64 Factors affecting Physical & Chemical Constants of Ghee
EFFECT OF THE METHOD OF PREPARATION ON THE CHEMICAL AND THE PHYSICA
CONSTANTS OF GHEE
In this country butter is prepared by the cream process and the curd
process. Generally, in the creamery process, the cream is separated from
milk, ripened with or without a starter and the butter churned in a barrel
churn. In the curd process the milk is curdled with an inoculum of the
previous batch and the butter churned in an indigenous churn (paddle churn).
On account of tropical climate and temperature butter is not stored in India
but is melted into ghee. Ghee can be prepared from butter (i) by the decan¬
tation method and (ii) by the method of boiling off the moisture.
(i) Decantation process.—In this process the butter is gently heated
(temperature not to exceed 100°C) and when the fat layer has separated and
the curd layer has coagulated, the fat layer is carefully drawn off. Then
the fat is heated for 10 to 15 minutes at temperatures not above 110°C
to remove traces of moisture. In this process the odour from heated casein
is not obtained.
(ii) Boiling-off process.—This is a widely practised process in this country.
The butter is heated on a gentle fire until all the moisture is boiled off and the
curd partially fried. In this way a rich aroma is developed in ghee which
may take up a cooked smell as well.
In the process of souring of cream or curd, the Reichert value, the most
important analytical constant of ghee, may be affected since the lower fatty
acid glycerides may be hydrolysed. Again, in the clarification process,
the butter is melted into ghee and the moisture is removed by the boiling-off
process, considerable acidity is developed in the fat [Banerjee and Doctor,
1938] which may help the decomposition of lower fatty glycerides and the
volatile products formed might be driven off, thus lowering the Reichert
value. This hydrolysis is all the more probable since butter is seldom melted
into ghee immediately after preparation, but generally after storage, only
when it cannot be disposed of as butter. Usually it develops a foul odour by
that time.
One hundred pounds of Murrah buffalo milk were divided into two parts
of 50 lb. each. The first part was gently heated and then cooled and inoculated
with sweet curd. It was allowed to sour for 24 hours at room temperature
(22°C). The second part was separated in a cream separator. A small portion
of the cream was cooled and churned at once. The separated butter was washed
twice and then melted in an electric air oven maintained at 105°C. The
clear fat layer was carefully removed by decantation and its Reichert, Polenske
and saponification values determined. All physical and chemical constants
of ghee have been determined throughout this investigation by the methods
described in the British Standard Methods for Chemical Analysis of Butter
[1938], and Report of the Analytical Methods Committee [1936]. The whole
operations of milking, separation of cream, preparation of butter and
ghee etc. were performed within two hours of milking and the sample (1)
represented the natural fat of milk.
The cream was then allowed to ripen without any starter and samples
were taken out at intervals of 12 (sample 2), 24 (sample 3) and 48 hours
(sample 4) and treated similarly to sample 1.