Food Adulteration and Its Detection. Jesse P. Battershall
in acid ranges between 0·3 and 0·8 per cent.
Extract[8] ranges between 32 and 50 per cent.
Insoluble leaf ranges between 43 and 58 per cent.
The table below may prove useful as indicating the requirements to be exacted when the chemist is asked to give an opinion concerning the presence of facing admixtures, or of exhausted or foreign leaves in a sample of tea.
Total ash should not be under 4·5 per cent. or above 7 per cent.
Ash soluble in water should not be under 40 per cent. of total ash.
Ash insoluble in water should not be over 3·25 per cent.
Ash insoluble in acid should not be over 1 per cent.
Extract (excepting in poor varieties of Congou tea) should not be under 30 per cent.
Insoluble Leaf should not be over 60 per cent.
The British Society of Public Analysts adopt:—
Total ash (dry basis), not over 8 per cent. (at least 3 per cent. should be soluble in water).
Extract (tea as sold), not under 30 per cent.
Below are the proportions of total ash, ash soluble in water, and extract found in 850 samples of tea (mostly inferior and faced), examined under the direction of the author in the U.S. Laboratory:—
Total Ash.
| Range | 5 to 5½ per cent. | 5½ to 6 per cent. | 6 to 6½ per cent. | 6½ to 7 per cent. | 7 to 8 per cent. | 8 per cent. and over. |
| Number | 21 | 76 | 102 | 194 | 421 | 36 |
| Per cent. | 2·47 | 8·94 | 12·00 | 21·64 | 49·53 | 4·23 |
Ash Soluble in Water.
| Range | Under 2 per cent. | 2 to 3 per cent. | 3 to 3½ per cent. | 3½ per cent. and over. |
| Number | 25 | 649 | 157 | 19 |
| Per cent. | 2·94 | 76·35 | 18·70 | 2·23 |
Extract.
| Range | 20 to 25 per cent. | 25 to 30 per cent. | 30 to 35 per cent. | 35 to 40 per cent. |
| Number | 21 | 151 | 499 | 179 |
| Per cent. | 2·47 | 17·76 | 58·70 | 21·05 |
The following tabulation exhibits the results obtained by the examination of various grades of Formosa, Congou, Young Hyson, Gunpowder, and Japan tea, made, under the supervision of the writer, by Dr. J. F. Davis.
It will be noticed, if the same varieties of tea be compared, that, with some exceptions, their commercial value is directly proportional to the percentages of soluble ash, extract, tannin, and theine contained.
| Variety. | Formosa Oolong, Choice, 1st Crop. | Formosa Oolong, Superior, 1st Crop. | Formosa Oolong, Choice, 3rd Crop. | Formosa Oolong, Superior, 3rd Crop. | Congou, Choicest. | Congou, Medium. | Congou, Common. |
| c. | c. | c. | c. | c. | c. | c. | |
| Price per lb. (wholesale). | 70 | 28 | 55 | 24 | 65 to 70 | 24 | 14 |
| p.c. | p.c. | p.c. | p.c. | p.c. | p.c. | p.c. | |
| Total ash | 6·50 | 5·96 | 5·80 | 6·34 | 6·22 | 6·36 | 6·58 |
| Ash soluble in water. | 3·60 | 2·86 | 3·12 | 3·60 | 3·56 | 3·00 | 2·88 |
| Ash insoluble in water. | 2·90 | 3·10 | 2·68 | 2·74 | 2·66 | 3·36 | 3·70 |
| Ash insoluble in acids. | 0·86 | 0·94 | 0·56 | 0·66 | 0·56 | 0·66 | 1·06 |
| Extract | 42·00 | 37·40 | 43·20 | 40·60 | 34·60 | 29·60 | 26·20 |
| Insoluble leaf | 54·90 | 59·55 | 52·70 | 56·55 | 60·75 | 64·80 | 68·75 |
| Tannin | 18·66 | 16·31 | 18·00 | 16·05 | 14·87 | 13·70 | 12·26 |
| Theine | 3·46 | 2·20 | 2·26 | 1·39 | 3·29 | 2·23 | 2·35 |