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U. S. DEPARTMENT OF AGRICULTURE,
BUREAU OF ANIMAL INDUSTRY.-BULLETIN No SO.
A. D. MELVIN, CHIEF oF BUREAU
INVESTIGATIONS IN THE MANUFACTURE
AND STORAGE OF BUTTER.
II.-PREVENTING MOLDS IN BUTTER TUBS.
L A. ROGERS,
f Cf r ia','!,i Cli.-e is' ld)aitt, s/i'1.iii,
Burlea, of .4,tlii al hIdastrl'.
GOVERNMENT PRINTING OFFICE.
ORGANIZATION OF THE DAIRY DIVISION.
Chidf- Ed H Webster.
Assistant Chif. C B. Lane.
Assistant: Win. Hart Dexter.
Buttler irnish.;gaton.'-: Chief, in charge; C. E. Gray, chemist and experimental maker;
C. W. FrYho'er, assistant: E. A. McDonald, W. S. Smarzo, W. J. Credicott, market
Market nilk ineralgatior.s- Assistant Chief, in charge; R. H. Shaw, chemist; George M.
('hce'e inretiqatlion.s: C. F. Done, in charge. American varieties: John L. Sammis, chem-
ist: Ja* W. Moore, expert maker. European varieties: Charles Thorn, mycologist;
Arthur W. Dox, chemist: T. W. Issajeff, expert maker.
South trn diurl yni r'tigution. s: B. H. Rawl, in charge; H. N. Saister, Duncan Stuart, J. A.
Conovwi, S E Barncs, J. WT. Ridgeway, J. E. Dorman, assistants.
Bejdhni) rlnd rnanagqreitnt inryliatlion.s. B. D. White, in charge; G. H. Parks, architect.
Dairy lahoratori(f: C. E. Gray, chemist, L. A. Rogers, bacteriological chemist.
RenoteJd btt(r factorit, MN. W. Lang. 510 Noithwestern Building, Chicago, Ill., in charge.
Rer ,cnitedt b.ttdr rmaketr Levi Wells, Laceyvitle, Pa., in charge.
Inspuctor.-: Robert McAdam, 510 Northwestern Building, Chicago, Ill.: George M. Whit-
aker, Washington, D C.; E. A. McDonald, Seattle, Wash.
Deputy irnsprctus. S. B. Willis, Boston, Mass.; R. A. McBride, J. H. Barrett, 6 Harrison
street, New York, N. Y.
LETTER OF TRANSMITTAL.
U. S. DEPARTMENT OF AGRICUILTL'RE,
BUREAU OF ANIMAL INDUSTRY,
I'aslhington, D. C., July 14, 1906.
SIn: I have the honur to transmit herewith, an(l to recommend
for publication as a bulletin of this Bureau, a manuscript entitled
"Preventing Molds in Butter Tubs," by L A. Rogers, bacteriolog-
ical chemist in the Dairy Division. This paper is the second in a
series on Investigations in the Manufacture and Storage of Butter.
Acknowledgment is made of courtesies and facilities extended by
the managers of the creameries at Eagle Lake, Minn., and Bloomer,
Wis., and by the Fox River Butter Company in connection with the
experiments reporteled in this bulletin.
A. D. MELVIN,
(Ch i ef of Bureau.
Hon. JAMES WILSON,
Secretary of Agriculture.
Condition- flI %orinl tli, i%"- Illi h I ii ilold-
Propagation m ild . . . . . . .
Grow lh of Fuiuli. in lint ir r tulib.... ..
Pie entionll of inuld,1 in iLii .......
Testing and 'ompirip,,ki o[r m,.ld- .
Method Of applIing p"ilt .I.u. ..
Cost of paraIfinin7 tul. ......
S u lu r n .r ..... .......... .. .. ....
Fic. I. Apparatu-; for paraffining tubs ........................................
. . . . . . . . - - - - - -
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Uni,,er,, oI Floiioda George A Smaiaers LiDiaries VI'Ih suppoil Ironi LYRASIS arid [he Sloan Founda.ion
nhup arcn,.e org delai'I Mi.esr O0uscle
PREVENTING MOLDS IN BUTTER TUBS.
There is probably no one trouble that causes butter dealers so
much annoyance as the growth of molds on tile inside of butter tubs.
This is a trouble that is not confined to any one geographical sec-
tion or to any one type of factory. It may be only an occasional
outbreak even in the best managed factory, or it may become a
chronic condition which the buttermaker is unable to control.
Before discussing the methods of preventing thlie growth of molds
in tubs it will be well to consider briefly some of the characteristics
of these tiny plants andl the conditions under which they grow.
CONDITIONS FAVORING THE GROWTH OF MOLDS.
Molds are plants and obey certain fixed laws governing the group
of which they are a type. They differ from the common plants
with which we are familiar in everyvlay life in that they possess none
of the green coloring matter by which the higher plants utilize the
energy of the sun's rays in building up their tissues. Hence they live
as well or better in darkness than in light, but are limited for their
food supply to materials that have been prepared for them by ani-
mals or by other plants. Almost any animal or vegetable matter
serves them for food. We find them growing on bread, meat, bones,
damp wood, leather, and many other things. Sugars and many of
the acids may be used, and we frequently find a luxuriant growth
of mold on foods containing sufficient sugar or acid to prevent tlhe
growth of bacteria or yeasts.
A certain amount of moisture is necessary for the growth of molds.
Growth will not occur on the surface of wood or leather unless it is
allowed to remain in a damp place.
Oxygen is necessary to the development of all living things.
Some of the bacteria which live only under conditions- that exclude
air completely seem to be an exception to this rule. These forms,
however, obtain their oxygen from certain constituents of their
food. The molds are unable to do this, and, like the higher plants,
live only where there is at least a limited supply of air.
While a certain amount of heat is essential to the growth of molds,
there is a wide range of temperature utinder which growth is possible.
Many of the molds grow most rapidly at blood heat, but continue
to grow slowly at temperatures near the freezing point. Other
varieties find the most favorable conditions at lower temperatures
and grow with comparative rapidity in ordinary refrigerators.
MANUFACTURE AND STORAGE OF BUTTER.
PROPAGATION OF MOLDS.
Molds reproduce themselves by yeastlike buds or by spores which
correspond more closely to the seeds of higher plants. The buds,
or conidia, as they are called, are easily destroyed; the spores, on
the other hand, (o account of their peculiar structure, resist for
some time conditions that would destroy the mold itself almost
instantly. Spores may be dried for years and yet under favorable
conditions they will germinate and in a surprisingly short time pro-
duce a myceliumni bearing millions of spores. They are able to endure
much more heat than the mold itself, but are destroyed by a short
exposure to boiling, water. In a dry condition they are much more.
Short exposures to disinfectants destroy the spores, but molds
readily adapt themselves to unfavorable conditions and are fre-
qiuently found growing in the presence of antiseptic sufficient to
inhibit completely the growth of bacteria.
These spores and conidia are formed in enormous numbers, and
on account of their minute s,,ize and exceedingly light weight are
carried about by every movement of air. It is therefore almost
impossible in practice to prevent entirely infection by molds. The
most efficient means of holding them in check is to provide condi-
tions unfavorable to their growth. This may be done by depriving
them of one or more uf the factors-food, air, moisture, or heat-
which have been mentioned as essential to their growth.
GROWTH (OF MOLDS IN BUTTER TU'BS.
Tubs can not b)e made or transported without contamination,
but if they are reasonably dry the spores will not germinate. If,
however, the wood is not well seasoned, or if the finished tubs are
held at the factory in a damp storeroom, the few spores grow and
in a short time the surface 4f the wood is covered with a growth of
mold. The tub may come from the factory in good condition and
be stored in the creamery in a damp place. This may he in the ice
house or next to the dalamp wall of the ice house or refrigerator. The
growth of mold may not be noticeable without close examination.
When the tubs are filled with butter, the air is excluded and the
molds are unal)le to grow, but after a few days the evaporation of
water causes the butter to shrink away from the tub, leaving a very
small air space. Favorable conditions of food, moisture, and air
are thus provided, and if the temperature is not too low growth will
It is a common belief that moldy refrigerators are responsible for
mold in butter tubs, but from the nature of the package it is very
improbable that the inside of the tub could become contaminated
after it is filled. Temperature and moisture conditions that, would
PREVENTING MOLDS IN BUTTER TUBS.
allow molds to grow on thle wall of a refrigerator would favor the
growth of imolds on the inside 4f the till), Inut the infectiotin inti.st comne
before the tbill) is put in the refrigerator. The growth ,f mhiids on
the walls could I e prevented Iby o(ccasi ially wipingZ tlie wall with a
cloth moistened i in a 5 per 'eplt en .lycerin .-,oltititn of corrosive sub-
limate. Til,; ouhld ,rivv the lewall a thin,. sticky coating in which the
floating spires w\mild lie held amli destrtivedl.
PREI!ENTIO0N OF MOiILDS IN T U.S.
The growtth of tolds in the tubill) mav be preventedl more (.r less
successfully (1) by stturinz t lie t tulbs in a dry place, (2 bI stMoring
the butter at a temperate tire Iwh the gr-'.vth pint. (31 by treating
the tubs in somne wa tio dlestrcv thlie minilds a81d their msptrs, or (4)
by treating ithe tubs w.ith smie preparation cn which miold. can not
The tubs imay conmei t tle butter maker hadly infected, or lie may
not have at his (co-i1mantl suitable -strage. Fe\ creanimeries have
refrigerators holding a temperature IOW i.'1-..ugh1 to inhibit tlie growth
of molds if other condition-. are favt'rablie. The butter minaker is
therefore frequently forced to resort to thle third mietlitl.
The methotI of steaming the tiul, is ,often used to dlestr 'y the ,oi'lds,
but this has not been very effective. It is (lillici t to lieat the tub
thoroughly by a steam jet, amnd tlie suldden .swVllinz of the tub fre-
quently breaks the hotops.
Soaking in a brine c'Intainin,: al1ut 5 per cent of frnildehydtle is
a mniethod somnetines uedI, antdi (')ne co issitn house recom(mnends
that the tubs be boiletl in brine andl that ,zilt be rubbed I on th(e inside
A few of the larger fatories have recently begun mitini thlie inside
of the tubs and boxes with paraffin. l'hi.- nut onlv dles.i ro*.s the mllilds
already present but gives a -urfaice in which miild.s will noit grow.
TESTING AND Ct' IM P.\ARISOIN (OF METIHOLPtS.
Various method s were tested anid compared by thle writer in a
creamery which had had serious trouble with nimolds a11 throiig h thlie pre-
vious surinmmer. The test was made in October, h lien the temperature
conditions were becoming unfavorable to thIe griwth if milds. The
factory was a new one, in excellent contlitiin, and tlie refrigerator,
which w'as better thau the average, was free froimi minoilds. However,
the tubs were stored in a damnip romi in lthe nitrth side of the creanm-
ery. The practice had been to submerge thle tuls o_,n the dlay before
they were used in a saturated brine which va-i boiled by blowing
steam into it, and to allow them to stand in the warmn brine over-
night. Before packing, the sides of the tubs were coated with salt.
This had not proved entirely effective.
MANUFACTURE AND STORAGE OF BUTTER.
For the experimental work thirty 20-pound tubs were secured and
divided into six lots of five each. Lot I was old tubs from various
sources, all showing more or less mold, while some were very moldy.
Lots II, III, IV. and V were new tubs received direct from. the factory.
Nearly all had a ring of mnold where the tubs were in contact. The
tubs of Lot II were purposely wet with an emulsion of moldy cheese.
Lot VI ,\as new tubs showing no mold.
The tubs of each lot were numbered from 1 to 5. Tub No. 1 in
each lot was soaked overnight in cold water in the usual way; No.
2 \\as boiled five minutes in a saturated brine and left in the brine
overnight ; No. 3 was soaked overnight in a brine containing 9 per
cent of commercial formalin; No. 4 was coated on the inside with
paraffin, the paraffin being applied either with a paint brush or by
pouring, while hot, into the tub, which was rotated until the fluid
hadl fioeed over the entire inside surface; No. 5 was immersed for a
few seconds in a bath of paraffin at 250': to 260 F. In each case
(le liint.urs were soaked in a salt solution.
A.ll of tlie tubs in each lot were filled from the same churning and
all held in the creamery refrigerator until shipped. The first lot was
lield ten days, the second nine, the third eight, the fourth seven, the
fifth six, and the last lot five days before shipment. The butter was
shipped in a refrigerator car and was received at Aurora, Ill., six days
later ind, was examined the following day. The results of the exam-
ination are given in the following table. In this table the tubs are
described as moldy only when there was an evident increase of the
,1ihl irihzinallv on the tub.
Ti"ilih ,Io, init r ',l! f t rti erimenf tro Irfatinq hbn ir prerention of mold.
I ,n N.. I Il 1 rratIrnvnt. conditionon.
S Intreated. ............ T1I1' and linr badly molded.
S Hot tbrine ............ ........ No m old.
I. .1 fBri in.- ormalldeh d- ..... Do
I LLuaih l \ %ith p.irailMin ..... Do.
5 Dripped in pdadlirarl.r .. ......... Do.
I Lnr n-ated... )Tub and liner badly molded.
S fit rineo .............. Do
II 3 li rit -forrrimallehyi. .......... No mold.
4I t'onted w th paraffin ...... Do.
5 Pipp,- in paraffin ...' Do.
I lnrtried..... .... .. ..Tw Badly molded.
I intr I r ten .... .... Two small spots of mold on tub and liner.
I :I Brne -forma ldeh dr, .... No mold
4 Coated with p,4rarfin. ..... Do.
5 lipped in paruffin . .. Do.
I ntrca ed .. .. ... ..... . Slightly moldy.
1 lIot brine .. ... .. Mold on outside .
IV. .3 Brinef-fr-rrail<'h iJ .d ...... Baidly molded.
4 CoAri-dl ith pirarTin.. ...... No mold.
S.5 Pippr.d in paraffin ... Do.
I L'ntnreald. . ... Tub and liner moldy.
2 Ilo n r r ............ .. .. .. N o m old.
V. Brnie-formalili'h 'e . Do.
4 ('nte'd \\ith paraffin .... Do.
5 Dipped in paralffin .. . ...... Do.
I Untreiaied .......... .... .... I Tub and liner moldy.
2 IHot brine ........ ... .....: No mold.
VI. .1 Brin--formaldh %it e ..... Do.
4, Co-iled with paraffin .. I Do
SDipprd in paraffin Do
II .. . __ __ __ __
PREVENTING MOLDS IN BUTTER TUBS.
It will be seen from this table that all of the untreated tubs became
moldy. Of the six tubs treated with hot brine one was badly molded,
one was slightly molded, and one had mold on the outside. Of the
six tubs soaked in the brine-formaldehyde mixture one was badly
molded. None of the tub, coated with paraffin showed any mold
whatever, anti the same was true of those dipped in paraffin.
It was evident that each of these methods checked the growth of
mold materially, but that paraffining was much more efficient than
the other two methods. If the temperature conditions. had been
more favorable to the molds it is probable that thliese differences
would have been greater.
This test, so far as it goes, indicates that the fornmaldehyvile treat-
ment is more efficient than the hot-brine method. Salt is at bes,,t a
weak antiseptic. Gripenberg' has shown that while the growth of
Penicillium, the mold most o mmnionlv found on butter, is retarded
by 5 per cent of salt, it will grow slowly in 10( and even 20 per cent
solutions. Twenty-five per cent of salt completely checked its
To treat tubs by the hrine-formiialdcehvde method or the hot-brine
method a vat should be made large enough to hold submerged thlie
tubs used in one day. The brine may be boiled by blowing steam
into it. The cost of either of these two methods is insignificant, as
the bath may be used repeatedly. The objections to these methods,
in addition to their inefficiency, would pro ibably be found in the dis-
coloring of the wood and, with the hot brine, in thIe exce.-s.sive weight
and swelling of the tub.
With paraffining not. only are the molds and their spores already
on the tub prevented from growing, hut thlie wood is covered with a
surface from which molds can not get nourishment. The wood is
made impervious to water, and thlie space between the tubill) and the
liner remains filled with water, so that the molds which may be on
the liner can not get the supply of air necessary to their growth. The
appearance of the tub is unchanged and is better than that of tubs
soaked in brine or water.
There is no advantage in dipping the tubs over coating the inside,
except that the outside will not become moldy. Dipping has the
disadvantage of extra cost and giving the outside of the tub a surface
which can not be marked with a pencil.
METHOD OF APPLYING PARAFFIN.
The paraffin should be applied in such a way that it will give an
even, thin coating which fills all the cracks and at the same time sinks
aGripenberg, R. Untersuchungen iber Schimmelbildung bei Lagerbulter Meddel
Muistiala Inst. Forsoksstat Mijiriafd, Ielsingfors, 1899. Review in Milch Zoitung, v. 28,
No. 40, pp. 626-628; No. 41, pp. 644-646. Bremen, 1899.
12 MANUFACTURE AND STORAGE OF BUTTER. iN
into the wood sufficiently to prevent the coating of paraffin from-4..,
cracking off. Thile application may be made with a brush, but it may,
also be accomplished by pouring a small amount of the melted paraffin ':
into the tub and rotating the tub until the paraffin has flowed over
the entire surface, taking care that it does not run down the outside :
of the tub. By the latter method a thinner, evener coating may be
applied than by using a brush. A
The temperature of the paraffin is important.. If the temperature .
is too low, thlie paraffin will cool rapidly, making a thick uneven coat-
ing; if the paraffin is too hot, it will sink into the wood and the cracks ;
will not be closed up. If the paraffin is melted by holding the '
receptacle in hot water or steam, it will be found advantageous to
heat the tub over a steam jet.
The paraffin can be applied most rapidly and satisfactorily by "
heating it to 250 or 26U F. This may be (lone on an oil stove, But
in creameries where steam is always available it will be better to :
arrange a small tank with a steam coil, as shown in figure 1.
',._'- ....I .
FIG I -A\pparatus for paraffiniiing tubs.
By connecting the coil in the bottom of the tank with the boiler
and opening the waste valve only enough to allow thle escape of the
water of condensation, boiler pressure may be maintained in the coil M
and the temperature of the paraffin raised to the required point.
COST OF PARAFFINING TUBS.
The question of the cost of paraffining tubs will doubtless be "
brought up as an objection to this method. The amount of paraffin 0
necessary to coat a 60-pound tub will vary with the method of apply-...
ing and the temperature of the paraffin. If the paraffin is hot enough,.:
PREVENTING MOLDS IN BUTTER TUBS.
this should not exceed 3 ounces per tub, and as a good grade of par-
affin may be purchased at about S} cents a pound the cost will be less
than 2 cents per tiub. But evenI this small sum would be a consider-
able item in a season's run and would be a serious objection in tome
factories. However, there is another factor which must be taken
into consideration. In an ordinary tub the loss by evaporation
from the outside and by absorption of water from the butter by the
tub is an appreciable quantity. Coating the tub with paraffin makes
it impervious to water, and this los-, is reduced to a nunimum.
To illustrate this point, 24 tubs were divided into two lots of 12 tubs
each. One lot was paraflined in the manner previously described,
and the other lot was soaked overnight with cold water in the usual
way. The tubs were weighed before filling and again after the butter
was packed. The 12 paraffined tubs contained at this time 757.
pounds of butter and the 12 tubs., soaked in watur 766- pounds. These
tubs were all filled from the same It of butter, were held in the
factory refrigerator three days, and were then shipped to the com-
mission house, where they were weighed on thle eight lih day after
packing. Each tub was weighetl -eparately, and the average weight
of three empty tubs was taken as the tare. The weight of butter
obtained in this way was for the paralffined tubs 756 pounds, a loss of
It pounds: for the soaked tubs 751, pounds, a loss of 71 pounds. In
other words, by the use of about 15 cents' worth of paraffin the price
of 6 pounds of butter was saved. In butter held in stora,,ge for any
length of time this saving would undoubtedly he much greater.
It should be remembered, however, t lhat paraffined tubs weigh from
1 to 2 pounds less than tubs prepared in the ordinary way, and unless
the tare is actually determined this difference will be lost to the
butter maker. This possibility may be avoided by soaking the tubs
before paraffining. To do thi, it is necessary to keep the paraffin
very hot, so that it will displace thle water in the pores of the wood,
or the soaked tub may be heated on a steam jet before applying the
The labor cost of paraffining need not be greater than in the usual
method of soaking tubs in cold water or brine. The apparatus needed
as here illustrated is simple and inexpensive.
SUM NM A RY.
The advantages of paraffining may hbe summarized as follows
(1) Certain prevention of moldy tubs.
(2) Prevention of mold on butter and liner by avoiding air space.
(3) Neater appearance of tub.
(4) Reduction of loss from shrinkage.
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