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Study and modelling of enzyme inactivation in the processing of green coconut water and orange juice by ohmic and dielectric heating

Grant number: 16/24265-1
Support type:Scholarships in Brazil - Doctorate (Direct)
Effective date (Start): April 01, 2017
Effective date (End): April 03, 2020
Field of knowledge:Agronomical Sciences - Food Science and Technology
Principal Investigator:Jorge Andrey Wilhelms Gut
Grantee:Eduardo dos Santos Funcia
Home Institution: Escola Politécnica (EP). Universidade de São Paulo (USP). São Paulo , SP, Brazil
Associated research grant:13/07914-8 - FoRC - Food Research Center, AP.CEPID
Associated scholarship(s):17/24163-7 - Inactivation kinetics of enzymes in green coconut water and orange juice by ohmic and conventional heating, BE.EP.DD

Abstract

In the processing of liquid foods, heat treatment is intended for inactivating microorganisms and enzymes that compromise the safety and product quality. Enzymes polyphenoloxidase (PPO) and peroxidase (POD) in green coconut water and pectin methylesterase (PME) in orange juice exhibit high thermal stability and the sensorial quality of fruit based products (color and taste) is sensitive to high temperatures, making it challenging to process these products without the addition of preservatives. The emerging technologies of ohmic heating and heating by focused microwaves are promising for promoting rapid volumetric heating without surface overheating and with a possible non-thermal effect on enzyme inactivation. Thus, the objective of this work is to study the inactivation of PME in orange juice and of PPO and POD in green coconut water to determine the respective kinetics in conventional and microwave heating, seeking identification of non-thermal effects in different processings and products. To study the inactivation kinetics by microwaves, batch tests will be performed in immersion thermal baths and in a chemical synthesis mini-reactor by focused microwaves with fiber optic temperature record. To study the inactivation kinetics by ohmic heating, batch tests will be performed in glass tubes with electric conductive or non-conductive caps immersed in an ohmic treatment cell filled with saline solution with thermocouple temperature record. The enzymatic activity will be evaluated by spectrophotometric methods. Kinetic models for prediction of residual activity will be adjusted and validated based on recorded temperature history using a non-linear optimization method linked to the numerical integration of lethality, thus avoiding the simplifying assumption of constant temperature. Stocastic Monte Carlo methods will allow estimating the uncertainty of the kinetic model parameters and, consequently, the prediction uncertainty. It is expected that this research will allow the elucidation of the non-thermal effects of microwaves and electricity on the inactivation of the enzymes of green coconut and orange juice. (AU)

Scientific publications
(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)
SIGUEMOTO, ERICA SAYURI; PIRES, MARCOS NEVES; FUNCIA, EDUARDO DOS SANTOS; WILHELMS GUT, JORGE ANDREY. Evaluation and modeling of a microwave-assisted unit for continuous flow pasteurization of liquid foods: Residence time distribution, time-temperature history, and integrated lethality. JOURNAL OF FOOD PROCESS ENGINEERING, v. 41, n. 8 DEC 2018. Web of Science Citations: 1.
SIGUEMOTO, ERICA SAYURI; FUNCIA, EDUARDO DOS SANTOS; PIRES, MARCOS NEVES; WILHELMS GUT, JORGE ANDREY. Modeling of time-temperature history and enzymatic inactivation of cloudy apple juice in continuous flow microwave assisted pasteurization. FOOD AND BIOPRODUCTS PROCESSING, v. 111, p. 45-53, SEP 2018. Web of Science Citations: 2.

Please report errors in scientific publications list by writing to: cdi@fapesp.br.