PRE-COOLING OF FRUITS 



1733 



nia, and last season work was begun on 

 cherries and fresh prunes in Oregon, and 

 raspberries in Washington. Special equip- 

 ment has been supplied In order to enable 

 the work to be carried on at different 

 points in the United States. 



In an article on "The Pre-cooling of 

 Fruit" ic the Year Book o£ the Depart- 

 ment of Agriculture for 1910, a general 

 discussion of the subject was presented, 

 and the following paragraphs are quoted 

 from that article: 



"The Heasons for Pre-cooHng. During 

 the maturing of a normal fruit on the 

 tree certain chemical and physiological 

 changes are constantly taking place 

 within the fruit itself. These changes. 

 which result in the acquirement of quality 

 and flavor, constitute the ripening pro- 

 cess. After a certain point is reached the 

 fruit becomes overripe, quality and flavor 

 are lost, and deterioration progresses un- 

 til eventually the fruit is destroyed by 

 fungous decay or fermentation or through 

 destructive physiological changes. 



"A fruit may be considered as a living 

 organism which has a definite span of 

 existence, the length of this span depend- 

 ing upon the conditions surrounding the 

 organism. The most important factor 

 which modifies this span of life is tem- 

 perature. When the fruit is removed 

 from the parent plant the life processes 

 constituting ripening are materially 

 hastened, and the life span is greatly 

 shortened if the fruit is allowed to re- 

 main warm for any considerable length 

 of time. Hence, the importance of re- 

 ducing the temperature as promptly and 

 rapidly as possible after the fruit is 

 pirkf'd. 



"The length of the life span differs with 

 the character of the fruit. It is shortest 

 in the soft fruits, such as berries, cher- 

 ries, peaches, apricots, plums and most 

 pears, and longest for the harder fruits — 

 citrus fruits and apples. It varies with 

 different varieties within the same group 

 of fruits. Some varieties of apples, for 

 example, keep longer than others; lemons 

 keep longer than oranges. The impor- 

 tance of quick and prompt cooling — pre- 

 cooling — then. Is greatest in the case of 



the soft fruits and least for the harder 

 fruits. Experience so far confirms this 

 rule. 



"Aside from the breaking down from 

 overripeness, fruits are subject to prema- 

 ture decay due to the attacks of various 

 fungi. The most common forms of these 

 fungi, however, have not the power to 

 penetrate the sound, unbroken skin of a 

 healthy, normal fruit. Most of the decay 

 occurring in fruits in transit and storage 

 starts at injuries and breaks in the skin, 

 caused almost entirely by rough handling 

 in preparing the fruit for market, either 

 in picking, grading, hauling or packing. 

 Wounds, bruises, scratches or abrasions 

 of any kind allow the organism of decay 

 to gain entrance. Other fungi which are 

 not dependent upon injuries to start, 

 attack fruits in transit and storage; but 

 these' forms of decay are much less prev- 

 alent. 



"The germination of the decay spores, 

 which are analogous to the seeds of 

 higher plants, is dependent upon proper 

 moisture and temperature conditions. 

 Germination does not take place while 

 the fruit is perfectly dry or when the 

 temperature is low. After the spores 

 have germinated, however, and the decay 

 has started within the fruit, even as low 

 a temperature as 32 degrees Fahrenheit 

 will not wholly check it. Growth of the 

 mold is only retarded and the decay con- 

 tinues slowly to develop." 



The prompt and rapid reduction of the 

 temperature below the point where decay 

 spores germinate prevents the develop- 

 ment of the disease. Some fruits which 

 have been rendered susceptible through 

 mechanical injuries occurring in handling 

 may be transported with only slight loss 

 from deca'y when promptly cooled. It is 

 not safe, however, to depend upon pre- 

 cooling to prevent decay which follows 

 improper handling. Pre-cooling should 

 never be expected to replace proper work. 

 The fact that it does not always effect- 

 ively replace careful handling is shown 

 by the Bureau Investigations with table 

 grapes. 



It has been the policy of the Bureau to 

 advise conservative caution in the appli- 



