FERMENTATION

Nelson Evening Mail, Volume 77, 23 October 1942, Page 3

FERMENTATION

ITS APPLICATION TO ARTS AND INDUSTRIES LOUIS PASTEUR’S WORK PHILOSOPHICAL SOCIETY LECTURE “Instead of setting a team of scientists to work wc can often employ countless millions of micro-organisms, m the shape of yeasts, bacteria anfl moulds, to work for us.” said Mr T. A. Gleiulinning. M.Sc.. F.1.C., in the course of his address to the Nelson Philosophical Society on the subject of "Fermentation as applied to the Arts and Industries.” The lecture was illustrated bv lantern slides and specimens. “Doubtless the most familiar examples are the production of alcoholic drinks and of bread, but quite apart from these, fermentation is responsible for the production of a whole host of things in general use, for example, enormous quantities of industrial alcohol. of vinegar, and of baker’s yeast.” said the lecturer. “The leather of which your shoes are made, your butter and cheese, tea. cocoa and tobacco have all suffered fermentation at some stage of their manufacture: cream of tartar, required for baking powder, is deposited during the fermentation and maturing of wine, and if the milk which you have carefully set aside for your early cup of tea should become sour during the night, you can safely attribute it to fermentation. “The Irish linen of which you arc justly proud was ‘retted’ or fermented in the green stage of flax to separate the fibre from the soft vegetable matter. The making of ensilage by the farmer, the purification of sewage by the septic tank, the natural purification of rivers in their course and. most important of all. the conversion of organic matter in the soil into plant food represent but a few of the fermentations on which our comfort and well being depend. EGYPTIANS MADE HOME-BREW “The phenomenon of fermentation must be almost as old as life itself, and the first that man learned to control and adapt to his needs were probably those which led to the production of wine and bread. Doubtless more time and effort were required to arrive at the production of beer. Nevertheless we find that art dales back to the Egyptians in 7000 8.C.. and both in Egypt and Babylon, the bakers and brewers were the same people. It may interest you to know that the Egyptians made home-brew’ by allowing barley dough to ferment until highly alcoholic. It was then dried, crumbled int 6 water and strained, the filtered liquid being known by the appropriate name of ‘boosa’ or ‘boo/a.' “In looking back upon the history of fermentation, we find no very clear or definite understanding of it until the time of Louis Pasteur who was still living in 1895. less than 50 years ago. “In the 15th century Paracelsus associated fermentation with disease, but this was mere speculation as the early scientists depended on theory and argument rather than On experiment and observation. Not until the beginning of the 17th century do we find any evidence of experiment, when Van Helmont found that, tlie gas carbon dioxide was produced in respiration, putrefaction. digestion and in the fermentation of wine. “Then followed the theory that substances in a state of putrefaction could transmit that state to another sound body and all that a ferment did was to communicate this movement to other part of tlie liquid to be, fermented. You will, of course, remember the parable of the little leaven which, hid in a measure of barley meal, leavened the whole lump. “Towards the end of the 18th century. the Scottish professor. Black, discovered that carbon dioxide and alcohol were the only products of the alcoholic fermentation of sugar, and the great French scientist. Lavoisier, using what was then a new instrument, the chemical balance, proved that the wc' ht of these two substances was exactly equal to the weight of the sugar fermented. “Now. these experiments were inaccurate and the conclusions faulty, but unfortunately they were not only accepted but actually confirmed, and consequently it was not until 1835 that two German, scientists (Kurtzing and Schwann) and a French scientist 'Caignard Latour) almost simultaneously made an examination of veast microscopically and observed that it consisted of ovoid or spherical globules, evidently living beings which reproduced themselves and acted on sugar, probably as a result of their growth. SCIENCE OF BACTERIOLOGY “Such then was the state of knowledge until the time of Pasteur, when fermentation left the realms of speculation for that of experimental science. His early work on the fermentation of wine, beer and vinegar led him straight on to the study of infectious diseases, and laid the foundations of a new science of bacteriology, proving that many diseases were caused by bacteria and could be transmitted from one person to another through the agency of bacteria. “In 1859 Pasteur established beyond doubt, by long, careful and arduous experiment that every form of fermentation is caused by micro-organisms which have found their way into or been deliberately introduced into the fermentable medium and that without their presence no fermentation can take place. I have given already many instances of fermentation, which produce such an obvious variety of results that you will not be surprised to learn they are due to a great variety of mi-cro-organisms. i.c.. those which are only visible through the microscope, and the greater portion of those may be roughly divided into yeasts, bacteria and moulds, or combinations of these.” The lecturer went on to explain the composition of each variety and the use to which each could be applied in the arts and industries. Quite opart from the production of wine. beer, vinegar and bakers' yeast the services of yeast could be employed in a very different direction—for the production of glycerine. Dealing with bacterial fermentation Mr Glendinning said the bacteria whose unwelcome presence was most familiar were those which decompose food, notably milk and meat. Of the commercial uses of bacteria, the best known was that of vinegar manufacture which consisted, briefly, of oxidation of alcohol (produced by yeast fermentation) to acetic acid, of which malt vinegar contained from 4 to 6 per cent. VALUABLE ACIDS Two other valuable acids formed by bacterial fermentation were lactic and butyric acids. The salts of lactic acid were used considerably in the dyeing of cotton and wool and in calico printing, while the acid itself was required in large quantities in the leather industry for neutralising the lime used for removing hair from skins- Lactic acid was used in pharmacy and the perfume industry whilst its compounds furnished solvents in the modern lacquer industry. The butyric acid ferment occurred in ripe cheese and was made industrially by the fermentation of glucose or cane sugar. The nitrocellulose lacquer industry had developed greatly and made demands

1 for large quantities of butyl alcohol ■ as a suitable medium for applying the lacquer. Mr Glendinning also referred to a i • bacterial fermentation {Process in j agriculture which had of late caused i - great interest among amateur gardeners—the decomposition of waste ' vegetable matter into humus by a ! micro-organism called Spirochoeta j Cytophaga which, with a plentiful! . supply of air. moisture and nitrogen , , gradually reduced a heap of waste vegetable refuse into humus, a ma-1 terial resembling in nutritive value | : for the soil, well rqtted farmyard j manure. In dealing with fermentation caused by moulds the lecturer said that although many moulds induced what ( was called putrefaction in many kinds of food and caused dry rot in ■ timber, as a class they performed useful work in clearing the surface of I the earth of dead bodies of animals, and plants. Moreover, they broke down organic matter into simple com- ’ pounds which became available for ! the nutrition of green plants. An important industrial use of a mould was in the production of citric acid. MEANS TO PREVENT IT “And lastly 1 must refer to some | ; of the means which we take to prei vent fermentation taking place, more especially in our food.” said Mr Glen- : dinning. “At the one extreme we have heat and at the other cold- If a food has been once completely sterilised, it can be kept indefinitely provided all micro-organisms are excluded. In biological work, culture media are kept in test tubes or in flasks plugged with cotton wool, which acts as a Alter to any organisms which would otherwise enter. Once the contents of the vessel are perfectly sterilised and the necessary precautions taken to prevent evaporation of moisture, they can be used long after they are sterilised- On this principle, canned foods are preserved. “Pasteurisation as applied most commonly to milk consists in heating it to 145 degrees F- for half-an-hour or to 160 degrees for live minutes and cooling rapidly to 50 degrees or lower. This destroys most bacteria.: but not their spores and thus delays fermentation. Similarly keeping qua- j lities are enhanced by cooking processes. Low temperatures check de- j velopment of bacteria but do not | 1 sterilise, yet chilling and freezing en- ; able us to successfully ship perish- 1 able goods half round the world- “ Fermentation is also checked by i drying, by sunlight, and in the case of jams and other conserves, by the i i use of sugar. Lastly, sterilisation j ! may be obtained by the use of disini fectants, or fermentation may be! greatly deferred by antiseptics. At ’ one time such chemical substances as bisulphites, salicylic acid, formalin and so on were very commonly added to preserve foods and drinks, at the expense of health, but to-day their use is either illegal or restricted to ; very small and probably harmless. amounts under the Food and Drugs I Acts.” _ dk I