H. C. VERMA, ZAL R. KOTHAVALLA AND E. V.
SESHACHARYULU
229
is a fair amount of general correlation between
the plate counts and reduction times of the
same samples of individual cows and buffaloes
at the Imperial Dairy Institute, marked dis-
crepancies occur in other cases. The latter
position is clearly brought out in Table IV
in which, samples showing different plate
counts have been arranged with their respective
reduction times. It will be seen that, on the
production side, out of the total of 662 samples
TABLE IV
Bacterial counts per ml.
of milk.
Production
200, 000 and below
200, 001 to 500, 000
500, 001 to 1 million
Over 1 million
Supply
200, 000 and below
200, 000 to 500, 000
500, 000 to 1 million
Over 1 million
Methylene blue reduction time in minutes
330 and over
397 (59.97%)
5 (6.58%)
... ...
49 (35.25%)
10 (12.19%)
...
...
329 to 240
262 (39.58%)
31 (40.79%)
14 (13.86%)
10 (11.68%)
90 (64.75%)
65 (79.27%)
8 (6.12%)
...
239 to 180
3 (0.45%)
28 (36.84%)
45 (44.55%)
14 (16. 28%)
...
7 (8.54%)
10 (20.41%)
1 (0.69%)
179 to 120
...
11(14.47%)
33 (32.67%)
27 (31.39%)
...
...
21 (42.86%)
18 (12.41%)
119 to 60
...
1 (1.33%)
9 (8.91%)
27 (81.39%)
...
... 15 (30.61%)
58 (40.00%)
Below 60
...
...
... 8 (9.31%)
...
...
... 68 (46.89%)
Total
No. of Samples
662
76
101
86
139
82
49
146
with plate counts of 200,000 and below, 397
(59.97 per cent.) gave reduction times of 330
minutes and over, 262 (39.58 per cent.) fell
between 240 and 329 min. and 3 (0.45 per cent)
between 180 and 239 min. On the supply side
139 samples gave plate counts of 200,000 and
below, of which only 49 (35.25 per cent) had
reduction times of 330 min. and over and 90
(64.75 per cent) fell between 240 and 329 min.
Similar observations have been made by other
workers. Malcolm and Renwick [1936] observ-
ed that a considerable proportion of milk
samples which attained the Grade A* standard
according to plate count reduced methylene
blue within 5 hr. On the other hand many
samples which could be classed as Grade A on
the basis of reduction time fell out on account
of plate count. Thomas and Tudor [1937] also
observed discrepancies. Nichols and Edwards
[1936] found that samples giving counts of
over one million per ml. reduced methylene blue
within two hours. Recently, Kudelka [1941]
observed a positive correlation; samples of milk
showing 50,000 bacteria per ml. reduced the
dye in about 5½ hr., while samples containing
over one million decolourized it in about 30 min.
Those between these extremes gave inter-
mediate reduction times. The results obtained
in this work are different from the findings of
Kudelka, but they fall in line with the observa-
tions of Nichols and Edwards, to some extent,
as a majority (161 out of 231) of samples
showing plate counts of over one million reduced
methylene blue within two hours.
Grade A* milk—
Memo. 139/Foods [1937]
.
.
.
.
.
Grade A milk—
Wilson, G. S. [1935]
.
.
.
.
.
Plate count per ml.
30,000 to 200,000
30,000 to 200,000
Methylene blue reduction
time
Winter
<5½ hr..
<6½ hr..
Summer
<4½ hr.
<5½ hr.
From the above it will be evident that there
is a lack of correlation between the plate counts
and reduction times of the same samples but
at the same time a general correlation is observ-
ed between plate counts of 200,000 and below
and the reduction times of 240 min. (4 hr.) and
over (Table IV). The fact that out of 801
samples which gave plate counts of 200,000 and
below, only 446 (55.68 per cent) and reduction
times of 330 min. (5½ hr.) and over while on the
other hand 798 (99.63 per cent) gave reduction
times of 240 min. (4 hr.) and over supports this
observation.
SUMMARY
(a) The bacteriological quality of milk pro-
duced and handled under different conditions
in Bangalore has been studied by the applica-
tion of methylene blue reduction test and plate
count, A total of 1340 raw milk samples of