4 _ BULLETIN 1025, U. S. DEPARTMENT OF AGRICULTURE. 
the finished beer of a reversible colloid formed by combination of hop 
tannin with a protein of the wort. The solubility of this colloid is 
decreased by cooling the liquid, with the result that turbidity ap- 
pears at low temperatures but disappears again on warming. In the 
Wallerstein process (10, p. 605-607 ; 27, 28, 29) a proteolytic enzym, 
which can be either pepsin, papain, or bromelin, is added to the 
beer at the end of the main fermentation in amounts of 1 to 2 grams 
per hundred liters. The protein-tannin compound is attacked and 
converted into simpler completely soluble products by the enzym, 
with the result that the beer remains clear irrespective of the tem- 
peratures to which it may later be subjected. 
Because of the number and diverse character of the constituents 
which it is desirable to remove, as well as the character of those which 
must be preserved, it appeared inherently improbable that enzyms_ 
could be successfully employed in the clarification of apple or grape 
juice or that, even if such a process could be developed, it could be 
made of such character as to be generally usable. Inasmuch as no 
indication could be found in the literature that any investigation into 
the possibilities had been made, some work was begun in 1918. It is 
still in progress and will be reported elsewhere. It has been possible 
under laboratory conditions to obtain satisfactory clarification com- 
bined with the preservation of the characteristic flavors of juices by 
the use of enzyms, but the method has not as yet been sufficiently sim- 
plified to meet the need for a method requiring no special technical © 
skill and usable on any scale. 
French cider makers lay much stress upon the coagulation of the 
pectins of apple must immediately after pressing as an essential step 
in the making of high-grade clear ciders. Warcollier (30) recommends 
that juices be held at 4° or 5° C. until the pectase present has coagu- 
lated the pectins which collect at the surface to form the “ chapeau,” 
or “ head,” and the settlement of cellular débris and dirt to the bottom 
has occurred. He suggests that elimination of most of the unde- 
sirable organisms which might injuriously affect the subsequent fer- 
mentation will thereby be effected. He states that-the juice will be 
perfectly limpid and clear if the conditions be made such that fer- 
mentation be prevented during the period of defecation. Arnou (3, 
p. 80-84) devotes a considerable section of his work to the subject, 
stating that the permissible range of temperature is from 6° to 12° 
C. and the time required from 12 to 24 hours. In case the juice is 
deficient in pectase, Arnou suggests the use of sodium or potassium 
carbonate, calcium sulphate, potassium metabisulphite, or sodium 
chlorid, and quotes Warcollier as advocating the use of 80 grams 
of tartaric acid and 30 grams of calcium carbonate per hectoliter of 
juice to hasten coagulation. He also remarks that apples from differ- 
‘ 2 
iogeceagney RE 
