11/07/2020
The use of enzymes in detergents
The use of enzymes in detergent formulations is now common in developed countries, with over half of all detergents presently available containing enzymes. In spite of the fact that the detergent industry is the largest single market for enzymes at 25 - 30% of total sales. Details of the enzymes used and the ways in which they are used, have rarely been published.
Dirt comes in many forms and includes proteins, starches and lipids. In addition, clothes that have been starched must be freed of the starch. Using detergents in water at high temperatures and with vigorous mixing, it is possible to remove most types of dirt but the cost of heating the water is high and lengthy mixing or beating will shorten the life of clothing and other materials. The use of enzymes allows lower temperatures to be employed and shorter periods of agitation are needed, often after a preliminary period of soaking. In general, enzyme detergents remove protein from clothes soiled with blood, milk, sweat, grass, etc. far more effectively than non-enzyme detergents. However, using modern bleaching and brightening agents, the difference between looking clean and being clean may be difficult to discern. At present only proteases and amylases are commonly used. Although a wide range of lipases is known, it is only very recently that lipases suitable for use in detergent preparations have been described.
Detergent enzymes must be cost-effective and safe to use. Early attempts to use proteases foundered because of producers and users developing hypersensitivity. This was combatted by developing dust-free granulates (about 0.5 mm in diameter) in which the enzyme is incorporated into an inner core, containing inorganic salts (e.g., NaCI) and sugars as preservative, bound with reinforcing, fibers of carboxymethyl cellulose or similar protective colloid. This core is coated with inert waxy materials made from paraffin oil or polyethylene glycol plus various hydrophilic binders, which later disperse in the wash. This combination of materials both prevents dust formation and protects the enzymes against damage by other detergent components during storage.
Enzymes are used in surprisingly small amounts in most detergent preparations, only 0.4 - 0.8% crude enzyme by weight (about 1% by cost). It follows that the ability to withstand the conditions of use is a more important criterion than extreme cheapness. Once released from its granulated form the enzyme must withstand anionic and non-ionic detergents, soaps, oxidants such as sodium perborate which generate hydrogen peroxide, optical brighteners and various less-reactive material all at pH values between 8.0 and 10.5. Although one effect of incorporating enzymes is that lower washing temperatures may be employed with consequent savings in energy consumption, the enzymes must retain activity up to 60 °C.
