76
Methods of Preparation of Ghee
organisms. The taste should be mild rather than sharp. Milk is usually boiled for a
short time and then allowed to cool ; while still lukewarm, a small quantity of the pre-
vious day's supply is put in for souring. The inoculum is required to be a lactic acid
starter. At present little information is available regarding the types of lactic acid bac-
teria used in the preparation of dahi in different areas, nor is anything known of the
relation of the types of organisms to the flavour and texture of the products dahi, butter and
ghee, [Karnad, 1939; Joshi and Ram Ayyar, 1936 ; Ram Ayyar, 1928 Madhok and Kapoor, 1942].
The variety of microflora in the seed curd and its relation to palatability and other qualities of
the products under the present conditions of production is not known. The manufacture of
dahi is of outstanding importance either as food, or as the intermediate product in ghee
manufacture.
Starters used in the case of creamery butter have been extensively studied in other
parts where butter is produced under scientifically controlled conditions. Starters or
bacterial cultures used for souring cream increase in butter the desired flavour and
aroma. A good starter is clean sour milk or curd (natural), while pure culture starters
are mixtures of strains of desirable bacteria—S lactis and S. cremoris are the lactic fer-
menting types and S. citrovorous, S. paracitrovorous and Beta coccus cremoris are citric
fermenting, aroma and flavour producing bacteria. Ripening of the starter or cream pro-
duces the pleasing, mildly acid nutty flavour the pleasing and attractive flavour of
butter. The lactose-fermenting and aroma producing bacteria in the ratio of about 80—85
to 15 produces the best flavour and aroma but not alone.
If a clean-flavoured soured milk or sweet curd of firm texture is used (natural starter),
it is as good as a pure strain of sweet curd for all practical purposes. A vigorous
growth of lactic bacteria keeps down the other microflora and the lactic acid produced
acts as a preservative unless the temperature is very high or the souring carried on for
a long period. Therefore, seed curd for souring was obtained from a number of places
and the conditions for the usual souring process of ghee manufacture were studied. A
survey of the microflora of the seed curd is beyond the scope of this enquiry and was
not done.
Experiments. Seed curd in different proportions was added to sterile milk in a number
of flasks in order to find out the proportion of seed curd required for proper souring. Seeding
was done in the evening and churning the soured curd next morning. It was found that 2.5
per cent by volume of seed curd was enough for all practical purposes.
Sterile milk was soured with the seed curd obtained from the following sources :
(1) Seed curd obtained from the home-made curd of one of the authors and it
was sweet in flavour and firm in texture. This was propagated from day to day by sub-
culturing in sterile milk tubes.
(2) Seed curd from students hostel.
(3) Village curd.
(4) Bazaar hotel curd.
(5) Pure culture of Lacto bacillus acidophilus from the Imperial Dairy Research In-
stitute, Bangalore.
The results of the experiments are given in Table III.
Seed curd obtained from mixed flora is better than pure simple cultures of lactic
acid becteria. The time of souring should not be long and should not exceed the time
when lactic bacteria have stopped growing. An acidity from 0.8 to 1 per cent lactic acid
is quite satisfactory though an acidity up to 1.5 per cent is not uncommon or unsatisfac-
tory. Good seed curd is obtained by using only sweet-smelling curd of firm and uni-
form texture and one that is not more than 24 hours old. Milk used for seed curd
culture should be vigorously boiled to keep down the undesirable microflora.
SOURING OR FERMENTATION
The process of fermentation of milk with starters or cultures for the preparation of butter'
cheese and milk beverages like Kefir, Yoghart, etc., has been widely studied. In India dahi
and lassi, which are soured or fermented products, occupy the same place. Dahi is essentially
a product of lactic fermentation of milk, but in common practice no pure cultures are used,
and the milk is fermented with the curd of a previous run. As a result the seed curd,
in the case of dahi, is not a pure culture but is composed of a mixed flora arising from
infection. As stated in the previous part, certain special features of lactic fermentation keep