Washing powders usually only contain one type of enzyme, though some have two or all three; the activity of these enzymes can be determined using a pH Stat titration
Enzymes are biological molecules that catalyse (speed up) chemical reactions.
Enzymes are specific - they will only work on particular molecules.
For example, the enzyme sucrase will only bind with and break bonds in sucrose, not any other type of sugar.
Another characteristic of enzymes is that they can be re-used over and over again.
A single enzyme will typically catalyse around 10,000 chemical reactions per second.
This means that only a tiny amount of enzyme is needed to have a huge effect on a reaction.
The rate of enzyme activity depends on the amount of enzyme present, and also the temperature and pH of the reaction solution.
The most favourable pH for many enzymes is 6-8, around neutral, but there are exceptions: pepsin, a digestive enzyme in the stomach, works best at pH 2.
People have been experimenting with ways to use the power of enzymes to clean clothing for a long time; in fact, the first patent was in 1913.
Because stains are made of different types of molecules, a range of enzymes are needed to break them down.
Proteases break down proteins, so are good for blood, egg, gravy, and other protein stains.
Amylases break down starches, and lipases break down fats and grease.
Washing powders usually only contain one type of enzyme, though some have two or all three.
The activity of these enzymes can be determined using a pH Stat titration.
The active enzymes to be investigated are weighed into the sample vessels in the form of aliquots of the solid substances and these are placed in the sample beaker.
The enzyme sample is first dissolved by adding a buffer solution.
Afterwards buffer solution is added (as well as other auxiliary solutions if required) and the initial pH value is adjusted, then the reaction is started by the addition of a defined volume of substrate solution (0.1-1.0ml).
In the reaction phase the pH value is held constant under vigorous stirring (using a homogeniser) by adding sodium hydroxide solution (pH stat titration) and the NaOH consumption is recorded as a function of time.
The reaction is terminated when either a given conversion (NaOH consumption) has been achieved, if the reaction rate (NaOH consumption per unit of time) is too small or after the maximum permitted reaction time has elapsed.
The system used for the automatic determination of the enzyme activities consists of an 815 Sample Processor, an 842 pH Stat Titrando, and several other 800 Dosinos for adding the substrate solution and various auxiliary solutions, etc.
Tiamo software controls the system.
After each sample has been titrated, the whole electrode assembly, homogenizer and burette tips are cleaned prior to the next sample.
