Changes of gallic acid mediated by ultrasound in a model extraction solution.

Ultrasound has been widely used as a new kind of auxiliary extraction technique in food industry, but its effect cannot be ignored on the potential degradation of the extracted target compound. In this paper, a model extraction solution was constructed with the standard gallic acid as target compound to be extracted, and its change was monitored by using high performance liquid chromatography (HPLC) under different ultrasonic extraction conditions, namely, solvent types, extractant concentrations, extraction time, extraction temperature, ultrasound power and frequency, in order to understand the effect of ultrasound on the extract during ultrasonic extraction and provide an objective evaluation of ultrasonic extraction of polyphenols. The results indicate that ultrasonic parameters had definite effect on the degradation of gallic acid during ultrasonic extraction, which implies that the extraction yield should not be over-focused in actual extraction applications of ultrasound, more attention should be paid to the potential degradation of the extracted target compound induced by ultrasound.