The effect of pressure in the preservation of milk - a preliminar

H., "The effect of pressure in the preservation of milk : a preliminary report" 1899.. THE EFFECT OF PRESSURE IN THE PRESERVA-TION OF MILK.. In thefirst experiments the milk was placed i

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Hite, B H., "The effect of pressure in the preservation of milk : a preliminary report" (1899) West Virginia Agricultural and Forestry

Experiment Station Bulletins 58.

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[The Bulletins and Reports of this Station will he mailed free to any citizen ofWest

Virginia upon written application Address Director of Agricultural Experiment

THE REGENTS OF THE WEST VIRGINIA UNIVERSITY.

Hon George 0 Sturgiss - - - Morgantown Hon James F Brown Charleston

Hon. a H Kunst - - - - Weston

Hon Richard Randolph McMahon - - Harper's Ferry

Hon James M Lee LewisburgHon James L Hamill Welch Hon John A.Campbell - - - New Cumberland Hon W.E Powell - ParkersburgHon p C Eastman Pt.Pleasant

James H. Stewart, A M., - Director and Agriculturist

A D Hopkins,Ph.D - Vice Directorand Entomologist

Bert H. Hite, M. S. Chemist

L C CoRBETT, M.S - - - - - Horticulturist

W. E.RuMSEY, B S. Agr - - AssistantEntomologist

T F Watson,B S - - - - AssistantChemist Horace Atwood, M. S - - - Assistant Agriculturist

C D Howard, B S - - - - Assistant Chemist

THE EFFECT OF PRESSURE IN THE

PRESERVA-TION OF MILK.

The souring of milk being due to the action of bacteria,methods forpreserving milk must either destroy the germsor

interfere withtheir work Barring anticeptics, which are

al-ways objectionable, the methods in general use arereduced tothree: sterilization, cooling and pasteurization The first

named method attempts to kill all the germs by heating themilk to about the temperature of boilingwater, andkeepingit

forthree or four successive days,or by heating it to a

some-what higher temperature for one longer period Sterilized

milk should keep indefinitely, butit has a"cooked" odorand

itsimply prevents their rapid multiplication and so interfe-es

with their action Ithas one great advantage, in thatit doesnot afi"ect, injuriously, the odor, taste, etc., ofmilk Pasteuri-

zation, which is a sort of compromise or combination oftheothertwo methods, andconsists in heating the milkfor ten tothirtyminutes at a temperature of 140°to 180° Farenheit, and

then quickly coolingit, greatlyreducesthe total germ content

ofmilk,and seemsto beparticularlyelFective in destroying thedisease germs so often present Thismethod has manyadvant-

ages, butas it does not kill all the germs, the milk mustbekept at alow temperature,or it will sour in a veryshort time

But one ofthese methods attempts to completelysterilize themilk,andit has a bad effecton the odor and taste ofthe milk

It will beobserved that these methods, in general use, are all

problem ofpreserving milk the efi"ect oftemperature has beenpretty wellworked out, and that it might be worth while to

some

From timetotime since the fall of 1897,but moreespeoially

containa preliminary report ofthe work on milk

In thefirst experiments the milk was placed in a tin tube

jibout a foot longby two inchesin diameter, and similar

gener-ally to the ordinary collapsible lead (or tinj paint tubes.The tin tube andits contents were then placed in an iron cyl-

inder abouteighteen inches long by three inchesin diameter,

Thecylinder wasconnected with agauge and the pressure plied to the water, and from this to the tin tube audits con-

ap-tents, by meansof a heavy screwdriven into the cylinder A

long lever was attached to the screw and the theoretical

pres-sure (neglecting friction) was something tremendous The

gauge, however, never registered more than a few hundred

attempted, a few dropsofwater would escape and the pressure

would fall It was hoped that even these pressures might

in-terfere with the multiplicationof the germs, and sopostponethe souringofthe milk A numberofsamples veere subjectedto

these pressuresfor two or three days, during which time they

all soured It was evidentthat much higher pressures would

haveto be used andthat a much moreefficient methodfor jectingliquids to pressure would have to be devised

which quantities of liquids, suitable forexperimental purposes,could besubjected to very high pressures Thelack of such a

methodis the more noticablein viewof the longlist of

labora-tory forstudying the effect of temperature, butthe great jority ofthe transformations with which the chemistor bacteri-ologist has to do are effected at ordinary or atmospheric

ma-pressures, which happen to be really very low pressures.Thatthe great majority of such transformations are far more

susceptible to slight changes in temperature than to what

is doubtless true, andit may be that therelative importanceof

the two agents in suchoperations isindicated fairly enough by

the usual laboratory equipment, and yet before taking itfor

granted that suchis the case itwould seemthat sciences

boast-ing so many duplicate devices for almost every operation,shouldafford one method at least by which the effect of pres-

sure could be studied through a much wider range than a few hundred pounds to the square inch

In considering the advisability of continuing the work onmilk underpressure, facts, such as thosejust mentioned, were

not encouraging, as they could only argue that the effect of

pressure was not generallyregarded as beingworthy of much

attention This was discouraging,because a line ofwork isingany very greatreturnsis not likely tobeso carefully neg-

prom-lected On the otherhand there was no method or apparatus

by which the effect of a very wide range of pressure could bestudied hadany one considered it worth while to do so,andit

might bethat this was the reason that the subject had been

neglected If so, the method itself might be worth working

tubeswas regarded as alongstep towards the solution of the

pressure on the water surrounding the tubes And this,

in-deed,was all that remainedto be done, butas one deviceafter

respect and discarded, thisonly remaining part ofthe problem began to assume proportions and a good reason for the lack

of such a method in general use would occasionally suggest

itself.

In order to subject a liquid to pressure the capacity ofthevessel containing the liquidmust be decreased, which suggests

at once a cylinder and piston But no simple piston and

cylinder could beexpectedtoholda liquidunder the pressures

which was determined

andpiston orcylinder that a liquid underhigh pressurewillnot

forceits wayout Indeed about the only contact thatis equal

to such cases is that between the particles of one continuouspiece of metal, from which it would appear that in order to

obtain the highest pressures theendofthe piston and walls of

the cylinder would have to be one solid piece for all positions

ofthe piston; or,that the liquidwould have to be completely

could berealized the pressures obtainable ought tobe limitedonly by thecrushingstrength ofthe materials (e g. steel) used

in the consti-uction of the cylinder If the liquid could besealed up in a cylinder made ofsome soft metal, such as lead,

this lead cylinder placed in a steel cylinder just large enough

to receiveit, and thepressure applied to the lead cylinder and

its contents,it would seem that the above conditions would be

practically realized Simpleas such an arrangement is, it

re-quired nearly three months to find a firmthat would take it. With one accord they all proceeded to explain why

under-the method mustfail,and to suggest some other arrangement

Finally, Mr Bert Oliphant, a student inthe writer's classinagricultural chemistry,brought the matter to the attention ofhis father, who was connected with the National Transit Com-

shorttime, the cylinder came to hand, withthe complimentsof

that company,-—this station's first and finest gift. Averticlesection ofthisdevice isshown in Fig 1.

Ascrew tap, collapsible, block tin tu,be, T, was filled withmilk,'closed securely with the cap and placed inthe lead tube

by heavy black surrounding

thetube, T,)which wasthenfilledwithwater,closedwith alead

lid,placed in the steel cylinder, C C, the lower end ofwhich

was closed with a steel plug, O, The cylinder was thenplaced between two steel blocks

B and R,in a testing machine

and the pressure appliedto the

lead tube and its contents by

means ofthe steel piston, P

But to take up some of the

partsalittle more indetail.

The collapsible tube, T, (see

also Fig 2) should be made of

block tin andthe cap should be

its way into the mouthofthe

tube, thus securely closing it.

Many ofthe tubes on the

when these are subjected to

pressure the cork practically

disappears, leaving thetube but

partially closed At first the

bottom ofthe tube was pinched or folded togetherin the usu^al

way, exceptthat the folds were pressed together in a vise. The

imperfectjointsobtained in this way were doubtless sible for a large number ofvery discouragingresults Itwas a

a lower temperature than the solder, and a soldering iron that

is hot enough to take ordinary solder will melt a hole inthetubes before it touches them Later in the work whenit was

evident that the bottoms must be closed with a solderjoint, a

prepared and withthis no further difficulties wereencountered.All thatis required ofthese tin tubesisthat they separate the

20 WEST STATION.

JL

pressureis the same on both sides ofthe walls ofthe tubes, so

softer they are the better

nThe lead tube is best shownin Fig 3, which

is a full size section At first the lids were

soldered on This was a tedious and

unsatis-factory operation,as the heat from the

solder-ing iron generally succeeded in raising the

agreeable to the germs within Later it was

the cut andthe contact surfaces ofthe lid and

the tube werescraped clean the pressurewouldseal themas effectually as the solder,and with

When the pressure isremoved the waterin

expandingto itsoriginalvolumewillsometimes

loosen the lid,and incase a high pressure has

been used the leadtube in stretching to its

ori-ginalcapacity will sometimes be pulledintwo,

case these are not serious matters So longas

the pressnreis being applied there is

absolute-ly no trace ofa leak

The cylinder referredto was six inches long

by six inchesin diameter, with ahole through

itone andfourth inchesindiameter, and made

ofordinary"low steel" or"machinesteel." The

plugsand pistons, O P, were of the same

although they would slip throughit easily, they were

The pressure wasappliedand measuredwithaKiehle'testingmachineof about twentytons capacity

machine forperiods of fiveminutes to three

Fig.

hours Owino; to the pressureofother lines of work this work was all done at night But one determination could be made

at a time, so as a rule not more than two determinationscould

be madein onenight

It was hoped that these pressureswould

tubes closed so thatnomore germscould

enter,themilkwouldremainsweet.Every

samplesoured So many samples would

pres-sures but forthe fact that defects in the

were hoped to followeach improvement.

At last when no further fault could be

that still higher pressures must be used,

and the one hundred ton hydraulic press,

shown in Fig 4 was ordered, but the

other orders that nearly three months

elapsed before the press arrived This

machine is of the '' fourrod punchtype,''

weighs about1,000pounds andhasa

capa-city ofconsiderably more than one

hun-dred tons Thepressure is applied with

the upperlever,shown inthe cut,and the

and easily relieved by means ofthe same

lever When not under pressure the ram

is quickly raised orlowered by means of

same material is embedded in |the lower

platen of the press Whenin operation

the plug, O, ofthe cylinder rests on this

22 WEST

A few applications of thirty to forty tons spread the low

steel cylindermentioned and mashed the pistons until theycould not be used The cylinder was then bored out to three

inches, and a tool steel "bush" inserted, which brought thehole down to the original size. Toolsteel plugs and pistons

were made and with this equipment several samplesof milk

were subjectedto pressures oftwo hundredthousandpoundsto

the square inch foraperiadofone or two minutes, and about

tonsfor five to sixty minutes In eachcase,samples('blanks')

ofthesamemilkweresealed up in the same way(in collapsible

tubes) andtreated in all respects like the samples just tioned, except that they were not subjected to pressure No

men-ice was used in any part ofthis work and all operations were

carried out at the temperature of the room,which during byfarthe greater part ofthe timestood at75° to80° F The milk

wasfurnished by alocal dairy

hours longer than the blanks, some ofthem forty-eight to sixty

one hour, remained sweet for more than aweek Thus couraged an attemptwas made tosubject othersamplesto nine-

en-ty tons, when with a loud report the tool steel bush split fromone end to theother From this it would appear that having

"tested" a cylinderto a high pressureonceis no guaranteethat

itwill stand such a pressure again The cylinder was boredout again and a larger (thicker walled) bush inserted, butthiswent to pieces at seventy tons Then followed a longlist of

pressures Most of these cylinders were of the same

dimen-sions as the one described, except that they were about aninch longer They were all madeofthefinesttool steel— some

ofthem of one solid piece, others "built up" of a numberof

concentric cylinders shrunk together The object in thelater

casebeing to make the outer partofthe cylinder carry moreof

would made one piece Whetherthis

OF 23accomplished, atleast to any very great extent, would bediffi-

cult to say Some ofthe highest pressures, however,weretainedwith cylinders constructed in this way Duringthese

more, (this beingthe pressurethathadyielded thebest results)and while cylinders were going to pieces much more rapidly

determina-tions have been tabulated in a number of ways, and these

tables,etc.,could be usedas convenient material with whichto

inflate this very brief report to several times itspresentsize.

It is preferred, however, to simply state such conclusions as

may be safely derivedfrom this data which are as follows:

Pressures ofover thirty tons per square inch (up toone dredtons) applied for one hour may generally be relied upon

hun-to postponethe souringofmilk for twenty-four hours

Thirty tons for an hour generally delays the souring just

hour willgenerally remain sweet for about four days And

an occasional sample will be foundthat certainly is not sour

have taken place in it.

Very similar results tothosejust mentioned will generallyfollow the use of about thirty tons for a period of ten to

twelve hours, i e. they will generally keep sweet for three to five days, and an occasional sample will not besour at the end

to obtain similar results with intermediate pressuresthese should be applied for some intermediate period oftime, and to some extent,at least, this appears to be true, al-

to thirtyfive tons, and eighty-five to ninety-five tons thatreceived the most attention The first sample subjected to

ninety tons happened to give one oftheexceptionally good

results mentioned above This led to many attempts toobtain