US2205381A - Preparation of winter oil from cottonseed oil - Google Patents

Description

Patented June 25,. 1940 PREPARATION OF WINTER OIL FROM COTTONSEED OIL Edayw. Eckey,.Wyomlng, and Robert G.Folzenlogen, Lockland,

- Ohio,

assignors to The Procter & Gamble Company, Cincinnati, Ohio,

a corporation of Ohio No Drawing. Application July 6, 1939. Serial No. 283,062 g Claims. (01. zso-42s) This invention relates to an improved process for preparation of winter'oil from cottonseed oil.

Its principal object is to prepare an oil.suit

able for a salad oil for table use, that is, one which will not become cloudydue to deposition of stearine even at the lowest temperatures ordinarily occurring in homes.

A further object is to shorten the time heretofore consumed in the commercial process of cooling cottonseed oil and the subsequent crystallization of the stearlne from same, with a corresponding reduction in the space required forthe operation.

Our process consists essentially in supercooling the oil by coolingit so rapidly from a temperature at which the oil is perfectly limpid to a temperature a few degrees below the temperatureat which the bulk of the stearine is to be crystallized out that the oil acquires a supercooled condition without separation of stearine, and then allowing the stearine ,to crystallize spontaneously from the oil'without further refrigeration but allowing the temperature of same to rise slightly due to the heat evolved by the crystallization of the stearine, after which the stearine is separated leaving an olein having the desired properties for use as a salad oil.

The oil ordinarily used in this process is what is commonly known as "summer yellow" cottonseed oil, although bleached oils can also be used if desired. This is produced from ordinary crude cottonseed oil by the well known alkali refining treatment. It is important that the oil be free from moistureand suspended matter or dissolved soap, etc.; if it is perfectly clear at a temperature of 70 F., it will be satisfactory in these respects.

Ordinary refined cottonseed oil (summer yellow oil) consists essentially of a. mixture of glycerides of various higher fatty acids, some of which glycerides are liquid at ordinary temperatures and others are solid. The mixture, however, is a clear liquid at ordinary room temperatures. At low temperatures,- however, some of the solid constituents crystallize out forming what is known as'-stearine and leaving a liquid portion known as olein."

' contains little, if any true stearic acidbut consists mainly of glycerides containing palmitic acid. vTemperatures belowabout F. generally show some separation of stearine but the bulk of the stearine does notseparate until -the tem-' The so-called stearine crystallizing temperature for a considerable time before crystallization sets in to any great extent. This is due to supercooling to which the oil is easily subject. The olein constitutes the ordinary winter oil of commerce and, for commercial purposes, it is required to pass the" cold test as described in the Rules of the National Cottonseed Products Association, wherein a four-ounce bottle of the oil must stand immersion in melting ice for five hours without becoming cloudy.

. Ordinary winteroils will develop cloudiness if held suiiiciently long in this test, but not in the livehour period prescribed. A further small quantity of stearine can "be separated from such winter oils by subjecting them to a second crystallization at a lower temperature than that ofthe first crystallization, and the oil willthen have a considerably longer cold test" and it will stand a correspondingly lower'temperature without clouding.

In making winter oil heretofore, the necessary refrigeration has usually been applied over. substantially the whole period during which crystallization is actually taking place. The coolingTias been accomplished, in one system, by first filling a large tank with the oil at a temperature-of- -'l0 F. to 90 F., at which temperature it is clear generally no agitation is used. Refrigeration inboth procedures is continued until .cryst'alliza-' tion of stearine has progressed to the desired extent. In either case the oil remains substantially stationary, so the transfer of heat is slow,

and these chilling processes on thelarge masses of oil commonly used usually require about thirty hours or more with the brine coil system,

and several days with the refrigerated air system,.

to chill the oil from -90? F. to the crystallization temperature and to continue the refrigera tion until the crystallization of stearine is substantially complete. The temperature at whichmost of the-stearine crystallizes from summer cottonseed oil is usually about 42 to 45 F., although the stearine usually begins to crystallize .at temperatures slightly below -60 F. The

crystallized stearine is then separated, usually by filtration in a filter press followed by blowing with air, thus obtaining the olein for use as salad oil.

Itf'is ipossible to recover commercially from average summer cottonseed OH in the above described manner, eighty-five per cent to eightyeight per cent of marketable winter oil with twelve per cent to fifteen per cent of marketable stearine having a titer test of 44 to 45 C., but

. tained more than a few degrees below that of the oil, the effect is to overcool those portions of the.

oil nearest to the refrigerating medium so that they may actually freeze solid without allowing the stearine to separate in grains from the olein; in other cases, the result may be a rapid crystallization .in the form of fine particles of stearine which cannot be filtered out. Agitation throughout the cooling and crystallizing period in large masses of oil likewise prevents crystallization of stearine in the form of large crystals which can be filtered.

In our process we cool the oil very rapidly,-

while it is moving over the refrigerating surface, so that a supercooling effect is obtained.

The entire cooling takes place before there is any separation of stearine, or at the most only a very slight separation. We accomplish this preferably by passingthe dry oil at a temperature' of at least 60 F., but warm enough to be clear and limpid, continuously into and through a suitable heat exchanger supplied with a cooling medium such as cold brine, the temperatures and rates of fiow of the two liquids being so regulated that the oil issues from the heat exchanger with the desired temperature. The oil should preferably be well agitated. during its passage through the heat exchanger in order to secure uniform cooling and to prevent excessive local cooling of any portion of the oil. The cooling operation may thus be made continuous, and the oil may be completely cooled without exposure to the refrigerating surface for m'ore than a minute or two, as only asmall amount of oil is in contact with the refrigerating surface at any one time. In. any event the cooling operation should not ordinarily extend over 30 minutes in order to assure the desired super--- cooling-effect. The temperature to which the oil is cooled should be about 2- to F. below the temperature at which the'stearine will separate' in large quantities or the temperature to which the oil will subsequently rise due to the heat of crystallization of the stearine. Th s latter temperature is referred to herein as the "temperature of graining. In this way all the re-' frigeration required for crystallizing the stearine in our process is applied to the oil before crystallizing actually begins. The best temperature to which the oil should be cooled is usually about 41 to 44, depending on the nature of the oil and the amount of stearine which it contains, but not-below 40 F., and can. be: readily determined in each case by a preliminary laboratory test or by observation of previous batches of the same oil. Care must be taken not to supercoolthe oil to 'an excessively low temperature,- as this may cause the subsequent separation of stearine to occur too rapidly and in a form diflicult to filter.

After cooling, the oil is accumulated in a suitable tank where it is held without further reduction of temperature, and with protection against changes of temperature due to other causes than the natural heat of crystallization, until the desired crystallization of stearine oc-' curs, which requires from ten to twenty hours for completion. During. the first few hours of this stage the oil is gently agitated, (usually about two-to six hours, or until crystallization is well under way), after which it is found best to allow the oil to rest without further agitation until the crystallization of stearine is completed. During this stage the temperature will riseseveral degrees, sometimes as much as 5 F., due to the heat of crystallization. The separation of stearine is considered complete when no further rise of temperature takes place, and then the oil is ready for separating the stearine by filtration or centrifuging, etc.

In practice we find it best to maintain the atmosphere surrounding the tanks of oil for'crystallizing at a temperature either the same as that of the oil or one or two degrees below the temperature of the oil, in order to assure that no access of heat to the oil takes 'place from outside sources during the crystallization; if this were not done, and if the surrounding air had a higher temperature than the oil, it would make necessary further cooling of the oil to offset the heating efl'ectof the higher surrounding temperature during the subsequent crystallization. It is not intended however to impart any additional refrigeration to the oil at this stage. 4

We prefer to. agitate the oil during the first portion of the crystallization stage with a gentle current of air or other gas, avoiding in all cases strong agitation, This is continued only until about the time when crystallization of stearine has produced noticeable turbidity, after which agitation is stopped. We find that if the oil has beencooled to as low as 41 F. about one hour of agitation is enough; if the oil has been cooled to 43"; we agitate about four hours; and if the oil has been cooled to about 44 to 45 we agitate as much as eight or ten hours. In any event the oil then remains quiet throughout the remainder of the crystallization period. Practically no temperature rise occurs during the period ofagitation when conducted as here specified, but after this is stopped and rapid crystallization sets in the temperature gradually rises and may go up as much as 5 F- The time required for crystallization can be considerably reduced by the process of seeding the super-cooled oil by adding asmall amount,-

such as about two to five per cent for example,

of the crystallized oil from a previous batch, or.

an equivalent quantity of crystallized stearine from a previous batch, which would amount to,

not over one per cent of. the stearine. This should be added to the oil immediately after cooling. I Q

The agitation is then limited to about one hour and the separation of stearine, is completed in a much shorter time than otherwise. oftentimes the time is as short as seven hours. I

The advantages of our new procedure are mainly the greatly reduced time for completion of the operation, the correspondingly reduced space required for production of a given amount of winteroil, and the reduced loss of refrigeration due to the greatly reduced time of chilling, It is novel, as far as we are aware, to find that cottonture below the final crystallizing point of the oil without separating stearine, and then without further refrigeration to have the stearine crystallize spontaneously in a form which will permit a satisfactory rate of filtering. This rapid chilling is contrary to all previous experience and theories for the production of winter oil.

-Having thus described our invention, claim and desire to secure by Letters Patent is:

l. A process for separating stearine from refined cottonseed oil which comprises cooling the oil from a temperature above-its graining temperature at which it is limpid to a temperature at least 2 F. below its temperature of graining but not below 40 F., the rate of cooling being sufiiciently rapid to avoid any substantial graining out of stearine during said cooling, then protecting the oil from any substantial change of temperature due to other causes than the natural heat of crystallization while stearinecrystallizes from the oil, and separating the grained stearine from the olein.

2. A process for separating stearine from'refined summer cottonseed oil which comprises cooling the dry oil while it is in motion, from a temperature above its graining temperature at' which it is limpid to a temperature at least 2 F. below its temperature of graining but not below 40 F., the rate of cooling being sufiiciently rapid to avoid any substantial graining out of stearine during said cooling, gently agitating the oil until substantial crystallization begins, protecting the ,oil from any substantial change of temperature due to other causes than the natural heat of crystallization until crystallization substantially ceases, and separating the grained stearine from the olein.

'3. A process for separating stearine from refined summer cottonseed oil which comprises cooling the dry oil while it is in motion, from a temperature above its graining temperature at which it is limpid to a temperature at least 2 F.

below its temperature of graining but. not. below whatwe- 40 E, the rate'o! cooling being sufficlently rapid to avoid any substantial graining out of stearine during said cooling, then adding to the cooled oil grained cottonseed stearine in solid form in an amount not exceeding one percent of the oil,

gently agitating the oil until substantial crystallization begins, protecting the oil from any substantial change of temperature due to other causes than the natural heat of crystallization until crystallization substantially ceases, and separating the grained stearine from the olein.

4. A process for separating stearine from refined summer cottonseed oil which comprises cooling the dry oil while it is in motion, from a temperature at which it is limpid, but at least F., to a temperature at least 2 F. belowits temperature of graining, but not below 40 F., within a period not exceeding twenty minutes, the rate of cooling being sufliciently rapid to avoid any substantial graining out of stearine during the said cooling, gently agitating the oil until substantial crystallization begins, protecting the oil from any substantial change of temperature due to other causes than the natural heat of crystallization until crystallization substantially ceases, and separating the grained stearine from the olein.

5. A process for obtaining from refined summer cottonseed oil an olein suitable for use as a salad I oil, which comprises supercooling the oil bycontinuously cooling a moving stream of the dry oil from a temperature at which it is limpid and above its graining temperature to a temperature from 2 to 5 F. below its graining temperature, the

rate of cooling being sufficiently rapid to avoid any substantial graining out of stearine during said cooling, gently agitating the oil until substantial crystallization begins, protecting the oil from any substantial change of temperature due to other causes than the natural heat of crystallization until crystallization substantially ceases, and

filtering the grained stearine from the olein,

EDDY w. ECKEY. ROBERT a. r'onzsnnoonn.