The trnL (UAA)‐trnF (GAA) intergenic spacer is a robust marker of green pea (Pisum sativum L.) adulteration in economically valuable pistachio nuts (Pistacia vera L.)

Abstract

BACKGROUND Pistachio (Pistacia vera L.) is an expensive culinary nut species; it is therefore susceptible to adulteration for economic profit. Green pea (Pisum sativum L.) kernels constitute the most common material used for adulterating chopped / ground pistachio nuts and pistachio paste. Food genomics enables the species composition of a food sample to be ascertained through DNA analysis. Accordingly, a barcode DNA genotyping approach was used to standardize a test method to identify green pea adulteration in pistachio nuts. RESULTS The trnL (UAA)‐trnF (GAA) intergenic spacer in the plastid genome was the target analyte in the present study. The barcode locus displayed a significant, discriminatory size difference between pistachio and pea, with amplicon sizes of 449 and 179 bp, respectively. Polymerase chain reaction‐capillary electrophoresis (PCR‐CE) analysis of the intergenic spacer resulted in the successful identification of species composition in the in‐house admixtures, which contained 5% to 30% of green pea. CONCLUSION The present work describes a fast and straightforward DNA test that identifies green pea adulteration in pistachio nuts without requiring a statistical data interpretation process. The plastid trnL (UAA)‐trnF (GAA) intergenic spacer length widely varies among plant taxa, so the PCR‐CE protocol that operates on the intergenic spacer holds the potential to reveal adulteration with a plethora of adulterants. The PCR‐CE assay described in the present work can be adopted readily by food‐quality laboratories in the public sector or the food industry as an easy and reliable method to analyze pistachio authenticity. © 2020 Society of Chemical Industry

A Novel High-Resolution Melting Method for Detection of Adulteration on Pistachio (Pistacia vera L.)

“…Thus, the authenticity of pistachio products must be validated to prevent consumers from buying adulterated products. There are several ways to detect adulteration of pistachio, such Raman hyperspectral imaging [4], DNA genotyping using the trnL-trnF intergenic spacer marker [5] and DNAfoil method [6]. Nevertheless, a closed-tube method, which is more sensitive, faster and cheaper, would be more useful to detect adulteration at lower ratios and prevent contamination during sample handling.…”

“…Identi cation of the adulterants at DNA level is more dependable since DNA is a stable molecule and exists in all tissues. Although a novel polymerase chain reaction (PCR)-based method targeting the trnL-trnF intergenic spacer with capillary electrophoresis (CE) was developed and successfully applied to detect green pea at the ratio of 5% [5], a more sensitive, faster and simpler method, which does not require post-PCR processing and electrophoresis, is still missing. A novel DNA hybridisationbased method DNAFoil was described in the literature [6] which is practical and easy to in eld usage product.…”

A Novel High-Resolution Melting Method for Detection of Adulteration on Pistachio (Pistacia vera L.)

“…Identification of the adulterants at DNA level is more dependable since DNA is a stable molecule and exists in all tissues. Although a novel polymerase chain reaction (PCR)-based method targeting the trnL-trnF intergenic spacer with capillary electrophoresis (CE) was developed and successfully applied to detect green pea at the ratio of 5% [5], a more sensitive, faster and simpler method, which does not require post-PCR processing and electrophoresis, is still missing. A novel DNA hybridisationbased method DNAFoil was described in the literature [6] which is practical and easy to in field usage product.…”

Capillary electromigration methods for food analysis and Foodomics: Advances and applications in the period February 2019–February 2021

“…By using a variant of competitive PCR for fragment amplification, relative quantification of Trait versus Non-Trait amplicons was performed, and the CE method allowed the quantification of 5% increments across the 0-100% range with a mean absolute error of 1.9%. CE methods have also been reported in the literature for the detection of DNA markers of food adulteration (such as the addition of green pea kernels to pistachio nuts [79], the use of apricot kernels as almond substitutes [80], or the use of Asian black truffles as black Perigord truffles [81]), or for food authentication [82]). In the case of pistachio adulteration, a barcode DNA genotyping approach using the trnL (UAA)-trnF (GAA) intergenic spacer in the plastid genome was used to identify green pea adulteration in pistachio nuts [79].…”

“…CE methods have also been reported in the literature for the detection of DNA markers of food adulteration (such as the addition of green pea kernels to pistachio nuts [79], the use of apricot kernels as almond substitutes [80], or the use of Asian black truffles as black Perigord truffles [81]), or for food authentication [82]). In the case of pistachio adulteration, a barcode DNA genotyping approach using the trnL (UAA)‐trnF (GAA) intergenic spacer in the plastid genome was used to identify green pea adulteration in pistachio nuts [79]. The PCR‐CE method allowed the identification of different in‐house admixtures, from 5% to 30% of green pea.…”