Cooking depends on two factors, time and temperature, and the second factor, temperature, has to be varied according to the type of product. The problem of the chemist then is to define the time at the given temperature necessary for a pie of a given size to be cooked correctly to yield a product satisfactory both to the palate and eye and from the point of view of its bacteriological standard. Where the oven used is of the travelling type—a type where the goods are fed into one end of the oven, the base of which is a moving band, and carried to the other end where they are discharged—an instrument has been designed which records not only the temperature but also the rate of travel, thus indicating the two factors, temperature and time. For the successful control of manufacture there are two aspects of primary importance. A stock‐control demonstrates that as a result of the consumption of certain amounts of raw materials a definite quantity of finished goods has been prepared for sale. This control however does not ensure that all the goods so produced are of the same composition, for under‐consumption in some may be offset by over‐consumption in others. The laboratory activities ensure that this possible inequality of final product does not take place. Therefore a joint control by means of stock control and laboratory control ensures that not only is the correct yield of finished product obtained from the amount of raw materials used, but also that the goods produced are of uniform character and composition. Where such a system is in force not only is the operator controlled but also the factory management; for a process having been standardised by this joint control, no deviation is allowed from the issued manufacturing instructions. But it must be stressed that the correct interpretation of this method does not stultify the initiative of the management staff; they still can make experiments, can still suggest alterations, but not until their suggestions have been incorporated in the official control can any changes be made in the method of manufacture. By constant attendance of chemists in the factory, by constant sampling of food in process of manufacture, by continued analysis and examination of the final product and by the stock control, the adherence to agreed recipes is assured. As mentioned previously the chemist is the interpreter of the art of the technician, but he is more than that. The dietitian can indicate what in calories, in vitamins and in trace elements is necessary to healthful feeding, but it remains for the food chemist with the knowledge of the technical expert to translate these requirements into practical terms so that the food manufacturer can produce an article of diet such that the consumer eats it with pleasure, thereby obtaining the maximum benefit. Moreover, ideas come for new food products, for new methods of production from people daily in touch with the actual manufacture; many ideas are brought by people from outside and ideas are given by competitive articles. The chemist puts the idea finally into production form. A recipe from Mrs. Beeton's Cookery Book cannot be applied as it stands to mass production, but the food chemist can often indicate those changes which will be necessary to translate such a recipe from the kitchen scale to the factory scale, from the scale of the gallon saucepan to the boiling tank with its charge of a ton weight. Investigational work is of a threefold character, for it is concerned with the modification and improvement of methods of analysis and control, with the study of fundamental chemical problems concerned with food materials, and with the development of manufacturing methods. Analysis for food control purposes must be very specialised in character. Whereas time is of little importance to the Public Analyst examining, for example, a sample of chocolate cake to see that it contains the implied amount of cacao matter, the control chemist analysing a sample of fruit‐pie‐filling, with a whole batch of such filling awaiting his report, is concerned essentially with the speed of the operation. Every control laboratory has to develop methods of analysis suitable to the end in view, and every new process, every modification of a standard process, a change in composition of raw materials, may necessitate an investigation into the technique of the method to be used. Investigations of a fundamental character are not necessarily stimulated with the idea of ultimate practical use to the firm, except in so far as they develop the initiative, the experimental sense, the interest of the chemical staff. It has however been a noticeable fact that often ideas have arisen from fundamental work which have been ultimately of great use in the preparation of food products. Sometimes many years have elapsed between the prosecution of a piece of research work and the sudden remembrance of a small fact, a peculiar reaction, which has been made use of to simplify control or to change the method of a section of the process of manufacture. The transition from the kitchen methods of preparation to the manufacture of food on a large scale has demanded much investigational work. Mass production and mechanisation are not synonymous, but they are so closely related in the modern world that the one needs the other for success. Mass production demands mechanisation and mechanisation, to be economically sound, requires mass production. Mechanisation is not possible unless the process to be mechanised is understood; and it is here, in the food industry—as in other industries—that the chemist has helped industry to develop. The operator engaged in hand‐dipping chocolate centres is able, with her palette‐knife and mass of chocolate in a warm bowl, to work the chocolate couverture continually, the appreciate the changing conditions of the small mass, to correct by her skill any change of consistence and to produce thereby a product of very nearly constant appearance and composition. But when the unit of chocolate mass is increased from a few pounds to hundredweights, and when the centres in their thousands pass through a cascade of chocolate mass and are so enrobed, no such continuous adjustments can be effected. Consequently the chemistry and the physics of chocolate couverture have to be understood; the effect of time and temperature on the fluid couverture, the effect of forced cooling on the enrobed chocolates have to be studied. The chemist has to carry out experiments and to indicate as a result of his investigations the conditions which will ensure a really standard product. Examples could be quoted in connection with baking problems, with jam boiling problems, and in fact with problems from every branch of food production. Mechanisation entails the use of machinery and the metals of which the machinery is constructed may have an unexpected result on the product being manufactured. The question of this type of contamination is of two‐fold interest. In the first place, the amount of metal taken into solution, either by purely chemical reaction, or by mechanical abrasion, must not be such that it will have any adverse effect on the health of those subsequently eating the food; in the second case, the effect of minute proportions of foreign metals on the flavour or keeping qualities must be studied; for example, tea is never brewed in an iron pot because a chemical reaction takes place by which a highly coloured compound is produced and gives to the infusion a blackish colour. This is an instance of a chemical change which takes place immediately. An example of a different type is provided by the milk industry. The flavour of milk is delicate and easily affected, and one change which may take place in it is the development of a “ tallowy ” flavour. The chemistry of the reactions which result in the development of this particular “ off ” flavour is not well understood, but one factor has been investigated, namely the effect of certain metallic contaminants. Coolers for milk—and obviously all milk has to be cooled subsequently to being heated to pasteurisation temperature—are often made of tinned copper. In time the constant cleaning which is necessary wears off the tin in certain places, small areas of copper appear, almost too small to be noticeable—and the milk then comes in direct contact with this metal. Copper, present only to the extent of a few parts in every million parts of milk, has a stimulating effect on the changes which result in the development of the “ tallowy ” flavour. Yet another example. The metal of which cans are made for the canning industry is iron covered with a thin layer of tin. But canned goods are often kept for long periods of time. Sometimes the cans begin to swell, the ends become somewhat rounded in shape. That may be caused by a very simple chemical reaction, not concerned with any spoiling changes taking place, but due to the reaction between the acid contents and the iron; the active constituents of the contents have gradually found their way through microscopic pinholes in the tin layer and the gas hydrogen is the result, the generation of which becomes eventually noticeable by the swelling of the can. These three examples, the first immediately apparent, the second booming noticeable in a few hours, and the last which may not be observed for months, indicate different types of effect of metal on food stuffs. This last could naturally be very much expanded, but the obvious conclusion is that plant must be considered in relation to the purpose to which it is to be put. Mass production demands consideration too from the hygienic standpoint, for difficulties on this score are inherent in food production. Not only have the methods of production to be studied from this point of view, but consideration has to be given to the bacteriological condition of the basic materials. This is generally impossible in small scale production and it is obviously also impossible, no matter what the scale of production, for each and every tin of canned goods to be examined, or every milk pudding to be submitted to bacteriological tests, but experience of continued tests gives the clue to those factors which must be watched and the precautions to be taken. Government action has been taken in many cases. For instance, in the delivery of meat the implementing of the precautions required by law has resulted in meat reaching the butchers or the food manufacturer in far better condition than previously and has reduced wastage caused by bacteriological spoiling. Consideration of the condition of raw materials brings to mind frozen eggs. Science has proved that eggs properly frozen are far more hygienic than eggs in shell so far as the food manufacturer is concerned. Moreover it can be definitely stated as a result of a large number of tests that Chinese frozen eggs from reputable firms in China are of the highest standard possible. The freezing of eggs on the large scale in China has reached a magnitude and a standard not surpassed anywhere in the world. This has been achieved by application of methods based entirely on scientific principles. Mass production has entailed investigation of methods whereby the onset of spoiling can be retarded. A loaf of bread immediately it is cooled after leaving the oven, be it the kitchen oven or the travelling oven baking 1,500 loaves an hour, has certain characteristics of freshness. How can those characteristics be retained? Night baking enables the householder to receive first thing in the morning a loaf baked an hour or so previously, but mass‐produced bread entails distribution over a wide area and the hour or two may spread out to six or seven before the housewife receives her loaf.
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