Processing is one of the most crucial factors affecting polyphenol content in foods. Therefore, the study is aimed at the evaluation of heat treatment effects (microwaving, steaming, baking, and boiling) on the content of chlorogenic acids, total polyphenols, and antioxidant activity of three varieties of sweet potato with different flesh colors (Beauregard—orange-fleshed, O’Henry—white-fleshed, 414-purple—purple-fleshed). According to high performance liquid chromatography analysis, chlorogenic acid was the predominant chlorogenic acid in sweet potatoes. Obtained results also suggested the purple-fleshed variety (414-purple) had significantly (p < 0.05) higher total polyphenol content and thus the highest antioxidant activity. Heat treatment positively influenced the chlorogenic acid content, total polyphenols, and antioxidant activity of sweet potatoes. Among the used methods, steaming had the greatest effect on the chlorogenic acids and total polyphenols, while microwaved samples showed the highest antioxidant activity (DPPH). The content of chlorogenic acids and total polyphenols decreased in the order of steaming > baking > microwaving > boiling > raw. However, the individual varieties differed not only in the flesh color but also in the reaction to the used heat treatment methods. Spearman’s correlation coefficient showed a strong correlation between chlorogenic acid and antioxidant activity.

Potatoes (Solanum tuberosum L.) are an essential food for the human diet and thus represent an important source of biologically active substances. This study aimed at investigating the content of bioactive substances (total anthocyanin and polyphenol contents and chlorogenic acid) in seven potato varieties (Belana, Cecile, Magenta Love, Mozart, Talentine, Toscana, and Violet Queen) with various flesh and skin colors. To evaluate the impact of potato maturity on the analyzed parameters, potato samples were harvested in two different periods (1st harvest—July and 2nd harvest—September). Total anthocyanin and polyphenol contents were determined spectrophotometrically, and chlorogenic acid by the HPLC-DAD method. Varieties with a colored flesh (Magenta Love and Violet Queen) showed the highest content of bioactive substances. The maturity level significantly (p < 0.05) affected the total content of anthocyanins and polyphenols in potatoes. Early to medium early varieties (Belana and Magenta Love) showed an increase in chlorogenic acid content during maturation, while in other varieties, chlorogenic acid decreased due to higher maturity. In terms of the content of bioactive substances with a possible positive effect on human health, the consumption of potatoes with colored flesh could be recommended.

Due to several centuries of ongoing mining activities, Middle Spiš (Slovakia) is one of the areas with a damaged environment. The contents of Fe, Mn, Zn, Cu, Ni, Pb, Cd, and Hg were determined in the soils and home-grown vegetables (potatoes, carrots, tomatoes). Except for Pb, the contents of heavy metals in the soils of some plots were higher than the limit values. Based on the values of Contamination factor (C_f), Degree of contamination (C_deg), Geo-accumulation index (I_geo), and Pollution load index (PLI), very high Fe, Cd, and Hg contamination (C_f ≥ 6), very high soil contamination (C_deg ≥ 20), extremely heavy Fe and Hg contamination (I_geo > 5), resp. moderately pollution to non-pollution (1 < PLI ≤ 2) was found in all plots. In vegetable samples, the maximum levels were exceeded for Cu, Pb, Hg (potato), Pb (carrot, tomato), and Hg (carrot, plot E). Bioaccumulation factor values BAF > 1 were for Cu (carrots, potatoes). Estimated daily intake values for all heavy metals were lower than their tolerable daily intake. Chronic daily intake of heavy metals ranged 2.495E−06 (Hg)—0.1416 (Fe) mg/kg/day. Based on Hazard index values, potato consumption poses a risk (0.8068–1.3057). The results showed that the monitoring of soils and cultivated production is necessary for the investigated area.

Sweet potatoes are reported to be a good source of bioactive compounds. The aim of this study was to evaluate the impact of different heat treatment methods (microwaving, steaming, and baking) and variety on the total polyphenol content and antioxidant activity of three sweet potato varieties – Beauregard (orange-fleshed), O’Henry (white-fleshed), and 414-purple (purple-fleshed). All investigated parameters were determined spectrophotometrically. The total polyphenol content was in the range of 0.53 (O’Henry) – 5.60 mg GAE.g-1 DW (414-purple) for raw flesh and 1.68 (O’Henry) – 7.03 mg GAE.g-1 DW (414-purple) for raw peel of sweet potatoes. Heat treatments caused an increase of total polyphenol content in sweet potatoes (0.98 (steamed O’Henry) – 28.04 mg GAE.g-1 DW (baked 414-purple)). In terms of antioxidant activity, the steamed samples of variety 414-purple showed the highest values of DPPH radical scavenging activity (4.51 µmol TE.g-1 DW) and Ferric reducing antioxidant power assay (19.57 µmol TE.g-1 DW) compared to the other treatment methods. Spearman´s test showed a strong positive relationship between both used methods for evaluation of antioxidant activity. All studied processing methods positively affected the total polyphenol content and antioxidant activity in sweet potatoes.