the word &# 34 ; nuts &# 34 ; in this invention includes peanut , almond , pecan nut , seed of pumpkin , walnut , sesame , sunflower seed , hazel nut , brazil nut , pistachio nut , cashew nut , macadamia nut , seed of pine tree , seed of rotus and so on . fats contained in nuts are composed of highly unsaturated fats , so they are rapidly oxidized after roasting or heating or frying . however coffee beans are relatively stable after roasting though they contain oxidation - sensitive aroma components . the reason for roasted coffee bean stability is ascribed to carbon dioxide gas which evolves during roasting owing to chemical reactions , and carbon dioxide gas remains after roasting in coffee beans . when hot water is poured onto ground roasted coffee beans , many bubbles evolve , which are composed chiefly of carbon dioxide gas . and also it is said that roasted coffee beans which do not release bubbles at the time of extraction by hot water lose their aromas . so it is probable that when carbon dioxide gas is pushed into nuts forcedly , it can prevent or retard oxidation of oils in the nuts . the inventors made some experiments to treat nuts with compressed carbon dioxide gas and found that in some cases oxidation velocities became much slower than untreated nuts . and the fact that nitrogen gas cannot replace carbon dioxide gas was also found out , too . the methods of this invention involves treatment of nuts with compressed carbon dioxide gas under heating conditions . carbon dioxide gas of pressure below 30 kg / cm 2 is effective enough . if higher pressure is chosen , a discharge of compressed gas after treatment requires more time , because rapidly discharging gas causes breakage of nuts owing to a violent vaporization of carbon dioxide dissolved into nuts tissues . temperature higher than room temperature but not too high to cause browning or roasting should be chosen to enhance carbon dioxide gas diffusion into nuts . it is also desirable to chill nuts quickly after carbon dioxide gas treatment to prevent damage from excess heating or browning and a loss of carbon dioxide gas from nuts . and also it is recommended to evacuate air from the treatment vessel before carbon dioxide gas treatment to remove oxygen completely . ( 1 ) its main part is a vessel which can hold compressed carbon dioxide gas therewith . ( 2 ) it has to have ( a ) door ( s ) or ( a ) gate ( s ) to put nuts into and take them out . of course these doors or gates should be airtight and withstand the pressure of the compressed gas . ( 3 ) the device has ( a ) heater ( s ) to heat nuts during treatment . these heaters can be composed of heat exchangers , e . g . pipe ( s ) or tube ( s ) or plate ( s ) or jacket ( s ) through which steam or hot water or hot oil or any other hot fluid can circulate , or electrical heater , or generators of radiation , such as infrared or microwave , can be provided . ( 4 ) it has ( a ) chiller ( s ) to chill nuts therewithin quickly after treatment . these chillers can be made in the same manner as the heater through which chilled water or chilled oil or any other chilled fluid can circulate . in some cases heaters can be used also as chillers , when hot fluid is replaced by chilled fluid . ( 5 ) it has ( a ) valve ( s ) through which compressed carbon dioxide gas is supplied into and discharged out of the vessel . in some cases a single valve can be used for introduction as well as release of the co 2 gas . ( 6 ) it is desirable to make a device in such a manner so that it can be rotated freely to make ( a ) door ( s ) or ( a ) gate ( s ) face upward or downward . in this case nuts are put into the device through ( a ) door ( s ) or ( a ) gate ( s ) when the door ( s ) or gate ( s ) are facing upwardly , and after treatment the device is rotated upside down and nuts are easily taken out when it ( they ) is ( are ) facing downwardly . ( 7 ) it is also preferable to attach ( a ) vibrator ( s ) on or in a device to facilitate taking treated nuts out of the device . ( 8 ) to save carbon dioxide it is also recommended to attach ( a ) compressor ( s ) and ( a ) container ( s ) or ( a ) bomb ( s ) to recover and store used carbon dioxide gas . ( 9 ) to discharge air and remove oxygen completely out of a device , it is also preferred to attach ( a ) pump ( s ) to a device . a typical structure of device of this invention is shown in fig1 . a main part of the device , i . e ., a vessel 1 can contain compressed carbon dioxide gas therewithin . through a door or a gate 2 nuts are put into and taken out of the vessel 1 . in this figure the door or gate 2 is placed downward , but when the vessel is rotated upside down , it faces upwardly . the vessel 1 can be rotated freely by a shaft 6 which is rotated by a motor 5 . when the door or the gate 2 is upward , nuts are easily put into the vessel 1 and when downward , they are easily taken out of the vessel 1 . heaters 3 are provided in the vessel 1 , which can be made as hollow plates or tubes or pipes to circulate hot fluid inside . and in this case heaters 3 are easily changed into chillers if chilled fluid is passed inside instead of hot fluid . a vibrator 7 is attached to make it easy to take treated nuts out of the vessel 1 . preferably a pressure gauge 8 , a thermometer 9 and a window 10 are attached to the vessel 1 to confirm a process condition in the vessel 1 . carbon dioxide gas is supplied from a bomb 13 through valves 16e and 16a into the vessel 1 . a pipe 4 is through the shaft 6b and is connected to a distributing pipe by means of a sealer 15 to enable the vessel 1 to be rotated . before supplying gas into the vessel 1 , a pump 14 evacuates air from the vessel 1 . after a treatment is finished , gas is discharged out of the vessel 1 through the pipe 4 by means of a compressor 11 . at that time compressed gas is chilled by a chiller 12 , then stored in the bomb 13 . commercial roasted peanuts 350 gr were put into a glass container which was placed onto the other same one without peanuts in an autoclave of 3l inner volume . after sealing the autoclave , carbon dioxide gas was supplied from a bomb until the inner pressure became 10 kg / cm 2 , then released rapidly to an atmospheric pressure . this procedure was repeated two more times to replace air for carbon dioxide gas in the bomb . then carbon dioxide gas was filled in the bomb to a pressure 10 kg / cm 2 and the autoclave was heated to maintain the temperature of peanuts between 70 °˜ 72 ° c . for an hour , then carbon dioxide gas was discharged for about 30 minutes , while the autoclave was placed at a room temperature , then the autoclave was opened to take peanuts out . these peanuts are called ( a ). the same commercial roasted peanuts treated in the same manner under the condition that the chilling the autoclave as well as discharging gas was done for 18 hours at a room temperature . ( a ), ( b ) and ( c ) were put in pouches which are made of polyethylene 80 μm thick and sealed with rubber bands . they were stored at a room temperature and periodically about 50 g of them were extracted with fresh ethyl ether of a chemical reagent grade to extract oils in soxlet extractor . extracted oils were condensed and dried completely in vacuo , then titrated to evaluate their acid values ( av : mg / gr ) and peroxide values ( pov : meq / 1000 gr ). ______________________________________ just after the after 1 after 2 treatment month month______________________________________ ( a ) av 1 . 36 1 . 11 1 . 01 pov 3 . 8 26 . 81 35 . 41 ( b ) av 1 . 25 1 . 13 0 . 94 pov 2 . 6 24 . 81 34 . 11 ( c ) av 1 . 38 1 . 08 1 . 64 pov 4 . 7 33 . 71 42 . 01______________________________________ roasted peanuts freshly roasted in a factory were treated with carbon dioxide gas in a similar manner described in example 1 . in this experiment they were treated under the condition of a pressure 25 kg / cm 2 and a temperature 120 °± 5 ° c . for an hour . after the treatment the autoclave was chilled forcedly by putting wet towels on its surface for about 2 hours till the inner temperature became 50 ° c ., then carbon dioxide gas was released for about 15 minutes . they were pouched in the same manner described in example 1 , then stored at 37 ° c . ______________________________________ just after the treatment after 1 month______________________________________treated av 0 . 92 0 . 93 pov 1 . 5 17 . 8untreated av 1 . 14 0 . 97 pov 12 . 1 51 . 8______________________________________ after 2 after 3 after 4 months months months______________________________________treated av 1 . 05 0 . 93 1 . 19 pov 38 . 3 37 . 4 40 . 8untreated av 1 . 17 1 . 17 1 . 21 pov 80 . 4 62 . 7 64 . 9______________________________________ commercial roasted peanuts were treated in a similar manner described in example 1 under the condition of a pressure 5 kg / cm 2 and a temperature 80 ° c . for an hour and the release of carbon dioxide gas was done for 30 min . without forced chilling at a room temperature . they were pouched in the same manner described in example 1 and stored at 37 ° c . ______________________________________ just after the after 1 after 2 treatment month month______________________________________treated av 1 . 45 1 . 11 2 . 32 pov 21 . 6 69 . 1 89 . 3untreated av 1 . 78 2 . 23 2 . 37 pov 64 . 7 113 . 2 129 . 4______________________________________ roasted peanuts freshly roasted in a factory were treated with compressed nitrogen gas under the condition of a pressure 25 kg / cm 2 and of a temperature 120 °± 5 ° c . before the treatment , air in the autoclave was replaced by nitrogen in the same manner described in example 1 . after the treatment , chilling the autoclave forcedly and releasing inner gas were done in the same manner described in example 2 . peanuts were packed in the same manner described in example 1 and stored at 37 ° c . ______________________________________ just after the treatment after 1 month______________________________________treated av 0 . 88 0 . 69 pov 1 . 0 34 . 0untreated av 0 . 90 0 . 90 pov 1 . 1 35 . 4______________________________________
disclosed is a novel method of treating nuts with a compressed carbon dioxide gas so as to make them oxidation - resistant . for carrying out the method , a device is used , which can contain a compressed carbon dioxide gas and which is equipped with door or gate to put nuts into and take them out of itself , heater to heat nuts in itself , chiller to chill nuts in itself , and valve to introduce a carbon dioxide gas into itself and release the gas out of itself . nuts as treated by the novel method with the illustrated device are to be satisfactorily oxidation - resistant when they are stored .