Comparison of conventional and ultrasound-assisted aqueous extraction of soluble matter and phenolic compounds from apple flesh

The extraction of soluble matter (°Brix), catechin and total phenolic compounds (TPC) from apple flesh was studied. A conventional aqueous extraction (CE) was done at different temperatures (50, 60, and 75 °C). A pulsed ultrasound-assisted extraction (UAE) was done at fixed temperature, T = 50 °C, and different specific energy input and total duration. The main attention was focused on correlations between oBrix, concentration of catechin, C, TPC, and selectivity of phenolics extraction. For UAE, the significant acceleration in extraction of catechin was observed for the short duration protocol as compared with long duration one. The maximum (saturation) levels for concentrations of catechin, Cm, and total phenolic compounds, TPCm, were compared. In correlation between Cm and TPCm, the two distinctive branches were observed for CE protocols and UAE protocols. Moreover, the relative contents of catechin in TPC were noticeably higher for UAE protocols as compared with CE protocols.