Cultivated and Selected Yeasts in Wine A brilliant Danish chemist, Emil Chr. Hansen took up the study of alcoholic fermen tations and 'disease ferments,' where Pasteur left off. He brought out many new facts with regard to the many different races or species of Saicharonsyces, which gave very different char acters to beers. Hansen found that it was prac tical to separate and cultivate the better species of races of brewer's yeasts. With great skill and much care he was able to select two varie ties of 'low' yeast and then he worked out a method for the cultivation of selected yeasts.
The use of pure cultivated yeasts has been attended with good results in wine-making. Musts which base been prepared with pure yeasts have been compared with musts fer mented at the same time without such yeast. In most cases the pure-yeast wine has been re warded as superior to the other. One practical value of employing pure cultivated yeasts in wine-making is that under proper conditions they will control the progress of fermentation, and thus overcome the influence of the unde sirable organisms in the must, such as mold fungi, wild yeasts, bacteria and mycoderma. By using selected yeasts from celebrated vintages, wine-makers have been able to obtain finer fla vors and bouquets, all of which adds to the quality and value of their product.
Fermentation and In order to grasp and properly understand the various prob lems connected with the phenomena of fermeti Ltion, it is necessary to say something about its relation to enzymt s. The term 'enzyme' is now used to indicate the soluble ferments secreted or formed in the yeast cell. Pasteur's theory makes fermentation a vital act, depend ing on a living organism. However, fermenta tion may also be a chemical act. About 20 years ago Buchner showed that alcoholic fermentation can he carried out by a soluble fer ment which is extracted from the yeast cell. So that we can have the phenomena of fer mentation without the growth and multiplica tion ofyeast cells. To this enzyme in the yeast extract Buchner gave the name zymase.
The effect of these recent discoveries in fer mentation may be very great and far-reaching, and just what practical form they will take in wine-making and other industries it is impos sible to predict.
The Vintage.— The word has come to have quite a wide signification. It may be used to include three distinct steps: (I) the gathering of the grapes; (2) the processes of fermentation, and (3) the general cellar operations connected with the care and handling of the new wine.
The practices of wine-makers are different in different countries and in different localities of the same country. This is owing to dif
ference in soils, climates, conditions, varieties of grapes used, and in the kinds or types of wines to be produced. And yet, the main prin ciples which give the best results in practice in one country arc practically the same in any other country where wine is made.
It should be borne in mind, however, that wine-making is partly an art and partly a science. As such, it cannot be learned and mas tered by reading, or from books. The best we can here do is to describe briefly some of the more important details connected with the manufacture of wines.
Gathering of the Grapes.— The general rule is that grapes should not be gathered till they have reached a state of complete maturity. This condition is shown by certain well-known indi cations, such as the brownish color of the stem. the softening of the berry and its easy separa tion from the stem, the skin is the juice becomes sweet, thick and somewhat sticky.
The wine-maker determines the best time for gathering the grapes by using various in struments, known as a must-scale, mustimeter, glucometer, etc. They are employed for the purpose of finding out the saccharine richness or strength of the grape juice, or must. To judge of the sugar content of the grapes a few hunches representing the average condition are first gathered, the juice is expressed and strained through a cloth, collected in a suitable recep tacle, and then the must-scale is carefully drop ped into it. The quality of the must will be in dicated on the stem of the scale. The grapes should he tvsted from day to day until the density. as shown on the scale, remains station ary, when it is time, as a rule, to gather the TiT) The oldest scale, that of Baum& was de %ised to indicate the specific gravity of liquids. or their weight, as compared with that of water. Later scales rise the density of the liquid direct. the density of water !wing indicated by O. The gliicomcter invented by Dr Guyot is very con venient and is used I v the French wine-makers. This scale indicate. at once, the decree flaurne, the quantity (,1 the mind per hectoliter, and the amount of alcohol that will result from the fermentation of the must per hectoliter The Salleron mustimeter is another very use ful instrument, highly regarded by French wine makers. The instruments mostly used in the United States are Oechsle's must scale and Ball ing's saccharometer. The must scales are also used during fermentation to determine when the sugar contained in the must has been par tially or entirely transformed into alcohol.