146 THE INDIAN JOURNAL OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY [VI, II
As this result confirmed the one obtained at Pusa, there is little doubt of the
superiority of this organism as a starter in dairy practice in India for producing
flavour in butter. It may not be out of place to point out here that the superiority
claimed is in respect of the use of single cultures only. It is possible and perhaps
natural to find, as was our experience in other investigations not reported here,
that a mixture of two different cultures may give a better-flavoured butter than
the one produced by a pure culture of the streptococcus under study used
singly. The cultures of the flavour-producing streptococcus investigated by us
may not be necessary for those dairies which may already be using starters which
contain the flavour-producing organisms in addition to the usual lactic acid orga-
nisms ; but dairies which are using indifferent starters will certainly benefit by
resorting to the use of cultures of the flavour-producing organisms similar to the
one investigated by us.
(6) Test for aroma and flavour-producing substances by the organisms in cul.
tures.—It was at first generally believed that the volatile acids produced by the
organisms were the chief cause of aroma and flavour in butter, because Evans
et al [1914], Hart et al [1914] and Evans [1918] had isolated and studied organisms
producing volatile acids from cheddar cheese and suggested that they are respon-
sible for volatile fatty acids and the flavour found to be developed during the
ripening of cheese ; and Hammer and Bailey [1919] had found volatile acids pro
duced by the citric acid fermenters in amounts equal to that of good starters.
Recent studies carried out in Europe, by Schmalfuss [1928], Schmalfuss and Barth¬
meyer [1928] and Van Niel, Kluyver and Derx [1929] have, however, clearly shown
that it is the presence of an organic compound " diacetyl" having the formula
CH 3 -CO-CO-CH 3, —the oxidation product of acetyl methyl carbinol—which is
responsible for the development of aroma in butter although the volatile acids
as a factor in the development of flavour is not ruled out. Michaelin, Farmer and
Hammer [1933] conducted a series of experiments with citric acid fermenters
associated with S. lactis in milk cultures and have confirmed the above results
obtained in Europe. These investigators found that the organisms S. citrovorus
and S. paracitrovorus produce considerable amounts of the above-named substances
in milk to which citric acid is added and likewise impart satisfactory flavour and
aroma to butter when inoculated conjointly with S. lactis. We, therefore,
attempted to find out whether " acetyl-methyl-carbinol and diacetyl" are formed
in milk alone and in milk to which citric acid has been added by the organism isola-
ted by us. For comparison we used two lactic acid organisms isolated from dahi
and also one of the several cultures which were kindly supplied to us by Dr. Hammer
of the Dairy Section of the Iowa State College of Agriculture. The procedure
of determination of acetyl-methyl-carbinol+diacetyl was the same as outlined
by Michaelin et al [1933] and consisted in steam-distilling 200 grms. portions of
milk cultures to which 40 c.c. of ferric chloride solution had been added and