Volume 2

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

  • Lewkowitsch, J. (Julius), 1857-1913.
Date:
1909
Catalogue details

Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

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

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

    23/848 (page 7)
    A description of the special methods used for the expression of each individual oil and fat will be given in the following chapter. Here it must suffice to glance at the modern methods of preparing, crushing, and expressing the oleaginous seeds, as carried out in the best-equipped establishments. Since the catalogues and advertisements of the engineering firms who make a speciality of this class of machinery supply excellent illustrations, it is not deemed necessary to reproduce them here, it being my intention in this work to lay greater emphasis on the chemical technology and general principles of the industries than on a full description of the machinery1 used and the details of manufacturing operations. The storage of the seeds requires special precautions. They must be kept dry so as to prevent heating, especially if they be brought into the store-house in a moist state. The enzymes in the seeds then act on the oil or fat, producing hydrolysis with the formation of mono- and diglycerides and of free fatty acids (this is readily detected in the case of moist rape seed, as under favourable conditions the dierucin formed crystallises out from the oil). The free fatty acids so formed are acted upon by the oxygen of the air, so that on pressing such seeds oils are obtained, which not only contain free fatty acids, but also leave the presses in a rancid state. The sequence of operations in treating oil seeds, oil nuts, etc., for the separation of their contained oils is at the present time as follows :—As a preliminary operation the oil seeds and nuts are freed from dust, sand, and other impurities, by sifting in an inclined revolving cylinder or sieving machine covered with woven wire, having meshes varying according to the size and nature of the seed operated upon. This preliminary purification is of the greatest importance; it is especially indispensable for the preparation of edible oils and fats. In the case of those seeds which contain pieces of iron (nails; hammer heads in the case of palm kernels), the seeds are passed over magnetic separators, which retain the iron. The seeds and nuts are decorticated (where required), the shells are removed by mechanical means (sifters, blowers), and the kernels (“ meats ”) converted into a pulpy mass or meal by passing through a hopper over rollers, consisting mostly of five chilled iron or steel cylinders, mounted vertically like the bowls of a calender (in older establishments by stamping or crushing and grinding between stones in edge runners). These rollers are finely grooved, so that the seed is cut up whilst passing in succession between the first and second rollers in the series, then between the second and third, and so on to the last, until it is sufficiently bruised, crushed, and ground. The distance between the rollers can be easily regulated so that the seed leaving the bottom roller has the desired fineness. The suitably comminuted mass, forming a more or less coarse powder (“meal”) is either expressed at the ordinary temperature, or 1 Cp. Lewkowitsch, Cantor Lectures on “ Oils and Fats : their Uses and Applications,” Journ. Soc. Arts, 1904.