This work aimed to investigate the effect of freezing on the oleuropein content obtained from olive leaves extracts. The extracts were obtained by microwave-assisted extraction using different solvents, pH, temperatures and microwave irradiation time. Afterward, HPLC was used to identify and quantify the amount of oleuropein in the extracts. A part of the extracts was immediately analyzed, and another was frozen for a week. The experimental results highlighted that the storage condition has a significant (p < 0.05) effect on the oleuropein content. Regardless of the extraction condition, the frozen storage was responsible for a decrease in the oleuropein content, ranging from 5.38 to 70.09%. These results indicate that it is important to consider the degradation of oleuropein in frozen olive leaf extracts so that subsequent applications are suitable.
Freezing effect on the oleuropein content of olive leaves extracts obtained from microwave-assisted extraction