POPULAR SCIENCE

Star (Christchurch), Issue 19240, 29 November 1930, Page 23 (Supplement)

POPULAR SCIENCE

(By

FERMENTATION. (Continued.) Of the processes which depend upon fermentation, none is of greater importance than that which has been carried on from the earliest days of man’s history—the fermentation of sugar, with production of alcohol. Manufacture of Alcohol. Alcohol is produced by the action of a particular ferment, or enzyme, zymase, on certain sugars. Zymase is secreted by the micro-organisms called yeasts, which thereby cause decomposition of such a sugar as grape-sugar, glucose, into alcohol and carbon dioxide. Fermentable sugar can be obtained not only from cane or beet sugar (which is largely employed in France in the form of beet-root molasses), but also from starch, which constitutes, in fact, by far the most important raw material for the manufacture of alcohol. The starch is of varied origin. In England it comes -mainly from maize, rice, wheat and bari'ey; in Germany, from potatoes; but probably in future times it will come mainly from the cellulose of wood-waste. The starch may be converted into glucose by heating with dilute sulphuric acid; or it may be converted into that fermentable sugar by the enzyme diastase, contained in malt. For the production of malt, barley grains are steeped for some days in water, and then spread out, or “ couched,” to a depth of two or three feet on the floor of the mal't-house. Soon the moist grains begin to sprout and to become hot. As the temperature must not be allowed to rise above 15deg C. (60deg F.) the “ couch ” is broken down and the germinating barley spread out in a thin layer, only a few inches in depth, turned over from time to time, so as to allow access of air to the living, breathing grains, and sprinkled with water when necessary. During the germination of the barley diastase and other enzymes are produced, and when growth has gone far enough it is stopped by allowing the rootlets to ■wither, and then drying the malt in a warm kiln. The malt, which still contains far more starch than sugar, together with the enzyme diastase, is crushed and mixed with hot water, and a quantity of raw grain or potato starch added. By the action of the diastase, best kept at a temperature just above blood heat (40deg to 60deg

A vessel in which the alcoholic : “wash” is boiled and so converted into vapour, which passes through the long neck B, into a spiral “worm” or condenser, C, kept cold by flowing water. The condensed vapour issues as whisky at D. The cold condenser water goes down to the bottom, by tube E, and leaves from the top, being warmed by its condensing action on the vapours

(§ u @ @ ® a m in in a is a a in a a a a a hh C. or 104 deg F. to 140 deg F.) the starch is converted into malt-sugar. When this process of “ mashing ” is complete, the liquid is boiled to destroy the diastase, and the sweet liquor qr “ wort ” is strained into the fermenting vats, where the proper culture of yeast is added. The fermentation of the sugar solution does not proceed indefinitely, for when the liquid or “ wash ” contains from 10 to 18 per cent of alcohol' (that is, several times as much alcohol as for beer) fermentation stops. To concentrate the alcohol and separate it from impurities, it is boiled off and condensed in special stills, whereby a mixture of alcohol and water containing 96 to 98 per cent of alcohol is obtained. To get “ absolute ” alcohol, this “ rectified spirits” is allowed to stand for some time over quick-lime (which in slaking absorbs the water), and then re-distilled. For industrial and other purposes alcohol finds abundant and varied uses. Not only is it employed as a heating agent, in spirit lamps, but it is also used, to some extent, as an ilfuminant (with incandescent mantles) and as a motor fuel. According to a recent newspaper announcement from London, it can now be produced at about 8d per gallon, in competition with petrol. Alcohol is also very extensively used as a solvent, in the preparation of varnishes, lacquers and enamels; in the manufacture of ether, chloroform, acetic acid, celluloid and xylonite, collodion, dyes, cordite and similar explosives—and many other substances. To render alcohol intended for such industrial purposes undrinkable, in order that the excise duty usually placed on alcohol for drinking may be removed, it is “ denatured ” by addition of wood naphtha and mineral naphtha (in the United States methyl alcohol' and benzine, in Germany methyl alcohol and pyridine bases from coal tar). Such industrial alcohol is called “ methylated spirit a name, then, more applicable to spirit from America and Germany than to that of Britain. mmm m urn m in in m © m in m @ si m in ® u i

J. J. S. CORNES,

8.A., B.Sc.)

Alcoholic Beverages. In the case of alcoholic beverages, although the ordinary ethyl alcohol is the most important ingredient, the taste, aroma and special character of each depends on the presence of small quantities of other substances, which depend on materials and preparation. These beverages may be classed into distilled liquors (spirits), wines and beers. In the case of “ whisky,” the process of fermentation is carried out as described; malted barley, mainly, is employed, but the wash is distilled from a simple pot still, as shown in the diagram. The result is not merely a mixture of alcohol and water, but one containing also small quantities of higher alcohols and their compounds (esters). The raw whisky is then placed in casks to mature, and during ripening the “aldehyde” substances become converted into acids to form other esters, which add aroma and flavour. In the case of “gin,” the distilled spirit is flavoured by re-distilling with juniper berries, coriander, or fennel; “brandy” is obtained by distilling wine, and its particular flavour depends on the class of wine used; while “rum” is distilled from fermented molasses. Such distilled liquors contain at least 40 or 50 per cent of alcohol—strengths which would kill yeast plants. Wines are prepared by fermenting grape-juice, which contains not only the sugars, glucose and fruetose, but also tartaric acid, essential oils, and colouring matter, giving various flavours and colours. Owing to the presence of a species of yeast on the grape itself, the fermentation of grape-juice must have been observed in warm countries, at a very early period in man’s history. After the first active fermentation the “new wine” is drawn into casks, which are filled full and loosely closed in order to prevent that access of air which might convert some of the alcohol into acetic acid—that is, convert the wine into vinegar. In the casks proceeds a “still” fermentation for several months, during which the yeast settles, and the crude salts of tartaric acid separate out as “argol,” the source of cream of tatar. After the wine has become clear, it is drawn off into casks, and allowed to ripen for two or three years before bottling. For the production of beers, malted grain is employed, but in the “mashing” process the conversion of starch into malt-sugar is not allowed to take place completely, a portion being converted only into the intermediate substance, dextrin—which gives “body” to the beer. (It is the substance that gives a

in the central spiral. Such distillation is required to produce beverages containing much more than 10 per cent of alcohol, because during fermentation the activity of the ferment zymase, and the multiplication of the yeast cells falls off and eventually ceases with the accumulation of the alcohol. Fermentation alone, therefore, produces only wines and beers.

m u m u m a m m m m m n m m m m m u m m gloss to the outside of a loaf, or to an ironed collar, and which is used as an adhesive on stamps or envelopes as “British gum”). Further, the nitrogenous compounds, the albuminoids and proteins, of the grain, was digested to peptones, which increase the nutritive properties of the beer. When mashing has gone far enough, the wort is drawn off, boiled with hops, and the clear liquid produced by settling is fermented with yeast. Whew the active fermentation has subsided, the new beer is run into casks, and slow fermentation is allowed to continue, the froth passing out through the bung-hole. Then the beer is drawn off into casks or bottles. Glycerine From Sugar. When sugar solutions are fermented by yeast (either for alcohol or for alcoholic beverages) some three parts °f glycerine are also formed from each 100 parts of sugar. By making the fermenting liquid slightly alkaline with sodium sulphite or sodium carbonate, the yield of glycerine can be increased up to 40 per cent of the sugar used. During the war, when Germany was short of fats, she obtained glycerine for her explosives by this method. Marmite. During the past quarter century, the attention of chemists has been drawn to the utilisation of the thousands of tons of veast which are produced annually (for, of course, the yeast grows and multiplies during fermentation) in excess of requirements. Since the yeast contains large quantities of proteins and carbohydrates as well as a little fat and mineral matter, dried yeast has been used as a food for cattle; and from It has also been prepared an extract (marmite) similar to extract of meat. It is, indeed, claimed to be superior to meat extract in having those accessory food substances, the vitamins. Anyway, marmite is something more than burnt onion! (To be continued.)