Chemical changes in the non-volatile fraction of Brazilian honeys during storage under tropical conditions

The chemical transformations of the non-volatile fraction of Brazilian honeys during storage in tropical condition were monitored. Five systems, namely: 1 – fresh samples; 2 and 3 – samples heated for 3 and 6 months at 35–40 °C; 4 and 5 – samples left under similar conditions to systems 2 and 3, but containing sodium metabisulphite (120 ppm), were tested. The major transformations during storage occurred in the free and lactone acidity, diastase activity and 5-hydroxymethylfurfural (5-HMF) content. Storage modified diastase activity and the content of 5-HMF to an extent that the samples could not remain classified as fresh honey. The action of sodium metabisulphite in the control of the 5-HMF formation seemed to be dependent on other honey characteristics, such as its botanical origin. Sodium metabisulphite also influenced the development of the internal esterification reaction that converts gluconic acid into its corresponding lactone.