FERMENTATION. 
7 1 s 
When' the bread is taken out of the oven, 
it is found to be lighter than when put in, as 
might naturally have been expected, from 
the evaporation of moisture which must have 
taken place at that temperature. Mr. Tibet, 
and the other commissioners who were ap- 
pointed to examine this subject, in conse- 
quence of a petition from the bakers of Paris, 
found that a loaf, which weighed, before it 
was put into the oven, 4.625 lbs., alter being 
taken out baked, weighed, at an average, 
only 3.813 lbs. or 0. 8121b. less than the 
paste. Consequently, 100 parts of paste 
lose, at an average, * 17.34 parts, or some- 
what more than one-fifth, by baking. They 
found, however, that this loss of weight was 
by no means uniform, even with respect to 
those loaves which were in the oven at the 
same time, of the same form, and in the 
same place, and which were put in and taken 
•out at the same instant. The greatest dif- 
ference, in these circumstances, amounted to 
.2889, or 7.5 parts in the hundred, which is 
about one-thirteenth of the whole. This dif- 
ference is very considerable; and it is not 
easy to say to* what it is owing. It is evi- 
dent, that if the paste has not all the same 
degree of moisture, and if the barm is not 
accurately mixed through the whole, it the 
fermentation of the whole is not precisely 
the same, that these differences must take 
place. Now it is needless to observe how 
difficult it is to perform all this completely. 
The French commissioners found, as might 
indeed have been expected, that, other things 
being equal, the loss of weight sustained is 
proportional to the extent of surface of the 
loaf, and to the length offline that it remains 
in the oven; that is, the smaller the extent 
of the external surface, or, which is the same 
thing, the nearer the loaf approaches to a 
globular figure, the smaller is the loss of 
weight which it sustains; and the longer it 
•continues in the oven, the greater ^ is the loss 
of weight which it sustains. Thus a loaf 
which weighed exactly 4 lbs. when newly 
taken out of the oven, being replaced as soon 
as weighed, lost, in ten minutes, .125 lb. of its 
weight; and in ten minutes more it again lost 
.0625 lb. 
Loaves are heaviest when just taken out 
of the oven ; they gradually lose part of their 
weight, at least if not kept in a damp place, 
.or wr ipped round with a wet cloth. Thus 
Mr. Tillet found that a loaf of 4 lbs. after 
being kept for a week, wanted .3125, or 
nearfy one-thirteenth, of its original weight. 
When bread is newly taken out of the 
oven, it has a peculiar and rather pleasant 
smell, which it loses by keeping, unless its 
moisture is preserved by wrapping it round 
with a moist cloth, as it does also the peculiar 
taste by which new bread is distinguished. 
This shews us that the bread undergoes che- 
mical changes ; but what these changes are, 
or what the peculiar substance is to which 
the odour of bread is owing, is not known. 
Bread differs very completely from the 
flour of which it is made, for none of the in- 
gredients of the (lour can now be discovered 
<m it. The only chemist who has attempted 
mi analysis of bread, is Mr. Geoti'roy. He 
found that 100 parts of bread contained the 
following ingredients : 
24.735 water 
32.030 gelatinous matter, extracted by 
boiling water 
39.843 residuum insoluble in water 
96 . 608 - 
3.392 loss 
100 . 
Fermentation, vinous. Under this 
name are comprehended every species of fer- 
mentation which terminates in the formation 
of an intoxicating liquid. Now these liquids, 
though numerous, may all be comprehended 
under two heads; those obtained from the 
juices of plants, and those obtained from the 
decoctions of seeds. These -two heads may 
be distinguished by the names of the most 
remarkable products belonging to each, viz. 
wine and beer. Let us take a view of each 
of these. 
1. Wins. — There is a considerable number 
of ripe fruits from which a sweet liquor may 
be expressed, having at the same time a cer- 
tain degree of acidity. Of such fruits we 
have in this country the apple, the cherry, 
the gooseberry, the' currant, &c. but by far 
the most valuable of these fruits is the grape, 
which grows luxuriantly in the southern parts 
of Europe. From grapes fully ripe may be 
expressed a liquid of a sweet taste, to which 
the name of must has been given. This 
liquid is composed almost entirely of five in- 
gredients, viz. water, sugar, jelly, gluten, and 
a mixed acid, partly saturated with potass. 
The quantity of sugar which grapes fully ripe 
contain is very considerable ; it may be ob- 
tained in crystals, by evaporating must to 
the consistence of syrup, separating the tartar 
which precipitates' during the evaporation, 
and then setting the must aside for some 
months. The crystals of sugar are gradually 
formed. From a French pint of must, the 
marquis de Bullion extracted half an ounce 
(French) of sugar, and -J-g. ounce of tartar. 
According to Proust, the Muscadine grape 
contains about 30 per cent, of a peculiar spe- 
cies of sugar. 
When must is put into the temperature of 
about 70°, the different ingredients begin to 
act upon each other, and what is called vi- 
nous fermentation commences. M he phe- 
nomena of this fermentation are, an intestine 
motion in the liquid, it becomes thick and 
muddy, its temperature increases, and car- 
bonic acid gas is evolved. In a few days the 
fermentation ceases, the thick part subsides 
to the bottom or rises to the surface, the 
liquid becomes clear, it has lost its saccha- 
rine taste and assumed a new one, its specific 
gravity is diminished; and, in short, it has 
become the' liquid well known under the 
name of wine. 
These changes are produced altogether by 
the mutual action of the substances contained 
in must ; for they take place equally, and 
wine is formed equally well, in close vessels 
as in the open air. 
If the must is evaporated to the consistency 
of a thick syrup, or to a rob, as the elder 
chemists termed it, the fermentation will not 
commence, though the proper temperature, 
and every thing else necessary to produce 
fermentation, should be present. But if this 
"syrup is again diluted with water, and placed 
in favourable circumstances, it will ferment. 
The presence of water therefore is absolutely 
necessary for the existence oi vinous fermen- 
tation. But, on the other hand, it the must 
is too much diluted with water, it either re- 
fuses to ferment altogether, or its fennenta- I 
lion is very languid. 
If the juice of those fruits which contain j 
but little sugar, as currants, is put into a fit- 9 
vourable situation, fermentation indeed takes I 
place, but so slowly, that the product is not | 
tune but vinegar; but if a sufficient quan- j 
tity of sugar is added to these very juices, I 
wine is readily produced. No substance 
whatever can be made to undergo vinous 
fermentation, and to produce wine, unless j 
sugar is present. Sugar therefore is ab>o- : 
lately necessary lor the existence of vinous 
fermentation; and we are certain that it is ] 
decomposed during the process, for no sugar i 
can be obtained from properly fermented 
wine. It has been sufficiently demonstrated I 
by the experiments of Macquer, and the ob- 
servations of Chaptal, that the strength of S 
tiie wine is always proportional to the quan- j 
tity of sugar contained in the must. From j 
the experiments of Bullion we learn, that 1 
when must contains little sugar, the fermen- < 
tation is rapid, but the product yields little j 
alcohol. When the proportion of sugar is j 
great, the fermentation is slow, but the pro- j 
duct yields much alcohol. 
All those juices of fruits which undergo the .] 
vinous fermentation, either with or without 1 
the addition of sugar, contain an acid. The* 
apple, for instance, contains malic acid; the] 
lemon, citric acid; the grape, tartaric and 
malic acids. The marquis de Bullion lias] 
ascertained that must will not ferment if all] 
the tartar which it contains is separated from 
it, but it ferments perfectly well on restoring j 
that salt. The same chemist ascertained, I 
that the strength of wine is considerably in- j 
creased by adding tartar and sugar to the] 
must. We may conclude from these facts,’ 
that the presence of a vegetable acid is ne-j 
cessary for the commencement of the vinous] 
fermentation. It deserves attention that Bui- ] 
lion obtained more tartar from verjuice than ] 
from wine ; and he observed that the more] 
the proportion of sugar in grapes increased,! 
the more that of tartar diminished. 
All the juices of fruits which undergo the j 
vinous fermentation contain an extractive] 
mutter, composed of what Deyeux has called j 
the sweet principle. This substance has not] 
been examined with much precision ; but it 
seems to consist of mucilage, gluten, and ex- 
tract. Now the presence ot this substance 
is also necessary for the commencement of 
fermentation. For sugar, though diluted with 
water, and mixed with a vegetable acid, re-1 
fuses to ferment, unless some mucilaginous: 
matter is added. Bullion found that sugar, 
tartar, and water, did not ferment; but on 
adding vine-leaves the fermentation became 
rapid. And Bergman found that sugar dis-1 
solved in four times its weight of water, and 
mixed with yeast, undergoes the vinous fer- 
mentation ; and the experiment has been 
often repeated since. In both these cases 
the ferment appears to be gluten. 
Thus we see, that for the production of 
wine, a certain temperature, a certain por- 
tion of water, sugar, a vegetable acid, and 
gluten, are necessary. M. Lavoisier found 
that sugar would not ferment unless dissolved 
in ai least four times its weight of water. 
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