CONCORD GEAPE JUICE. 
although low temperatures during heating are very desirable for at- 
taining quality, higher temperatures give a better dissolution of the 
fruit and a better yield of juice. As is evident from what has just 
been said, it is not possible to fix a definite temperature for the heat- 
ing process. The temperature, however, should be between 135° 
and 150° F. The time required for heating is simply the time nec- 
essary to heat to the desired temperature. 
By the heating of the crushed fruit the skins are drawn upon for 
color and body. A cold-pressed juice lacks the body and color of 
the hot-pressed juice, so this may be said to be the character-forming 
step. The effect of heating upon the chemical composition of the 
pressed juice may be seen by a comparison of the data given in Table 
3, which shows the chemical composition of juices pressed from the 
heated and unheated fruit. 
To obtain the cold-pressed juice a well-mixed sample of the pulp 
from the stemmer was pressed by hand through several thicknesses 
of cheesecloth and filtered through cotton. This gave the sample 
mentioned in Table 3 under the heading " Before heating." The 
same batch of pulp was again sampled after it had been heated to 
150° F. in the cooker and the juice expressed in the same manner. This 
gave the sample in Table 3 under the heading "After heating." 
Table 4 summarizes the results given in Table 3, and shows the 
increases in the various ingredients caused by heating the pulp. 
Table 3. — Chemical composition of hot and cold pressed Concord grape juices. 
Ex- 
peri- 
Juice pressed 
before or 
after 
heating. 
Solids, 
per 
100 cc. 
Sugar 
as in- 
vert 
before 
inver- 
sion, 
per 
100 cc. 
Non- 
sugar 
solids, 
per 
100 cc. 
Total 
acid 
as 
tar- 
taric, 
per 
100 cc. 
Total 
tar- 
taric 
acid, 
free 
and 
com- 
bined, 
per 
100 cc. 
Ash, 
per 
100 cc. 
Alka- 
linity 
of solu- 
ble ash, 
N/10 
acid, 
per 
100 cc. 
Alka- 
linity 
of in- 
soluble 
ash, 
N/10 
acid, 
per 
100 cc. 
Free 
tar- 
taric 
acid, 
per 
100 cc. 
Cream 
of 
tartar, 
per 
100 cc. 
Gms. 
Gms. 
Gms. 
Gms. 
Gms. 
Gms. 
Cc. 
Cc. 
Gms. 
Gms. 
17.20 
14.36 
2.84 
0.78 
0.63 
0.26 
30.0 
3.0 
0.14 
0.56 
17.83 
14.58 
3.25 
1.12 
1.04 
.46 
55.8 
4.8 
.13 
1.05 
16.33 
13.88 
2.45 
.74 
.63 
.27 
33.2 
2.8 
.09 
.62 
17.25 
13.62 
3.63 
1.01 
.97 
.43 
52.4 
4.0 
.12 
.99 
16.10 
13.74 
2.36 
.84 
.61 
.20 
22.4 
3.6 
.22 
.42 
17.17 
13.74 
3.43 
1.16 
1.01 
.33 
49.2 
4.4 
.21 
.93 
16.57 
14.32 
2.25 
.75 
.55 
.22 
25.2 
2.8 
.13 
.47 
18.50 
15.12 
3.38 
1.10 
.98 
.39 
44.0 
4.0 
.26 
.83 
15.66 
13.38 
2.28 
.80 
.65 
.22 
24 .4 
2.6 
.24 
.46 
16.44 
13.29 
3.15 
1.07 
.96 
.33 
38.0 
3.8 
.33 
.71 
16.28 
13.91 
2.37 
.79 
.57 
.23 
26.0 
3.6 
.13 
.49 
17.41 
13.83 
3.58 
1.09 
.94 
.37 
41.2 
4.4 
.26 
.77 
Tan- 
nin 
and 
color- 
ing 
mat- 
ter, 
per 
100 cc. 
/Before . . 
i\After.... 
I/Before . . 
* \\ After.... 
o '/Before.. 
6 \After.... 
. /Before.. 
* 1 After..., 
K '/Before.. 
i\After.... 
ft '/Before.. 
6 ,\After... 
Gms. 
0.08 
.24 
.07 
.19 
.06 
.20 
