Mapping the Antioxidant Activity of Apple Peels with Soft Probe Scanning Electrochemical Microscopy

Abstract

We present a non-invasive electrochemical strategy for mapping the antioxidant (AO) activity of apple peels, which counterbalances oxidative stress caused by various external effectors. Soft carbon microelectrodes were used for soft probe scanning electrochemical microscopy (SECM) enabling the gentle and scratch-free contact mode scanning of rough and delicate apple peels in an electrolyte solution. The SECM feedback mode was applied using ferrocene methanol (FcMeOH) as redox mediator that gets electrochemically oxidized at the soft probe and diffuses towards the apple peel where it gets regenerated by certain AOs leading to a redox mediator recycling and increased current signal. The global AO activity in the apple peel including lenticels and regions with artificially degraded AOs were mapped using the soft microelectrodes. Finally, in an apple cross-section the higher and homogeneous AO concentration in the peel with a heterogeneously decaying AO gradient towards the apple inward was visualized, demonstrating the adequate micrometer resolution of the SECM probe and the possibility to get information of the interior AO activity of the apple.

Reactive oxygen species metabolism and phenylpropanoid pathway involved in disease resistance against Penicillium expansum in apple fruit induced by ϵ‐poly‐l‐lysine

“…Apple fruits are welcomed by consumers because they are rich in fiber, sugar, vitamins, minerals and phenolic compounds . Antioxidants in apple fruit are beneficial for health with respect to diabetes, obesity and chronic heart and vascular disorders . Other bioactive substances such as ursolic acid are found with antimicrobial, anti‐inflammatory and antitumor activities .…”