Partial purification and characterization of the quality deteriorating enzymes from Indian pink guava (Psidium guajava L.), var. Lalit.

Peroxidase (POD), polyphenol oxidase (PPO), ascorbate oxidase (AO) and pectin methylesterase (PME) from 'Lalit' guava variety have been purified using BioGel P-100 and UNOsphere Q resins. POD, PPO, AO, and PME were partially purified to 28, 30, 36 and 30 fold; single band on SDS-PAGE represented a molecular weight of 21, 70, 75, 50 kDa, respectively. Optimum pH for POD and AO was 6.5 whereas, PPO and PME showed optimum pH in the alkaline range of pH 8.0 and 8.5, respectively. AO showed optimum activity at 25 °C, POD and PPO showed optimum activity at 35 °C; however, PME showed maximum activity at 55 °C. AO was the most heat labile whereas, PME was the most heat stable enzyme studied and may carry an important role in the thermal processing of guava pulp as an indicator of the efficacy of treatment.