ABSTRACTS
97
dioxide and sulphuric acid in a suitable solvent,
as aqueous acetone. The sodium salt is finally pre-
ated from strong sodium carbonate solution. Bacterial
tissue cells in milk reduce resazurin to resorufin,
altimately to dihydroresorufin. The larger the bac-
and cell contents, the faster is the dye reduced.
Test is carried out at a concentration of 1 in 200,000
lk. The following standards for resazurin are sug-
d:—
1) A content of 60 per cent ± 3 per cent of free
urin.
2) The content of resorufin should not exceed 3 per
cent.
3) It should give a water-clear solution on production
calihe solution (0.05 per cent).
4) At a concentration of 1:200,000 in fresh normal
d Shorthorn milk of 3 to 4 per cent fat, a Tintometer
reading of not less than 6 should be obtained.
5) It should be free from any substances stimulating
hibiting bacterial growth in the concentration used.
lesnzuria is most easily purified by a repeated pre-
--ion of the sodium salt from saturated sodium car-
le solution. [E. V. S.]
Resazurin test for sterility of milk churns.
J. G.DAVIS and D.W. WATSON. Dairy Indust.
(8) 415, 1943.
method suggested by the authors consists in rins-
the churns with 500 ml. of sterile strength Ringer
tion and adding one ml. of the rinse to 10 ml. of
le separated milk in streile test tubes. The tubes are
bated at 22°C. for 24 hours. One ml. of 0.005 per cent
zurin solution is then added to the samples which are
ed in a water bath at 37°C. Readings are taken in a
parator after 10, 30 and 60 minutes, using a tube of
rated milk as a control. Any sample, reducing to a
number 5 or less in 30 minutes, is regarded as unsatis-
ory and has a count of more than 500 organisms per
of the rinse. Those samples, reducing to disc number
30 minutes, are regarded as very bad with a count
the order of 20-30 million per churn. The sterile
rated milk to be used should be sterilized at 100°C.
one hour on three consecutive days and should be aged
at least one week but not more than three months.
plate counts of the churns are determined on yeastrel
using ¼ strength Ringer solution for the dilution of
rinse. [E. V. S.]
paration and merits of churned cultured
butter-milk. C. L.ROADHOUSE. 1942, Milk.
Pl Mon. 31, 32.
author has described a method for making pleas-
flavoured, churned, cultured butter milk, containing
ter granules and between 1 and 2 per cent of milk
eh does not readily 'whey off'. The method consists
asteurizing the skim milk between 185° and 190°F.
one hour and pasteurizing the cream separately at
°F. for 30 minutes. Then 0.75 per cent fat in the
m of cream along with approximately 1 per cent starter
added, setting the milk at 70°F. and ripening to an
dity of 0.7 to 0.8 per cent before churning. Then it
hurned at 68° to 72°F. by circulating the culture
ongh a centrifugal pump and returning it to the vat.
t is added at the rate of 2.2 ounces to each 100 pounds
of milk. Then 0.025 per cent sweet cream is added, and
finally the buttermilk is cooled to 40°F. or below. The
butters may be coloured to whatever tint is desired. The
butter granules remain more evenly distributed if the
butter milk is not bottled until after it is stored for
several hours. After storage, it should be agitated to
distribute the butter granules before bottling. In order
to retain the original flavour of churned cultured butter
milk, the bottles should be surrounded by ice during
delivery, and consumers should be advised to keep it cools.
(E. V. S.)
Fly control in stables. Use of 'Gesarol' or the
new 'DDT' in the control of stable flies-
R. WIESMANN. Soap 19 No. 12 PP. 117, 119,
141, 143. New York, N. Y., 1943. (Transla-
tion of Eine Neue Methode der Bekampf ung
der Fliegenplagen in stallen. Anz. Schad-
lingsk. 19 No. 1 PP. 5-8. Berlin, 1943)
THE principal disadvantage of the usual methods con-
trolling flies in animal sheds in Switzerland is their lack
of residual effect. Numerous large scale tests showed that
various species of flies are killed in a short time by contact
with deposits of Gesarol (a spray concentrate containing
5 per cent 22-bis (parachlorphenyl)—1,1, 1-trichlorethane,
commonly known as DDT). In one experiment, which is
described as an example of this, the bottoms and covers of
petri dishes were sprayed with 1 per cent Gesarol and
five freshly caught adults of Musca domestica L. were
put into each dish after the deposits had completely dried.
Flies were transfered to untreated dishes after exposure
for 0.5, 1, 2, 5, 10, 20 and 60 minutes, and the effect was
observed. There was none at the time of transference.
Primary paralysis occurred 40 minutes after the shortest
exposure and 10 minutes after the others. Secondary
paralysis occurred in six hours, and 35, 35, 30-35, 30, 25-30,
20 and 20 minutes after the various exposures and death
in 35, 8, 7.8, 6, 5, 3.4 and 3-4 hours, respectively. Results
with Stomoxys Calcitrans L. were substantially the same
time. The dry deposits on glass retain their potency for
at least three months. The chemical acts as a neurotoxin,
and the paralysis begins in the legs of the flies because
the chemotactic sensorial organs in the tips of the tarsi
come into direct contact with the deposit. In view of the
results of the preliminary tests, the wall and ceilings of a
shed containing ten cows and two heifers were thoroughly
sprayed with I per cent Gesarol on 20 June 1942. There
was a large manure pile near the shed in which M. domes-
tica and S. calcitrans were breeding in enormous numbers,
and thousands of flies of these two species could be counted
on the walls and ceillings before spraying. The cows
were very restless. While spraying was in progress, the
flies dropped to the ground immediately and soon died.
The shed was free from flies every morning until 10
July, 100-200 had entered by evening, but had been des-
troyed by morning. It remained practically free from
flies until 25 July, although a slight decrease in effec-
tiveness was becoming noticeable on 18th. The cows
were quiet throughout this period and milk yield increased.
On 1 August nearly 1,000 flies were counted in the shed
and a second application of: spray was made. Two
applications, thus timed, will give protection for the whole
fly season.
Reproduced from the Review of Applied Entomology,
September, 1944.