46 



BITTER PIT INVESTIGATION. 



GROWTH. 



In the life history of an apple there are three distinct periods— growth, ripening, and decay. 

 In the growth, complex chemical changes occur which are not too well known, but some of them 

 have been definitely determined. 



The organic matter of the apple is primarily formed in the green leaves of the tree and in 

 the green skin of the fruit itself. There the chlorophyll grains, in the presence of sunlight, 

 manufacture starch, which is converted into sugar by the action of a ferment, and is conveyed to 

 the growing portions of the fruit. Some of this sugar is reconverted into starch by starch-forming 

 bodies, not to be stored up as reserve material, however, but to be used in building up new tissue, 

 at least the cell-walls. 



If apples are examined at different periods of growth, it is found that, with the increase in 

 sugar, there is a decrease in starch, and that the free malic acid gradually becomes less. When an 

 apple is full grown, it still contains starch and malic acid, but towards the period of ripening there 

 is a decrease in both. It is generally considered that the sweetness of an apple depends on diminished 

 acidity and an increased percentage of sugar, but sour apples frequently contain more sugar than 

 fruit of a sweeter kind, so that the taste is dependent on the absence of the acid. While the apple 

 is growing, there is very little variation in the percentage of water. 



RIPENING. 



In the ripening of the fruit, certain changes take place which can be followed by ordinary 

 observation. The skin usually changes its colour, the relatively hard flesh becomes soft, the sour 

 taste turns to sweetness, and a delicate aroma is generally developed, characteristic of the variety. 

 When the chemist follows the changes, he finds that the starch in the unripe fruit has become 

 converted into sugar, and the agreeable flavours are apparently due to ethers which have been 

 produced by the union of the vegetable acids with alcohol formed by the partial breaking down of 

 the sugar. The formation of alcohol does not require the presence of yeast, as in ordinary 

 fermentation, for if an apple is placed m a jar containing no oxygen the ordinary oxidation of sugar 

 into carbonic acid and water does not take place, but it is broken down into the less oxidized form 

 of alcohol. 



The pectin bodies present in the pulp of apples to the extent of 0.2 to 0.6 per cent, show a 

 marked diminution in the process of ripening, but Pfeffer (115) doubts whether this decrease is due 

 to their conversion into sugar, &c. 



RIPENING OF APPLES IN ORDINARY AND COLD STORAGE. 

 This has been specially studied by Bigelow (100), and he gives analyses of several varieties 

 picked at different dates and kept in ordinary and cold storage respectively. From the results 

 obtained, it appears that " the changes in composition (the content of starch, sugar, and acids) in 

 cold storage do not greatly differ from those which occur in common storage, the chief difference 

 being in the rapidity with which the changes take place." 



^When samples were removed from cold storage and kept in ordinary storage, it was found 

 that " the apples ripened much more rapidly than those kept in cold storage, and that, before the 

 samples were destroyed by rot, they had closely approximated the composition attained by the 

 apples m cold storage some months later." The ripening which takes place upon the tree and that 

 which occurs after picking, or during the period of after-ripening, is not quite identical in its results 

 It is the general opinion of fruit-growers that the proper time to pick apples is when they have 

 attained their maximum size and weight, even although hard, since it is found that they keep better 

 and have a hner flavour than when allowed to ripen on the tree. 



