K. S.
RANGAPPA,
AND
B.
N.
BANERJEE
103
THE EFFECT OF STORAGE VESSELS ON THE KEEPING QUALITY OF GHEE
As discussed before, it was felt necessary to compare the changes that would take
place when clarified butter was stored under similar conditions. For this purpose, ghee
was stored in a villager's earthenware, (an old and used vessel)'that was smeared with butter
and ghee, another similar vessel that was heated to 100°C. for 12 hoars to kill the
microflora present; a new and unused vessel, and a glass conical flask. These vessels
were loosely covered and there was exposure to air; they were stored at 37°C. for a month.
The results are given in Table III.
TABLE III
Effect of storage on ghee
Storage
vessel
Old pot
Hented pot
New pot
Glass
Acidity and flavour of ghee.
Days of storage
0
0.089
Good
flavour
„
„
„
7
0.11
Faintly
oily
0.10
Fair
0.06
No
flavour
0.08
Good
14
0.11
Faintly
oily
0.10
Fair
0.03
No
flavour
0.03
Fair
30
0.25
Oily
0.17
Faintly
off
0.09
No
flavour
0.06
Fair
At the end of the storage
Vitamin A
Lovibond
B units
8.2
8.2
6.6
8.8
Carotene
Lovibond
Y units
2.2
2.2
1.1
2.2
Induction
period in
hours
6
6
nil
12
Vitamin A content of fresh ghee
Carotene
content
„
„
Induction period
„
„
= 11.0 B. U, per gram
=2.5 Y.U.
„ „
= 23 hours.
N. B.—The results of storage of ghee in old clay pots and even in heated pots point to the fact that the
presence of old ghee (rancid or oxidised , even in minute quantities in crevices or pores of the storage vessel
serves as a cause of degradation of good ghee. Storage in a new clay pot which is porous starts oxidation at a
higher rate, as the pores offer a greater surface for the oxidation of ghee in thin layers. Even in a glass vessel,
unless the material is stored out of contact with air, it will slowly oxidise. Ghee should therefore be stored
in non-porous vessels, filled up to the neck and sealed out of contact with air. There should not be even traces
of oxidised or old ghee in the joints or corners of the container.
Discussion. Lipase present in milk is responsible for a very slight increase in acidity
of unpasteurized cream or butter. Rogers [1904], Rogers and associates [1911] and Davies
[1932] have worked on the activity of milk lipase. The rise from this cause is according to
Rogers 0.01 per cent in 19 days. Davies found the rise in acidity to be from 0.072 per
cent to 0.189 per cent in control salted butter, 0.058 to 0.180 in control unsalted
and 0.068 to 0.080 in control pasteurized butter in seven days. Milk lipase is weakened
when heated to 66°C. and destroyed at 80°C.
Rogers has found lipase to be the cause of increased acidity in canned butter on standing.
Data from Indian firms also point to high increase in acidity in canned butter on storage.
In loose butter this increase is very rapid and almost destructive. This is due to lipase
from the uncontrolled microflora of milk, of seed culture and souring. The acidity in
Indian tinned butter rises from three to four times the initial value in five months, but
in the loose form under village conditions, the rise is four times in a week, and 25 times
in a fortnight. In winter, i. e. when the temperature is very low, microbial growth is slow
and the rise in acidity of stored butter is very much less. The rise of acidity is pro-
portional to the temperature, and the nature of the microflora. With pure lactic acid