title: Impact of pH and Total Soluble Solids on Enzyme Inactivation Kinetics during High Pressure Processing of Mango (Mangifera indica) Pulp.
abstract: This study was undertaken with an aim to enhance the enzyme inactivation during high pressure processing (HPP) with pH and total soluble solids (TSS) as additional hurdles. Impact of mango pulp pH (3.5, 4.0, 4.5) and TSS (15, 20, 25 °Brix) variations on the inactivation of pectin methylesterase (PME), polyphenol oxidase (PPO), and peroxidase (POD) enzymes were studied during HPP at 400 to 600 MPa pressure (P), 40 to 70 °C temperature (T), and 6- to 20-min pressure-hold time (t). The enzyme inactivation (%) was modeled using second order polynomial equations with a good fit that revealed that all the enzymes were significantly affected by HPP. Response surface and contour models predicted the kinetic behavior of mango pulp enzymes adequately as indicated by the small error between predicted and experimental data. The predicted kinetics indicated that for a fixed P and T, higher pulse pressure effect and increased isobaric inactivation rates were possible at lower levels of pH and TSS. In contrast, at a fixed pH or TSS level, an increase in P or T led to enhanced inactivation rates, irrespective of the type of enzyme. PPO and POD were found to have similar barosensitivity, whereas PME was found to be most resistant to HPP. Furthermore, simultaneous variation in pH and TSS levels of mango pulp resulted in higher enzyme inactivation at lower pH and TSS during HPP, where the effect of pH was found to be predominant than TSS within the experimental domain.
  
  
  CONCLUSIONS
  Exploration of additional hurdles such as pH, TSS, and temperature for enzyme inactivation during high pressure processing of fruits is useful from industrial point of view, as these parameters play key role in preservation process design.
authors.affiliation: Agricultural and Food Engineering Dept, Indian Inst. of Technology, Kharagpur, P.O. Box 721302, West Bengal, India.
authors.forename: Neelima
authors.initials: N
authors.lastname: Kaushik
authors.affiliation: Agricultural and Food Engineering Dept, Indian Inst. of Technology, Kharagpur, P.O. Box 721302, West Bengal, India.
authors.forename: Tejaswi
authors.initials: T
authors.lastname: Nadella
authors.affiliation: Agricultural and Food Engineering Dept, Indian Inst. of Technology, Kharagpur, P.O. Box 721302, West Bengal, India.
authors.forename: P Srinivasa
authors.initials: PS
authors.lastname: Rao
mesh_terms: D002265:Carboxylic Ester Hydrolases / Q000737:chemistry*; D004156:Catechol Oxidase / Q000737:chemistry*; D005511:Food Handling / Q000379:methods*; D005638:Fruit / Q000201:enzymology*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D031022:Mangifera / Q000201:enzymology*; D009195:Peroxidase / Q000737:chemistry*; D011312:Pressure; D012995:Solubility; D013696:Temperature
chemical_list: D004156:Catechol Oxidase; D009195:Peroxidase; D002265:Carboxylic Ester Hydrolases; C022323:pectinesterase
keywords: inactivation rate constant; pectin methylesterase; peroxidase; polyphenol oxidase; response surface methodology