The same authority regards 50 per cent. of starch as the minimum standard for unadulterated pepper. The granules of pepper-starch are characterised by their exceedingly small size, being only about ·008 mm. in diameter.
The proportion of ash in genuine pepper seldom exceeds 7 per cent., of which not over 1⁄10th should consist of sand; but in the commercial article, the total ash often approximates 10 or 12 per cent., 40 or 50 per cent. of which is sand and other insoluble substances.
Composition of Pepper Ash.
| Potassa | 31·36 |
| Soda | 4·56 |
| Magnesia | 16·34 |
| Lime | 14·59 |
| Ferric oxide | 0·38 |
| Phosphoric acid | 10·85 |
| Sulphuric acid | 12·09 |
| Chlorine | 9·52 |
The list of adulterations used as admixtures to pepper, as well as to most other ground condiments and spices, is quite extensive, and includes such cheap and neutral substances as ship-bread, corn, ground cocoanut shells, beans, peas, hulls of mustard seed, sand, etc., etc. It is stated that in England large quantities of preparations consisting of linseed-meal, mustard husks and rice-meal, known to the trade respectively as P.D., H.P.D., and W.P.D., are very generally employed in the adulteration of pepper. P.D. (pepper-dust), would appear to also signify the sweepings collected from pepper factories, and sometimes fortified with cayenne, the manufacture of which article has given rise to a special industry. It is utilised as a diluent of the various spices, the sophisticated products being sold as “P.D. pepper,” “P.D. cloves,” “P.D. cinnamon,” etc. Unfortunately the character of most of the adulterants of pepper, as of other spices, is such, that little assistance is afforded the analyst by chemical tests. A microscopic examination of the suspected sample furnishes far more trustworthy information and should in all instances be employed, comparative observations being made with an article of known purity.
The appearance of several of the starch granules of various flours often found in adulterated condiments and spices is represented in Plate IX.
In the special case of pepper, it is of advantage to make chemical determinations of the moisture, ash, piperin and resin.
Moisture.—The proportion of moisture is estimated by the ordinary method of drying a weighed portion of the pepper in a platinum capsule at 100°, and noting the loss in weight sustained.
Ash.—The dry sample is incinerated, and the amount of mineral residue determined. As already intimated, the proportion of sand present is of especial import.
Piperin and Resin.—The pepper is repeatedly digested with absolute alcohol, the mixture filtered and the filtrate evaporated to dryness over a water-bath. The extract is weighed and then treated with sodium hydroxide solution, in which the resin is soluble. The alkaline liquid is then removed, and the remaining piperin dissolved in alcohol, the solution filtered, evaporated to dryness, and the weight of the residue determined. The proportion of piperin in unadulterated pepper ranges from 4·5 to 5·5 per cent., that of resin from 1·7 to 2 per cent.