The common types of yeasts are incapable of acting on milk sugar, but they can ferment glucose, maltose, and cane sugar, forming equal amounts of alcohol and carbonic acid gas, which causes the effervescence of fermented and carbonated drinks.
All yeasts grow best in an acid medium, hence those fermenting milk sugar find suitable conditions for growth in sour milk or whey.
There are, however, some types of yeasts found in milk and its products that are able to ferment milk sugar.
Not only gas-forming bacteria may be the cause of gassy cheese, but the lactose-fermenting yeasts may cause similar trouble.
It is therefore possible that this mode of decomposition plays some part in the production of fusel oil, but in the case of culture yeastsit is entirely subordinated to the mode next to be discussed.
The universality of the enzyme carboxylase inyeasts and the rapidity of its action on pyruvic acid form the strongest evidence at present available in favour of the pyruvic acid theory.
This has been shown for the juice and zymin from bottom yeasts by Buchner [Buchner, E.
All these changes may occur at ordinary temperatures in the presence of a catalyst, and in so far resemble the processes of fermentation by yeasts and bacteria.
A further difference consists in the fact that with certain yeasts the rate of fermentation of glucose is somewhat increased by monosodium phosphate whilst that of mannose is unaffected [Euler and Lundeqvist, 1911].
Armstrong [1905] has shown that all yeasts which ferment glucose also ferment fructose and mannose.
The English top yeasts as a rule give poor results [see Dixon and Atkins, 1913] and sometimes yield totally inactive maceration extract.
The yeasts produce alcohol and CO{2} while the bacteria change the casein of milk, rendering it more digestible.
Rogers[177] has determined that this flavor is caused by yeasts (Torula) which produce fat-splitting enzyms capable of producing this undesirable change.
Ordinarily yeasts are rarely present in good cheese, but in cheese affected with this trouble they abound.
Some species, however, and some yeasts as well possess the peculiar property of taking the oxygen which they need from organic compounds such as sugar, etc.
Enzyms of these types are frequently found among the bacteria and yeasts and it is by virtue of this characteristic that these organisms are able to break down such enormous quantities of organic matter.
Among them are a large number of the bacteria, although yeasts and allied germs are often present and are likewise able to set up fermentative changes of this sort.
Yeasts and some fungi are capable of growth, but more particularly the bacteria.
This solution when used for curdling the milk often adds undesirable yeasts and other gas-generating organisms, which are later the cause of abnormal ferment action in the cheese (See page 186).
Russell and Hastings[65] have found these milk-sugar splitting yeasts particularly abundant in regions where Swiss cheese is made, a condition made possible by the use of whey-soaked rennets in making such cheese.
Such among plants are the yeasts with which most of us make our bread, and a few of us brew our beer.
These in turn are less alive than the lowly water plants and yeasts and molds which have no wood or bark at all.
At the end of this time the yeasts are killed by plunging the tube in water heated to 80°C.
By this method she confirmed Williams' view that the "bios" of Wildier was apparently identical with vitamine "B" and that most yeasts require this vitamine for their growth.
Here moulds and yeasts and rusts were stunted by the sunlight.
There were, for example, paramecium as big as grapes, and yeasts had increased in size so that they bore flowers visible to the naked eye.
For instance, in studying the growth of the psychrophylic bacteria, the yeasts and the moulds, the cold incubator is employed for all media.
Although the existence of auto-intoxication in the higher plants is still only a hypothesis, the natural death of bacteria and yeasts by poisons which they themselves produce is an ascertained fact.
In this respect, the vital conditions of the simplest plants, such as yeasts and bacteria, have been investigated much more fully.
The bacteria produce lactic acid and theyeasts alcohol.
As a commercial process, the activity of yeasts is increased by submitting them to weak doses of substances (fluoride of sodium) which, given in larger quantities, would kill them.
Taking all the soured milks that are produced by natural processes, it may be said that the greater number of them contain not only microbes that produce lactic acid, but also yeasts that cause alcoholic fermentations.
Micrococci, and thatyeasts occasionally form only one spore in the cell.
Oaks, the slime has a beery odour and white colour, and abounds in yeasts and other fungi to the fermentative activity of which the odour and frothiness are due.
Examining the yeasts under the microscope, immediately after decantation, we found that both of them remained very pure.
To do this we poured off the liquids in A and B, collecting the yeasts on tared filters.
Sucrose is a non-reducing sugar, forms no osazone, and is not directly fermentable by yeast, although most species of yeasts contain an enzyme which will hydrolyze sucrose into its component hexoses, which then readily ferment.
Further, galactose is fermented by some yeasts (although not by all), but much less readily than are the other sugars, and the temperature reaction is quite different with galactose than with the others.
Since it has been demonstrated that the different imperfections in the fermentative process are due to bacterial impurities, commonly in the yeasts which are used to produce the fermentation, methods of avoiding them are readily devised.
On the one hand, bacteria were not recognised as a class of organisms by themselves--were not, indeed, distinguished from yeasts or other minute animalcuise.
The study of yeasts and the methods of keeping yeast from contaminations has revolutionised the brewing industry.
Bacteria and yeasts are both microscopic plants, and perhaps somewhat closely related to each other.
In their general power of producing chemical changes in their food products, yeasts agree closely with bacteria, though the kinds of chemical changes are different.
Next spring certain small insects (green-fly and the like) carry some of these yeasts from the earth to next year's fruits.
Bode (1936) studied the flora of Periplaneta americana and cultured Aspergillaceae and Mucorinae from the insect's body surface and intestinal contents; he also found nonsporulating yeastsin P.
Molds, like yeasts, thrive in mixtures containing sugar, as well as in acid vegetables, such as the tomato, where neither yeasts nor bacteria readily grow.
Yeasts are easily killed, so they can be left out of consideration in canning vegetables.
Of homemade yeasts there are almost as many varieties as there are cooks.
In the fermenting vats growing yeasts are often contaminated by spores of undesirable species from the atmosphere, and result in producing conditions unfavorable for the purposes desired.
By means of tincture of iodine starch adulteration in compressed yeasts may be detected.
Wines, for example, for hundreds of years have been fermented by the yeasts which adhere to the grape in the “bloom” on the outside of the fruit.
Both of these yeasts are of the same species, and either can be converted into the other by the changing of the temperature during propagation.
There were, for example, paramoecia as big as grapes, andyeasts had increased in size until they bore flowers visible to the naked eye.
Since few flowers bloomed, they were reduced to expedients that once were considered signs of degeneracy in their race: bubbling yeasts and fouler things, or occasionally the nectarless blooms of the rank giant cabbages.
The cloud drifted slowly along over the surface of yeasts and moulds, over toadstools and variegated fungus monstrosities.
There were even some mouldy yeasts of a brighter green and slime much more luridly tinted.
Yeasts have been found by Hastings[12] to cause an objectionable fermentation in Wisconsin cheese.
The cattle feed and the air of the barn always contain considerable numbers of yeasts and mold spores.
While the bacteria are normally the more important, frequently yeasts and molds produce significant changes in milk and other dairy products.
If the relative humidity goes too high, the surface slime of bacteria and yeasts becomes very heavy, soft and almost liquid, and follows the openings into the cheese with resultant damage to appearance and flavor.
Besides bacteria, there are other forms of the lower orders of plants found in milk, such as yeasts and molds.
Another point in the cultivation ofyeasts has been elucidated by a number of workers, chief among whom perhaps is Hansen, namely, methods of obtaining pure cultures.
The object of this was to ascertain whether all yeasts produced the same mycelial growth on the surface of the fermenting fluid.
Previously to Hansen's work the only way of differentiating yeasts was by studying morphological differences with the aid of the microscope.
Other yeasts are stated to form sulphurous acid in must and wort.
In the United Kingdom the employment of brewery yeasts selected from a single cell has not come into general use; it may probably be accounted for in a great measure by conservatism and the wrong application of Hansen's theories.
It was not recognized that many of the diseases of fermented liquids are occasioned by foreign yeasts; moreover, this process, as was shown later by Hansen, favours the development of foreign yeasts at the expense of the good yeast.
Certain yeasts exercise a reducing action, forming sulphuretted hydrogen, when sulphur is present.
By this method several races of Saccharomycetes and brewery yeasts were isolated and described.
Culture yeasts have also been successfully employed in the manufacture of wine and cider.
Saccharomycetaceae include the well-known yeasts which belong mainly to the genus Saccharomyces.
Pure cultures were insufficient to produce keffir, while mixed cultures of Bacterium acidi lactici and yeasts were effective.
It does not ferment with ordinary yeast, but certain special yeasts which are made use of in the preparation of keffir, koumiss, etc.
The fermentation necessary for the two latter products only proceeds, too, at a much lower temperature, at which yeasts play an important part.
Adametz[55] failed to isolate Dispora, and came to the conclusion that ordinary lactic bacteria and yeasts played the most important part in the fermentation.
This would no doubt tend to explain the phenomenon observed by Kuntze that milk is not so rapidly fermented by organisms of this group as when cultures of diplococci and yeasts are added.
In addition, yeasts were found in almost every sample examined, but were regarded more as accidental infections rather than as essential to the formation of a typical product.
On the other hand, the yeasts and algae required carbon dioxide and yielded copious amounts of oxygen as they grew.
The above list will hopefully give you a few useful examples demonstrating the appropriate usage of "yeasts" in a variety of sentences. We hope that you will now be able to make sentences using this word.
