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In the three-year field trials (2009–2011) at two locations with different altitudes a total of 14 potato cultivars with different colour of flesh (yellow, white, red and purple) were grown. The content of total glycoalkaloids (TGA) was determined by HPLC. TGA content ranged from 18.8 to 102.4 mg/kg fresh matter and none of the cultivars reached the value of risk to human health. Conclusive and decisive influence on the content of the TGA was re corded in genotype. Individual cultivars reached 0.47 to 1.45 of the TGA content in the control cv. Agria. In terms of the colour of the flesh the highest TGA content was found in group of red-fleshed cultivars (1.53 × higher than the average of cultivars with yellow or white flesh); while red-fleshed cv. Rote Emma reached the absolutely lowest TGA content of 14 cultivars, which confirms the decisive role of genotype. On warm, dry habitats in the lowlands a higher TGA content was observed when compared with the amount raised in a typical potato field.

A B S T R A C T The objective of this two-year study was to determine the main carotenoids in 15 varieties of potatoes (Solanum tuberosum L.) with different flesh colour – white, yellow, red and purple and two varieties of Solanum phureja. Content of total anthocyanins in pigmented potatoes was also determined and compared with the carotenoid level. Potatoes were cultivated in two localities with different soilclimatic conditions. Content of carotenoids and anthocyanins was affected by variety and locality. Moreover, carotenoid content was influenced by the growing year. Content of total carotenoids ranged from 0.779 to 13.3 mg/kg dry matter (DM). The main carotenoid was lutein in all varieties (54–93%) furthermore violaxanthin, neoxanthin, zeaxanthin and b-carotene were identified in most of the analysed samples. The highest carotenoid content was found in S. phureja varieties. The pigmented varieties Blaue Anneliese, Violetta, Olivia (all purple) and H.B. Red (red) showed comparable carotenoid level with the yellow-fleshed variety Agria; other pigmented varieties contained similar carotenoid levels as white-fleshed varieties. Content of total anthocyanins ranged from 210 to 2419 mg/kg DM and correspond to flesh colour intensity. A weak correlation between carotenoids and anthocyanins was found (r 2 = 0.33). Thus some coloured varieties could be a good source of both studied phytochemicals.

The impact of selected factors – cultivar, storage, cooking and baking on the content of total anthocyanins (TAC) in coloured-flesh potato cultivars has been studied. TAC ranged from 248.5 to 2257.8 mg kg −1 dry matter (DM). TAC difference between cultivars was statistically significant. Cold storage (4 °C) influenced TAC differentially. In the Violette and Highland Burgundy Red cultivars TAC increased by 18.5% and 12.1% respectively, and in the Valfi cultivar it decreased by 33.9%. Baking increased TAC 3.34 times whereas cooking in boiled water increased it 4.22 times. Correlation between antioxidant activity (AOA) and TAC ( r 2 = 0.659) has been found. The Violette, Vitelotte and Highland Burgundy Red cultivars with the highest TAC showed high AOA and the Shetland Black cultivar and the cultivars Salad Blue and Blue Congo with a “marbled” texture showed the lowest TAC and AOA. Individual anthocyanidins are fingerprints of colour-fleshed potato cultivars.

The aim of this study was to determine that the total anthocyanin content (TAC) and antioxidant activity (AOA) in potato flesh with different colours grown in the Czech Republic. Four yellow- or white-, six purple- and four red-fleshed varieties were grown in 2009 at two different sites (Valecov – highland, seed potato area at 460 m a.s.l., Přerov nad Labem – lowland, new potatoes area at 178 m a.s.l.) in precise field trials. For purple- and red-fleshed varieties, average TAC values ranged from 61.5 to 573.5 cyanidin mg/kg of FM and significant effect of the variety of the TAC was found. High content reached the Violette and Vitelotte varieties with dark purple flesh, and the low est content the Blue Congo variety with light purple marbled flesh. Significantly higher TAC was found in a lowland area Přerov nad Labem, which is probably related to drought stress. The lowest AOA was achieved by a group of varieties with yellow or white flesh – averaging 82.8 mg ascorbic acid equivalent/kg FM, in a group of red-fleshed varieties it was higher 4.34 times and in a group of purple-fleshed varieties even 5.03 times higher. Also between purple-and red-fleshed varieties significant differences in AOA were found, both high and low values of AOA showed the same varieties as in the case of the TAC. Among experimental sites higher AOA was also demonstrated at Přerov nad Labem. Correlation analysis showed a strong correlation between AOA and TAC (r = 0.8099).

in precise field trials in the years 2004–2008 in the Czech republic the effect of conditions of location, variety and mineral fertilization on ascorbic acid content (aa) in potatoes with different tuber flesh color was investigated. Significant was the effect of variety. The Marabel variety with the highest aa content (248 mg/kg FW) exceeded other eight varieties by 13.4–74.1%. The valfi variety, in five-year trials the only variety with purple colored flesh, ranked among analyzed varieties moderately below average. in addition, in the year 2008 the group of seven varieties with purple and red tubers was evaluated and aa content lower by 15.2% compared to the group of varieties with yellow flesh was determined. also, significant differences were determined between the varieties with coloured tubers; the highest aa content was found in the red-fleshed variety Highland Burgundy red (234 mg/kg FW). a negative effect on aa content in tubers was observed at increased intensity of n fertilization (at 180 kg n/ha, aa decreased by 12.4% compared to 100 kg n/ha). Enhanced levels of potassium and magnesium fertilization had no effect on the aa content. The effect of location on aa content was not shown; however, from the four locations in average of five years a pronounced trend of the highest content of ascorbic acid on the location Přerov nad labem with the highest temperature averages during vegetation period of experimental years was determined (by 0.9°C, 2.3°C, and 5.9°C higher compared with other locations).

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 Czech Republic from 2004–2008 the impact of location conditions, varieties with yellow, purple and red flesh and mineral fertilization on the content of total polyphenols (TP) and chlorogenic acid was investigated. The highest TP contents were reported at two locations with extreme climatic conditions; in those under stress due to low temperatures in the vegetation period at the mountainous area Stachy (5.89 mg TP/g DM) and those under drought stress in the warm lowland location Přerov nad Labem with light sandy soil (5.81 mg TP/g DM). The five-year experiment with the purple-fleshed Valfi variety (13.29 mg TP/g DM) reached 2.46 to 3.18 times higher content of TP in comparison with eight yellow-fleshed varieties. The yellow-fleshed Karin variety (5.39 mg TP/g DM) outperformed TP content of other yellow-fleshed varieties by 3.1 to 29.1%. In another experiment conclusive differences between the eight varieties with purple and red flesh were found; the highest TP content was detected in cv. Violette (25.9 mg TP/g DM) with the darkest purple flesh. As to the chlorogenic acid content similar relationships between varieties were found as in the case of TP. High linear correlation (r = 0.8536) was found between the content of chlorogenic acid and the content of TP. Among the treatments of mineral N, P, K and Mg fertilization, the content of TP was only affected by a treatment with a higher dose of K and Mg, causing a decrease in TP content.

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.