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

  • Hassall, Arthur Hill, 1817-1894.
Date:
1876
Catalogue details

Licence: Public Domain Mark

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

Provider: This material has been provided by The University of Glasgow Library. The original may be consulted at The University of Glasgow Library.

    19/968 (page 7)
    ) 7 CHAPTER II/ ON THE PRESERVATION OF FOOD. It will be desii-able before entering on the question of tbe adulteration of food to devote a short cbapter 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 ot their supposed commercial importance, but they may be all referred to the following heads :—to preservation by temperature, includino- an eleva- tion of temperature, resulting in more or less complete cooking, and a reduction of temperature, as by freezing; by the exclusion of cm,&a when animal and vegetable substances are enclosed m hermetically- sealed tins; by coatinc/ the surface, as by paraffin, or when an artificial coating is formed by the coagulation of the _ albumen by plunging it into hot water; by immersing or 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 moisture ; by the extraction of certain lorinciiiles 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, alum, 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 all precautions, cannot be alto- gether excluded from the preserved materia] j by carbonic acid, which acts by exclusion of the air, and the substitution of an atmosphere unfavourable to decomposition. In manv cases more than one of the above agencies are at work m the preservation of the food, as for example in tinned meats, in which not only is the air excluded, but the albumen of the meat is coagulated by cooking; in preserved 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 temjm-ature.—Heat is employed for the double purpose of partially cooking the materials to be preserved, whereby the