104 FRUITS AND FRUIT PRODUCTS. 



I 



From the above it is evident that in the examination of jams and simi- 

 lar products starch can best be detected in cells clinging to the fibro- 

 vascular bundles, which may be separated as directed under "Tech- 

 nique " (p. 106). In the tomato the last traces are found in the placental 

 region. In the strawberry it remains longest in the central part of the 

 pulp or enlarged receptacle. As in the apple, portions of the fruit 

 bruised before maturing retain the starch practically unchanged. 



In green pears considerable starch is present, but it disappears at a 

 comparatively earlier stage of ripening than in the apple. In peaches 

 it seems to disappear still earlier, for only in specimens greener than 

 would probabl}^ be used in canning was there an appreciable amount 

 found. In the quinces, though firm and sound, onl}^ a faint trace was 

 found October 8, while apples — Rambo, Northern Spy, Baldwin, 

 Greening, Russet, and others — obtained 'at the same time from the 

 same orchard in Michigan showed an abundance of starch.* Althougli 

 grapes were examined in various stages of maturing, from green to 

 perfectl}^ ripe, no starch was found. The same was true of the rasp- 

 berries. It should be said here, however, that the grapes were 

 gathered late in the season, after the first frosts, which may have has- 

 tened the disappearance of the starch had there been any in normal 

 conditions. Strawberries, up to the time the flush of ripening appears, 

 show a small amount of starch, but this seems to disappear before 

 many of them would have been picked for market or canning. In 

 the case of tomatoes the starch persists somewhat longer, but seems to 

 disappear approximately with the last traces of green color, although 

 the main portion is gone before this. Tomato starch, except on long 

 boiling, does not swell up and become as mucilaginous as that of 

 apple, but remains as little clots within the cells. 



From the above it appears that we are able to assign the presence of 

 starch in fruit products to any one or all of three causes, viz, (1) the use 

 of immature or green fruit; (2) the use of apple pulp; (3) the addition of 

 starch as such. It should be remembered here, however, that the absence 

 of starch in no way precludes the possibility of apple pulp having been 

 used. Although boiling tends to remove starch from the cells, as is 

 readily seen in the case of many apple jellies, yet long-continued 

 boiling is required to remove it so thoroughly from the cells that they 

 will not show a greater starch content than the surrounding liquid 

 when the iodine test is applied. Even in the case of apple butter 

 more starch was found within than outside the cells. This fact may 

 be used to advantage for detection of commercial starch in pulped 

 products, such as ]ams, preserves, and marmalades; but it must be 

 used with caution, since a small amount of starch might be added to 

 products made from starch-containing fruits without detection. Even 



*A11 of these varieties, with the exception of Hambo, are winter apples, some of 

 them ripening late in the winter. 



