Impact of Microwave Assisted Infusion on the Quality and Volatile Composition of Olive Oil Aromatized with Rosemary Leaves.

Olive oil with rosemary leaves by microwave assisted infusion (MAI) as an alternative to conventional infusion (CI) was evaluated. Microwave heating was applied to the mixture in order to accelerate diffusion of the rosemary volatile compounds into the olive oil. The volatile components of the aromatized oils were quantified by HS-SPME/GC-MS, as well as several quality indexes such as free fatty acids (FFA), peroxide value (PV), specific coefficients of extinction, chlorophyll and carotenoid content, and color assessment. Fatty acid profiles of the oils aromatized by MAI were compared to those produced by CI. Results showed that the infusion time is reduced from 12 h to 10 min when utilizing MAI in place of CI. MAI treatment caused a slight increase in FFA levels, and specific extinction coefficient indices (K (232) and K (270)). PV during MAI remained unchanged for the first 3 min, after which there was an observable increase. All physico-chemical values were found to be well below the maximum permitted limits. The MAI treatment reduced chlorophyll and carotenoid levels during the final step of aromatization, thus affecting final color. The MAI aromatized oil was characterized by its clear green color (L*, a*, b* parameters). Fatty acid analysis showed that MAI slightly changed the fatty acid composition of the olive oil. This study indicates that MAI appears to be a viable and rapid method to flavor olive oil with rosemary leaves.