STUDIES ON THE METHODS OF PREPARATION OF GHEE*
I. ACIDITY IN GHEE
By K. S. RANGAPPA and B. N. BANERJEE, Department of Biochemistry, Indian
Institutue of Science, Bangalore
(Received for publication on 13 November 1945.)
A CIDITY in butter fat or ghee is responsible for a number of undesirable changes in it,
and should be prevented or reduced to a minimum. Unfortunately, however, in the pre-
paration of butter and ghee by the indigenous process (curd process) or the creamery process,
souring takes place, and this gives rise to the incorporation of acids in butter and ghee. The
souring is practised as it imparts certain desirable properties to butter and ghee, such as taste,
flavour and the like. Butter and ghee can be made directly from milk without souring or
without any acids developing in them [Banerjee and Doctor, 1938], but such products taste
like granulated oil with a slight milky flavour and do not possess any of the valuable pro-
perties for which butter or ghee is prized. Lately, in Western countries, neutralization of
cream after souring is being resorted to in order to produce low acid butter. Nothing is
done, however, in the indigenous process to reduce acidity, or minimize the effect of acidity
in ghee. In this paper only the role of acidity in ghee or butter, by the desi (curd)
process has been studied.
Acidity is developed in two ways ; first it develops during the process of manufacture
from milk to ghee, and secondly in course of storage before consumption. A number of
factors come into play in the two processes of the development of acidity. There is a third
factor which develops acidity in butter or ghee lipase, present in milk, and microflora
of souring or of contamination ; but this part of the subject is reserved for a separate study and
is not included in the present one.
Microflora present in milk from the time of milking to the time of processing produce
acids in milk. This is a preventible factor ; and if the healthy practice of sterilizing or boil-
ing milk as soon as possible after milking is followed, this defect can be removed. Besides,
this is an important item in the problem of supply of clean and healthy milk and is
therefore omitted from this study. Generally, milk is processed by boiling to reduce
microbial damage. There is, still, a lapse of time between the process of boiling and
seeding with curd for souring. In the process of souring, a number of factors come into
play ; the length of souring, temperature, microflora, acidity and quantity of seed curd.
Without entering into the study of the souring process the formation of acidity during
souring has been recorded in a number of expriments to follow up the development of acidity
in curd, butter, ghee and its control.
Acidity development in souring and manufacture
In order to study this factor, milk obtained within two hours of milking from a dairy was
heated in an autoclave for 20 minutes, cooled, and then incubated with seed curd. Buffalo
milk was used, and its fat content varied from 7.0 to 8.5 per cent. The quantity of seed
curd added was 2.5 per cent and its acidity, about 1.4 per cent. lactic acid. The seed curd
was maintained in the laboratory from day to day inoculations in culture tubes. The acidity
of the milk to start with was 0.09 to 0.11 per cent lactic acid. Two litres of milk were soured
at 24°C., 30°C., 35°C., 40°C., and 45°C. At the end of 6, 8, 12, 24, 36, and 48 hours samples
were drawn, and the acidity of the curd determined. Ten cubic centimeters of homogeneous-
ly mixed curd was mixed with 10 c. c. of water and titrated against N/10 NaOH with
phenolphthalene as an indicator. The curd was then churned in a domestic bottle churn
to prepare butter. Wäter was added from time to time equal to the volume of the curd
for separation of the fat. The butter was washed three times with twice its volume of
water, and then its acid value was determined. Ghee was prepared from the butter in
*In this paper the quality and constants of ghee are expressed as follows :—
1. Acidity as percentage of lactic acid unless otherwise mentioned,
2. Vitamin A as Lovibond blue units per gram with Carr and Price reagent.
3. Carotene as Lovibond yellow units per gram.
4. Quality of ghee denoter, flavour, texture and colour,
(a) Flavour can be expressed as clean, poonounced, pleasant, aromatic with no taint and free from
yeasty, cheesy, curdy and other flavours
(b) Texture can be expressed as firm, granular, pasty and semi liquid.
(c) Colour is yellow, but may be pale, greenish, or deep with an orange tint,
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