Water Determination in Bee Products Using the Karl Fischer Titration Method
Journal of Apicultural Science, Vol.53 No.2, 2009
One of the most widely used techniques for water content determination in food is Karl Fischer (KF) titration. Compared to other methods based on loss of weight, the primary advantage of the Karl Fischer titration method is its high selectivity to water. The aim of the study was to develop and validate the Karl Fischer method for moisture determination in pollen loads, royal jelly, bee venom and propolis. The effects of sample weight and mixing/homogenization time were investigated. A study of the main validation parameters (repeatability and reproducibility) of the elaborated methods for the studied bee products was also conducted.
Optimal parameters (sample weight and minimal mixing/homogenization time) for water determination in bee products using the Karl Fischer method were established as follows: sample weight: 0.10 - 0.20 g and time of sample homogenization: 120 s for bee-collected pollen, 0.05 - 0.10 g and 120 s for bee venom, 0.02 - 0.05 g and 180s for royal jelly and 0.20g and 300s for propolis, respectively. The coefficient of variation of the results received for series determinations of water content in each studied bee product with the exception of propolis, conducted at repeatability and reproducibility conditions did not exceed 10%.
Mean values for water content of the bee products were as follow: 6.99% for bee venom, 18.34% for fresh and 6.25% for dried bee-collected pollen, 62.56% for royal jelly and 2.30% for propolis. These results will be used to establish water requirements and will be introduced into the International Honey Commission (IHC) standards.