Authors:E. Rytel, G. Lisińska, and A. Tajner-Czopek
The quality of potato tubers and their chemical composition are influenced by genetics as well as the soil fertility, weather conditions, the soil profile, and the chemical treatments that are applied. This field study on potato cultivation methods was conducted near Wrocław (Lower Silesia), Poland. The variables used in the study included the potato cultivar [Asterix, Pirol (medium-to-early maturing varieties) and Syrena (medium-to-late maturing variety)] and the potato cultivation technology (organic, integrated and conventional). The experiment was conducted from 2005 through 2007.The purpose of this study was to compare the effects of ecological (organic), integrated and conventional cultivation methods on the nitrate and glycoalkaloid content of potato tubers. The cultivation method was determined to have a significant effect on the toxic compound concentrations in the potato tubers. The lowest glycoalkaloid and nitrate (NO3−) concentrations occurred in the potato tubers from the ecological plots. Mineral fertilization, especially the high N rates that were used in the conventional potato cultivation method, increased the glycoalkaloid content by 76% and the nitrate (NO3−) content by 25%, as compared to the potato tubers from the ecological plots. Mineral fertilization in the integrated and conventional systems increased the chaconine content of potato tubers by 22%, as compared to the samples from the ecological plots, whereas the solanine content was the lowest in the potato samples collected from the plots cultivated in a conventional manner.
The texture changes during the initial phase of blanching of potatoes, carrots and green peas at different blanching times (0–240 s) and temperatures (85 °C, 95 °C, 100 °C) were investigated. The breaking force (N) was determined by compression or Back extrusion tests with an Instron texture tester. Electronmicroscopic studies (SEM) were made to support the interpretation of the results.For each vegetable several sections of changes of the breaking force (lnF) were identified. For potatoes a three phase change of the breaking force by all temperatures (85 °C, 95 °C, 100 °C) was observed. In the first of the 3 different observed stages of potato blanching the breaking forces increased with time (0–40 s). In the second and third stage of the blanching process of potato a linear relationship was found between the logarithm of the breaking force and the blanching time. The second phase observed was faster (40–160 s) than the consecutive slower third phase (160–240 s).For green peas the change of the breaking force (lnF) can be described by two consecutive first rate reactions. A faster decreasing period between 0–25 s was followed by a slower decreasing one between 70–140 s. Between the first and second stage of the blanching process there was an initial lag period (25–70 s), which will not be described here. In the period after 140 s, there was not any change, this period is constant.For carrots the fastest change can be observed at 100 °C compared to the results at 85 and 95 °C. A three-phase curve was observed as well. An initial lag period (0–90 s) was followed by a faster (90–190 s) and a slower (190–240 s) decreasing one. In the second and third stage of the blanching process of carrots a linear relationship was found. For the changes of the breaking force (lnF) a kinetical approach was applied, reaction rate constants and apparent activation energies were calculated. The kinetical approach helps to compare and forecast changes at different process conditions.
Authors:Margit Kollaricsné Horváth, Borbála Hoffmann, István Cernák, Szilveszter Baráth, Zsolt Polgár, and János Taller
Significant differences in nitrogen use efficiency (NUE) were detected previously among potato cultivars. Exploration of the genetic background may facilitate the breeding of cultivars with highly effective nitrogen use.
Expression of NUE genes was analyzed at three different N-supply levels in five potato genotypes. Correlations of NUE gene expressions and agronomical parameters with such indices as the nitrogen uptake efficiency, nitrogen utilization efficiency, NUE, and harvest indices were analyzed.
The correlations between expression level of the nitrate–reductase, nitrite–reductase, ammonium transporter, and asparagine synthase genes and different agronomically important parameters were detected.
Our results contribute to more rational, genotype-dependent nitrogen use in potato production and have relevance in breeding of new cultivars with better nitrogen utilization, as well as in production of seed potato.
Authors:A. Lugasi, D. P. F. Almedia, and E. Dworchák
The chlorogenic acid and the total polyphenol content were analysed in two different potato varieties (Kennebec, Agria) grown under five different nitrogen fertiliser rates (0, 75, 150, 225, 300 kg ha-1). Chlorogenic acid content ranged between 6.0-22.3 mg kg-1 fresh weight and was not influenced by fertiliser levels. The chlorogenic acid in potato tubers accounted for almost 90% of the total polyphenols. Free radical scavenging and antioxidant activities of the tubers were also analysed. Ethanolic extracts if the tubers showed marked hydrogen-donating activity in the experiment using 1,1-diphenyl-2-picrylhydrazyl (DPPH), they had reducing power as measured by the Fe(III)?Fe(II) reaction, but did not exhibit H2O2 scavenging activity assessed with a chemiluminescence method. Potato extracts showed significant, although weak Cu(II)-chelating activity and inhibited the autoxidation of linolenic acid as measured by the thiocyanate method. Chlorogenic acid containing extract of potato, can act as primary and secondary antioxidant in prevention of oxidative stress. The strong correlation between the antioxidant activity and the level of total pholyphenols suggests that the phenolic compounds are important antioxidant components of whole potato tubers. Variety had minimal, while nitrogen fertiliser rate had no effects on the levels of the studied characteristics.
Authors:R. Tömösközi-Farkas, Zs. Polgár, M. Nagy-Gasztonyi, V. Horváth, T. Renkecz, K. Simon, F. Boross, Z. Fabulya, and H. Daood
Anti-nutritive components in multi resistant potato cultivars were investigated in relation to conventional and organic farming for three years. Glycoalkaloids, nitrate, nitrite, asparagine, and glutamine contents of tubers were examined. Farming technology was found not to have an effect on the level of glycoalkaloids, which was influenced mostly by the genotype and season. Nitrogen fertilisation caused significant increase in nitrate, asparagine, and glutamine contents as compared to organic farming. Nitrite content was found to be more independent of farming technologies than nitrate. Tubers of cultivar Rioja had the lowest nitrate content irrespective of season or technology. In conclusion, the absolute amount and changes of different anti-nutritive components of potato tubers were influenced differently by the technology, genotype, and season in a complex manner. Organic farming had no effect on the glycoalkaloid content, but the nitrate levels had a tendency to be lower compared to conventional farming. This can be seen as a positive effect of organic farming.