An opto-electronic system for in-situ determination of peroxide value and total phenol content in olive oil

• A method to measure peroxide value and total phenol content in olive oil is shown.
• An emulsion between oil sample and a suitable chemical reagent is created.
• The optical density of the emulsion is measured with a LED/photodiode system.
• A good correlation between the measured data and the reference methods is achieved.
• A portable embedded system for in-situ olive oil quality control has been built.

The quality of olive oil is essentially determined by the product free acidity and peroxide value, while the total phenol content is also important for a high antioxidant capacity. Generally, these parameters are measured with laboratory analysis, that are expensive and may require a few days. Thus, a cheap and easy technique usable by untrained personnel, “on-site” and producing results “in real time” during production is desirable, particularly as far as small olive oil mills and packaging centers are concerned. This paper describes a technique to determine peroxide value and total phenol content in olive oil, that is based on the measurement of optical density of an emulsion between a suitable chemical reagent and a small quantity of the oil of interest. The optical density is measured by illuminating the sample with a LED with peak wavelength of 569 nm for peroxide value and 835 nm for total phenol content. The experimental results show good correlation (R2 = 0.883 and 0.895 for peroxide value and total phenol content, respectively) between data measured with the standard methodology and the technique of this work, implemented also in the form of a portable embedded system.