Evolution of invertase activity in honey from Castanea sativa and Rosmarinus officinalis collected in Granada

The content of alpha-glucoxidase in two varieties of honey covered by the Granada Honey Protected Denomination of Origin Regulatory Board is studied. The evolution of invertase activity was followed for 10 months, in 12 monofloral chestnut honey samples collected in the Alpujarra area of Granada and 9 monofloral rosemary honey samples collected in la Resinera, Valle de Lecrin and in the Sierra de Baza for 10 months. The invertase was measured in the months of June 2005, September 2005, January 2006 and finally in the month of April 2006. We obtained an invertase activity in fresh chestnut honey of 194.6 +/- 3.6 U/kg, with a range between 188.7 U/kg and 199.5 U/kg. After 10 months at ambient temperature, the chestnut honey lost between 28.3% and 39.8% of the initial values of alpha-glucosidase, with an average of 33.4%+/- 3.3%. In the rosemary honey we obtained average invertase values of 69.4 +/- 14.9 U/kg, with a range between 56.9 U/kg and 91.9 U/kg. After 10 months at ambient temperature, the rosemary honey lost between 19.3% and 32.3% of the initial alpha-glucosidase values, with an average of 28.1%+/- 4.4%.