116 



THE AGRICULTURAL NEWS. 



April 11, 1914. 



FRUIT AND FRUIT TREES. 



COLD STORAGE OF FRUIT AND 

 VEGETABLES. 

 II. 

 The following is the second and final part of the 

 article on the above subject of which Part I appeared 

 in the last issue of this journal: — 



It is desirable that further experiments should be made, 

 in the same manner as those referred to above, on the pro- 

 duction of carbonic acid by various kinds of fruit at different 

 temperatures much lower than 30° C. Definite and com- 

 prehensive information on respiration at rather low temper- 

 atures would no doubt be very useful in relation to 

 cold storage. 



Feeble respiration takes place at 0' C, and even at 2° 

 to 4° C , and it continualh' increases as the temperature rises, 

 until injury from high temperature begins. Within a few 

 degrees above freezing point respiration is no doubt very 

 slight, and it is owing to this fact that fruit can be kept for 

 a considerable time in refrigerating chambers. Suitable 

 temperatures for different purposes have been found by 

 experience, but more precise knowledge of the behaviour of 

 fruit at these temperatures is required. 



A matter requiring special attention in the storage of 

 fruit is aeration. Air should have as free access to the fruit 

 as possible, and therefore large masses of fruit should not be 

 closely crowded together. Good circulation of the air should 

 also be kept up, and for this the current of cold air from the 

 refrigerating machine may often be sufficient, but in some 

 cases ventilating fans have been used. The amount of care 

 nece.=sary in the matter of aeration depends, of course, 

 largely on the temperature chosen for the storage chamber, 

 as well as on the kind and condition of the fruit. 



In the case of the transport of peaches in America in 

 refrigerator cars, injury to the fruit is stated to be common, 

 and the injury has been found to be most frequent in the 

 central part of the top tiers of boxes. Cold air is led along 

 the bottom of the car, and, though diffusion and circulation 

 equalize the temperature to some extent, it may be assumed 

 that the upper strata of air have a somewhat higher tempera- 

 ture than the lower, and therefore that the fruit in the upper 

 boxes respire more actively than the rest. The explaEation 

 is therefore suggested that the injury is 'due to insufficient 

 oxygen and to an accumulation of carbon dioxide withm the 

 paper wrappers in which peaches are so often shipped.' The 

 preventive would no doubt be more uniform cooling, with 

 better aeration if necessary. 



It must be remembered that active respiration means 

 an appreciable evolution of heat by the respiring tissues. 

 Hence, in the case of large masses of fruit, if this heat is not 

 rapidly conducted away, the temperature of the fruit (and 

 of the air adjoining it) will rise, whereby the respiration will 

 be further increased, and so on. Such heating at 'com- 

 pound interest' will be liable to occur locally, wherever aera- 

 ti-on is insufficient, and may continue until the local tempera- 

 ture is considerably higher than the general air temperature 

 in the refrigerating chamber, and may lead to the loss of 

 portions of the fruit. 



Should the temperature in the cold storage chamber be 

 allowed to rise until respiration is very active, it may be 

 found that the refrigerating apparatus will be unable to 

 reduce the temperature of the fruit again, and this has been 



experienced, e.g, in shipments of bananas. The fruit then 

 ripens rapidly and spoils. 



The difficulties to be contended with in arranging for the 

 cold storage of vegetables may be illustrated by the following 

 case. 



An insulated storage room of about (1,000 cubic feet 

 capacity was fitted with a refrigerating machine, which easily 

 reduced the air in the room, when empty, to a temperature of 

 27°F. ( - 3'(_'.). A temperature of .'lo'F. (2°C.) was required, 

 and it was expected that the arrangements would be satisfac- 

 tor}'. A trial was then made as to storage. Six tons of 

 vegetables were put into the room, and the temperature 

 started at .o9°F. (1.5°C.), but the machine was only able to 

 reduce this to 50 F. .(10°C) in ten hours. The refrigerator 

 was then stopped, and in twelve hours the temperature was 

 .59°F. and after fifteen hours more it stood at 66°F. (19'C). 

 The air, moreover, was found to be badly vitiated by carbonic 

 acid. The final rise of temperature was due to the respira- 

 tion of the vegetables and not to conduction through the 

 walls, since the outside temijerature during the last twenty- 

 four hours had not been higher than 52° F. (11' C), having 

 varied between this and 45" F. (7°C.). 



In anotlier trial the machine was started first, and the 

 temperature was reduced tn 38°F. Then 21 tons of cabbage 

 and spinach were put into the store. The temperature was 

 raised by this to -IS°F., and after an hour with the machine 

 still running it rose to 49°F. After five hours' run it stood 

 at 45 'F., and refused to go lower. 



In this case the free air in the storage chamber was well 

 circulated. The unsuccessful result indicates that the vege- 

 tables required to be less crowded, or to be cooled in small 

 batches before being brought into the store. The air must 

 have been a good deal entangled among the vegetables, so 

 that convection currents in the interior of the mass in 

 each box would be slow, and consequently the loss 

 of heat in this way was not rapid enough to outbalance 

 the heating dite to respiration Had the vegetables been cooled 

 before being placed in the storeroom, their respira- 

 tion and self-heating would have been slow, and the 

 refrigerating arrangements might perhaps have been able to 

 deal with them efficiently, though unable to cope with the 

 combined task of cooling the substance of the vegetables, and 

 also removing the heat generated by respiration at or near the 

 starting temperature. The entanglement of air and consequent 

 ditficulty of cooling would probably be much greater in a box 

 spinach, for instance than in a box of the same dimensions 

 containing fair-sized rounded fruit such as apples or oranges. 

 It can hi readily understood that the matter of cold 

 storage of fruit and vegetables is not a simple one. The 

 treatment required by different kinds of fruit or vegetables 

 may vary considerably as to spacing out, packing, aeration 

 and temperature. Much information has been gained by 

 practical experience, but further knowledge is required, so 

 that any failure causing loss of produce may be attributed to 

 its precise cause, and, if possible, prevented for the future. 



In conclusion reference should be made to another 

 important point in connexion with the cold storage of 

 vegetables and fruit, namely, the cost of the refrigerating 

 plant and the running expenses. For although it may be 

 quite possible to keep a chamber at a desired temperature 

 when filled with vegetables or fruit, yet the outlay involved 

 in connexion with the packing and unpacking and the laying 

 out of the material on shelves, in addition to the cost of 

 running the special refrigerating plant, may be so great 

 as to render the undertaking impossible from the commer- 

 cial point of view. (Kerv Bulletin of Miscellaneons Infor- 

 mation, No. 1, 1914.) 



