10 Enzymes Enzymes are natural catalysts. The metabolism of all 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 microorganisms (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 break down fats and oils. In biscuit making we are a little concerned 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, but we have a growing interest in 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 contain- ers, 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. Enzyme activity is temperature, time and pH dependent so it is very difficult to specify the exact quantities to use for a given reaction. It is best to be guided, in the first instance, by recommendations from the supplier. Optimum temperatures for proteinase enzymes are generally 62 Enzymes 63 much above normal dough temperatures. As a general guide, the rate of enzyme catalysed reactions increases by between 1.5 and 3 times for each 10°C rise in temperature. It is therefore important to be critical and careful in temperature and time control where proteinase is used. The dough standing time should be as long as is convenient so that the effects of using the beginning and end of a batch are not significantly different in terms of the proteinase action. A three hour proteinase reaction time is a commonly chosen period. 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 is needed in monitoring times and temperatures 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. 10.1 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.