Moreover, honey contains certain minor constituents like minerals, and other saccharides, proteins, enzymes, amino acids, vitamins, organic and phenolic acids, flavonoids, carotenoids,
volatile substances and products of the Maillard reaction. During processing, honey is usually warmed in order to lower its viscosity, and to prevent crystallisation or fermentation. Temperatures of 32–40 °C do not affect honey quality; however, the use of higher temperatures leads to the formation of an important degradation product, 5-hydroxymethylfurfural (or 5-(hydroxymethyl)furan-2-carbaldehyde, 5-HMF) (Anklam, 1998 and Turhan et al., 2008). 5-HMF is a furanic compound which is formed as an intermediate in the Maillard GSK126 chemical structure reaction (Ames, 1992) from the direct dehydration of sugars under acidic conditions (caramelisation) during thermal treatments applied to foods (Kroh, 1994). Under acidic conditions, 5-HMF can be formed even at low temperatures (Lee & Nagy, 1990), although its concentration significantly increases with an increase in the temperature of thermal treatments, or during long periods of storage. In addition to temperature, the amount of 5-HMF formation in foods is dependent on the type of sugar (Lee & Nagy, 1990), pH (Gökmen, Açar, Köksel, & Açar,
2007), water activity (Gökmen et al., 2008 and Kroh, 1994) and the concentration of divalent cations of the media (Gökmen & Senyuva, 2006). The Codex Alimentarius of the World Health Organisation Venetoclax datasheet and the European Union have established a maximum quality
level for the 5-HMF content in honey (40 mg kg−1) (Alinorm 01/25, 2001 and Directive 2001/110/EC, 2001). The Brazilian regulations set a maximum 5-HMF content of 60 mg/kg (Brasil, 2000). However, the toxicological Lck relevance of 5-HMF has not been clearly demonstrated. Cytotoxic, mutagenic, carcinogenic and genotoxic effects are among the in vitro activities attributed to HMF ( Murkovic and Pichler, 2006 and Teixidó et al., 2006). The determination of 5-HMF in foods has been traditionally performed by the spectrophotometric method described by White (1979). Several other methods have been developed, employing high performance liquid chromatography (HPLC) with UV detection (Aquino et al., 2006, Gaspar and Lucena, 2009, Michail et al., 2007, Pereira et al., 2011, Spano et al., 2009, Xu et al., 2003 and Zappalá et al., 2005). In addition, liquid chromatography with pulsed amperometric detection (Xu et al., 2003), refractive index detection (Xu et al., 2003) or coupled to mass spectrometry (LC–MS) (Gökmen and Senyuva, 2006 and Teixidó et al., 2008) has been used to analyse 5-HMF in several foodstuffs. Recently, techniques of gas chromatography coupled to mass spectrometry (CG–MS) (Teixidó et al., 2006), and electrochemical biosensors (Lomillo, Campo, & Pascual, 2006) has been proposed for the analysis of 5-HMF in honey, baby foods, jam, orange juice and bakery products, among substances.