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

BACKGROUD: 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     

Variety and storage conditions affect the precursor content and amount of acrylamide in potato crisps

BACKGROUND: Acrylamide, a probable human carcinogen, is formed from the amino acid asparagine and reducing sugars when potato products are processed at high temperatures. This is a two‐year study on five Swedish‐grown potato clones, two of which are adapted to cold storage. The clones represented a wide range of precursor concentrations: asparagine, 3.7–15.3 mg g^?1; reducing sugars, 0.9–14.9 mg g^?1. Crisps were prepared in laboratory‐scale equipment mimicking industrial processing conditions. RESULTS: Potatoes stored at 4 °C had significantly higher levels of glucose and fructose than potatoes stored at 8 °C. Acrylamide levels were significantly higher in crisps made from potatoes stored at 4 °C. Two clones with a large difference in asparagine concentration but similar glucose and fructose concentrations gave crisps with significantly different acrylamide contents. The lowest levels of acrylamide were found in crisps made from the potato variety with the lowest asparagine concentration. CONCLUSION: The findings show that variety and storage conditions influence the levels of precursors. Acrylamide formation in crisps can be reduced by using potato varieties with low levels of both asparagine and reducing sugars. Mass transport of precursors during heating is suggested to be important for acrylamide formation in potato crisps. Copyright © 2007 Society of Chemical Industry     

Quantitative analysis of phenolic components and glycoalkaloids from 20 potato clones and in vitro evaluation of antioxidant,cholesterol uptake,and neuroprotective activities

Potato (Solanum tuberosum L.) is one of the most important food crops in the world and provides essential nutrients. With an aim to develop potato varieties for functional food or nutraceutial applications, we have conducted metabolomic profiling, total phenolics, chlorogenic acid, anthocyanins, and glycoalkaloids analyses on 20 selected potato clones within the Canadian potato breeding program of Agriculture and Agri-Food Canada. Pigmented potatoes in general contain higher levels of phenolic components, including chlorogenic acid and anthocyanins. Levels of phenolics were retained with granulation processing of pigmented potato tubers, but glycoalkaloids were significantly reduced with granulation. The pigmented potatoes also have higher antioxidant activity reaching up to 35% of that for berries, measured as their potency in scavenging DPPH radicals. Extracts of the 20 potato clones (peel, tuber, and granule) were also evaluated for in vitro effects on liver LDL cholesterol uptake and protection of cortical neurons from cell death caused by oxygen glucose deprivation (OGD). These potato extracts in general showed mild activity in enhancing LDL cholesterol uptake in liver HepG2 cells, and also protected cortical neurons against OGD induced cell death, with extracts from granules of six of the potato clones showing significant neuroprotective effects. The bioactive components are not dependent on pigmentation of potato clones. These novel bioactivities identified in potatoes warrant in-depth investigations in the future. Taken together, our results provide further evidence for the enhanced health beneficial components in potato.     

Textural and pasting properties of potatoes (Solanum tuberosum L.) as affected by storage temperature

Fresh tubers from five potato (Solanum tuberosum L.) cultivars were stored at different temperatures (4, 8, 12, 16 and 20 °C) and 80–90% relative humidity for 18 weeks after harvest to examine the effect of storage temperature on their textural and pasting properties. Texture profile analysis was performed on raw and cooked potatoes using an Instron universal testing machine to measure textural parameters such as fracturability, hardness, cohesiveness, adhesiveness and springiness. Both raw and cooked potato tubers showed a considerable reduction in all textural parameters upon storage, irrespective of the storage temperature employed. Raw potatoes showed a decrease in fracturability and hardness with increasing storage temperature, whereas their cooked counterparts showed the opposite trend. The extent of change in the textural properties of both raw and cooked potatoes also varied among the different cultivars. Fresh and stored tubers from all cultivars were freeze‐dried, ground into flours and analysed for amylose content and pasting properties. The amylose content of flours prepared from potatoes stored at 4 and 8 °C was observed to be considerably lower than that of flours prepared from potatoes stored at 16 and 20 °C. Pasting characteristics such as peak viscosity, setback and final viscosity increased with increasing storage temperature, while the reverse was observed for pasting temperature, when studied using a rapid visco analyser. Breakdown in viscosity of the flour pastes from all cultivars was considerably reduced during storage, irrespective of the storage temperature employed. Copyright © 2006 Society of Chemical Industry     

Effect of methyl jasmonate on quality and antioxidant activity of postharvest loquat fruit

BACKGOUND: Loquat fruit is rich in natural antioxidants and has shown a remarkably high antioxidant activity. To search for an effective method for maintaining or even improving antioxidant activity during postharvest storage, we investigated the effect of 10 µmol L^?1 methyl jasmonate (MeJA) treatment on levels of major individual sugars and organic acids, total phenolics, total carotenoids, total flavonoids and antioxidant activity in loquat fruit during storage at 1 °C for 35 days. RESULTS: The MeJA‐treated fruit exhibited significantly lower levels of respiration rate, ethylene production, phenylalanine ammonia‐lyase and polyphenol oxidase activities, and higher levels of sugars, organic acids, total phenolics and total flavonoids than control fruit. Meanwhile, the treatment also maintained significantly higher antioxidant activity as measured by the scavenging capacity against 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH), superoxide and hydroxyl radicals, and by the reducing power test compared to the control. There was a significant positive linear relationship between total phenolic content and DPPH radical scavenging activity. CONCLUSION: MeJA treatment can improve the quality and functional properties of harvested loquat fruit by maintaining a higher level of antioxidants and enhancing antioxidant activity. Copyright © 2009 Society of Chemical Industry     

Antioxidant capacity in cultivated and wild Solanum species: the effect of wound stress

Wild potatoes are of increasing interest as a gene pool in breeding. In this study, 23 genotypes of two cultivated (S. tuberosum subsp. andigena, S. phureja) and two wild Solanum species (S. chacoense, S. pinnatisectum) were evaluated for contents of soluble phenols and soluble proteins as well as their antioxidant capacity measured as ascorbic acid and trolox equivalent. Amounts of phenols present in tuber tissue ranged from 0.25 to 2.84 mg kg(-1) fw. On average, S. pinnatisectum (pnt) exhibited 3.9-fold greater quantities of phenols in its tuber tissue than the other Solanum species. In pnt tissue, high phenol content coincided with high levels of soluble proteins and antioxidants. It is concluded that an involvement of individual accessions of pnt in breeding could be profitable for the antioxidant potential and thus for the nutritional value of new potato cultivars. The results also revealed that soluble phenols as well as proteins present in tuber tissue substantially contributed to the total antioxidant capacity of potatoes. Moreover, it was found that quantities of soluble phenols, proteins and antioxidants increased notably upon wounding the tubers, a fact which underlines the role of all these components in wound stress responses of potatoes.     

Fatty acid composition, antioxidants and lipid oxidation in chicken breasts from different production regimes

Chicken breast from nine products and from the following production regimes: conventional (chilled and frozen), organic and free range, were analysed for fatty acid composition of total lipids, preventative and chain breaking antioxidant contents and lipid oxidation during 5 days of sub‐ambient storage following purchase. Total lipids were extracted with an optimal amount of a cold chloroform methanol solvent. Lipid compositions varied, but there were differences between conventional and organic products in their contents of total polyunsaturated fatty acids and n‐3 and n‐6 fatty acids and n‐6:n‐3 ratio. Of the antioxidants, α‐tocopherol content was inversely correlated with lipid oxidation. The antioxidant enzyme activities of catalase, glutathione peroxidase and glutathione reductase varied between products. Modelling with partial least squares regression showed no overall relationship between total antioxidants and lipid data, but certain individual antioxidants showed a relationship with specific lipid fractions.     

Microbiological quality of fresh-cut sweet potatoes

Sweet potato roots were dipped in various concentrations of chlorine for 5 min at 1 or 20 °C before and after slicing, and then stored at 2 or 8 °C for 14 days to evaluate the effects of different chlorine treatments and storage temperatures on the microbiological quality of fresh‐cut sweet potato slices. The microflora of fresh‐cut sweet potato slices was dominated by mesophiles, followed by psychrotrophs and fungi initially and during storage. The 2 °C storage was necessary to keep the microbial load at a low level. No spoilage was observed in fresh‐cut sweet potatoes at both storage temperatures for 14 days. Chlorination of sweet potatoes before slicing was not effective in ensuring acceptable microbiological quality of fresh‐cut sweet potatoes. Dipping slices in 200 ppm chlorine at 1 °C reduced the population of all micro‐organisms during storage.     

Effect of temperature on lipid‐derived volatile compounds in boiled potato during storage

BACKGROUND: The aroma of boiled potatoes is greatly appreciated by consumers. Although it is formed by 150 volatile compounds, only a few seem to actually contribute to the characteristic aroma. In addition, potatoes have to be stored at a low temperature after harvest to guarantee a year‐round supply. However, even at low temperatures, tuber volatile composition is modified during storage. The aim of the present study was to investigate the effect of storage temperature on boiled potato volatile constituents, mainly focused on lipid‐derived components, by considering different varieties stored at 4 °C and 8 °C. RESULTS: It was found that fewer lipid‐derived components were obtained when the potato tubers were stored at 4 °C rather than 8 °C. Specifically, the amounts of 2,4‐decadienal isomers and hexanal increased with the storage time, particularly at 8 °C. Similarly, pentanal and nonanal, which are autoxidation products, occurred to a greater extent at higher temperatures. In contrast, the levels of sugar‐derived compounds, in general, increased during storage at 4 °C rather than 8 °C as a result of higher content of sugars at low temperature. CONCLUSION: The effect of storage temperature on lipid‐derived volatile components in boiled potato appears to depend on the variety studied. Generally speaking, lower temperatures during storage promote sugar content and, as a consequence, sugar‐derived products. At the same time, lower temperatures result in less lipid oxidation and, therefore, a fewer lipid‐derived compounds. Copyright © 2009 Society of Chemical Industry     

Lipids of potato tubers. Effects of storage temperature on total,polar and sterol lipid content and fatty acid composition of potato tubers

Potato tubers (Majestic and Bintje varieties) were stored at 5 and 20 °C for up to 24 weeks. Only minor differences were observed in lipid composition of tubers stored at the two temperatures. Linolenic acid levels were slightly lower in the 10 °C stored tubers, although no significant differences were found in the proportions of the total polyunsaturated fatty acids of tubers at 5 and 20 °C. The effects on the fatty acid composition of Pentland Crown potatoes of short term storage at 30 °C are reported. It is concluded from this and from previous papers in this series that neither the choice of potato variety, nor of storage temperature for a given variety, is likely to reduce the polyunsaturated fatty acid content of potato sufficiently to avoid the problems experienced commercially in the oxidative degradation of polyunsaturated fatty acids to produce off-flavours in potato products. The large changes in the proportions of the different classes of sterol lipids which have been reported to occur in potatoes during storage were not confirmed by the present studies.     

不同品种紫薯抗氧化物质及体外抗氧化活性比较

为比较福建产区主栽紫薯抗氧化物质成分含量及其体外抗氧化活性,对7个不同品种紫薯中总酚、总黄酮、总花色苷及花青素组分进行了分析,并测定其清除自由基活性。结果表明:福宁紫3号紫薯中所含抗氧化活性成分如总酚、总黄酮、总花色苷和花青素的含量均为最高。通过高效液相色谱法分析测定紫薯中含有的花青素单体主要为飞燕草色素、芍药色素和矢车菊色素,不同品种紫薯中花青素组成及含量表现出的一定的差异性。福宁紫3号紫薯表现出较强的自由基清除活性,0.5 mg·L-1紫薯鲜样提取液DPPH自由基、OH自由基及ABTS清除率分别达到88.4%、49.1%、90.1%。 相对于其他品种,福宁紫3号紫薯在抗氧化活性成分含量及体外抗氧化活性方面表现最佳。     

A comparative study of composition and postharvest performance of organically and conventionally grown kiwifruits

Postharvest performance of organic and conventional ‘Hayward’ kiwifruits grown on the same farm in Marysville, California, and harvested at the same maturity stage were compared in this study. Quality parameters monitored included morphological (shape index) and physical (peel characteristics) attributes of the initial samples. Maturity indices (CO₂ and C₂H₄ production, firmness, color, soluble solids content and acidity) and content of compounds associated with flavor and nutritional quality (minerals, sugars and organic acids, ascorbic acid, total phenolics, and antioxidant activity) were determined at 0, 35, 72, 90 and 120 days of storage at 0°C, and after 1 week of shelf‐life simulation at 20°C, after each storage duration. Organically and conventionally grown kiwifruits had similar soluble solids content at harvest, but conventional kiwifruits had a higher firmness and L* value, and a lower hue angle and chromaticity, resulting in a lighter green color when compared with the organic kiwifruits. These differences were maintained for all the storage durations, with the soluble solids content increasing more in conventionally grown kiwifruits. The two production systems resulted in different morphological attributes since organic kiwifruits exhibited a larger total and columella area, smaller flesh area, more spherical shape, and thicker skin compared to conventional kiwifruits. All the main mineral constituents were more concentrated in organic kiwifruits, which also had higher levels of ascorbic acid and total phenol content, resulting in a higher antioxidant activity. Sugars and organic acids composition was not affected by the production system. Copyright © 2007 Society of Chemical Industry     

Effects of preparation procedures,packaging and storage on nutrient retention in peeled potatoes

The effects of preparation procedures and packaging on vitamin C, dietary fibre, sugars, ash and moisture contents were studied in prepeeled packaged potatoes during two cultivation seasons. The potato cultivars Bintje, Van Gogh and Nicola were studied. Potatoes of the Nicola cultivar had the highest initial vitamin C and sugar contents. Retention of nutrient contents in packaged, prepeeled potatoes was very good after a 7-day storage period. Vitamin C contents were higher in packaged potatoes than in fresh tubers when ascorbic acid was used in the washing solution but the levels decreased during the 7-day storage period. When calcium chloride was added as well into the washing solution vitamin C contents remained high throughout the storage period. These results show that it is possible to preserve the nutritional contents of packaged potatoes over a 7-day storage period. Cooking decreased vitamin C contents by about 30% and keeping the potatoes hot for 1 h after cooking decreased vitamin C contents a further 10%. © 1998 SCI.     

Sprout inhibition of potatoes with soft‐electron (low‐energy electron beams)

The surfaces of potatoes were irradiated with electrons of different energy levels, and the effects on sprouting were investigated. Electrons at 270 keV or higher effectively inhibited sprouting of four cultivars of potatoes, cvs Danshaku, Hokkaikogane, Toyoshiro and May Queen, even after storage at 23 °C for 4 months. Sugar contents in tubers treated with 270‐keV electrons were lower after storage for 3 months than their levels before electron treatment. The levels of glucose, fructose and sucrose were significantly lower in the tubers treated with 270‐keV electrons than in low temperature (5 °C)‐stored tubers. The results indicate the potential of low energy electron treatment for the shelf‐life extension of potatoes as an alternative to treatments with gamma‐rays or chemicals. Copyright © 2004 Society of Chemical Industry     

Cultivar choice provides options for local production of organic and conventionally produced tomatoes with higher quality and antioxidant content

BACKGROUND: Tomatoes (Solanum lycopersicum L.) are widely consumed and well known for their health benefits, many of which have been associated with the high levels of antioxidants present in tomatoes. With a growing interest in local and organic foods, it would be helpful to determine whether farmers could naturally improve the quality and antioxidant content of tomatoes for sale in local markets. This study evaluated antioxidant properties, quality attributes, and yield for 10 tomato cultivars grown for 2 years using certified organic and conventional practices. RESULTS: Cultivar and year effects impacted (P < 0.05) all tests conducted, while growing method influenced (P < 0.05) yield, soluble solids content, ascorbic acid, and antioxidant radical scavenging capacity. Even when accounting for year‐to‐year variability, cultivars in the highest groups had 1.35‐ to 1.67‐fold higher antioxidant levels than cultivars in the lowest groups. ‘New Girl’, ‘Jet Star’, ‘Fantastic’, and ‘First Lady’ were always in the highest groups, while ‘Roma’ and ‘Early Girl’ consistently had the lowest antioxidant content. CONCLUSION: Compared to production practices and environmental effects of years that are generally beyond the control of small‐scale producers, choice of cultivar provides the simplest and most effective means of increasing antioxidant properties. Knowledge of tomato cultivars with naturally higher antioxidant levels could assist smaller‐scale producers to grow fruit that may provide a competitive advantage and the opportunity to capitalize on the increasing popularity of locally grown, high‐quality fresh produce. Copyright © 2010 Society of Chemical Industry     

Effect of freezing/thawing conditions and long‐term frozen storage on the quality of mashed potatoes

The effects of freezing temperature (−80, −40 or −24 °C) and thawing mode (microwave or overnight at 4 °C) on quality parameters of mashed potatoes made from tubers (cv Kennebec) and from potato flakes were examined, as was the effect of long‐term frozen storage on the quality of mashed potatoes. Mashed potatoes were tested for texture profile analysis (TPA) and cone penetration, oscillatory and steady rheometry, colour, dry matter, Brix and sensory analyses. In natural mashed potatoes, TPA hardness and oscillatory parameters showed that processing resulted in a softer product than the fresh control. The parameters were lower in the samples thawed at 4 °C than in those thawed by microwave at all the freezing temperatures used, which may be ascribed to gelatinisation of the starch released from damaged cells. Differences from the freshly prepared product decreased when the samples were frozen at −80 °C and thawed by microwave. No difference was found in sensory acceptability between samples frozen at −80 and −40 °C, which probably reflects the panellists' mixed preferences for air‐thawed versus microwave‐thawed samples. Increasing the time in frozen storage led to a natural mash with a firmer texture, higher L*/b* value and Brix; nonetheless, panellists found the samples at 0, 3 and 12 months of frozen storage equally acceptable. In commercial mash, penetration and oscillatory parameters showed that processing made for a firmer product than the fresh control, probably owing to retrogradation of gelatinised starch. Thawing mode had a significant effect on parameters, which were lower in the samples thawed at 4 °C. The structure and quality of commercial mash was more detrimentally affected by freezing and, therefore, we would not recommend either freezing or frozen storage of this mashed potato in the used conditions. Natural mash made from Kennebec potatoes should be frozen quickly and thawed by microwave in the conditions described to obtain a product more similar to that freshly made. If the samples are frozen by air blasting at −40 °C, the product can withstand frozen storage for one year. Copyright © 2005 Society of Chemical Industry     

彩色马铃薯“剑川红”和“转心乌”花色苷的抗氧化分析

彩色马铃薯"剑川红"和"转心乌"富含花色苷,为探明2种马铃薯中花色苷的体外抗氧化活性差异及其组合效果,使这种价格低廉、取材方便的食材得到更好的开发和利用。本研究以抗坏血酸(VC)为对照,采用1,1-二苯基-2-三硝基苯肼(1,1-diphenyl-2-picrylhydrazyl,DPPH)自由基法、2,2’-联氮-二(3-乙基-苯并噻唑-6-磺酸)二铵盐(2,2’-azinobis-(3-ethylbenzthiazoline-6-sulphonate),ABTS)自由基法、羟自由基(·OH)法、超氧阴离子自由基(O_2~-·)法等4种体外抗氧化模型评价了云南地方特色马铃薯品种"剑川红"和"转心乌"花色苷的抗氧化活性。结果表明:"剑川红"和"转心乌"的花色苷具有很好的抗氧化活性,且与质量浓度成正相关,其清除自由基的能力是抗坏血酸的10.7~31.3倍;"剑川红"和"转心乌"对4种自由基的清除能力依次为ABTS+·DPPH自由基O_2~-··OH;"转心乌"花色苷对4种自由基的清除效果比"剑川红"花色苷强;二者的花色苷之间没有拮抗作用,且有一定的协同或增效作用,协同或增效效果因自由基的不同而有所差异。     

Tuber components affecting acrylamide formation and colour in fried potato: variation by variety,year, storage temperature and storage time

Variation in asparagine and glucose contents, identified as precursors for acrylamide development in model experiments, has been studied in eight potato clones during long‐term storage at 3 and 10 °C. In addition, glutamine, fructose and sucrose contents were determined and the role of all five substances in colour formation in fried potato products was assessed. Large genotype differences were found in all characteristics, and the ranking order was almost the same for different years and storage times. Breeding for potatoes with low asparagine levels as well as low reducing sugar levels might be another way, in addition to altering processing parameters, to keep the acrylamide level low in fried products. Storage per se at low temperature did not result in higher asparagine levels. The risk that elevated reducing sugar levels during low‐temperature storage might lead to increased acrylamide levels needs further investigation. The determined tuber components accounted for only 11–60 per cent of the total variation in fry colour after storage at 3 °C. It is suggested that screening based on crisp colour in November, perhaps complemented with a few later controls on interesting clones, could be useful for sorting out clones with good crisping abilities during the rest of the low‐temperature storage season. Copyright © 2004 Society of Chemical Industry     

Exogenous methyl jasmonate diminishes the formation of lipid‐derived compounds in boiled potato (Solanum tuberosum L.)

BACKGROUND: During potato storage the tubers tend to develop off‐flavours, mainly due to lipid‐derived aldehydes, whose formation is increased after boiling or processing. This may become a problem when boiled or precooked potatoes are used. Methyl jasmonate (MJ) is a phytohormone capable of modifying plant and food composition. The aim of this work was to control the formation of off‐flavours in different cultivars of raw potato during storage by MJ treatment. RESULTS: The use of Carbowax 20M as support in MJ emulsion resulted in significantly (P < 0.05) lower levels of lipid‐derived compounds than the use of lanolin. Levels of the lipid‐derived aldehydes propanal, hep‐2‐enal, nonanal, oct‐2‐enal and hexanal, although dependent on variety, generally decreased significantly (P < 0.05) after treatment with MJ/Carbowax 20M emulsion. Sugar‐derived compounds such as pyridine and furfural, however, were not affected by this treatment. CONCLUSION: Treatment with MJ/Carbowax 20M can be used to diminish the formation of off‐flavours in boiled potato. However, this treatment is not useful to avoid the sweetening caused by sugar‐derived products. Additional advantages of exogenous MJ are a delay in the appearance of sprouting and aging and hence prolongation of the storage life of potato tubers. Copyright © 2010 Society of Chemical Industry