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

• Published in: Talanta (Oxford) Vol. 206; p. 120226
• Main Authors: Marbello, O.D., Valbuena, S., Racedo, F.J.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.01.2020
• Subjects: absorbance; avocado oil; cooking fats and oils; extra-virgin olive oil; food industry; heat; linseed oil; Non linearity; Nonlinear parameters; nutritive value; organic compounds; Organics compounds; oxidative stability; photonics; refractive index; sesame oil; thermal stability; thermal stress; Thermic stress; Third order electric susceptibility; transmittance; vegetable oil; vegetables; Z-scan; Thermic stress; Third order electric susceptibility; Nonlinear parameters; Z-scan; Non linearity; Organics compounds
• ISSN: 0039-9140; 1873-3573; 1873-3573
• DOI: 10.1016/j.talanta.2019.120226

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. [Display omitted] •Was found that all oils have a non-linearity of self-defocusing, which means a negative non-linear refraction index. All oils show an increase in the non-linear refractive index as function of the power of the incident beam.•It was found that n2 increases as the sample is exposed to a higher temperature, while β has the opposite effect.•The temperature raise can be related to the unsaturation process of fatty acids, the formation of free radicals due to the presence of oxygen and the smoke point of extra virgin olive oil.•The Z-scan technique provides information that be related to different parameters the quality of the oil.