Submitted to: LWT - Food Science and Technology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/13/2013
Publication Date: 1/10/2014
Publication URL: http://handle.nal.usda.gov/10113/58042
Citation: Sampedro, F., Phillips, J.G., Fan, X. 2013. Use of response surface methodology to study the combined effects of UV-C and thermal process on vegetable oxidative enzymes. LWT - Food Science and Technology. 55:189-196. Interpretive Summary: Eliminating the function of certain enzymes is essential to avoid detrimental changes in food quality when developing a new processing technology or treatment for the preservation of fruit and vegetable-based food products. Ultraviolet C (UV-C) is considered as an emerging technology for food processing. The effect of various UV-C processing parameters on three enzymes involving in oxidation was studied. Results show that each enzyme has different responses to the changes in temperature, UV-C dose and pH, and the responses can be predicted by mathematic models. The information will help food industry in applying and validating UV technology to enhance microbial safety and preserve liquid foods.
Technical Abstract: The effects of ultraviolet processing (UV-C) (temperature, exposure time, and wavelength) and an environmental parameter (pH) were studied on three oxidative enzymes, namely, lipoxygenase (LOX), peroxidase (POD) and polyphenoloxidase (PPO) by using a central composite design. An initial screening design revealed all factors had a significant effect on enzymatic activity except wavelength which showed a negligible effect. Second-order polynomial equations successfully fitted the experimental data with prediction errors of 7.0, 8.0 and 18% for LOX, POD and PPO, respectively. A synergistic effect was found between temperature and 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. Predictive models developed using second-order polynomial equations indicated that enzyme activities were reduced after an exposure time of 10 min at 60°C or higher temperatures at any pH condition. UV doses used in this study were lower than those applied by other authors to obtain complete enzymatic inactivation in fruit juices. There is a need for validation of the processing conditions used in this study in high absorbance liquid food matrices.