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

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.

Simple sequence repeats amplification: a tool to survey the genetic background of olive oils

A reliable DNA extraction method for use on extra virgin olive oil based on a commercial kit was defined, and the possibility of using this DNA for fingerprinting the original cultivar was demonstrated. The genetic traceability of single-cultivar virgin olive oil from two cultivars [Carolea and Frantoio] was achieved by identifying the varieties from which they were produced. This involved the analysis of DNA sequences using a panel of seven simple sequence repeats [SSRs] to provide genotype-specific allelic profiles. The amplified SSR fragments and the DNA profiles from the monovarietal oil corresponded to the profiles from the leaves of the same cultivar. The most reliable SSR in providing correct allele sizing in distinguishing either singlecultivar olive oil samples or the different ratios of their blends are DCA3, DCA4, DCA16, DCA17, and GAPU101, while DCA9, GAPU59 produced less concordance against data obtained by the genetic analysis of leaf samples. To have reproducible results, PCR product purification and selection of a set of markers with a highly robust amplification pattern is suggested