U.S. flag

An official website of the United States government

Dot gov

Official websites use .gov
A .gov website belongs to an official government organization in the United States.


Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.


Main content area

Use of response surface methodology to study the combined effects of UV-C and thermal processing on vegetable oxidative enzymes

Fernando Sampedro, John Phillips, Xuetong Fan
Lebensmittel-Wissenschaft + Technologie 2014 v.55 no.1 pp. 189-196
enzyme inactivation, temperature, acidity, vegetables, ultraviolet radiation, absorbance, catechol oxidase, equations, exposure duration, linoleate 13S-lipoxygenase, models, response surface methodology, pH, wavelengths, synergism, enzyme activity, fruit juices, peroxidase, prediction
The combined thermal (25–65 °C) and ultraviolet processing (UV-C) effects on lipoxygenase (LOX), peroxidase (POD) and polyphenoloxidase (PPO) at different pH values (4.0–7.0) were studied using a central composite design. An initial screening design revealed that all factors had a significant effect on enzymatic activity except wavelength which showed a negligible effect. A synergistic effect was found between temperature and UV exposure time for POD and PPO and between pH and exposure time for LOX. LOX enzyme was affected by acidic conditions. POD was UV-C labile whereas PPO was the most UV-C resistant enzyme but was thermolabile. Second-order polynomial equations indicated that enzyme activities were inactivated after exposure to 58.2 mJ/cm2 UV at 60 °C or higher temperatures at any pH condition. Combination of UV and thermal processing allowed the use of low energy/doses to obtain complete enzymatic inactivation. This study may serve as a basis to design UV-C processes for the inactivation of enzymes in liquid matrices.