Direct Automatic Determination of Bitterness and Total Phenolic Compounds in Virgin Olive Oil Using a pH-Based Flow-Injection Analysis System

Abstract

Flavor and taste are sensorial attributes of virgin olive oil (VOO) highly appreciated by consumers. Among the organoleptic properties of VOO, bitterness is related to the natural phenolic compounds present in the oil. Sensorial analysis is the official method to evaluate VOO flavor and bitterness, which requires highly specialized experts. Alternatively, methods based on physicochemical determinations could be useful for the industry. The present work presents a flow-injection analysis system for the direct automatic determination of bitterness and total phenolic compounds in VOO without prior isolation, based on the spectral shift undergone by phenolic compounds upon pH variation. This system enables a complete automation of the process, including dilution of the sample and its sequential injection into buffer solutions of acidic and alkaline pH. The variation of the absorbance at 274 nm showed a high correlation with bitterness and the total phenolic content of VOO, due to the close relationship between these two parameters. Thus, the proposed method determines the bitterness and phenolic compounds, with results similar to those from reference methods (relative errors ranging from 1% to 8% for bitterness and from 2% and 7% for phenolic compounds). The precision evaluated at two levels of both parameters ranged between 0.6% and 1.5% for bitterness and between 0.7% and 2.6% for phenolic compounds.

The Cu-MOF-199/single-walled carbon nanotubes modified electrode for simultaneous determination of hydroquinone and catechol with extended linear ranges and lower detection limits

“…To date, various techniques, including spectrophotometry [3], chromatography [4], mass spectrometry [5], pH-based flow injection analysis [6], fluorescence [7] and electrochemical methods [8][9][10][11][12][13][14], have been applied to the detection of HQ and CT.…”

Simultaneous determination of hydroquinone and catechol at PASA/MWNTs composite film modified glassy carbon electrode

“…Reliable analytical procedures are required for sensitive simultaneous determination in various matrices. So far, a great deal of methods have been established for their determination, including liquid chromatography [1,2], synchronous fluorescence [3], chemiluminescence [4,5], spectrophotometry [6], gas chromatography/mass spectrometry [7], pH based-flow injection analysis [8], electrochemical methods [9][10][11][12][13], etc. However, some of these mentioned methods have the disadvantages of time-consuming, high cost, low sensitivity and complicate pretreatment, electrochemical methods provide an easy and fast way in environmental analysis.…”

Simultaneous Determination of Hydroquinone, Catechol and Resorcinol at Graphene Doped Carbon Ionic Liquid Electrode

“…Therefore, a highly sensitive and selective analytical method is necessary for the simultaneous determination of the three dihydroxybenzene isomers. Up to now, various methods have been exploited for the determination of the dihydroxybenzenes, such as high performance liquid chromatography (HPLC) [3,4], spectrophotometry [5,6] Electrochemiluminescence [7], synchronous fluorescence [8], gas chromatography/mass spectrometry [9], capillary electrochromatography [10], pH-based-flow injection analysis [11], and electrochemical methods [12][13][14][15][16][17][18][19][20][21][22][23]. Among these methods, electrochemical method is of particular interest due to its high sensitivity, low cost, good selectivity, and rapid detection.…”