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Open AccessArticle

Determination of the Acidity of Waste Cooking Oils by Near Infrared Spectroscopy

Departamento de Ingeniería Química, Facultad de Química, Universidad de Sevilla, C/Profesor García González, 1, 41012 Seville, Spain
Departamento de Ingeniería Energética. E.T.S. de Ingeniería, Universidad de Sevilla, Camino de los Descubrimientos, s/n, 41092 Seville, Spain
School of Food Engineering and Nutrition Sciences, Shaanxi Normal University, Xi′an 710062, Shanxi, China
Author to whom correspondence should be addressed.
Processes 2019, 7(5), 304;
Received: 29 April 2019 / Revised: 15 May 2019 / Accepted: 15 May 2019 / Published: 21 May 2019
Waste cooking oils (WCO) recycling companies usually have economic losses for buying WCO not suitable for biodiesel production, e.g., WCO with high free acidity (FA). For this reason, the determination of FA of WCO by near infrared (NIR) spectroscopy was studied in this work to assess its potential for in situ application. To do this, FA of 45 WCO was measured by the classical titration method, which ranged between 0.15 and 3.77%. Then, the NIR spectra from 800 to 2200 nm of these WCO were acquired, and a partial least squares model was built, relating the NIR spectra to FA values. The accuracy of the model was quite high, providing r2 of 0.970 and a ratio of performance to deviation (RPD) of 4.05. Subsequently, a model using an NIR range similar to that provided by portable NIR spectrometers (950–1650 nm) was built. The performance was lower (r2 = 0.905; RPD = 2.66), but even so, with good accuracy, which demonstrates the potential of NIR spectroscopy for the in situ determination of FA of WCO. View Full-Text
Keywords: free acidity; NIRS; partial least squares; waste cooking oil free acidity; NIRS; partial least squares; waste cooking oil
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García Martín, J.F.; López Barrera, M.C.; Torres García, M.; Zhang, Q.-A.; Álvarez Mateos, P. Determination of the Acidity of Waste Cooking Oils by Near Infrared Spectroscopy. Processes 2019, 7, 304.

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