ABSTRACTS
121
From a detailed discussion of the various principles underlying the fixation of
time-temperature combinations for pasteurisation the author concludes that treating
milk at 138°F. for 30 minutes, 140°F. for 20 minutes, 145°F. for 5 to 10 minutes,
150°F. for 2 to 5 minutes or 160°F. for 12 seconds will completely destroy tubercle
bacilii. The time-temperature combinations employed in the H.T.S.T. method
have been shown to provide a fairly large margin of safety because of the additional
heating and holding involved therein.
The effectiveness of pasteurisation as a method for reducing the bacterial content
of milk is according to the author entirely dependant on the quality of raw milk.
It is asserted that large numbers of thermoduric organisms contaminated through
poor cleaning and sterilisation of dairy farm utensils generally render pasteurisation
less effective. In view of the fact that assessment of bacterial quality of pasteurised
milk by determination of colony count is apt to be vitiated by the initial incidence
of thermoduric organisms the author has advocated the use of ½ hour methylene
blue reduction test for the purpose.
Under the head ' Pasteurisation and keeping quality ' the importance of post-
pasteurisation contamination in the spoilage of bottled milk is discussed in detail.
The author is of the opinion that the majority of the thermoduric organisms are not
so very detrimental to the keeping quality of processed milk as the addition of coli-
form organisms or actively souring streptococci at later stages. The significance
of spore formers in the spoilage of milk is dealt in detail and mention is made
of the fact that some spore formers stimulate acid production by lactic streptococci.
The incidence of Bacillus Cereus and Mycoides—two closely related sporing aerobes—
in raw milk supplies and the cause for the fault known as ' broken' or ' bitty '
cream are indicated. The author has expressed the view that the role of thermophiles
is more menacing in holder plants than in H.T.S.T. plants although even in these
plants proliferation may occur in the regenerating and filtering sections. (M.R.S.)
The relation of Carotenoid and Vitamin A Content of Summer Milk to the Carotenoid
Content of Pasture Herbage. HIBBS J. W. KRAUSS W. E. AND MONROE C. F.
(1949). J. Dairy Sci. 32, 955
T HE relationship of the carotenoid content of the pasture grasses to the caro-
tenoid and vitamin A content of the milk produced on these pastures has been
investigated. The cows were fed during the pasture season of three consecutive
years in three groups. One of the groups was pastured on permanent blue grass,
the other on the same pasture with supplemental hay fed ad libitum during milking
time and the third on various legume mixtures without supplemental hay.
The carotenoid content of the pasture herbage and the carotenoid and vitamin
A content of the milk samples composited from individual cows before turning
them to pasture and subsequently at periodic intervals when the animals were fed
on the pasture were determined.
The pasture carotenoids varied from 100 per gm. to 400 per gm. The results in-
dicate that milk carotenoids increased rapidly from 3 per gm. following the beginning
of pasture consumption and reached a peak of about 16 per gm. within 1½ months
of feeding regardless of whether the pasture is of permanent blue grass or is a mixture
of legumes. Milk vitamin A showed an initial rise upto 7 per gm. and then a tendency