6 BULLETIN 656, U. S. DEPARTMENT OF AGRICULTURE. 
CRUSHING AND STEMMING THE FRUIT. 
The crusher consists of two rollers of metal, usually bronze, revolv- 
ing at high speed. The rolls are set in such a manner as to avoid the 
crushing of the stems and seeds. The stemmer is a cylindrical re- 
volving drum, inside of which are arranged revolving fingers that 
separate the berries from the stems. The crushed berries and liber- 
ated juice pass through openings in the side of the drum and fal 
through to the cooker, while the stems are pushed out of the drum 
by the fingers. 
HEATING THE CRUSHED FRUIT. 
From the stemmer the crushed fruit and the liberated juice fall 
into the heating kettles, commonly called cookers. 
The grape berry may be divided into two main parts, the skin and 
the pulp. The pulp of the grape is practically colorless and carries 
most of the juice. The skin furnishes the coloring matter so much 
desired by the manufacturer of Concord grape juice, as well as less 
desirable ingredients. The juice of the pulp is sweet and pleasant 
but lacks body and character. The juice from the skin is highly 
colored, high in acid and tannin, and hi mineral ingredients and 
body, but low in sugar. By judiciously mixing these two juices a 
better product, of more pleasing appearance, is obtained than would 
result from either of these juices alone. 
Such a modified juice is obtained by the simple operation of heating 
the crushed fruit to suitable temperatures. The very closest atten- 
tion is required, however, to secure the best results. Temperatures 
which are too high give the juice a harsh taste, lacking in quality but 
high in coloring matter, and if carried to excess may ruin the flavor 
and aroma completely. On the other hand, low temperatures do 
not draw sufficient color, and such juices are wanting in body, though 
pleasant in taste and aroma. 
In choosing the best temperature for heating the crushed fruit, th« 
quality of fruit must be taken into consideration. Ripe fruit oi 
fruit that has been air-ripened yields its desirable ingredients at a 
lower temperature than immature fruit. Also the pressing proc< 
must be considered in connection with the heating, as by applying 
more or less pressure the color, tannin content, and body of the juice 
may be regulated, the greater pressure giving the more color, tannin, 
and body to the juice, as well as delivering the greater amount of 
juice. It is apparent that to regulate the tannin content and the 
body of a juice by using a smaller amount of pressure, means a loss 
of juice. Consequently it is better to regulate the heating process 
and not rely altogether upon the pressing process to correct th( 
quality of the juice. In this connection it should be said thai 
