A comparison between Helianthus annuus and Eucalyptus lanceolatus honey

A comparison between physico-chemical, enzymatic activities and rheological properties of Helianthus annuus and Eucalyptus lanceolatus honey was made. Eucalyptus lanceolatus honey showed higher protein, diastase and catalase activity than Helianthus annuus honey, while proline, conductivity, total acidity, free acids and lactone content were higher in Helianthus annuus honey. Consistency coefficient and activation energy for Wow were lower for Helianthus annuus than Eucalyptus lanceolatus honey. Confirmation of monofloral origin of honey types was accomplished through microscopic examination. The effects of convective and microwave heating on hydroxymethylfurfural (HMF) formation in both honey types were also investigated. Total acidity, free acids and lactone content increased in both honey types during heating. HMF formation varied linearly with temperature and time of heating in both honey types. Microwave heating of both honey types also caused an increase in HMF formation. Effect of storage of honey, heated under different conditions, on HMF content was also investigated. Statistical analysis revealed that storage duration had the greatest effect on HMF formation, followed by heating duration and heating temperature, in Helianthus annuus honey, while heating duration showed the most pronounced effect, followed by heating temperature and duration, in Eucalyptus lanceolatus honey. (C) 1999 Elsevier Science Ltd. All rights reserved.