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Advisor(s)
Abstract(s)
O mel é um fonte importante de micro- e macro-nutrientes e, contém cerca de 80 a 95 %
de açúcar, geralmente com predominância da frutose e glucose. Desta forma, o mel tornou-se
um alimento consumido em larga escala em todo o mundo, existindo um crescente interesse em
garantir a sua qualidade. Uma parte desse processo consiste em aferir o teor de 5-
hidroximetilfurfural (HMF) na sua composição.
O HMF é um aldeído cíclico produzido a partir da degradação de açúcares através da
reação de Maillard. A concentração de HMF é um importante indicador da qualidade e frescura
do mel, uma vez que este composto está presente em quantidades vestigiais no mel fresco.
Devido aos efeitos tóxicos do HMF, encontra-se legislado na União Europeia que o mel pode
conter, no máximo, 40 mg/kg de HMF ou 80 mg/kg no caso de ser de origem declarada de
regiões de clima tropical. A técnica mais utilizada para determinação do HMF no mel tem sido
a cromatografia líquida de alta eficiência (HPLC), no entanto devido à necessidade de métodos
mais simples, baratos e rápidos a determinação eletroquímica baseada em polímeros
molecularmente impressos (MIP) tem-se mostrado uma alternativa cada vez mais interessante.
Assim, neste trabalho foi desenvolvido um sensor eletroquímico com base em MIP para a
análise seletiva do HMF, usando elétrodos de carbono em papel.
O sensor MIP foi desenvolvido por eletropolimerização de uma solução contendo ácido
4-aminobenzóico (monómero funcional) e HMF (molécula molde), por voltametria cíclica.
Foram otimizadas as condições de polimerização e caracterizou-se o sensor obtido. O sensor
mostrou uma resposta linear num intervalo de concentrações de 0,005 a 1,0 mmol/L com um
limite de deteção (LOD) e um limite de quantificação (LOQ) de 0,09 e 0,30 mmol/L,
respetivamente
Por fim, analisaram-se amostras de diferentes méis e compararam-se os resultados do
sensor MIP com aqueles obtidos por HPLC, o que demonstrou uma boa semelhança. Validando
assim a eficácia do MIP construído e o seu potencial para ser utilizado como uma alternativa
para a análise de HMF.
Honey is an important source of micro- and macro-nutrients and contains around 80 to 95 % of sugar, usually with a predominance of fructose and glucose. Honey has therefore become a widely consumed food all over the world and there is a growing interest in guaranteeing its quality. Part of this process involves determining the content of 5-hydroxymethylfurfural (HMF) in honey. HMF is a cyclic aldehyde produced from the degradation of sugars through the Maillard reaction. The concentration of HMF is an important indicator of the quality and freshness of honey since this compound is present in trace amounts in fresh honey. Due to the toxic effects of HMF, it is legislated in the European Union that honey may contain a maximum of 40 mg/kg of HMF or 80 mg/kg if it is of declared origin from regions with a tropical climate. The most widely used technique for determining HMF in honey has been high performance liquid chromatography (HPLC). However, due to the need for simpler, cheaper, and faster methods, electrochemical determination associated with molecularly imprinted polymers (MIP) has become increasingly popular. In this study, a paper electrode MIP-based electrochemical sensor was developed for the selective analysis of HMF. The MIP sensor was developed by electropolymerizing a solution containing 4- aminobenzoic acid (functional monomer) and HMF (template) by cyclic voltammetry. The polymerisation conditions were optimised, and the sensor obtained was characterised. The sensor showed a linear response over a concentration range of 0.005 to 1.0 mmol/L with a limit of detection (LOD) and limit of quantification (LOQ) of 0.09 and 0.30 mmol/L, respectively. Finally, several honey samples were analysed, and the results of the MIP sensor were compared with those obtained by HPLC, which showed a good similarity. This validated the effectiveness of the MIP sensor and its potential to be used as an alternative for HMF analysis.
Honey is an important source of micro- and macro-nutrients and contains around 80 to 95 % of sugar, usually with a predominance of fructose and glucose. Honey has therefore become a widely consumed food all over the world and there is a growing interest in guaranteeing its quality. Part of this process involves determining the content of 5-hydroxymethylfurfural (HMF) in honey. HMF is a cyclic aldehyde produced from the degradation of sugars through the Maillard reaction. The concentration of HMF is an important indicator of the quality and freshness of honey since this compound is present in trace amounts in fresh honey. Due to the toxic effects of HMF, it is legislated in the European Union that honey may contain a maximum of 40 mg/kg of HMF or 80 mg/kg if it is of declared origin from regions with a tropical climate. The most widely used technique for determining HMF in honey has been high performance liquid chromatography (HPLC). However, due to the need for simpler, cheaper, and faster methods, electrochemical determination associated with molecularly imprinted polymers (MIP) has become increasingly popular. In this study, a paper electrode MIP-based electrochemical sensor was developed for the selective analysis of HMF. The MIP sensor was developed by electropolymerizing a solution containing 4- aminobenzoic acid (functional monomer) and HMF (template) by cyclic voltammetry. The polymerisation conditions were optimised, and the sensor obtained was characterised. The sensor showed a linear response over a concentration range of 0.005 to 1.0 mmol/L with a limit of detection (LOD) and limit of quantification (LOQ) of 0.09 and 0.30 mmol/L, respectively. Finally, several honey samples were analysed, and the results of the MIP sensor were compared with those obtained by HPLC, which showed a good similarity. This validated the effectiveness of the MIP sensor and its potential to be used as an alternative for HMF analysis.
Description
Keywords
Honey HMF electrochemical sensor MIP paper electrodes