High resolution melting analysis of DNA microsatellites in olive pastes and virgin olive oils obtained by talc addition

Abstract

Talc (hydrated magnesium silicate) is a physical coadjuvant that can be employed in the production of extra virgin olive oil to increase yield. The adsorbent properties of talc could hamper DNA recovery, leading to false negatives in DNA analysis. The aim of this work was to verify the effect of talc addition on olive oil DNA by targeting four selected microsatellites. Olive processing trials were carried out at two different levels of talc (1 and 2%) and without talc (control). DNA extraction yield and purity level were ascertained, and High Resolution Melting (HRM) analysis of microsatellites was subsequently applied to the extracted DNA. Neither the DNA extraction yield nor the A260/230 and A260/280 ratios showed significant differences between control and talc‐treated samples. Higher values of A260/230 and lower yields were observed in olive oils than in olive pastes. The DNA microsatellites analyzed showed identical HRM profiles in all the samples, excluding any effect of talc and confirming the genetic homogeneity of the olive lot processed (cv. Coratina).Practical applications: High added‐value mono‐cultivar extra virgin olive oils are niche products very appreciated by consumers. DNA analysis is able to reveal mixing with cultivars different from those declared in the label. The use of talc in olive oil industries has progressively increased to improve yield. The results obtained prove that the DNA‐based methods set up until now to check the authenticity of extra virgin olive oil can be effectively carried out also in oils produced by using talc. In addition, the results are among the first applications of HRM to the food sector and evidence the feasibility of this technique along the olive oil chain for checking both olive pastes and oils.Talc (hydrated magnesium silicate) is a physical coadjuvant that can be employed in the production of extra virgin olive oil to increase yield. The adsorbent properties of talc could hamper DNA recovery, leading to false negatives in DNA analysis. By means of High Resolution Melting (HRM) analysis, DNA samples from talc‐treated olive pastes and oils were compared with untreated control based on the shape of temperature‐shifted melting curves. For the same microsatellite, the different samples analyzed showed almost identical HRM profiles. This result excluded any effect of talc addition during olive processing in the analysis of DNA microsatellites of olive oil.