Patent GB-344394-A (GB)
Title: Improvements in or relating to the preservation of animal and vegetable substances
IPC: A23L3/3445
Filed: 1929-12-04
Abstract: In preserving animal and vegetable materials by storing them in closed chambers through which an air current containing hydrocyanic acid is passed, the hydrocyanic acid is added by automatically or otherwise giving part or all of the fresh air current a fixed carbon dioxide content and then passing it over cyanogen compounds, e.g. alkaline cyanides, which are readily decomposed by carbon dioxide, the current being thus charged with an equivalent amount of hydrocyanic acid.ALSO:Animal and vegetable materials such as meat, fats, fish, eggs, fruit, vegetables, animal skins, and glands and other animal organs are preserved by maintaining them in closed chambers in contact with an atmosphere containing not less than 0,004 per cent and preferably 0,006-0,008 per cent by volume of hydrocyanic acid.  The hydrocyanic acid concentration may be maintained in the chamber by continuously passing therethrough an air or other inert gas current charged therewith, the gas being passed through a regeneration chamber, for example a scrubbing tower through which aqueous hydrocyanic acid flows in countercurrent, before re-entering the chamber.  The liquid may be automatically or otherwise maintained at the necessary hydrocyanic acid concentration.  The gas current is regulated so that the gas leaving the storage chamber contains at least 0,003-0,004 per cent by volume of hydrocyanic acid.  The gas may be passed in different directions e.g. first in one and then in the opposite direction through the chamber, to ensure uniform distribution of the gas flow through the chamber.  The gas current may be kept saturated with moisture so as not to alter appreciably the natural moisture content of the products treated, e.g. meat, or may be such as to remove moisture from the products, or to effect cooling.  Hydrocyanic acid may also be added by automatically or otherwise giving part or all of the fresh air current a fixed carbon dioxide content and then passing it over cyanogen compounds, e.g. alkaline cyanides, which are readily decomposed by carbon dioxide, the current being thus charged with an equivalent amount of hydrocyanic acid; the air current leaving the storage chamber may be freed from hydrocyanic acid, for example by treatment with alkalies, active carbons, silica gel or other absorption agents from which it can be recovered.  The introduction and removal of the gas may be periodic instead of continuous.  In another form, the total quantity of hydrocyanic acid required during the whole process of preservation is introduced at the start, care being taken that the concentration does not in general fall below 0,004 per cent by volume at any stage, the limit being above this if the free space in the storage chamber is comparatively small.  Instead of introducing all the hydrocyanic acid at once, preferably aliquot portions are added, e.g. every 8-14 days.  An increased amount of hydrocyanic acid is required with substances of higher water content and also when higher temperatures than normal are used.  The temperature is in general kept below 20 DEG  C., and is preferably 6-10 DEG  C.  The hydrocyanic acid may also be added to the storage chambers by introducing substances containing it or compounds capable of yielding it, e.g. mixtures of kieselguhr &c. with liquid hydrocyanic acid, or potassium cyanide, alkaline-earth cyanides, or addition compounds of hydrocyanic acid with metal chlorides such as the chlorides of iron and aluminium. The chambers are so constructed that the atmosphere therein can easily be replaced by fresh air; the hydrocyanic acid may be recovered from the air current leaving the chamber.  Substances such as water or alkalies which absorb or destroy hydrocyanic acid are excluded from the storage chambers.  As rusted iron is also detrimental, surfaces of unprotected iron are also excluded. Constituents having a disturbing action may be removed from the substances to be preserved, e.g. glands and other materials containing a large amount of water may previously be subjected to dehydration by pressure or other treatment.  Examples are given of the treatment of meat, including veal, and apricots.  Only small quantities of the hydrocyanic acid remain in the materials treated and these have no toxic effect or can easily be removed e.g. by aeration.