Molecular Identification of Economically Motivated Adulteration of Red Pepper Powder by Species-Specific PCR of Nuclear rDNA-ITS Regions in Garlic and Onion

Abstract

Economically motivated adulteration (EMA) of food is a matter of great concern in Korea due to its unfavorable effects on public distribution orders. EMA of red pepper powder is typically done with a mixture of garlic (Allium sativum) and onion (Allium cepa), leading to a reduction in red pepper powder content. To establish a rapid and accurate detection method for EMA red pepper powder, we designed species-specific PCR primers based on the internal transcribed spacer regions of garlic and onion DNA. Among the examined DNA extraction methods, the DNA extraction kit with a silica gel column was found to be a time-saving, high-purity, and high-yield method. When the designed species-specific PCR primers were used for designed EMA red pepper powder with different mixture ratios of garlic and onion, the target ingredients were detected in a concentration-dependent manner. Furthermore, duplex PCR allowed specific simultaneous detection of garlic and onion. Real-time quantitative PCR assay was successfully used to detect garlic and onion quantitatively in binary mixed samples containing as little as 0.05 % of these components. When we examined EMA red pepper powder collected from the Ministry of Food and Drug Safety using a conventional PCR assay, the newly designed PCR primers successfully detected the target ingredients.