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Proceedings Paper

Monitoring of high refractive index edible oils using coated long period fiber grating sensors
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Paper Abstract

Monitoring the quality of high refractive index edible oils is of great importance for the human health. Uncooked edible oils in general are healthy foodstuff, olive oil in particular, however, they are frequently used for baking and cooking. High quality edible oils are made from seeds, nuts or fruits by mechanical processes. Nevertheless, once the mechanical extraction is complete, up to 15% of the oil remains in oil pomace and in the mill wastewater, which can be extracted using organic solvents, often hexane. Optical fiber sensors based on long period fiber gratings (LPFG) have very low wavelength sensitivity when the surround refractive index is higher than the refractive index of the cladding. Titanium dioxide (TiO2) coated LPFG could lead to the realization of high sensitivity chemical sensor for the food industry. In this work LPFG coated with a TiO2 thin film were successfully used for to detect small levels of hexane diluted in edible oils and for real time monitoring the thermal deterioration of edible oils. For a TiO2 coating of 30 nm a wavelength sensitivity of 1361.7 nm/RIU (or 0.97 nm / % V/V) in the 1.4610-1.4670 refractive index range was achieved, corresponding to 0 to 12 % V/V of hexane in olive oil. A sensitivity higher than 638 nm/RIU at 225 ºC was calculated, in the 1.4670-1.4735 refractive index range with a detection limit of thermal deterioration of about 1 minute.

Paper Details

Date Published: 5 May 2015
PDF: 7 pages
Proc. SPIE 9506, Optical Sensors 2015, 95061A (5 May 2015); doi: 10.1117/12.2178811
Show Author Affiliations
Luis Coelho, INESC Porto (Portugal)
Diana Viegas, INESC Porto (Portugal)
José Luís Campos Oliveira Santos, Univ. do Porto (Portugal)
Jose Manuel Marques Martins de Almeida, INESC TEC (Portugal)
Univ. de Trás-os-Montes e Alto Douro (Portugal)


Published in SPIE Proceedings Vol. 9506:
Optical Sensors 2015
Francesco Baldini; Jiri Homola; Robert A. Lieberman, Editor(s)

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