Patent GB-511492-A (GB)
Title: Improved process for the preservation or storage of living vegetable substances, particularly fruit and vegetables
IPC: A23B7/152
Filed: 1937-11-16
Abstract: 511,492. Preserving vegetable &c. materials. NICHOLSON, A. O. Nov. 16, 1937, No. 31415. [Class 49] In a gas storage process for preserving living vegetable materials exhibiting respiratoryaction, particularly fruit, vegetables, flowers and plants, the gaseous atmosphere is maintained at a pressure below atmospheric and contains a percentage of oxygen just sufficient to maintain the materials alive, a percentage of carbon dioxide sufficiently high to act as a depressant on the natural respiratory action and a small quantity of a chemical substance adapted to retard the activity of fermentation enzymes in the materials without being added thereto, this substance consisting of formaldehyde, or sulphur dioxide of which 1-4 per cent. may be used, or hydrocyanic acid, phenol or mercury salts, of which 0.003-0.009 per cent. may be used, or ammonium fluoride. The vegetable materials may first be subjected to a reduced pressure, e.g., 1-20 in. of mercury, lower than that used for storage, to remove occluded gases. The storage gas may periodically be reconditioned to correct its composition or be replaced, if desired continuously, by fresh gas of the desired composition. As shown, fruit or vegetables are placed in a gas-tight storage chamber 1, which is preferably heat insulated, in an atmosphere containing 2¢-10 per cent. of oxygen and 2¢-17 per cent. of carbon dioxide, reduced pressure being maintained by an exhauster 18. Gas of predetermined composition may be supplied to the chamber 1 through a pipe 2 from a gasometer 3. Alternatively, a gas-conditioning system may be employed consisting of a circulating pump 7, a carbon dioxide extraction unit 8, which may consist of a chamber packed with coke through which a solution of sodium, carbonate is caused to percolate, an oxygenextraction unit 9 which may contain copper filings or shavings heated to red heat, a deodorizer 10, a dehumidifier 11, and an ozonizer 12. Excess of carbon dioxide may be removed from the chamber 1 by supplying air through inlet 13 to the unit 9 in which its oxygen content is reduced and diluting the atmosphere in the chamber with the product, or by removing carbon dioxide from the storage gas in unit 8. The oxygen content of the storage gas may be increased by supplying air to the system through pipe 14. Carbon dioxide may be supplied through an inlet 16. Reduction of the oxygen content and increase of the carbon dioxide content may also be effected by combustion, e.g., by passing the storage gas through an electric arc 15 between carbon electrodes, hydrocyanic acid being simultaneously produced in quantities sufficient to retard the enzyme activity. The chemical substance-retarding the enzyme activity may alternatively be introduced into the gas through a pipe 17, liquid being vaporized or sprayed into the gas, the introduction being effected away from the vegetable materials. The storage gas may be reconditioned periodically, e.g. every 24 hours. The chamber may be ventilated for several minutes with fresh or ozonized air prior to filling with fresh gas. A pump 20 maintains circulation of the gas in the chamber and a cooling coil 19 controls the temperature.