Single Base Extension and Fourier-Transform Infra-Red Spectroscopy Techniques; Further Approaches in Discriminating Hazelnut-Adulterated Olive Oil

Abstract

Background:Confirmation of olive oil authenticity and particularly virgin olive oil has a great importance. Several advanced chemical and genetic analyses have been used to monitor especial components; however each has its limitations especially when detecting hazelnut-adulterated olive oil. Objectives:The objective of this research is to assess the presence of trace amount of hazelnut oil in olive oil (less than 10%) by Single Base Extension (SBE) and Fourier Transform InfraRed Spectroscopy (FTIR). Materials and Methods:The study was based on the analysis of chloroplast DNA sequences using SBE to detect Single Base Polymorphism (SNPs) in highly preserved DNA regions among species to differentiate pure and adulterated olive oil by means of two parallel tools; ABI PRISM automatic sequencer and the SNaPshot lit (APPLERA). Fourier -Transform InfraRed technique has been used for FTIR spectrum comparisons of pure olive oil and hazelnut-adulterated one as well. Results:Total DNA was extracted successfully from pure and hazelnut-adulterated olive oil, and it provided properly acceptable amplification with the primers designed on chloroplast region of both species and admixture oil of them in different ratios; 50: 50, 70: 30, and vice versa. However, for lesser than 10% hazelnut oil in olive oil only SBE analysis provided recognizable results. FTIR spectra of oil samples were assessed at frequency regions of 4000 - 700 cm-1. Eight wave numbers (3007, 1373, 1237, 1120, 1098, 1032, 965, and 722 cm-1) out of eleven differentiating ones were selected as candidate wave-numbers to distinguish pure and adulterated olive oil. Conclusions:SBE technique proved to be an effective strategy to verify olive oil authenticity, especially from hazelnut-adulterated olive oil. However, FTIR technique provided trustable results only when higher than 10% hazelnut oil is present in olive oil.