Use of Raman spectroscopy for analyzing edible vegetable oils

ABSTRACT

Vegetable oils provide high nutritional value in the human diet. Specifically, extra virgin olive oil is one of the main ingredients of the Mediterranean diet, which is among the healthiest of eating practices. This article reviews the use of Raman spectroscopy for analyzing edible vegetable oils including olive oil. Although the spectra for edible vegetable oils are similar, they exhibit some differences which, however small, enable their discrimination. Thus, Raman spectra allow one to determine the degree of unsaturation of oils. This property is correlated with the iodine value but much faster and simpler to obtain. The degree of unsaturation can be used to classify and authenticate oils, which is especially useful with high-quality oils. In fact, adulteration with mixtures of more inexpensive oils can be easily detected by Raman spectroscopy. This technique additionally allows some minor components present in unsaponifiable matter to be identified. Fats in general and vegetable oils in particular, are prone to oxidation. Thus, double bonds in them are oxidized to form triglycerides. Vegetable oils are widely used for frying and Raman spectroscopy allows for their oxidative stability against heating at the usual frying temperatures to be assessed.

KEYWORDS:

• Raman spectroscopy
• edible oil
• vegetable oil
• degree of unsaturation
• oxidation of oils

Funding

The authors gratefully acknowledge funding by Spain's Ministerio de Educación y Ciencia (Project MAT-2013-44463-R), Feder Funds and to the Consejería de Innovación, Ciencia y Empresa de la Junta de Andalucía.