Apple pomace liquefaction with pectinases and cellulases:analytical data of the corresponding juices

Apple juices were produced by way of a two-stage process consisting of traditional enzyme treatment of the mash with pectinases for the premium juices and pomace liquefaction with different pectinases and cellulases for the extraction juices. Premium and extraction juices were analysed separately. Calculated to an equal juice strength of 12° Brix, there was an increase of D-galacturonic acid and cellubiose in the extraction juices. Released galacturonic acid from cell wall material was found at levels ranging from 107 mg/l to 1239 mg/l. This was an essential contribution to the total titrable acid of the extraction juices. The sum of phenolic substances determined by high performance liquid chromatography was significantly higher in all the extraction juices than in the corresponding premium juices. Among the phenolics, the dihydrochalcone phloretin 2′-glucoside (92–110 mg/l) showed an increase of 4 to 5 times the concentration in the respective premium juices. Quercetin derivatives were mainly present in the extraction juices; here the values were between 32 mg/l and 38 mg/l. Under the influence of strong pectolytic or cellulolytic enzyme activities, oligo- and polysaccharides are released from the apple cell wall material, resulting in colloid concentrations of up to 15 g/l in the extraction juices. High concentrations of polyphenols and pectic polysaccharides can lead to technological problems. However, pomace liquefaction may also turn out to be suitable for obtaining value-added foods. In respect to nutritional aspects, enzymatic treatment of pomace offers the opportunity of releasing apple polyphenols and polysaccharides contained in the pomace to a greater extent and obtaining them preparatively. Received: 2 December 1999