OPTIMIZATION OF SEQUENTIAL ULTRASOUND-ASSISTED EXTRACTION – HEATING TREATMENT TO OBTAIN PECTIN FROM MALUS DOMESTICA ‘FĂLTICENI’ POMACE

Abstract

In this study, a sequential ultrasound-assisted extraction – heating treatment (UAEH) was applied for pectin extraction from Malus domestica ‘Fălticeni’ pomace. The extraction procedure involved a sonication at 20 kHz and 100% amplitude for 30 min (solid-to liquid ratio of the apple pomace-water mixture of 1:10, pH of 1.8), followed by a heating treatment at different temperatures (70, 80 or 90 °C) and time (60, 120 or 180 min). It was observed that with the increase of temperature and time, pectin yield and the degree of esterification increased. At the same time, the increase of temperature determined a decrease of the galacturonic acid content of the extracted pectin. A Box-Behnken response surface design was used to optimize the effects of process variables on the pectin yield and physico-chemical properties. The optimum conditions to obtain a maximum yield of 6.85%, with a 69.694 g/100 g galacturonic acid content and 80.09% degree of esterification of the extracted pectin were the temperature of 85.71 ºC and 147 min heating time.