The Length Polymorphism of the Locus psbA-trnH is Idyllic to Detect the Adulterations of Black Pepper with Papaya Seeds and Chili

Abstract

Black pepper (Piper nigrum L.) is an important spice. The adulteration of black pepper seeds and powder with papaya seeds, green chili and red chili can be seen and limited studies have been conducted to detect these adulterants. The objectives of the present study were to assess the appropriateness of morphometric methods to discriminate papaya seed and chili adulterations in black pepper and to establish a DNA based strategy to detect these adulterations. A necessary adulteration series of seeds and powders were prepared for the analyses along with commercial samples. The appearance of the seed and powder samples were slightly different but not very distinct among the pure and adulterated samples emphasizing the need of a biochemical approach to detect the adulteration. The adulterated and commercial black pepper samples received lower pungency ranks compared to that of pure samples. QIAGEN DNeasy® Plant Mini Kit was successful in extracting PCR amplifiable DNA from any sample without papaya seeds and the modified CTAB method was able to extract required PCR amenable DNA from any sample with papaya seed material. The universal DNA barcoding primer pair, psbA-trnH, was used to amplify the DNA. Black pepper DNA yielded 200 bp band, chili and papaya DNA yielded 450 bp band and DNA from adulterated samples produced both 200 bp and 450 bp bands. Therefore this strategy can be used to detect papaya / chili adulterations in black pepper.