this article: RK Sharma, Surfactants: Basics and Versatility in Food Industries, PharmaTutor, 2014, 2(3), 17-29

1. Introduction of Surfactants
“A Surface Active Agent, Surfactant, is a substance, when present in system has the characteristics of adsorbing on to the surface/interface of the system and of altering to a mark degree of the surface/interfacial free energy of the system”. In general, many solutes even when present in very low concentration alter the surface energy of their solvents in their solutions to an extreme degree are considered as the Surfactants.

Fig.1 : Surface active agent (Surfactant) molecule

Surfactants are amphiphiles containing both hydrophobic (nonpolar) and hydrophilic (polar) moieties that confer ability to accumulate between fluid phases such as oil/water or air/water, reducing the surface and interfacial tensions and forming micelles/emulsions.This is a uniqueness and versatility of these compounds. In English the term surfactant designates a substance which exhibits some superficial or interfacial activity. It is worth remarking that all amhiphiles do not display such activity; in effect, only the amphiphiles with more or less equilibrated hydrophilic and lipophilic tendencies are likely to migrate to the surface or interface. It does not happen if the amphiphilic molecule is too hydrophilic or too hydrophobic, in which case it stays. In other languages such as French, German or Spanish the word "surfactant" does not exist, and the actual term used to describe these substances is based on their properties to lower the surface or interface tension, e.g. tensioactif(French), tenside(German), tensioactivo(Spanish). This would imply that surface activity is strictly equivalent to tension lowering, which is not absolutely general, although it is true in many cases.

Good starting points to get information and understanding about the surfactants are found in classic books like those of Rosen1,Myers2, Mittal3,4 and Shinoda5. Other books on surfactants including Karsa’s, Industrial Applications of Surfactants Series7,8and the Marcel Dekker Inc. (dekker.com/) was publishing more than 100 volumes in Surfactant Science Series9 since 1966. There are also glossaries and dictionaries available which one covering terminology in surfactant science and technology10. The most comprehensive source for surfactant information on the internet is probably Huibers’ The Surfactants Virtual Library, which contains over 1000 links to surfactant and detergent related web sites11.

Conventional surfactants are amphipathic molecules with polar head groups, which may be anionic, cationic, non-ionic and zwitterionic, and hydrophobic tails, that may be hydrogenated or fluorinated, linear or branched. Recently, some interest has been devoted to the new class of so-called Gemini surfactants. They are composed of two polar heads flanked by a spacer to which hydrophobic tails are linked; the spacer can be rigid or flexible, polar or apolar. Attention has been also addressed to polymeric surfactants which are copolymers with two or more blocks

Fig.2 : Classification of Surfactants

having variable monomeric compositions. A peculiar class of surfactants is represented by the cyclodextrins which possesses the properties of inclusion and of self-organization simultaneously, resulting very promising materials for an enhanced encapsulation of variety of solutes sparingly soluble in water12.

The most commonly used anionic surfactants are alkyl sulphates, alkyl ethoxylate sulphates and soaps. Most of the anionic surfactants are carboxylate, sulfate and sulfonate ions13. The straight

chain is a saturated/unsaturated C12-C18 aliphatic group. The water solubility potential of the surfactant is determined by the presence of double bonds in it14. Cationic surfactants are mainly cetrimide which has tetradecyltrimethyl ammonium bromide with minimum amount of dodecyl and hexadecyl compounds. Other cationics are benzalkonium chloride, cetylpyridinium chloride etc are effective compounds. Non-ionic surfactants contribute to making the surfactant system less hardness sensitive.

Fig.3 : Few examples of Surfactants

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