Food : its adulterations, and the methods for their detecton / by Arthur Hill Hassall.

  • Arthur Hill Hassall
Date:
1876
Catalogue details

Licence: Public Domain Mark

Credit: Food : its adulterations, and the methods for their detecton / by Arthur Hill Hassall. Source: Wellcome Collection.

    23/973 page 7
    CHAPTER II. ON THE PRESERVATION OF FOOD. It will he desirable before entering on the question of the adulteration of food to devote a short chapter to the subject of the various methods employed for its preservation. The methods resorted to are exceed- ingly numerous, and many of them have been patented on account of their supposed commercial importance, but they may be all referred to the following heads :—to preservation by temperature, including an eleva- tion of temperature, resulting in more or less complete coolring, and a reduction of temperatm-e, as by freezing; by the exclusion of air, as when animal and vegetable substances are enclosed in hermetically- sealed tins; by coating the surface, as by paraffin, or when an artificial coating is formed by the coagulation of the albiunen by plunging it into hot water; by immersing ot: mixing the sub- stances to be preserved with a material which acts in the pre- servation mainly by the exclusion of air, as syrup or sugar; by compression, which serves to exclude the air partially, as also to remove superfluous moistiu-e ; by the extraction of certain principles of meat by means of water, and the subsequent inspissation of the extract; by the use of various antiseptic substances, as alcohol, acetic acid, salt, saltpetre, aliun, creosote, and charcoal; by the employment of certain acids and gases, as sulphurous acid and the sulphites, especially sulphite of soda, which retard decomposition by combining with the oxygen of the air, which, in spite of aU precautions, cannot be alto- gether excluded from the preserved material; by carbonic acid, which acts by exclusion of the air, and the substitution of an atmosphere unfavourable to decomposition. In many cases more than one of the above agencies are at work in the preservation of the food, as for example, in tinned meats, in which not only is the air excluded, but the albmuen of the meat is coagulated by cooking; in presei-ved milk, in which the greater part of the water is removed by evaporation, the albumen coagulated by the heat employed, and the air partially excluded by the addition of powdered sugar. We will now give some brief examples illustrative of each of the methods of preservation above referred to. Elevation of temperature.—Heat is employed for the double purpose of partially cooking the materials to be preserved, whereby the
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