Black pepper (Piper nigrum) is by monetary value, the most widely traded spice in the world, accounting for 20 percent of all spice imports. The global pepper production peaked in 2003 with over 355 000 tons , but has fallen to 271 000 tons in 2008 and still declines due to a series of issues including poor crop management, disease and weather. The global trade in black pepper powder alone is estimated to be 32 400 tons worth about 99.5 million U.S. dollars, which represents about 12% of the total global pepper export revenue.
The rather high cost coupled with the decreasing volume of this commodity is an invitation to adulteration. Especially spice powders are highly subjected to admixing or substitution with inferior substances. Compared to whole spices, spice powders and paste are more vulnerable to adulteration because foreign matters go into it largely undetected.
With increasing globalization, and liberalization of markets many countries are importing black pepper and re-exporting it as whole commodity or as value-added products. It has been discovered that in some cases left over pepper used for the extraction of piperine (alkaloid responsible for the pungency of pepper) was sold as black pepper powder, fortified with other pungent substances. Pepper was also reported to be adulterated with papaya seeds (Carica papaya) and wild Piper species (Piper attenuatum, Piper galeatum). On the other hand researchers in India found out that ginger powder was also adulterated with chilli (because of the pungency). This led to the question if chilli (Capsicum sp.) is perhaps more widely used to substitute black pepper especially in powdered products.
I guess it comes to no surprise that indeed results of a study by Indian researchers showed chilli adulteration in two out of nine market samples. The markers psbA-trnH, rbcL, rpoC1 were used in their study - one of them, rbcL, is actually an official DNA barcode region, the others were once discussed and tested for their inclusion in the standard. All three markers were capable to detect the adulteration and what's even more striking is the fact that the colleagues were able to detect the presence of chilli in as low as 0.5% of the total amount of spice powder.
When it comes to the use of black pepper in the kitchen I prefer the freshly grounded and thereby more aromatic one. Seems it was a good decision not to buy any powder.