THE CLARIFICATION OF FRUIT JUICES. 5 
ent districts of France (hence presumably of different varieties) 
show differences in the readiness avith which coagulation of the pec- 
tins is obtained, that neither green nor overripe fruits give satisfac- 
tory results, that juices low in acid and tannin content coagulate 
readily, and that successful coagulation is obtained only when fer- 
mentation is prevented during the period of defecation. 
It has been impossible in the laboratory of the Bureau of Plant 
Industry to produce such results as are described by these authors 
without having recourse to some of the chemical treatments which 
they suggest. At a temperature of 4° C. pectase is inactivated or 
acts so slowly as to fail entirely to bring about coagulation of the 
pectins. At higher temperatures alcoholic fermentation is not pre- 
vented and usually proceeds so rapidly as soon to make it impossible 
to classify the juice as unfermented. It is possible to produce almost 
instantaneous coagulation of pectins by some of the chemical treat- 
ments outlined by the French writers cited, but such treatments are 
not to be recommended, for the reason that their employment seri- 
ously detracts from the beverage quality of the juice. 
CLARIFICATION BY THE FORMATION OF A PRECIPITATE. 
Various methods of clarification employed in wine making and 
vinegar making may be grouped together, since they all depend upon 
the production in the liquid of a voluminous precipitate, which 
gradually subsides, carrying down with it the particles causing 
turbidity. A rather careful study of such methods indicates that 
none of them can be expected to give satisfactory results with un- 
fermented juices. The method of clarifying wines most widely em- 
ployed by European wine makers and most fully discussed in works 
on wine making is precipitation by the addition of tannin and 
gelatin. Since the precipitate is the product of a definite chemical 
reaction, perfect results are obtainable only when the quantities of the 
reagents are exactly adjusted, a slight excess of gelatin forming a 
stable colloidal suspension. But tannin is present in every fruit 
juice (its quantity showing wide differences with varieties and con- 
siderable differences in a single variety when grown in different 
years or under differing cultural and environmental conditions), and 
this tannin enters into the reaction with gelatin. For this reason the 
amounts of tannin and gelatin to be employed must be determined 
by experiment for every juice, and with such viscous materials as 
grape and apple juices the outcome of such experiments can be cer- 
tainly determined only after some days. This alone makes the 
method impracticable. The further fact that the tannin of a juice 
plays an essential réle in determining its characteristic flavor and 
that its removal results in marked alteration of flavor makes the 
