| Summary: | Polyphenol oxidase (PPO) inactivation in five whole and peeled Irish potato cultivars was investigated using high-pressure processing (HPP) at 400 MPa and 600 MPa for 3 min. PPO activity was significantly lower in most of the HPP-treated samples, while the highest PPO inactivation was observed after HPP at 600 MPa. No significant (<i>p</i> > 0.05) changes were observed on the total phenolic content and antioxidant activity of all the HPP-treated potatoes. Regarding individual phenolic acids, chlorogenic acid was decreased significantly (<i>p</i> < 0.05) in all studied varieties with a concomitant increase (<i>p</i> < 0.05) in caffeic and quinic acid. Similarly, ferulic acid was also increased (<i>p</i> < 0.05) in all studied varieties after the HPP treatment, while there was a variation in rutin and 4-coumaric acid levels depending on the cultivar and the sample type. Anthocyanins in the coloured whole potato varieties (i.e., Kerr’s Pink and Rooster), tentatively identified as pelargonidin-<i>O</i>-ferulorylrutinoside-<i>O</i>-hexoside and pelargonidin-<i>O</i>-rutinoside-<i>O</i>-hexoside, also exhibited significantly (<i>p</i> < 0.05) higher levels in the HPP-treated samples as opposed to those untreated. Glycaemic indices of the potatoes treated with HPP did not differ with the corresponding untreated cultivars.
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