Thermal and High-Pressure Stability of Pectin-Converting Enzymes in Broccoli and Carrot Purée: Towards the Creation of Specific Endogenous Enzyme Populations Through Processing

Abstract

The thermal and pressure stability of broccoli and carrot pectin-converting enzymes, in particular pectinmethylesterase (PME), β-galactosidase (β-Gal), and α-arabinofuranosidase (α-Af), were investigated in vegetable puree matrices. In situ enzyme inactivation by thermal and high-pressure processing (respectively 5 min at 25–80 °C at 0.1 MPa and 10 min at 0.1–800 MPa at 20 °C) was evaluated by measuring the residual enzyme activity in crude extracts of treated carrot, broccoli floret, and broccoli stem puree samples. PME was completely inactivated in all vegetable puree matrices after a 5-min treatment at 80 °C. After a treatment at 800 MPa (20 °C, 10 min) only 77–90 % of pressure stable PME was inactivated, depending on the matrix. β-Gal and α-Af enzymes were inactivated in the vegetable puree matrices by thermal treatments respectively at 67.5–72.5 and 80 °C. These enzymes showed some pressure resistance: treatments respectively at 600–700 and 600–750 MPa were necessary for one log-reduction of β-Gal and α-Af activity in the different purees at 20 °C. Under the assumption of a first-order inactivation model, inactivation rate constants and their temperature or pressure dependency were determined for the different enzymes. Based on differences in process stability of the enzymes in the individual puree matrices, the feasibility for the creation of specific endogenous enzyme populations by selective processing was evaluated.