Enzymes are natural catalysts. All metabolism of living organisms is effected by enzymes and the range of reactions involved is incredibly wide.

Food materials are broken down by enzymes internally by animals and externally by micro-organisms (fungi and bacteria). There are three main ranges of enzymes that are of interest to the food scientist; they are amylases that act on carbohydrates, proteinases that act on proteins and lipases that breakdown fats and oils. In biscuit making we may be concerned a little with the amylases in connection with yeast fermentation. We do not make active use of lipases but must be aware that they can cause deterioration in certain circumstances, for example, in the shelf life of nuts or oat flour. We do have a growing interest in the proteinases which break down or modify the flour proteins.

Diastatic malt flour is the normal source of amylase for bakers but proteinases are available as standardised preparations.

For various technical reasons the proteinase obtained from Bacillus subtilis is deemed the most suitable for use in doughs. It is sold either as a stable powder standardised in activity by dilution with a maltodextrin or corn starch, or as a liquid of standardised activity with added stabilisers and preservatives. In sealed containers, under cool dry conditions, the loss of activity is normally less than 10% in one year.

In the case of the powdered material it is best to disperse it in 4-5 times its weight of water before addition to the dough. The enzyme is readily soluble but in the cases where corn starch is used as the dilutent this will, of course, not dissolve.

By breaking the length of the protein chains in gluten, proteinase enzymes have a similar, but not exactly the same, effect as sodium metabisulphite on the elasticity and extensibility of a dough. Unlike SMS, proteinase continues to act with time and will eventually result in a very short and unmanageable dough. Care with times and temperatures are needed but most particularly in the handling of excess dough such as cutter scrap.

Proteinase has advantages over SMS because it is denatured by heat and being a protein itself has no toxicity problems. Also it does not react with the heat stable vitamins.

Thus, the use of proteinase in dough is to effect reductions in viscosity and elasticity which are desirable for the machining of certain biscuit doughs, especially when flours with gluten which has a high resistance value are used.

Safety aspects of handling proteinase enzymes

Care should be taken when handling proteinase, particularly powders, because inhalation or contact with delicate skin membranes can cause irritations or allergic reaction. The wearing of a simple dust mask is usually sufficient but advice is usually given by the proteinase supplier.