THERMAL INACTIVATION of PECTINESTERASE IN PAPAYA PULP (pH 3.8)

Abstract

In order to establish the thermal process required by acified papaya pulp (pH 3.8) var “formosa”, a study was carried out on the kinetics of thermal inactivation of the heat resistant enzymes present in the pulp. Since no peroxidase activity was detected, the study was focused on pectinesterase. The heat inactivation curves at 75, 77 and 80C showed a change in slope indicating the presence of two different portions of the enzyme, one heat labile and the other heat resistant. the decimal reduction times (D value) of pectinesterase were 0.8, 0.3 and 0.2 min for the heat labile portion and for the heat resistant portion 16.7, 7.2 and 3.7 min, respectively. The temperature‐dependency factor for the heat labile portion was 9.2C and 7.8C for the thermostable portion, while the activation energies were 258.3 and 304.4 Kj/mol. These values were within the range of 167.5–418.7 Kj/mol reported in the literature for the thermal inactivation of enzymes. Thermal destruction studies with Clostridium pasteurianum, conducted at the same temperatures used for the inactivation of the enzyme, showed that the heat resistant portion of pectinesterase presented greater thermal resistance and should be used as target for the establishment of the required process.

Development of an optimised papaya pulp nectar using a combination of irradiation and mild heat

“…Heat treatment temperature and time were chosen based on the work of Magalhães, Tosello, and de Massaguer (1996). Our results were within the ranges of residual pectin methylesterase activities found by Castaldo et al (1997) in thermally processed fruit preparations.…”

“…Some of the stable form of PE may have only been partially denatured and may have regained activity over time (Magalhães et al, 1996). A follow-up PE assay was performed after consistometry measurements were completed.…”

Thermal inactivation of exogenous pectin methylesterase in apple and cloudberry juices

“…In order to prevent the detrimental, post-processing effects of the enzyme, the residual PME is inactivated by thermal treatment (Eagerman & Rouse, 1976). The knowledge of its thermal stability is also important for that reason that PME inactivation is used to the estimation of an index of sterilization adequacy (Magalhães, Tosello, & Massaguer, 1996;Nath & Ranganna, 1977;Valdramidis et al, 2007).…”

Variable Retort Temperature Profiles for Canned Papaya Puree

“…For designing the profiles of papaya puree (pH 3.8), the pectin methyl esterase (PME, EC 3.1.1.11) was used as the target enzyme, using the thermal resistance values ( D 77C = 7.2 min, z = 7.8C) reported for papaya puree at pH = 3.8 (Magalhães et al . ). At a constant lethal temperature, the heating time for enzyme inactivation is where D is the decimal reduction time, a 0 is the initial activity and a is the final activity.…”