THE  TROPICAL  AGRICULTURIST. 
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Analyses  of  Black  and  Green  Teas.  (Bell.) 
Black  Tea.  Green  Tea. 
Congou.  Young  Hyson. 
Moisture 
8-20 
5-96 
Theine  ... 
324 
2-33 
Albumin,  insoluble 
17-20 
16-83 
Do  soluble 
•70 
•80 
Extractive  by  alcohol  con- 
taining nitrogenous  matter 
6-79 
7 05 
Dextrin  or  Gum  ... 
— 
*50 
Pectin  and  Pectic  Acid  ... 
2-60 
3-22 
Tannin 
16-40 
27-14 
Chlorophyll  and  Resin  . . . 
4-60 
4-20 
Cellulose 
34-00 
25-90 
Ash 
6-27 
6-07 
100-00 
100-00 
According  to  Professor  Church  good  average 
black  tea  as  imported  may  be  fairly  represented 
by  the  following  figures: — 
Analysis  of  good  average.  Black  Tea. 
Water  , 
In  100  parts. 
8-0 
Albumenoids  ... 
17-5 
Theine  ..* 
3-2 
Tannin 
17-5 
Chlorophyll  and  Resin  . 
4-5 
Essential  Oil  ... 
•4 
Minor  extractives 
8-6 
Cellulose,  &c.... 
34-0 
Mineral  matter 
6-3 
The  following  table  of  analyses  shows  the 
composition  of  the  ash  of  seven  descriptions  of 
tea.  The  table  is  quoted  from  Dr.  Bell’s  work 
on  “ The  Chemistry  of  Foods.” 
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The  constituents  of  tea  already  enumerated  may 
be  divided  into  substances  soluble  and  substances 
insoluble  in  water.  Of  these,  the  former  only  are 
of  dietetic  importance  to  tea  drinkers.  The 
soluble  substance  or  extractive  matter  contain 
s 
most  of  the  tannin,  a large  portion  of  the  theine, 
and  of  the  essential  oil.  Tt  contains  also  pectin, 
mineral  matter,  and  a small  fraction  of  the 
albumenoids  present  in  the  leaf.  On  account  of 
the  insolubility  of  the  greater  part  of  the 
albumeniods,  infusion  of  tea  has  a low  nutritive 
value,  but  it  possesses  important  stimulative 
properties  on  account  of  the  essential  oil  and  theine 
that  are  present. 
Tannin. — The  tannin  of  tea  is  commonly  re- 
garded as  identical  with  gallo-tannic  acid.  Dr. 
Bell  is  of  opinion,  however,  that  while  in  its  re- 
actions it  exhibits  a close  relation  to  this  sub" 
stance,  yet,  from  its  comparative  instability,  and 
the  modifications  it  undergoes  under  chemica^ 
treatment,  the  tannin  of  tea  differs  in  some  im- 
portant respects  from  gallo-tannic  acid.  Tannin 
G the  most  abundant  of  the  soluble  ingredients 
of  tea,  and  it  is  to  it  that  tea  owes  its  astringency 
or  strength.  Analysis  usually  shews  a higher 
precentage  of  tannin  in  green  than  in  black  tea. 
Essential  Oil  of  Tea. — This  ingredient  of  tea 
appears  for  the  most  part  to  be  developed  by  the 
process  of  manufacture.  It  is  present  in  very 
small  proportion,  yet  the  characteristic  taste  and 
smell  of  tea  is  very  largely  due  to  this  ingredient. 
When  tea  is  distilled  with  water,  the  colorless 
distillate  which  passes  over  possesses  the 
characteristic  odour  of  tea  to  a marked  degree,  al- 
though no  oil  whatever  is  visible.  By  saturating 
the  distillate  with  a salt  such  as  chloride  of  calcium, 
shaking  the  solution  with  ether,  and  then  allowing 
the  separated  gtherial  solution  to  evaporate,  a 
portion  of  the  oil  may  be  obtained  as  a residue. 
It  is  an  oil  of  a yellowish  colour,  and  passes  into 
a resinoid  state  by  exposure  to  the  air. 
Theine.  — This  alkaloid  of  tea  is  a highly  nitro- 
genous substance,  containing  about  29  per  cent 
of  nitrogen,  whereas  albumen,  the  most  abundant 
nitrogenous  constituent  of  plants,  contains  some- 
what less  than  16  per  cent.  The  tea  leaf  contains 
nitrogen  in  both  forms,  and  the  Japanese  take  ad- 
vantage both  of  the  stimulating  theine  and  the 
nutritive  albumen  by  powdering  their  finest  teas 
and  consuming  this  along  with  the  infusion.  The 
alkaloid  theine,  like  the  alkaloid  quinine  in  some 
of  the  cinchonas,  appears  to  be  increased  by  the 
exclusion  of  light  for  a time  from  the  growing 
plant,  the  total  nitrogen  being  also  thereby 
