Development and optimization of an efficient qPCR system for olive authentication in edible oils

- Olive oil authentication by qPCR depends on primer design and DNA amplificability.
- Four olive-specific qPCR systems, based on trnL, are designed and validated.
- The D-trnL system is selected on account of its high specificity and sensitivity.
- DNA from different categories of olive oils was detected by the D-trnL system.
- The design of the D-trnL system is suitable for olive oil authentication.

The applicability of qPCR in olive-oil authentication depends on the DNA obtained from the oils and the amplification primers. Therefore, four olive-specific amplification systems based on the trnL gene were designed (A-, B-, C- and D-trnL systems). The qPCR conditions, primer concentration and annealing temperature, were optimized. The systems were tested for efficiency and sensitivity to select the most suitable for olive oil authentication. The selected system (D-trnL) demonstrated specificity toward olive in contrast to other oleaginous species (canola, soybean, sunflower, maize, peanut and coconut) and showed high sensitivity in a broad linear dynamic range (LOD and LOQ: 500 ng - 0.0625 pg). This qPCR system enabled detection, with high sensitivity and specificity, of olive DNA isolated from oils processed in different ways, establishing it as an efficient method for the authentication of olive oil regardless of its category.