New York AGRICULTURAL EXPERIMENT STATION. We 
A STUDY OF THE CHEMISTRY OF HOME-MADE 
CIDER VINEGAR.* 
L. L. Van SLYKE. 
SUMMARY. 
1. Purpose of Work.—The primary object of the work was to 
learn why many home-made cider vinegars fail to reach the legal 
standard of 4.5 per ct. of acetic acid and 2 per ct. of cider 
vinegar solids. The investigation was extended so as to include 
(1) the composition of apple juice of different varieties of apples, 
(2) the changes in composition that apple juice undergoes during 
-alcoholic and acetic fermentations, (3) conditions affecting these 
changes and (4) the destructive fermentation of vinegar on long 
standing. 
2. Composition of Apple Juice—Analyses are given for 122 
samples of apple juice representing 83 varieties of apples, all 
American-grown. The average composition of these juices is as 
follows: 
Specific gravity, 1.056 
Solids, é 18.28 ‘per. ct. 
Reducing sugars, TA1 per ct. 
Sucrose, 3.28 per ct. 
Ash, 0.29 per ct. 
Fixed acid (malic), 0.51 per ct. 
Of these constituents, sugar is the most important in relation 
to the manufacture of cider vinegar. The quantity of sugar in 
apple juice is dependent upon the variety of apple and upon t': 
stage of ripeness, unripe or over-ripe apples containing less sugar 
than ripe apples. 
3. Alcoholic Fermentation of Apple Juice—Apple juice left 
exposed to the air is acted upon by yeast cells everywhere present, 
*A reprint ofjBulletin No. 258. 
