A SIMPLE 'RAM-KO' METHOD FOR THE ESTIMATION OF FAT IN MILK
By C. S. RAM AYYAR and ZAL R. KOTHAVALLA, Imperial Dairy Institute, Bangalore
(Received for publication on 9 May 1942)
(With one text-figure)
MILK fat is commercially a very valuable consti-
tuent of milk. Hence a simple, quick and in-
expensive method for its estimation is always
helpful. The most commonly used methods are
the Babcock and the Gerber. Both these methods
give accurate and reproducible results but their
main drawback is the rather high initial cost of
the outfit. Further, the handling of chemicals
such as strong sulphuric acid involved in the tests
by unskilled hands is dangerous. Hence the
utility of these two methods under Indian condi-
tions is rather limited. Several simple butyro-
metric methods using alkaline solutions have been
put forth mainly with the object of simplifying
the outfit to be used. Notable amongst these
are Gerber's, Hoy berg's, Neusal's Sin-acid and
Ha-Ha. The greatest handicap in spreading the
use of these alkaline butyrometric methods is that
the composition of the alkaline solution used in
the tests is kept a trade secret. In the present
studies, an attempt has, therefore, been made to
evolve a method based on. similar principles,
which would prove accurate, simple and economi-
cal and which requires no costly item, like a centri-
fuge.
EXPERIMENTAL
In this experiment, the Gerber test was adopted
as the standard for comparing the results obtained
with it with the experimental results. The butyro-
meter used for the purpose of the present study
was the one used for the Ha-Ha method for the
determination of fat in milk (Fig. 1). In this test,
9.7 ml. of milk and 6.5 ml. of the special alkaline
solution were mixed together and maintained at
52°C. in a water bath, with frequent shaking, for
about 30 minutes when the separated fat was
read on a scale graduated in per cent.
FIG. 1. Special type of butyrometer used in the experiment
(1) Effect of using different concentrations of
sodium hydroxide. Repetto is quoted by Harvey
and Hill [1936] as recommending for his centri-
fugal method, the use of 6.5 per cent sodium
hydroxide solution. Trials were carried out using
9.7 ml. of milk, 5.5 ml. of sodium hydroxide
solutions of varying strengths from 5.0 to 10 per
cent and 1 ml. of iso-butyl alcohol in the butyro-
meter referred to above. The tubes were kept in
a water bath at 52°C. for about half an hour,
giving frequent shakings, when fat separated out
as a clear layer. The results obtained are shown
in Table I. All determinations were carried out
in duplicate, and the average figures obtained are
only presented in this and other tables. Six trials
were conducted in each series.
TABLE I
Ef f ect of using different concentrations of sodium
hydroxide
Milk used
Pasteurized, milk .
Fresh milk . .
Buffalo milk . .
Gerber
4.1
5.4
6.8
5 per
cent
NaOH
3.7
4.8
6.0
6.5 per
cent
NaOH
3.9
5.0
6.2
7.5 per
cent
NaOH
4.0
5.6
6.9
10 per
cent
NaOH
4.2
5.9
7.0
These data show that, using sodium hydroxide
solution of 5.0 and 6 .5 per cent strength, the
results for fat were always lower than those
obtained in the Gerber test. With 7.5 per cent
sodium hydroxide, the fat percentage was fairly
close to that given by the standard method, but
the results were not consistent, sometimes being
lower and sometimes higher. With a higher
concentration of sodium hydroxide, the results
were definitely higher. This shows that sodium
hydroxide alone is not a satisfactory reagent for
fat testing.
(2) Effect of using different alcohols. Trials
were next carried out to see if the use of some other
alcohol improved the results. For this purpose,
amyl, butyl, iso-propyl and iso-butyl alcohols were
tried along with 5.5 ml. of 6.5 per cent sodium
hydroxide solution. The results obtained are
shown in Table II.
From this, it is clear that iso-butyl alcohol is
the only satisfactory alcohol which could be em-
ployed with alkaline solution as a fat-clarifying
agent in milk.
(3) Selection of suitable alkali. As pointed out
before, it was found necessary in the course of the
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