CHEMICAL COMPOSITIONS AND NON-ENZYMATIC BROWNING COMPOUNDS OF THAI HONEY: A KINETIC STUDY

Chemical composition (reducing sugar and amino acid contents and hydroxymethylfurfural [HMF] level) and physicochemical properties (water, color and pH) were determined in floral Thai honeys (seven samples): longan (Euphoria longana L.), Siam weed (Eupotorium odortum L.) and multifloral varieties. The kinetics of the Maillard reaction occurring in honey was also investigated by monitoring the quantity of reactants (sugars and amino acids) and product (HMF) at high temperature (25-85C) in short time periods (0-14 days) under different storage conditions (light and dark). The results revealed that temperature and storage time strongly affected the Maillard reaction, more than light conditions. The first order rate constant (k), activation energy (Ea) and frequency factor (A) for amino acid degradation were deduced from the data, supporting a first order reaction with activation energy of 78.3-79.1 kJ/mol and frequency factor of 4.83 x 10(10)-5.90 x 10(10) day(-1). HMF formation exhibited zero order kinetics with activation energy of 135.4-139.6 kJ/mol and frequency factor of 3.47 x 10(22)-17.17 x 10(22) g% day(-1).