The effect of the conditions of cultivation on the content of polyphenol compounds in the potato varieties Agria and Karin

Tyrosine, caffeic acid and chlorogenic acid are the major potato polyphenolic substrates of polyphenoloxidase contributing to enzymic browning of potatoes. Ascorbic acid is a naturally occurring inhibitor of colour formation. Differences in the rates of browning are due to quantitative rather than qualitative differences of the responsible potato constituents. In 1995 and 1996 field trials were performed to estimate total polyphenol contents in two potato varieties Agria and Karin from twelve localities. From two localities potatoes that have been cultivated in conventional and ecological alternative way were investigated. During the whole experimental period with Agria and Karin varieties, a tendency towards higher total polyphenol compounds in the tubers cultivated in ecological way was shown. Polyphenol content was determined spectrophotometrically by Folin-Ciocalteau reagent at a wave length 765 nm. In the variety Agria from the beet growing locality Uhrineves the content of total polyphenolic compounds in the tubers of potatoes cultivated in conventional way was 32.15 mg/100 g and in alternative way 34.50 mg/100 g, in the variety Karin were the corresponding values 45.75 mg/100 g and in the ecologically cultivated 54.75 mg/100 g. This increase was 5.75% in the variety Agria and 19.67% in the variety Karin in comparison with the potatoes cultivated by conventional classic method. This tendency has been proved also in the results obtained from the potato growing region Valecov where in the tubers cultivated in ecological way was found total polyphenols 44.65 mg/100 g in the variety Agria and 49.25 mg/100 g in the variety Karin, whereas in potato tubers cultivated in conventional way the corresponding values were 37.40 and 46.95 mg/100 g, resp. The increase of 19.39% in the variety Agria and 4.90% in the variety Karin was recorded. The potatoes cultivated in beet growing regions had the content in average lesser amounts of polyphenolic compounds (Agria 35.54 mg/100 g, Karin 51.54 mg/100 g) in comparison with the potatoes cultivated in the potato growing regions (Agria 37.49 mg/100 g, Karin 57.08 mg/100 g). From these; results it could be concluded that harder conditions of climate in potato growing region can cause an increase of the content of polyphenolic compounds. The average polyphenol content in the year 1995 in the variety Agria was 35.84 mg/100 g and in the year 1996 37.19 mg/100 g, in the variety Karin the corresponding values were 52.54 mg/100 g and 56.08 mg/100 g, resp. The polyphenol content of potato tubers is influenced by the genotype of the given variety, growing region and the way of growing and by specific features of the given year (the results from the 1995 year were statistically conclusive).