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The impact of peeling and three cooking treatments (boiling, baking and microwaving) on the content of selected phytochemicals in white-, yellow-, red- and purple-fleshed potatoes was investigated. Ascorbic acid and chlorogenic acid contents were determined by HPLC-DAD, total anthocyanin content by pH-differential spectrophotometry, glycoalkaloid, α-chaconine and α-solanine contents by HPLC-ESI/MS/MS. All cooking treatments reduced ascorbic and chlorogenic acid contents, total glycoalkaloids, α-chaconine and α-solanine with the exception of total anthocyanins. The losses of ascorbic and chlorogenic acids were minimised with boiling and total anthocyanin levels retained the highest. Boiling of peeled tubers decreased contents of total glycoalkaloids (α-chaconine and α-solanine) and appeared as the most favourable among the three tested methods. Moreover, due to higher initial levels, red- and purple-fleshed cultivars retained higher amounts of antioxidants (ascorbic acid, chlorogenic acid and total anthocyanin) after boiling and may be healthier as compared with white or yellow cultivars.

In precise field trials in the years 2010 and 2011 the effect of genotype and location in cultivars with yellow, white, purple or red flesh on the content of chlorogenic acid (CA) and in 2011 and 2012 the effect of organic cultivation were evaluated. The results show a statistically significant effect of genotype to CA content, which ranged from 74.0 mg/kg fresh matter (FM) (Agria) to 825 mg/kg FM (Vitelotte). Demonstrable effect of flesh colour on CA con tent between cultivars with coloured flesh was found (430 mg/kg FM) in comparison with cultivars with yellow or white flesh (71.1 mg/kg FM). For cultivars with coloured flesh rather the genotype specific cultivar ruled than the purple or red flesh colour. In terms of the influence of location, higher CA levels were found on warm locations with frequent periods of drought in comparison with locations of high altitude climatic conditions which are favourable for potato cultivation. In the organically grown potatoes significantly higher levels of CA were found as compared with conventional treatment.