214 BUTTER-MAKING. 
Cream I. 
Sugar. Acid. Pet Ba ae 
1st ripening period.......... .1% produced 04% 83% 
2d ue PS Sia Geese Che als 1 ae .06 .395 
Cream II. 
Ist ripening period.......... .1% produced 08% 58% 
2d es OB, ahah Daehn wl ne .06 .64 
3d we SE asd te atest 1 ef .045 -82 
Cream ITI. 
1st ripening period.......... .1% produced -051% 58% 
2d ot ES gies. 6a aes ane 1 ee 050 63 
-3d aE OO ean ailalitees me e .016 -68 
Average of 8.experiments...  —.1 ee 05+ 
Conn states that the lactie acid produced in cream during 
ripening is not always of the same kind. Some species of 
bacteria produce the kind which turns the plane of polarization 
to the left; other species produce the kind which turn it to 
the right, and still other species produce the so-called inactive 
lactic acid. The most common are those which produce acid 
that turns the plane of polarization to the right. 
The souring of cream, according to Conn, is not due to the 
development of lactic acid alone. Two kinds are produced, 
(1) fixed, and (2) volatile. The fixed acids appear to be chiefly, 
if not wholly, lactic acid, and the volatile are chiefly acetic and 
formic acids. The fixed acids are produced in the greatest 
proportion. 
In the table quoted above, it will be seen that during the 
first ripening period of sample 3, .1% sugar produced .051% of 
acid, while during the last or third ripening stage .1% of sugar 
produced .016% of acid, being only about one-third of that 
produced during the first ripening period. The same is true 
in experiment II, where three separate analyses were made of 
the cream. It is difficult to account for the constant decrease 
of lactic acid in proportion to the sugar decomposed in the 
advanced stage of the ripening period. Is it the lactic acid 
already present that decomposes into other products when so 
much acid is formed? Or do the bacteria continue to decom- 
pose the sugar, but the by-products being of a different nature? 
