100 



THE AGRICULTURAL NEWS. 



Maech 28, 1914. 



FRUIT AND FRUIT TREES. 



COLD STORAGE OF FROIT AND 

 VEGETABLES.* 



I. 



The storage of fruit is a matter of some commercial 

 importance, and a thorough knowledge of the best conditions 

 for keeping ripe or unripe fruit of different kinds will oe of 

 great value in relation to the conveyance of fruic to 

 a distance, and for other purposes. The methods at present 

 in use, including refrigeration, have made it possible to o^rry 

 many kinds of fruic for long sea voyages. The partial spoil- 

 ing of a cargo of fruit is, however, a not uncommon occur- 

 rence, and attention is therefore called to the possibility of 

 effeciing improvements in method. The finding of such 

 improvements will be greatly helped by a good knowledge of 

 the physiological processes going on in fruits at different 

 stages of ripening and at diti'erent temperatures, and it appears 

 that much still remains to be learnt on this subject. 



A paper recently publishedf records a number of experi- 

 ments on the respiration of fruits, made with the obj ct of 

 gaining fresh data, which might be useful in connexion with 

 fruit storage. The paper also contains a summary of litera- 

 ture dealing with diti'erent matters relating to the process of 

 respiration. 



In the experiments described in this paper, the respira- 

 tion of diti'erent fruits when kept in air, in nitrogen, and in 

 hydrogen was measured, and the keeping power of fruits in 

 these gases and in carbonic acid gas was also tesiea. 



An experiment with ripe cherries was carried on for 

 about sixty hours at 30°C, and gave the following result. The 

 average hourly production of carbonic acid reckoned in milli- 

 grammes (mg.) per hundred grammes (grm. )^of cherries was 

 14' 2 in air, 12-0 in nitrogen, and 1T3 in hydrogen. In this 

 case the fruit was kept in a continuous current of the respec- 

 tive gases. Another experiment was differently arranged, 

 the gases being left undisturbed, except for half an hour 

 twice a day, when they were drawn through the vessels con- 

 taining the fruit as in the first experiment. Here the 

 amounts of carbonic acid given off are represented by the 

 figures 122 in air, 99 in nitrogen, and 10 9 in hydrogen. 

 It is seen that in these two experiments the production of 

 carbonic acid in an atmosphere of nitrogen or hydrogen, i.e., 

 in the absence of oxygen, is not far behind that in air, or in 

 other words anaerobic respiration is not much less than 

 aerobic. 



Experiments were made with two varieties of ripe grapes 

 and gave the result that respiration was as active in nitrogen 

 and hydrogen as in air, more so in fact in some cases. One 

 of the experiments carried on for 114 hours at 3U°0. gave 

 5'2 mg. of carbonic acid per 100 grammes of fruit per 

 hour in air, G'2 in nitrogen, and 7 '3 in hydrogen. The other 

 experiment (thirty-four hours at 37'C.) gave 99 in air, 95 in 

 nitrogen, and 102 in hydrogen. 



The above experiments show that in ripe fruits at 30°C. 

 anaerobic respiration may be as rapid as aerobic, or not much 

 less so. 



An experiment was also made with unripe fruit, and 

 this showed a different behaviour. (Jreen peaches, about 

 half grown, gave off 13'4 mg. of carbonic acid per 100 grm. 



*The footnotes in the original (see Kevi Bulletin of Mis- 

 cellaneous Information, No. 1, 1914) have been omitted. — Er>. 



tSce Bulletin 330, Cornell University A'^icultural Experi- 

 ment Station, 



of fruit per hour in air, 64 in nitrogen, and 6-1 in hydrogen. 

 Here the anaerobic is only about half the aerobic respiration. 

 The difference between this ratio and those in the previous 

 experiments may be attributed to the presence of growing 

 tissues in the unripe fruit. 



Germinating wheat was chosen as another example of 

 actively growing tissue, and gave a similar result to the green 

 peaches in one case namely, 128 mg, in air, 60 in nitrogen, 

 and 65 in hydrogen. In a second experiment there was 

 a much greater difference between the amount of carbonic 

 acid produced in the presence and absence of oxygen, the 

 values being 335 mg. in air, 78 in nitrogen, and 64 in 

 hydrogen. 



It appears then from the different experiments that ripe 

 fruit differs from unripe fruit in its respiratory processes 

 respiration in the former being to a great extent independent 

 of an external supply of oxygen, while in the latter about 

 half the respiration is stopped in the absence of oxygen. 

 This is regarded as indicating that respiration in ripe fruit 

 is probably maintained (or the most part by enzymes which 

 work independently of oxygen, while in unripe fruit the 

 respiration is partly of the same nature, but is as much due 

 to processes dependent on the presence of oxygen. The latter 

 processes may be enzymatic, but it is probable that the 

 direct metabolism of the protoplasm plays a considerable 

 part in them. 



A calculation has been made in order to give an idea 

 of the volume of carbonic acid given off' in these experi- 

 ments. The amount produced per hour by 100 crammes of 

 ripe grapes at 30° C. was 5-2 mg. This would measure about 

 2-9 cubic centimetres, and the grapes at this rate would 

 give off a volume of carbonic acid equal to their own 

 bulk in about 326 hours, while the cherries in the first 

 experiment would produce a corresponding amount in 

 11 '8 hours. 



Other experiments were made on the keeping quality 

 of fruits in air and in other gases. In one case apples of 

 one variety were placed in jars of air, nitrogen and hydrogen, 

 and left for thirteen days. In each jar some apples were fairly 

 ripe, and others somewhat green. At the end of the experiment 

 the apples in air were in very good condition, while those in 

 nitrogen and hydrogen had lost their red colour, and had 

 turned brown, both their appearance and flavour being much 

 as in half-baked apples. This effect in nitrogen and 

 hydrogen was shown not to be due to micro-organisms, but 

 to the anaerobic respiration of the fruit. This shows the 

 necessity of aeration when apples are kept for a considerable 

 time at the temperature of the experiment, which was 

 2r to 23° C. 



Another experiment was made with peaches, and it 

 was found that they became brownish and acquired a bad 

 flavour in the absence of oxygen, and that the softening of 

 hard, unripe specimens was greatly decreased in carbonic 

 acid, and to a considerable extent in nitrogen and hydrogen, 

 as compared with air. 



In two experiments referred to above it was found that 

 ripe cherries respired much more rapidly than ripe grapes in 

 the ratio of 14'2 to 5'2. In view of the better keeping 

 properties of grapes as compared with cherries, it is suggested 

 that the rate of evolution of carbonic acid may be more or 

 less proportional to the rate of spoiling of ripe fruit, and 

 this may also be proportional to the enzyme content of the 

 fruit, since the processes concerned are probably chiefly due 

 to the action of enzymes. Hence, if the factors controlling 

 the production of enzymes were sufticiently understood 

 additional means might perhaps be found for improving the 

 keeping quality of fruit. 



