Many of the enzymes in washing powders have been changed to suit their function. Enzymes are long chains of amino acids that determine their properties; improved performance can be achieved by changing the amino acids in the chain. Proteases used in washing powders can be altered so they that they are less easily damaged by bleaches in the wash. Fat busting lipases can also be altered, usually, lipases do not usually function well in water, by altering the enzymes more efficient enzymes can be used.
Enzymes are widely used in food and drink processing. Added enzymes in food have been used for many years to enhance flavour, texture, digestibility and quality. Also, a wide range of commercially produced enzymes are now used for food production. Some examples are amylases (used for brewing and baking) and pectinases (used in winemaking and fruit juice production). Many products receive enzymatic treatment, the following table outlines a few uses of enzymes in food production:
Pectinases are essential for breaking down pectin in the processing of fruit to make juice. Pectin holds together cells of fruits and when the fruit is extracted this produces gels. The pectinases enable clear juice to be filtered off. Pectinases and other enzymes are now an integral part of fruit juice technology
Other enzymes added include cellulases, The addition of cellulases during extraction at 50 °C improves the release of colour compounds from the skins of fruit. This is particularly useful for treating blackcurrants and red grapes. Increasingly cellulases are being used at the time of the initial pectinase addition to totally liquefy the plant tissue. This makes it possible to filter juice straight from the pulp without any need for pressing.
Glucose oxidase is another example, Glucose oxidase catalyses the breakdown of glucose to produce gluconic acid and hydrogen peroxide. This reaction utilises molecular oxygen. Glucose oxidase (coupled with catalase to remove the hydrogen peroxide) is therefore used to remove the oxygen from the headspace above bottled drinks, reducing the non-enzymatic browning due to oxidation, which might otherwise occur.
This table summarises the different types of enzymes used in fruit production;
There is a growing interest in enzymes due to their low operating temperatures and pressures and their high specificity. But there are disadvantages; these include the expense of producing enzymes and their high sensitivity to pH and temperature.
These disadvantages can be overcome by enzyme immobilisation. This involves chemically linking the enzyme to a solid support or trapping it inside beads of gel, these methods mean that enzymes can be re-used. Immobilisation permits the re-use of costly enzymes because these enzymes do not dissolve in immobilised form and do not get washed away at the end of the reaction. Immobilised enzymes used in industry include glucose isomerase, which is used for high-fructose syrup and penicillin acylase, this enzyme is expensive so it is used in immobilised form in immobilised form in large stirred tank bioreactors, from which it can be recovered for re-use. An example is lactase, this is very expensive and is immobilised on an inert material (e.g. porous beads). The substrate is passed over the enzyme, which is placed in a column. This method is used to make whey syrup, which is used in confectionery.
Enzymes are widely used for analytical reasons. Many biological fluids such as blood are complex mixtures, and analysis of substances such as glucose requires specific, accurate and sensitive techniques. Enzymes are the basis for many tests for biochemical compounds.
One of these is ELISA, which detects tiny amounts of proteins in biological fluids. ELISA is widely used in the diagnosis of infectious diseases, where it can detect antigens and antibodies. It can also be used to detect hormone levels and in food quality control.
Glucose levels in the blood can be detected glucose oxidase, which is used as a basis for a biosensor. The enzyme catalyses the reaction between glucose and oxygen to give gluconic acid. An oxygen electrode gives a measure of the oxygen consumption and therefore the glucose level in the blood, because the higher this is the more oxygen is consumed. Applications of biosensors include clinic testing and detention of toxins in food and water.
Many diagnostic test strips that include enzymes have been developed for clinical tests. For instance, glucose in urine can be measured with test strips with glucose oxidase and peroxides immobilised on a cellulose pad. This pad changes colour and can be read off on a colour chart.
Bibliography
Roberts, Reiss and Monger (1993) Biology; principles and processes
Toole (1995) A level Biology
Madden (1998) An NCBE guide to enzymes in action
Microsoft (1996) Encarta 97 encyclopaedia
Homework sheet ENZ-4
Sheet A25 The efficiency of washing powders
The Observer (1990) Enzymes passage
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