Enzymes may constitute a safety hazard 5:
Generally, the consumer will not experience enzymes in a concentrated form and this reduces the risk but does not eliminate it;
The body's defences are designed to cope with a wide range of enzyme activities present in natural food and there is no evidence that enzymes added to food are an exception;
Enzymes from plant and animal sources that are usually consumed by man do not require toxological testing as those of microbial origin. Bacterial and fungal toxins are recognized as extrimely toxic to humans and may also be carcinogenic. Because of this toxin problem of microbial origin, minimum testing requirements and guidelines for good manufacturing practices have been defined to avoid contamination of.
Each country has defined their own regulations with respect to permission of food additives. Furthermore, the lists of national requirements tend to change quickly. For the export and import of foods between countries and for adequate manufacturing the industries must rely on experts in trade associations or associations of researchers for the latest informations.
A few enzymes have been approved in the United States of North America by the "U.S. Food and Drug Administration" and can be legally used in food processing (Y.H. Hui, 1992 6)
The approval requisites always include the following rules:
The microbial strain is nonpathogenic and nontoxic (for man or other animals)
The enzyme is produced in a process that completely removes the microorganism from the enzyme product
The amount of enzyme to be used in the enzymatic reaction does not exceed the minimum required to produce its intended technical effect
The enzyme product is maintained under refrigeration from production to use and is labelled to inform of the need of this storage condition
The enzyme production conditions must garantee that the enzyme extract is free from certain toxins characteristic of erroneous growth procedures of the enzyme producing strain
Milk itself contains a large number of enzymes, some of which are important in milk processing:
The two major uses of enzyme technology in the dairy industry are:
Calf rennet is the most used rennet. The active enzyme present is an acid protease, designated as rennin or chymosin.
The microbial rennets have already been accepted in most countries as alternative coagulants in the production of a number of cheeses.
Another application is the use of calf chymosin produced by recombinant microorganisms like yeasts.
There are however other particular applications of enzyme technology in the production of highly specialized milk products.
Enzyme-modified cheeses are produced by addition of individual or multiple lipase and proteinase enzyme preparations to natural cheeses in order to accelerate the natural biochemical changes involved in traditional cheese ripening.
Enzyme-modified cheese makes it possible for the food technologist to:
The degree of modification can be controlled to develop a variety of:
Enzyme modified cheese products are used in processed cheese, cheese spreads, cheese dips, cheese snacks, biscuits and cheese cake.
Several methods for accelerating cheese ripening are being presently investigated in order to minimize storage costs, which represent a significant proportion of the total production process cost.
In the traditional brewing process, malt both acts as a raw material (starch and protein source) and as an enzyme source.
There are four enzymes in malts which are of major importance in the beer industry:
It is desirable to create conditions to utilize these activities to the maximum.
Improved process economics can be obtained by replacing part of the malt with industrial enzymes and unmalted grains such as barley. Commercially available industrial enzymes for the brewing process consist of:
Low-calorie beers can be produced using amyloglucosidase which reduces the level of unfermentable polysaccharides. The resultant high content in fermentable sugars can be diluted in order to reduce the alcohol concentration.
Proteases, such as papain, are used in chill-proofing to prevent haze formation in stored beers.
b-glucanases are used to catalyze the degradation of glucan gums therefore reducing filtration problems.
a-acetolactate decarboxylase (ALDC), recently commercialized, reduces the need for a maturation period.
In fruit processing it is very important to achieve a good maceration of the fruit tissue. The most used enzymes in use in this industry, Pectinases, are used with this aim.
There are many distinct commercial preparations combining main activities of polygalacturonase, pectin esterease and pectin lyase. These pectinases offer several advantages:
Hemicellulases, amylases, glucanases and proteases are also commonly used as processing aids.
There are different enzyme "cocktails" optimized acordingly to:
The raw materials used in the production of alcohol consists of mixtures of many different sugar-containing and starch-containing materials:
The use of enzymes of vegetable origin (malt and koji) is expensive and this is why industrial enzymes have nearly totally replaced these enzyme sources. As a result the predictability of the process is improved and a product of consistent quality is obtained.
Enzymes, in particular proteases, are widely used to increase the value and availability of proteins.
It is possible, by controlled proteolysis, to take advantage of the functional properties of proteins (such as viscosity, whipping ability and emulsifying power).
Examples of applications include:
The natural tenderization of meat is a slow process brought about by endogenous enzymes (neutral protease and collagenase).
Industrial enzymes preparations are used to accelerate this process in order to reduce moisture loss and shrinkage of the tissues. This preparations involve plant proteases (papain and bromelain).
To achieve an even distribution of the enzymes in the tissue, preparations are sprinkled on the surface of meat and injected under pressure in the interior.
The raw material in the baking industry is flour: a mixture of starch, protein (gluten), lipids, glucan and some wheat (naturally-occuring) enzymes. The most important enzymes contained in flour for the baking process are the amylases and proteases.
a-amylases produce dextrins, which are further broken down to sugars by naturally occuring b-amylases, thus improving yeast fermentation, bread volume and crust colour.
Dextrins formed by the action of a-amylases also reduce staling rate, thereby prolonging the freshness of baked products.
The a-amylase content of the flour is greatly dependant on the conditions of growth and harvesting as it increases during germination. This content must be supplemented or diluted to a suitable value in order to achieve a good quality bread without damaging the operational qualities of the process.
The proteases act on the protein material, weakening the gluten.
Proteases from various sources are commonly used to optimize the rheological properties of bread doughs made from strong wheat or, in biscuit and wafer production, to reduce gluten elasticity.
Hemicellulases (or cellulases and pentosanases) are used to improve the baking properties of stiff rye flours. Hemicellulases can also be used to improve dough properties and bread quality in the production of wheat breads.
Another known enzyme application in the baking industry is the use of lipoxygenases which are added to the dough by addition of soya flour or in improvers to whiten the bread.
Combined addition of oxidative and hemicellulolytic enzymes improves dough and bread properties and is a good alternative to the chemical additives, such as potassium bromate, whose use is being increasingly restricted by legislation (J. Tramper, 1994 7).
The addition of extra enzymes to the dough enables the baker improved control of the baking process, the advantages being:
Several enzymatic processes have been developed to modify the properties (melting characteristics, etc) of natural fats and oils. Particularly, lipases, phospholipases and pectinases can be used for interesterification processes, ester syntheses and olive-oil extraction.
The main current application of lipase catalysed processes is in the production of valuable confectionary fats.
Many other new potencial applications of lipases have been proposed of which some will certainly be economically feasible (J.Tramper, 1994 7):