Study of the nonlinear optical response and thermal stability of edible oils using the Z-scan technique

Organic compounds and vegetable origin oils are subject to scratiny in the photonics and nonlinear optics area, due to their high non-linear response: a characteristic linked to the molecular nature of these compounds and their own chemical bond. In the food industry, quick and non-invasive studies are needed to evaluate the nutritional quality of edible products. The nonlinear optical response of 4 vegetable oils was analyzed: extra virgin olive oil (EVOO), extra virgin sesame oil (EVSO), extra refined linseed oil (ERLO) and virgin avocado oil (VAVO), using the Z-scan technique. Where the third order electric susceptibility value (χ³), refractive index (η₂) and characteristic non-linear absorption coefficient (β) were determined for each compound. Parameters that were found by measuring the transmittance as a function of the excitation power using a Nd: YAG laser of 532 nm operating in CW mode. In addition, the η₂ response was compared according to the oil type, it was determined that EVOO presents a greater non-linear response at low excitation potencies. Therefore, an additional study was performed on samples exposed to thermal stress to evaluate oxidative stability, again using the Z-scan technique n order to review the relationship between nonlinear optical properties with chemical changes resulting from heating.