Chemical technology and analysis of oils, fats and waxes / by Dr. J. Lewkowitsch.

  • Julius Lewkowitsch
Date:
1914
Catalogue details

Licence: In copyright

Credit: Chemical technology and analysis of oils, fats and waxes / by Dr. J. Lewkowitsch. Source: Wellcome Collection.

Provider: This material has been provided by UCL Library Services. The original may be consulted at UCL (University College London)

    57/980 (page 37)
    xni and Algerian olive oils deposit, however, so much, stearine that they must be demargarinated before beiag placed on the market. For the latter piu'pose, centrifugals ^ have been proposed, but nothing definite can be stated as to their success. It appears to the author rather doubtfid whether proper demargarination can thus be effected. In a wider sense, the term demargarinating includes also those processes in which fats which are soM at the ordinary temperature are resolved iato two portions of different consistence, generally termed stearine and oleine. As examples may be given the preparation of oleomargariae and tallow oil from tallow, of lard oU from lard (see Vol. III. Chap. XV.), and the separation of oleic acid from stearic acid. Preserving Oils and Fats It has been pointed out in the first chapter that oils and fats, if carefully protected from access of light, air, and moisture, retain their state of neutrality indefinitely, and ia confirmation the fact was adduced that fats buried with the mummies in Egyptian tombs had remained neutral for several thousand years. In practice it is, of course, impossible rigidly to exclude contact with air during handling, and it is a matter of daUy experience, most noticeable ia the case of edible oils and fats, that in com-se of time, sooner or later, according to the conditions observed in keeping, they turn rancid. The cause of rancidity has been traced, in the fia-st instance, to initial hydrolysis (see Vol. I. Chap. I.), which is accelerated in the case of unrefined oils and fats by the presence of enzymes. In the preparation of the majority of commercially prepared oils and fats, the enzymes may be considered as having been destroyed, owing to the elevated temperature employed in the refining operations. Where, however, large quantities are prepared merely by rendering at low temperatures (premier jus, lard), the temperature may not be sufficiently high through- out the whole mass to destroy the enzymes completely, so that there may remain intact a quantity of enzymes sufl&cient to cause hydrolysis and subsequently rancidity. Where the possibility of accelerated hydrolysis due to the presence of enzymes is excluded, a small amount of moisture is sufficient, under favom-able conditions (the most important of which is a somewhat high temperature), to cause hydrolysis and rancidity which follows in its wake. It is therefore obvious that it is not only necessary to employ the greatest care in refining, but that it is essential for the preservation of the refined product to exclude as far as possible the presence of moisture. Since, however, even properly filtered fats retain water up to one-half per cent, without revealing its presence by a turbid appearance, oils and fats should be stoi'cd at as low a temperature as possible. In the case of edible oils and fats (which demand the greatest care ' E. Bertainchand, IXmargarinalion des huiles dela rbjion de tydx. TiiiiiH, ]903.