Thermal and high-pressure stability of purified polygalacturonase and pectinmethylesterase from four different tomato processing varieties

Polygalacturonase (PG) and pectinmethylesterase (PME) were extracted and purified from four tomato varieties (Galeon, Malpica, Perfectpeel and Soto) used in the processing industry. The processing stability (thermal and high pressure) of PG and PME from the four varieties was analyzed, and they all showed the same behavior. PG was present in two isoforms, PG1 (inactivated at 90 degrees C, 5 min) and PG2 (inactivated at 65 degrees C, 5 min). In contrast, PG1s and PG2s showed the same pressure stability, both can be inactivated at room temperature in the pressure range of 300-500 MPa. On the other hand, purified PMEs could be thermally inactivated (5 min, 70 degrees C) but 50% of its activity remained after high-pressure treatment (850 MPa., 15 min, 25 degrees C). High pressure processing can thus be used for selective inactivation of PG in tomato processing (while keeping PME intact). This fact could open prospectives; for improving texture/rheology of processed tomato based products; however further research in the texture/rheology area is needed. (C) 2005 Elsevier Ltd. All rights reserved.