Single base extension and Fourier-transform infra-red spectroscopy techniques; further approaches in discriminating hazelnut-adulterated olive oil

ABSTRACT

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. The objective of this research was 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]. The study was based on the analysis of chloroplast DNA sequences using SBE to detect Single Nucleotide Polymorphisms [SNPs] in highly preserved DNA regions among olive and hazelnut species to differentiate pure and adulterated olive oil by means of two parallel tools; ABI PRISM sequencing and AcycloPrime Single Nucleotide Polymorphism Detection. Fourier -Transform InfraRed technique was used for FTIR spectrum comparisons of pure olive oil and hazelnut-adulterated one, as well. 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 their admixture oil 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]] of eleven differentiating ones were selected as candidate wave-numbers to distinguish pure and adulterated olive oil. 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.