Total phenolic, total anthocyanin and phenolic acid concentrations and antioxidant activity of purple-fleshed potatoes as affected by boiling

Phenolic Compounds in the Potato and Its Byproducts: An Overview

The potato (Solanum tuberosum L.) is a tuber that is largely used for food and is a source of different bioactive compounds such as starch, dietary fiber, amino acids, minerals, vitamins, and phenolic compounds. Phenolic compounds are synthetized by the potato plant as a protection response from bacteria, fungi, viruses, and insects. Several works showed that these potato compounds exhibited health-promoting effects in humans. However, the use of the potato in the food industry submits this vegetable to different processes that can alter the phenolic content. Moreover, many of these compounds with high bioactivity are located in the potato's skin, and so are eliminated as waste. In this review the most recent articles dealing with phenolic compounds in the potato and potato byproducts, along with the effects of harvesting, post-harvest, and technological processes, have been reviewed. Briefly, the phenolic composition, main extraction, and determination methods have been described. In addition, the "alternative" food uses and healthy properties of potato phenolic compounds have been addressed.

Comparison of the postprandial effects of purple-fleshed and yellow-fleshed potatoes in healthy males with chemical characterization of the potato meals

The aim of the current study was to characterize the anthocyanin content and composition of a purple potato landrace cultivar (Solanum tuberosum 'Synkeä Sakari') and to compare the postprandial effects of purple-fleshed potatoes, yellow-fleshed potatoes and bilberries in potato starch on postprandial glycemia and insulinemia in healthy males. The purple potato meal caused smaller insulinemia than the yellow potato meal (iAUC 120 min 1347 and 2226, respectively, p = 0.012 and iAUC 240 min 1448 and 2403, p = 0.007) or the bilberry meal (iAUC 120 min 1920, p = 0.027). The purple potato meal caused a smaller plasma glucose at 40 min postprandially compared with the yellow potato meal (p = 0.044). The results of this study suggest that anthocyanin-containing purple-fleshed potatoes influence the postprandial insulinemia positively. Since potatoes are the world's largest non-grain commodity, replacing yellow-fleshed potatoes with purple-fleshed potatoes as staple food could have large potential in maintaining public health.

The content of total polyphenols in different varieties of Solanum tuberosum grow in Spiš area

Phenolic compounds are the predominant antioxidants in nutrition and their study is currently being paid much attention. These antioxidants act synergistically; polyphenol compounds protect vitamin C and β-carotene, which in turn helps to increase the effect of vitamin E. Potatoes are very popular vegetables in Slovakia, not only in terms that they are easy to prepare, but also by the fact that they combine the wholesomeness of cereals and delicacy and characteristic chemical composition of vegetables. It is important that they find their place in our diet. Nutritional value of potatoes is determined by the content of nutrients such as protein, starch, fat, minerals, and absence of toxins, as well as by a significant content of bioactive components from the group of polyphenols. The study was performed in order to analyse 7 Slovak potato varieties from Spiš area, according to biologically active compounds: such as polyphenols. The content of total polyphenols was determined by the method of Lachman et al., (2003). The lowest determined content of total polyphenol (mg.kg-1 dry matter) in locality Spišský Štvrtok was measured in a variety Victoria (795.05 mg.kg-1 dry matter) and the highest content of total polyphenols in locality Spišský Štvrtok was measured in variety Laura (1238.42 mg.kg-1 dry matter). In the locality Odorín was determine the lowest content of total polyphenols in variety Red Anna (974.09 mg.kg-1 dry matter) and the highest content of total polyphenols was determined in variety Laura (978.95 mg.kg-1 dry matter). Between all varieties in locality Spišský Štvrtok was confirmed the statistically significant difference in the influence of the variety in the contents of total polyphenols (mg.kg-1 DM). This varietal dependence was not appear in samples taken in the locality Odorín. The total polyphenols content of the potatoes can be influenced by other factors, for example locality. In this case, there were statistically significant differences in the content of total polyphenols in variety Laura obtained from two different localities.

Dependence among total polyphenols content, total antioxidant capacity and heavy metals content in potatoes

Polyphenols belong to the most significant compounds with antioxidant effects in potatoes. Their content depends on several factors. The most important factor is the variety of potatoes and the conditions of their growing such as temperature, rainfall, altitude, agronomic and chemical characteristics of the soil. We have compared two potato cultivars in the study which have been grown in the Slovak localities Dolné Obdokovce and Vrbová nad Váhom (cv. Agria) and Nitra, Radošina and Vrbová nad Váhom (cv. Impala). In lyophilized samples of potatoes total polyphenols content in ethanolic extracts using Folin-Ciocalteu agens and in methanolic extracts total antioxidant capacity using DPPH were spectrophotometrically determined. The average total polyphenols content in the potato variety Impala was 604.26 ±120.70 mg.kg-1 dry matter (DM) and 529.37 ±59.35 mg.kg-1 DM in the variety Agria. The average value of total antioxidant capacity, expressed in % inhibition, was 8.44 ±1.68% in the potato variety Impala and 8.09 ±1.14% in Agria. The results obtained were evaluated by One-way analysis of variance ANOVA (LSD-test), using Statistical Analysis Software Statgraphics. Mutual correlations among the total polyphenols content, total antioxidant capacity and heavy metals concent (Pb, Ni, Cd - determined using atomic absorption spectrometry (AAS) method: Cd, Pb: GF-AAS and Ni F-AAS) were evaluated using the correlation and regression analysis (Microsoft Excel). Statistically significant interdependence (p <0.05) was only confirmed between the Cd content and total antioxidant capacity in both cultivars, or between the Ni content and total antioxidant capacity in the variety Impala.

Domestic cooking methods affect the phytochemical composition and antioxidant activity of purple-fleshed potatoes

The effects of domestic cooking methods (boiling, baking, steaming, microwaving, frying, and stir-frying) and a new cooking method (air-frying) on the composition of phytochemicals (phenolics, anthocyanins, and carotenoids) and the antioxidant activity in purple-fleshed potatoes were investigated. Compared with raw potatoes, reductions of 23.59-90.42%, 7.09-72.44%, 7.45-83.15%, and 20.15-76.16% in the vitamin C, total phenolic, anthocyanin and carotenoid contents, respectively, was observed after cooking. Decreases of 7.88%, 21.55%, 22.48, 6.31%, and 61.38% in DPPH radical-scavenging activity was also observed after boiling, steaming, baking, microwaving and stir-frying, respectively, whereas an increase of 30.52% was noted after air-frying. A correlation analysis revealed that the antioxidant activity was in accordance with the total phenolic content and that this activity showed the lowest correlation with the vitamin C content. Among all of the cooking methods investigated in this study, stir-frying retained only slight levels of the phytochemicals and antioxidant activity observed in raw potatoes, whereas steaming and microwaving were able to retain most of the health-promoting compounds found in raw potatoes and may thus be suitable methods for cooking potatoes.

Improving potato drought tolerance through the induction of long-term water stress memory

Knowledge of drought tolerance in potato is limited and very little is known about stress memory in this crop. In the present study, long-term stress memory was tested on tuber yield and drought tolerance related traits in three potato varieties (Unica, Désirée and Sarnav) with contrasted yields under water restriction. Seed tubers produced by plants grown under non-restricted (non-primed tubers) and restricted (primed tubers) water conditions were sown and exposed to similar watering treatments. Tuber yield and leaf greenness of plants from primed and non-primed seeds as well as tuber carbon isotope discrimination (Δ(13)C) and antioxidant activity (AA) responses to watering treatments were compared. Higher tuber yield, both under non-restricted and restricted water regimes, was produced by primed Sarnav plants. The decrease of tuber yield and Δ(13)C with water restriction was lower in primed Unica plants. Long-term stress memory consequently appears to be highly genotype-dependent in potato. Its expression in plants originated from primed tubers and facing water restriction seems to be positively associated to the degree of inherent capability of the cultivar to yield under water restriction. However, other effects of priming appear to be genotype-independent as priming enhanced the tuber AA in response to water restriction in the three varieties.

Impact of cooking, proving, and baking on the (poly)phenol content of wild blueberry

Accumulating evidence suggests that diets rich in (poly)phenols may have positive effects on human health. Currently there is limited information regarding the effects of processing on the (poly)phenolic content of berries, in particular in processes related to the baking industry. This study investigated the impact of cooking, proving, and baking on the anthocyanin, procyanidin, flavonol, and phenolic acid contents of wild blueberry using HPLC with UV and fluorescence detection. Anthocyanin levels decreased during cooking, proving, and baking, whereas no significant changes were observed for total procyanidins. However, lower molecular weight procyanidins increased and high molecular weight oligomers decreased during the process. Quercetin and ferulic and caffeic acid levels remained constant, whereas increases were found for chlorogenic acid. Due to their possible health benefits, a better understanding of the impact of processing is important to maximize the retention of these phytochemicals in berry-containing products.

Effect of hydrothermal processing on total polyphenolics and antioxidant potential of underutilized leafy vegetables, Boerhaavia diffusa and Portulaca oleracea

OBJECTIVE

To investigate the effect of different processing methods on antioxidant properties of acetone extract of aerial parts from Boerhaavia diffusa and Portulaca oleracea.

METHODS

The total phenolic and flavonoid contents were determined by Folin-Ciocalteau and aluminum chloride method, respectively. FRAP, metal chelating activity, DPPH, ABTS, nitric oxide, hydroxyl and superoxide radical scavenging activities, carotene/linoleic acid bleaching activity were used for the determination of antioxidant capacity.

RESULTS

The total phenolics in Boerhaavia diffusa (82.79-162.80 mg GAE/g extract) were found to be higher when compared to that of Portulaca oleracea (22.94-10.02 mg GAE/g extract). Hydrothermal processing enhanced the level of inhibition on synthetic radicals such as DPPH (3 439-309 549 mmol TE/g extract) and ABTS (17 808-53 818 mmol TE/g extract) as well as biologically relevant radicals such as superoxide anion (70%-90%) and nitric oxide (49%-57%). In addition, boiling of the vegetables were found to be maximum capacity of FRAP (6 404.95 mmol Fe (II)/g extract) and metal chelating activity (1.53 mg EDTA/g extract) than the respective raw samples.

CONCLUSIONS

The present investigation suggests that the processing enhance the functionality and improves the availability of bioactive substances of these vegetables. In addition, they also exhibited more potent antioxidant activity. Therefore these natural weeds from the crop land ecosystem could be suggested as cost effective indigenous green vegetables for human diet and potential feed resources for animals. Further extensive studies on role and importance of those weeds in sustaining the agro biodiversity are also needed.

Content of polyphenols in coloured and yellow fleshed potatoes during dices processing

The purpose of the research was to examine the effect of the laboratory production of dried potato dice on the content of phenolic compounds in one yellow-fleshed potato variety and four blue-fleshed potatoes varieties. Coloured-flesh potato varieties were characterised by about three times higher amount of total phenolic content than traditional yellow-fleshed ones. The predominating phenolic acids in potato were chlorogenic acid and its isomers, which account about 90% of total phenolic content in tubers. The phenolic acid content decreased by 80% after peeling the blue-fleshed potatoes and by 60% after peeling the yellow variety. The dried potato dice obtained from yellow-fleshed potatoes had no content of phenolic acids but produced from colour-fleshed potatoes contained about 4% of the original phenolic content of the raw material. Chlorogenic acid amounted about 97% of total phenolic acid content, and the rest was neochlorogenic acid.