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Chemometrics and Intelligent Laboratory Systems

1 SFVI KR    lournul homepage: www .elsevief .com/locate.chemol8b

A rapid validation of the antioxidant capacity of food commodities based on their fluorescence excitation emission spectra as applicable to coffee and peppermint extracts

Joanna Orzeł, Michał Daszykowski ¹

Imtuuir of Chemazry. The Urómfry of Silnia. 9 Szkolno Szreń. 40-406 Katowice Połond

ARTICIE I N F O

ABSTRACT

Anicie huzory.

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A nowel and rapid apprtuch to scieening anlioxidanr content i¹ proposrd lis usefulness is illusirated for coffee and peppermint extrjcti. The antioiidani prcpertirs ofeartracij were prrdicied from their eicitarion-emission fluorescence mairices using the partlal least squares and the N-wzy parna) least squares regresslon. The total amioKidam capaclry and the total phenolic content were esiimated using oxygen radical absorhance capacity (ORAĆ) and Folin-Ciocalteau assays. respecrively. Predlction errors of calibration models desctibing the total antmKidant ronieni evatuaied using the ORAĆ assay were equal to 448J3 (6.29¹) and 647.74 (9 041) of the Trotox equivalents for coflee and peppermint extTacts. respertiveły. The predirtion error of the toul phenolic content for coffee extracts was aboul 0270 (7j02%) expressed as gallic and equlvalents. The limits ofdetection were below 05.43 of the Trolox equivaleno and 0 038 of the gallic acid equivalents. and the relatiwe standard deviarion was in a rangę of between 1.61S and 7.131

C 2014 EJsevier B.V. Ali righrs reserved.

1. Introduction

A lifestyle rhat ensures a long and healthy life requires introducing into ones diet food commodities that contain vital components neces-sary to maintain our body in good health (vitamins, omega 3 fatty acids. microelements. etc.). Potentially. these can help to reduce the chance of developing diseases (such as Alzheimers, cancer and athero-sderosis) or inhibit the aging process. Due to their abiliry to deacóvate free radicaJs. anrioxidants are claimed to be one of the most important vital food components. The antioxidant properties of food products as well as their content of Chemical compounds that are recognized as antioxidants vary considerably 111. The total amount of antioxidants contained in a sample. which has the ability to scavenge free radicals, is described by the total antioxidant capacity (TAC) parameter. It is eval-uated using antioxidant capacity assays |2|. The assays that have been developcd to datę are based on the Chemical rcaction between antioxi-dants and artificially generated free radicals. The reaction is monitored using an instrumental technique. for instance, specrrophotometry. fluorimetry or election paramagnetic resnnance spectToscopy. Another approach that is used to estimate the TAC parameter aims to evaluate the antioxidant content in samples by the quantification nf some known antioxidants (e g., using chromatographic methods). in this case. the TAC value is expressed as the sum of quantified antioxidant compounds (3). however. the result cannot be compared with the TAC value of active anrioxidants that are obtained from the chemical-based assays. Moreover. often concenrrations of certain antioxidants do not resembie rheir rrue TAC These phenomena can be expłained by a possi-ble synergic effect and/or redox interacóons between Chemical components 12). The evatuation of the TAC for different food commodities has become quite popular these days. Standard assays. which are based on a Chemical reaction. e.g.. theTrok>x equivalent antioxidant capacity assay (7EAC) |4|. the DPPH assay [2J2-diphenyi-1-picryihydrazyl| |5). the fer-ric reducing ability of plasma (FRAP) |6) or the oxygen radical anttoxi-dant capacity assay (ORAĆ) [7| are frequentły used for the eva!uation of the TAC of vegetables [ 1). froits (8). alcohoł free beverages (e.g^ cofTee [9)) and alcoholic beverages that is beers and wines (10.11J. Although all of the methods that have been developed to estimate the TAC va!ue are routinely applied. they are time or reagent consuming. A routine and rapid analysis with available assays that is applicable, e.£, during the production process or monitoring the TAC of food products is difhcult to perform in an on-line setting

On the other hand, many antioxidant compounds exhibit fluorescent properties and thus they can be screened using a fast. sensiove and non-destructive analytical technique - fluorescence spectroscopy. To datę. fluorescence spectroscopy has been successfully applied for screening the properties of various products (e.g.. riboflavin in dairy products 112)) °^r some gJobal properties induding the shelf life of yoghurt or beer |13.14). The aniioxidams that are contained in a complex food sample have different spectral characterisrics (i.e. characterisric excita-tion and emission wavelengths). The basie emission spectrum that is collected for a single excitation wavelength is insufficient to describe

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