Abstract: The effects of three cooking methods: microwave (25 W/g for 3.5 min), baking (60 ℃ for 2 h), and water boiling (100 ℃ for 15 min) on the major nutrients and bioactive substances in two varieties of purple-fleshed potato were analyzed so as to provide a scientific basis for the thermal processing of purple-fleshed potato. The results showed that after heat treatment, the contents of vitamin C, ash, starch, and total phenols (calculated as chlorogenic acid) decreased. After microwave treatment, the protein contents of the two varieties increased by 3.29% and 3.21%, but decreased by 2.20% and 1.97% after baking and 1.91% and 1.41% after boiling treatment, respectively. The anthocyanin content of the Black Diamond cultivar increased by 22.92% and 16.67%, respectively, after microwave and water boiling treatment, but decreased after baking treatment. In addition, microwave treatment significantly improved the reducing capacity of purple-fleshed potato anthocyanin extract, and the anthocyanin extract significantly enhanced the expression levels of nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase 1 (HO-1) in RIN-m5F pancreatic islet β cells and reduced the expression level of nuclear transcription factor kappa B (NF-κB). In conclusion, microwave treatment was the best heat treatment method for purple-fleshed potato.

Key words: purple-fleshed potato; heat treatment; anthocyanin; antioxidant; pancreatic β cells