Author: Herr Dr. Amoneit
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Evalutaion of Virgin Olive Oil Bitterness by Multivariate Analysis of Ultraviolet Spectra of the Phenolic Extract
María E. Escuderos*, José Antonio García Mesa  
Instituto de Investigación y Formación Agraria, Pesquera, Alimentaria y de la Produccción Ecológica – IFAPA (Andalusia Regional Government) 
Mengíbar, Jaén (Spain)

Bitterness is considered as a positive sensorial attribute of the virgin olive oils (VOO) and enhances the overall flavour with notes related to unripe olive fruit. Bitterness is positively linked to the presence of phenolic compounds in the medium. Also, due to the positive contribution of the phenolic compounds to the olive oil oxidative stability and human health, consumers are increasing their consumption of oils with high bitterness intensity. As a result, bitterness evaluation is becoming an important area in olive oil research. 
The standard method for analysis the bitter taste of VOO is sensory analysis using a trained panel (EC Reg. 1348/2013). However, this method is not simple, being a rather time-consuming process, because a taster only can analyze twelve samples per day to avoid depletion of the senses of smell, taste and touch. Therefore, methods of bitterness evaluation based on physico-chemical determinations could be more useful for the industry. In 1992, Gutiérrez-Rosales et al. proposed a simple analytical method based on the solid-phase extraction (SPE) of the bitter compounds measured by spectrophotometric determination at 225 nm. In 2007, Beltrán et al. proposed an easy method to estimate the oil bitterness intensity without any sensory evaluation by measuring the total phenol content. 
In this work, a simple, fast and inexpensive method has been developed to evaluate the perceived sensorial bitterness intensity of a VOO. This method has only two steps: firstly, a liquid-liquid extraction (without hexane) of the polar compounds of the virgin olive oil is made; and secondly, the scan UV absorbance (200 – 350 nm) of this hydrophilic extract is measured. Using partial least square discriminant analysis (PLS), good correlations between the ultraviolet spectra and sensorial bitterness have been obtained.

*Corresponding author: mariae.escuderos@hotmail.com (María E. Escuderos)