Measurement of polyphenol oxidase activity using optical waveguide lightmode spectroscopy-based immunosensor

Polyphenol oxidase (PPO) is an important quality index during food processing involving heat-treatment and sensitive determination of PPO activity has been a critical concern in the food industry. In this study, a new measurement of PPO activity exploiting an optical waveguide lightmode spectroscopy-based immunosensor is presented using a polyclonal anti-PPO antibody that was immobilized in situ to the surface of a 3-aminopropyltriethoxysilane-treated optical grating coupler activated with glutaraldehyde. When analysed with a purified PPO fraction from potato tubers, a linear relationship was found between PPO activities of 0.0005607–560.7 U/mL and the sensor responses obtained. The sensor was applicable to measurement of PPO activity in real samples that were prepared from potato tubers, grapes and Kimchi cabbage, and the analytical results were compared with those obtained by a conventional colorimetric assay measuring PPO activity. When tested for long-term stability, the sensor was reusable up to 10th day after preparation.