654 
THE TKOPICAii A.GIIICULTUEIST. [April 1. 1902. 
.he advisable to pluck as early as possible in the day, 
and some planters have stated that teas made from 1 
leaves plucked early in the morning are better than ; 
others. This would also have a considerable bearing 
on the beneficial effect or othewise, of shade on the 
. quality of tea grown beneath it. To investigate this 
question, we examined leaf plucked at 6 a. m., 2 p. m. 
and 6 p.m., (and occasionally at 10 p.m.) for several 
days under conditions of severe drought and excessive 
moisture. 
The result of these microscopical investigations show 
that the enzyme (or Us zymogen) is present in ab- 
undance at all boms and under all conditions, so 
: that it would be diflicult to ascribe improved quality, 
if any, in early plucked leaf to a particular abundance 
of enzyme. . „ ^ , , , 
Since an enzyme is present in all tea leaf under 
all conditions, the next point to determine is its 
, function in the plant, and its action during the manu- 
facture of tea. 
As regards the function of the enzyme in the living 
tea plant, it is difficult to make any definite 
statements at present since there are so few optically 
visible store-products in the leaf requiring its action 
to render them soluble. This point is further inves- 
tigated, and we can only state that the activity of 
the enzyme is apparently connected with the glne- 
cosidal products in the leaf and possibly with the 
• proteids. 
The enzyme has been isolated, by one of us, and 
its action determined on a solution of tannin, prepared 
from tea, with the result of a browning of the liquid 
and the formation of a small proportion of srgar. 
We would not, however, place too much reliance 
on this reaction until confirmed by further tests, as 
the tannin of tea is so prone to undergo change, 
that the chemical processes necessary for its isola- 
tion might induce a somewhat similar change. The 
best practical method of proving the effect of the 
eneyme would be to isolate a large quantity of it 
from a highly flavoured tea, and to add this to a 
- low country tea during manufacture and so determine 
any enhancement of flavour, 
METHOD OF EXTRACTION. 
The simplest method is to bruise the withered leaf 
in contact with hide powder or sheet gelatine for 
'■ some hours, then to remove the gelatine, which has 
' now become very tough and leathery, and to again 
bruise the leaf with a small quantity of water at 
■ about 80° F. The damp mass is then subjected to 
high pressure to express all the juices, which are 
then filtered as rapidly as possible, and precipitated 
with several volumes of alcohol. After some hours 
the bulk of the solution is poured off from the 
flooculent precipitate which has subsided, and this is 
again treated with water to dissolve the enzyme, 
the solution filtered and again precipitated with 
several volumes of strong alcohol. The precipitated 
enzyme can be re-subjected to this treatment to fur- 
ther purify it, and finally collected and dried at the 
' ordinary temperature to a whitish powder, or it can 
be collected and disolve in water to a nearly colourless 
solution. 
Both the powder and solution prepared in this 
manner give a deep blue reaction with gum guiacum, 
and as other products which are known to also give 
a blue reaction with this test have been removed 
by the method of preparation, except perhaps traces 
of proteid, we may conclude that the reaction in 
the original leaf i? almost certainly due to the pre- 
sence of the enzyme. 
Tannin, gallic acid, caffeine and other products in 
tea have been tested separately, and found not to 
any re-action with the resin. 
If the C'V'/.yme has anything to do with flavour in tea, 
the questions to ))e solved are : — 
Ist. Is it acting during the growth of the leaf ? 
Sod Docs it only act after development from an 
nert form (zymogen) during the withering process, 
3rd, Does it act during or after tolling, since then 
the contents of the cells are more or less expreEsed 
and mixed with one another. 
1st. The enzyme is no doubt active in the leaf dar- 
ing the life of the plant at all elevations, and the fact 
that the flavour of tea does not appear until we get 
into higher elevations would tend to show that its 
activity had little, if anything, to do with the fla- 
vour. 
The maximum activity of other enzymes is asso- 
ciated with a definite range of temparature frequent- 
ly above that prevailing even in the low country of 
Ceylon ; hence we might infer that the activity of 
the enzyme in tea would be greatest in the hot 
low country, and yet we know that these teas have 
much less flavour than those grown in the high 
country 
2nd, The presence of a zymogiu or mother enzyme 
was indicated in many of our experiments. Freshly 
cut sections of leaf frequently gave no reaction with 
the gum guiacum test, until after frequent moisten- 
ings and exposure to air. This could only be due 
to the zymogen being rapidly converted by oxida- 
tion into the active enzyme. Again withered leaf 
invariably gave a quicker and more intense reaction 
than the fresh leaf, which would aleo indicate a 
similar change. Again sections frequently give a 
more intense blue reaction after trentment with 
hydrogen peroxide, which may aleo be due to the 
rapid oxidation of the zymogen into the active enzyme, 
or possibly to a direct action between the two reagents 
themselves. 
The Chinese method of withering tsa leaf may also 
be dependent for its success partly on the fact that 
the frequent throwing in the air and gentle patting 
with the hands allows an oxidation of the zymogen 
into the enzyme. 
Assuming that the abundance of enzyme is desir- 
able, It would seem worth our while to employ a 
system of withering which would permit of a degree 
of oxidation suflBcient to convert the whole of the 
zymogen into the active form. 
Experiments in this direction, and also on the 
effect of light in the development of the active en- 
zyme in the leaf are now being made. 
3rd. In the rolling process one might expect that 
very large percentage of the cells would be raptured, 
and their contents mixed with one another and ex- 
posed to the air. It is. however, surprising that 
only a very small percentage of cells are really broken, 
and the material which is expressed has mainly been 
driven through the cell walls. 
Examination of rolled leaf revealed about the same 
amount of enzyme as in the withered leaf, and only 
differed from it in being more diffuse. In order to 
get the zymogen or enzyme more exposed to the air, 
high pressure during rolling would be suggested, as 
this would no doubt insure the rupturing of more 
cells, and the more intimate mixing of cell contents. 
In practice, however, it has been frequently found 
that white great pressure increases the strength of 
the tea, the flavour becomes more or less masked 
or diminished. 
Several tests have proved that the enzyme ia entirely 
destroyed by suflicient heat in the ordinary process 
of drying but its action is probably increased to a 
marked extent for the first few minutes in the dry- 
ing machine, as it has often been demonstrated, that 
the actual temperature of the leaf while wet is usually 
80° to 100° F. below the temparature of the air in 
the machine, which would represent a tempera* 
lure in which the majority of enzymes are most 
active. 
The enzyme or its action is also entirely destroyed 
by steam, as is shown in the manufacture of green 
tea, and there are one or two points in this connec- 
tion which probably indicate the true action of the en« 
zyme in the manufacture of black tea. 
The first of these is the fact that tea leaf ihorougKly 
wilted by steam will not acquire the brown coppery 
