Fleshed Potato Research Articles

The influence of dehydrated potatoes processing on the glycoalkaloids content in coloured-fleshed potato

The aim of this study was to determine the effect of different temperatures of blanching and pre-drying used in the laboratory production of dried potato dice on the content of glycoalkaloids in red and blue fleshed potato varieties.Studied potatoes of coloured fleshed varieties were characterised by a low glycoalkaloids content at 5.47mg100g−1. The production of dehydrated potato dice influenced on the decrease in glycoalkaloids content in potato products. The majority of these compounds were removed during the peeling (70%) and blanching process (29%). Potato dice blanched at the highest temperature (85°C) and pre-dried at 120°C was characterised by the lowest quantity of glycoalkaloids content, whereas the highest content of these compounds was found in dice blanched potato at the lowest temperature (65°C) and pre-dried at 120°C. The blanching process much influenced on the decrease in glycoalkaloids content than pre-drying process.

Effects of Lactic Acid Fermentation on Sensory Profile of Orange Fleshed Sweet Potato

Lacto-products processed by lactic acid fermentation are known to have nutraceutical attributes and create variety in the beverage composition. Due to their high nutritive value, they are beneficial to human health when consumed regularly. In this study orange fleshed potato varieties (Zapallo, Nyathiodiewo and SPK004/06) were fermented with Lactobacillus plantarum MTCC 1407 at 25 ± 2°C for 48 h and kept for 28 days to make lacto-pickles. An optimization of process conditions was done by varying brine levels with fermentation time. The fermented products were subjected to panelist evaluation for flavour profiling. The product sensory scores were (1.5-2.5) on a 5 point hedonic scale ranging from dislike slightly to like much. The product with brine levels at 4 and 6% were found to be most preferred. The findings from this study indicate the acceptability of the developed lacto-pickles and suggest that the development of new products from sweet potato with functional attributes could improve its consumption among families while enhancing the shelf life of the product. . It was concluded that the β-carotene rich, sweet potato lacto-pickle is a novel product which could find wide acceptance with good prospects for commercialization in small-scale industries.

Glycemic Index of Sweet Potato as Affected by Cooking Methods

Understanding the effect of cooking on glucose availability will aid in the recommendation for including sweet potatoes as a regular component in American diets. Heating breaks down starch granules to allow amylopectin and amy- lose to be more readily digested by pancreatic amylase, which theoretically should increase the glycemic index of sweet potato. Twelve volunteers consumed 25 g of available carbohydrate from sweet potato skin and flesh sepa- rately that were subjected to conventional cooking methods: baking at 163 °C for 1 hour; microwaving for five minutes in a 1000 watt microwave; dehydrating at 60°C for 16 hours; and steaming at 100°C for 45 minutes. Available carbohydrate was determined by difference from proximate analysis of protein, lipid, total dietary fiber, moisture, and ash. Fasted par- ticipants measured blood glucose levels at 0, 30, 60, 90, and 120 minutes after consuming 25 g of carbohydrate from test foods or glucose. Glycemic indices calculated from these methods for steamed, baked and microwaved sweet potato flesh were 63 ± 3.6, 64 ± 4.3 and 66 ± 5.7, respectively, indicative of a moderate glycemic index food. However, dehydrated and raw sweet potato flesh had a low glycemic index (41 ± 4.0 and 32 ± 3.0, respectively). Steamed skin, baked skin, and dehydrated flesh did not have a statistically different glycemic index (P> 0.05) from that of raw sweet potatoes. A second experiment confirmed the low glycemic index of raw sweet potato, especially the skin, and showed that a commercial ex- tract of the sweet potato cortex, Caiapo, tended to lower the glycemic index of white potato to a level that was not differ- ent from the raw sweet potato peel. The physiological mechanism for the lower glycemic index was not due to a greater release or a greater clearance of insulin during the glycemic response. Depending on cooking methods, Beauregard sweet potato flesh and skin may be considered low and medium glycemic index foods, which may prove beneficial for diabetic or insulin-resistant consumers.

Differences in anthocyanin content and antioxidant activity of potato tubers with different flesh colour

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 (Valečov – 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 lowest 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).

한국산 8 품종 고구마분말의 특성

Sweet potato powders made from eight Korean varieties, including purple-fleshed, orange-fleshed, and commercial dry type sweet potatoes, were investigated for physicochemical and pasting properties to develop processed food. Crude protein and lipid contents of Shinjami and Borami were higher than those of other varieties. The lightness value of raw sweet potato flesh was the highest value in Shinchunmi, and the lowest in Shinjami. Using the color difference (<TEX>${\Delta}E$</TEX>), color similarities compared to the white plate occurred in the following order; purple-fleshed > orange-fleshed > commercial dry type sweet potatoes. Total and damaged starch contents were significantly different (p<0.05). Total starch content of sweet potatoes was higher in commercial dry sweet potatoes (61.89-70.46%), particularly Shinchunmi (70.46%) but lower in orange-fleshed sweet potato (48.87 and 49.53%, respectively). Water binding capacity of Yeonwhangmi, swelling power and solubility of Shinyulmi were the highest values (174.70, 25.54 and 87.49%, respectively) among them (p<0.05). But oil absorptions of Shinyulmi and Shinchunmi showed lower values (97.08 and 97.54%, respectively). All sweet potato powders had an A type x-ray diffraction pattern. The initial pasting temperatures of sweet potato powders ranged from 69.50 to <TEX>$75.95^{\circ}C$</TEX> and the amylolytic enzyme in sweet potato powder lowered pasting viscosity.

Analyses of Plasmas Produced by Laser Ablation of Fresh Aliments

Detection and analysis of trace mineral elements in vegetables, and more generally in food by laser-induced breakdown spectroscopy (LIBS) promises applications with expected outcomes in nutrition quality. LIBS ensures contactless, real-time measurements of multielemental samples without any preparation of the samples surface. However, its application to analyses of aliments such as vegetables has one main drawback. Organic materials are strongly inhomogeneous and the physical properties that govern the processes of laser energy absorption, material ablation and plasma formation depend on a large number of parameters making calibration with standard samples impossible. This technique requires therefore a calibration-free approach that allows one to deduce the relative elemental concentrations from the intensities of spectral lines emitted from the laser-produced plasma. The main difficulty of such an approach is related to the temporal and spatial variation of the plasma properties. Therefore we have performed spectroscopic analysis of the plasma produced by Nd:Yag laser ablation of potato flesh and skin. The emission spectra recorded with an Echelle spectrometer with ICCD detector were compared to the spectral radiance computed for a plasma in local thermal equilibrium to deduce the mass fractions of the mineral elements.

COLORED POTATOES (SOLANUM TUBEROSUM L.) DRIED FOR ANTIOXIDANT-RICH VALUE-ADDED FOODS

Colored potatoes (Solanum tuberosum L.) are a significant source of antioxidants frompolyphenols,carotenoidsandascorbicacid.Inthisstudy,theretentionof total antioxidants in fresh colored potatoes and processed potato flakes prepared as potential ingredients for snack foods was studied. Total antioxidant capacity, total phenolics and total anthocyanins were higher in purple potato flesh compared with those from red, yellow and white potato cultivars. Peeled purple potatoes were blanched and dehydrated by freeze drying (FD), drum drying and refractance window drying to prepare potatoflakes. Resultsshowed no significant losses in total antioxidant capacity and total phenolic content in flakes in all drying methods obtainedunderstudy.However,45,41and23%lossesintotalanthocyaninscontent were observed in potatoflakes after FD,drum drying and refractive window drying, respectively.Colored potatoes could provide an excellent source of antioxidant-rich ingredient for the production of nutritionally enhanced food products.

Low Catalyst Loadings for the Production of Carboxylic Acids from Polysaccharides and Hydrogen Peroxide

The oxidation of starch, xylans, potato flesh and wheat flour by H(2)O(2), in the presence of MSO(4) (M=Cu, Fe) as catalyst, led to depolymerization, and formation of solutions containing polyhydroxycarboxylic acids. Some of these oxidized compounds facilitate the process, leading to efficient transformations even with very low amounts of catalyst.

Evaluation of minor element concentrations in potatoes using laser-induced breakdown spectroscopy

We have performed spectroscopic analysis of the plasma generated by Nd:YAG laser irradiation of flesh and skin of fresh potatoes. From the spectra recorded with an Echelle spectrometer 11 minor elements have been identified. Their relative concentrations were estimated by comparing the measured spectra to the spectral radiance computed for a plasma in local thermal equilibrium. According the moderate plasma temperature of about 6500 K at the time of spectroscopic observation, the electrons are essentially generated by the ionization of the minor metal atoms, making plasma modeling possible although the organic elements may be out of equilibrium. Among the spectral lines selected for the analysis, the Na I 588.99 and 589.59 nm doublet was found to be partially self-absorbed allowing us to estimate the number density of sodium atoms. The value was found to agree with the number density predicted by the plasma model. As a result, the relative concentrations of the detected minor elements have been estimated for both the flesh and skin of the potatoes. Among these, aluminum and silicon were found to have relatively large mass fractions in the potato skin whereas their presence was not detected in the flesh. The present study shows that laser-induced breakdown spectroscopy is a promising tool to measure the elemental composition of fresh vegetables without any sample preparation.

Effect of Pepsin Hydrolysis on Amylase Activity and Lack of Amylase Inhibitory Activity of Sweet Potato Protein

The objectives were to determine the effect of pepsin hydrolysis on amylase activity and test for amylase inhibitory activity of Beauregard sweet potato protein. Protein was extracted from sweet potato flesh, peel, and leaf. Samples with or without pepsin digestion at pH 2 were run on SDS PAGE. Proteins resistant to pepsin digestion were found in the flesh, peel, and leaf. Amylase activity and amylase inhibitory activity were determined using starch as substrate, sugar reducing ends as product, and dinitrosalicylic acid as the detection medium. Dinitrosalicylic acid reacts with sugar reducing ends to absorb at 540 nm. No amylase activity was found in the leaf extract. Digestion with pepsin eliminated amylase activity in the flesh and peel extracts. Amylase inhibitors were not apparent in any of the fractions before or after pepsin hydrolysis. Amylase inhibition by sweet potato protein does not appear to be the mechanism for the low glycemic response to Beauregard sweet potatoes. Gastric digestion is likely to eliminate native amylase activity in the sweet potato thereby requiring pancreatic amylase to digest carbohydrate in vivo.Support: N.C. Sweet Potato Commission.Grant Funding SourceN.C. SWEET POTATO COMMISSION

Dietary protection against free radicals: a case for multiple testing to establish structure-activity relationships for antioxidant potential of anthocyanic plant species.

DNA damage by reactive species is associated with susceptibility to chronic human degenerative disorders. Anthocyanins are naturally occurring antioxidants, that may prevent or reverse such damage. There is considerable interest in anthocyanic food plants as good dietary sources, with the potential for reducing susceptibility to chronic disease. While structure-activity relationships have provided guidelines on molecular structure in relation to free hydroxyl-radical scavenging, this may not cover the situation in food plants where the anthocyanins are part of a complex mixture, and may be part of complex structures, including anthocyanic vacuolar inclusions (AVIs). Additionally, new analytical methods have revealed new structures in previously-studied materials. We have compared the antioxidant activities of extracts from six anthocyanin-rich edible plants (red cabbage, red lettuce, blueberries, pansies, purple sweetpotato skin, purple sweetpotato flesh and Maori potato flesh) using three chemical assays (DPPH, TRAP and ORAC), and the in vitro Comet assay. Extracts from the flowering plant, lisianthus, were used for comparison. The extracts showed differential effects in the chemical assays, suggesting that closely related structures have different affinities to scavenge different reactive species. Integration of anthocyanins to an AVI led to more sustained radical scavenging activity as compared with the free anthocyanin. All but the red lettuce extract could reduce endogenous DNA damage in HT-29 colon cancer cells. However, while extracts from purple sweetpotato skin and flesh, Maori potato and pansies, protected cells against subsequent challenge by hydrogen peroxide at 0°C, red cabbage extracts were pro-oxidant, while other extracts had no effect. When the peroxide challenge was at 37°C, all of the extracts appeared pro-oxidant. Maori potato extract, consistently the weakest antioxidant in all the chemical assays, was more effective in the Comet assays. These results highlight the dangers of generalising to potential health benefits, based solely on identification of high anthocyanic content in plants, results of a single antioxidant assay and traditional approaches to structure activity relationships. Subsequent studies might usefully consider complex mixtures and a battery of assays.

Special quality traits of coloured potato breeding clones: Anthocyanins, soluble phenols and antioxidant capacity

AbstractBACKGROUD: Coloured potato varieties rich in anthocyanins are of increasing interest in breeding to upgrade the nutritional quality of tubers. The objective of this study was to examine purple fleshed breeding clones for anthocyanins, soluble phenols and their antioxidant capacity, and to compare them in this respect with purple and white/yellow fleshed potato cultivars.RESULTS: Within the coloured potato group, the breeding clones had the highest contents of anthocyanins, with values ranging from 0.94 to 1.75 g kg−1 fresh weight. In cultivars and clones with purple flesh the amounts of soluble phenols were 2.6‐times higher than in white/yellow fleshed potatoes. In addition, coloured clones exhibited 4.4‐fold higher antioxidant activity, which was correlated with phenols and anthocyanins. But there were no major differences between the two potato groups in dry matter, starch, crude protein and reducing sugars.CONCLUSIONS: The involvement of purple fleshed potatoes in breeding led to increased anthocyanin and phenol contents of the resulting progeny. The high level of bioactive plant phenols coincided with an enhanced antioxidant activity, known for its positive health effects. Copyright © 2008 Society of Chemical Industry

Factors Influencing Consumer Preference of Fresh Potato Varieties in Maine

Tuber color and appearance are important factors that influence consumer decision-making. In order to evaluate which factors are important to consumers in Maine, we surveyed 275 people over two years and four locations to assess fresh potato consumption patterns and to determine how specific potato characteristics influence variety selection. A majority of the study participants were women between the ages of 41 and 60. Over 60% of survey participants cooked and consumed fresh potatoes between one and three times per week, and over 84% of participants reported that baked, mashed, or roasted potatoes were their preferred methods of preparing fresh potatoes. Over 96% of survey participants expressed that potatoes were a healthy food, although more than a third stated that they limited their carbohydrate consumption. The most important potato characteristics found to influence fresh potato purchase were skin quality and place of origin with 30% and 41% of participants giving each of these factors the highest possible score. Participants appear to recognize the importance of the industry, and many expressed interest in buying locally grown potatoes. Skin quality was the most important characteristic influencing preference for whole white and yellow skin varieties (seven of eight varieties) evaluated in the study. Skin quality also influenced variety selection of whole red skin potatoes in five of eight varieties. This suggests that more research is needed to develop varieties and production methods that produce attractive blemish-free potatoes. When participants could see the potato flesh, it significantly influenced variety selection with all potatoes. Flesh color was the most important characteristic of halved potatoes with 13 of 14 possible varieties. Pictures showing potato flesh color may also help retail sales of table stock varieties. The yellow fleshed varieties with white and purple skins were quite popular, but yellow flesh, red skin varieties were less popular.

Factors Influencing Consumer Preference of Fresh Potato Varieties in Maine

Tuber color and appearance are important factors that influence consumer decision-making. In order to evaluate which factors are important to consumers in Maine, we surveyed 275 people over two years and four locations to assess fresh potato consumption patterns and to determine how specific potato characteristics influence variety selection. A majority of the study participants were women between the ages of 41 and 60. Over 60% of survey participants cooked and consumed fresh potatoes between one and three times per week, and over 84% of participants reported that baked, mashed, or roasted potatoes were their preferred methods of preparing fresh potatoes. Over 96% of survey participants expressed that potatoes were a healthy food, although more than a third stated that they limited their carbohydrate consumption. The most important potato characteristics found to influence fresh potato purchase were skin quality and place of origin with 30% and 41% of participants giving each of these factors the highest possible score. Participants appear to recognize the importance of the industry, and many expressed interest in buying locally grown potatoes. Skin quality was the most important characteristic influencing preference for whole white and yellow skin varieties (seven of eight varieties) evaluated in the study. Skin quality also influenced variety selection of whole red skin potatoes in five of eight varieties. This suggests that more research is needed to develop varieties and production methods that produce attractive blemish-free potatoes. When participants could see the potato flesh, it significantly influenced variety selection with all potatoes. Flesh color was the most important characteristic of halved potatoes with 13 of 14 possible varieties. Pictures showing potato flesh color may also help retail sales of table stock varieties. The yellow fleshed varieties with white and purple skins were quite popular, but yellow flesh, red skin varieties were less popular.

The effect of test conditions on failure parameters during uniaxial compression of potato tissue

SummaryUniaxial compression tests were performed on potato flesh. Cylindrical samples of diameters (19.05 and 25.4 mm) and heights (5, 10, 15 and 20 mm) were tested under non‐lubricated, lubricated and increased friction conditions. The deformation rate effect was also examined by performing compression tests at 50, 100, 200 and 400 mm min−1. In the present study, parameters derived from compression to failure were failure strain (ε), engineering stress (F/A0), true stress (F/Af), apparent elastic modulus (E) and energy at failure (Uv). As compared with non‐lubricated friction condition, lubrication increased significantly the average ε value and decreased significantly the average F/Af value, but appears to have lower significant effect on the average F/A0, E and Uv values. Failure strain, engineering stress and energy at failure increased with deformation rate, whereas true stress and apparent elastic modulus decreased. Failure strain increased with sample diameter and decreased significantly with sample height, whereas the rest of the failure parameters decreased when both sample dimensions increased. As compared with non‐lubricated friction condition, lubrication results in a higher influence of deformation rate on the averageε, F/A0 and Uv values, a similar influence of sample diameter on the average F/Af and E values, but a lower influence of sample height on all the failure parameters. In turn, increased friction results in a higher influence of deformation rate and mainly the sample height on the averageε, F/A0 and Uv values, but a lower influence of sample diameter on all the failure parameters. Principal components analyses showed that principal component 1 is determined by ε, F/A0 and Uv, and is strongly influenced by sample height, whereas component 2 is dominated by E, and is mainly influenced by sample diameter.

Fracture behaviour of potato samples (cv. Desiree) under uniaxial compression

Uniaxial compression tests were performed on potato flesh. Cylindrical samples of heights (5, 10, 15 and 20 mm) and diameters (19.05 and 25.4 mm) were tested under non-lubricated, lubricated and increased friction conditions. Sample flatness ( λ = 4height/diameter of sample) of specimens ranged between 0.79 and 4.20. Displacement rate effect was also examined by performing tests at 50, 100, 200 and 400 mm min −1. Measured fracture parameters were Cauchy strain ( ε C), engineering stress ( F/ A 0), true stress ( F/A f), work of fracture ( W f), and the apparent elastic modulus ( E). Fracture parameters showed a dependence upon sample flatness when no lubricant was used, which decreased with lubrication and increased with increasing friction conditions. A lower flatness ratio led to an increase in stress at a given strain level, i.e. the material appeared to be stiffer than it truly is. Shorter samples and increased friction resulted in an observed dependence upon displacement rate; a higher displacement rate resulted in a lower fracture stresses for a given strain level. Lubrication increases significantly the Cauchy strain, and reduces the true stress, values. Cauchy strain was found to increase with displacement rate and decreased when the flatness ratio increased. Engineering stress, true stress, and work of fracture decreased as displacement rate and sample flatness are increased. Lubrication was found to reduce the effect of displacement rate on the Cauchy strain. Sample flatness influenced engineering stress, work of fracture and apparent elastic modulus, whereas displacement rate influenced true stress and apparent elastic modulus. Increased friction resulted in a higher sample flatness influence on all fracture parameters. Results show that for any compression test with potatoes, it is possible to determine optimum conditions that will minimize the effects of the test on fracture parameters.

The analysis of frictional, displacement rate and sample dimension effects on fracture parameters from uniaxial compression of potato

Uniaxial compression tests were performed on potato flesh. Cylindrical samples of heights (5, 10, 15 and 20 mm) and diameters (19.05 and 25.4 mm) were tested under non-lubricated, lubricated and increased friction conditions. Sample flatness ( l = 4 height/diameter of sample) ranged between 0.79 and 4.20. The effects of lubrication upon the measured fracture parameters derived from compression tests, ie compressive Cauchy strain ( ε), compressive stress ( σ), apparent compressive elastic modulus ( E) and the work of fracture ( W) are reported. Sample height had the more significant effect on ε and sample flatness had the more significant effect on σ. Sample diameter had the more significant effect on E, and both sample height and flatness had the more significant effects on W. Surface lubrication increased ε, but appeared to have a low effect on the rest of the mechanical parameters due to the fluid released from the flesh during testing. Increased friction increased W, due to the sum of the energy actually involved in compressing the food plus those required to overcome surface friction as the sample expands. Lubrication reduced the influence of other factors such as sample height and removed sample diameter effect (contact area) on the E, while increased friction increased sample height and flatness effects. Linear combinations of fracture parameters extracted by linear discriminant analysis (LDA) pointed out that Cauchy strain was the fracture parameter that strongly contribute to distinguish between the levels of lubricant studied. At each friction condition, LDA showed that sample height has the highest signification on the fracture parameters, being the main discrimination found between 5 mm and the rest of the heights.

CDNA cloning and expression of anthocyaninbiosynthetic genes in wild potato (Solanumpinnatisectum)

The purple anthocyanins in potato tuber skin and flesh are primarily derived from petunidin. cDNA clones encoding the enzymes involved in anthocyanin biosynthesis, chalcone synthase (CHS), flavanone 3-hydroxylase (F3H), dihydroflavonol 4-reductase (DRF), and UDP-glucose: flavonoid 3-0- glucosyltransferase (3GT), were isolated from Solanum pinnatisectum by RT-PCR with degenerated primers. Sequence comparison showed that they share 76-96% identities with each corresponding solanaceous gene reported previously. Each gene is a member of a multigene family. The spatial expression analysis indicated that these genes were preferentially expressed in flowers, stolons and terminal buds, and their transcripts could not detected in roots except 3GT. All the genes were induced expression in tuber skins by white light, and followed by anthocyanin accumulation. This is the first report cloning and expression of anthocyanin biosynthetic genes in wild potato (Solanum pinnatisectum). Key words: Anthocyanin, expression, gene cloning, wild potato species

Modelling the area expansion ratio on uniaxial compression of cylindrical potato samples

Uniaxial compression tests were performed on potato flesh. Cylindrical samples of heights (5, 10, 15 and 20 mm) and diameters (25.4 and 19.05 mm) were tested under lubricated (mineral oil), non-lubricated (natural) and increased friction (emery paper) conditions. Sample flatness (force free area/loaded area) ranged between 0.79 and 4.20. Deformation rate effect was also examined by performing compression tests at 50, 100, 200 and 400 mm min −1. In this study, parameter derived from compression to failure was failure strain ( ε r %). It was established a method for determining the area expansion ratio, AF/ A 0 (actual maximum area in contact with the loading platens/original area) at several deformation levels ( ε %). For that, loaded area was determined at deformation levels (20%, 40% and 80%) by planimetring of a graphic mark, and then adjusted by regression with respect to deformation level. From this regression, area expansion ratio at failure, AF r/ A 0 was obtained by replacing at each equation corresponding failure strain value. Cylindrical potato samples compression was accompanied by a significant cross-sectional area expansion, evidencing a far-ideal area expansion. For lubricated and non-lubricated friction conditions, increasing deformation rate and sample diameter increased AF r/ A 0, whereas increasing sample height decreased the ratio, mainly under non-lubricated condition. Lubrication causes an increase of AF r/ A 0 average value, near 5% with respect to that obtained with non-lubricated friction condition, meaning a lower influence of deformation rate and sample height, but a higher flatness influence. Effect due to surface lubrication was smaller than in previous compression tests on cheeses, which could be attributed to release of fluid from the damaged tissue of the potato flesh which relatively reduced lubricant effectiveness.

Red and purple coloured potatoes as a significant antioxidant source in human nutrition - a review

Potatoes regarding their consumption are a significant antioxidant source in human nutrition. The main potato antioxidants are polyphenols, ascorbic acid, carotenoids, tocopherols, -lipoic acid, and selenium. The most contained polyphenolic antioxidants in potatoes are L-tyrosine, caffeic acid, scopolin, chlorogenic and cryptochlorogenic acid and ferulic acid. In red and purple potatoes are in addition contained acylated anthocyanins and pigmented potatoes display two to three times higher antioxidant potential in comparison with white-flesh potato. Red potato tubers contain glycosides of pelargonidin and peonidin, purple potatoes glycosides of malvidin and petunidin. New red and purple flesh potato varieties are breeded for their use in food and in the non-food industry. Anthocyanins of potatoes are also useful in the protection against potato blight.