不同加工方式对紫色马铃薯中酚类物质的影响

紫色马铃薯富含花青素、绿原酸等多酚类物质,是价格低廉、取材广泛的天然抗氧化剂来源。为探明加工方式对紫色马铃薯中酚类物质的影响,最大程度地保留抗氧化活性物质,以3个紫色马铃薯品系和白色马铃薯品种‘夏波蒂’为实验材料,采用蒸制、微波和水煮3种加工方式进行处理,分析加工前后紫色马铃薯块茎中花青素、绿原酸、自由态多酚、结合态多酚的含量及抗氧化活性的变化。结果表明,3种加工方式均导致紫色马铃薯花青素含量的降低;与对照品种‘夏波蒂’相比,蒸制和微波处理后紫色品系马铃薯自由态多酚、结合态多酚、绿原酸的含量及抗氧化活性均更高,而水煮处理后,除结合态多酚的含量增加外,其余成分的含量均显著降低。因此,微波和蒸制加工可以更好地保留紫色马铃薯中的多酚类物质,从而发挥其抗氧化作用。     

Antioxidant,anti-inflammatory and DNA scission inhibitory activities of phenolic compounds in selected onion and potato varieties

Processing of onion and potato produces a large amount of discards, mainly skins. This study compared the antioxidant activity of skin and flesh phenolics of selected onion (Pearl, Red, Yellow and White) and potato (Purple, Innovator, Russet and Yellow) varieties. All tests were carried out separately for the soluble and insoluble-bound phenolic constituents of onion and potato samples. The potency of the phenolic extracts in the inhibition of radical-induced DNA scission, human low-density lipoprotein (LDL) cholesterol oxidation and LPS-stimulated cyclooxygenase-2 (COX-2) expression in J774A.1 mouse macrophage cells were monitored. Results showed that the soluble extracts had a higher phenolic content and antioxidant activity than the insoluble-bound extracts in most of the assays. Both onion and potato phenolics exhibited notable inhibition of LDL cholesterol oxidation, DNA scission and COX-2 expression at concentrations as low as 5 μg/mL. Pearl onion skin and Purple potato peel phenolics exhibited the highest activities among the tested onion and potato varieties, respectively.     

Investigation of the contents of phenolic and alkaloidal compounds of gamma irradiated potatoes during storage

The contents of phenolic cinnamic acids and coumarins as well as of the glycoalkaloids of gamma irradiated potato tubers have been studied in detail. Gamma irradiation up to 3 k Gy had no effect on the glycoalkaloid contents of two potato tuber varieties during a four months storage period. The phenolic compounds behave differently and show a considerable change during storage in potatoes irradiated at the highest dose level, 3 k Gy. A time dependent change of phenolic extracts was observed. This change of phenolic compounds could be partly ascribed to the β-glycoside of scopoletin (coumarin, 7-hydroxy-6-methoxy) and was accompanied by a general decrease of chlorogenic acid, the main hydroxy-cinnamic acid of potatoes.     

Quality of organically and conventionally grown potatoes: Four-year study of micronutrients, metals, secondary metabolites, enzymic browning and organoleptic properties

The quality of potatoes from organic and conventional farming was investigated in this study. Tubers of eight potato varieties, organically and conventionally produced at one or two geographical sites in controlled field trials, were collected in four consecutive harvests from 1996-1999. The parameters analysed included nitrate, trace elements (As, Cd, Co, Cu, Fe, Hg, Mn, Ni, Pb, Se, Zn), vitamin C, potato glycoalkaloids, as well as chlorogenic acid, polyphenol oxidase and rate of tuber enzymic browning. The results indicated lower nitrate content and higher vitamin C and chlorogenic acid content to be the parameters most consistently differentiating organically from conventionally produced potatoes. Elevated concentrations of glycoalkaloids were also observed throughout the experiments in some potato varieties grown in organic farming systems. Principal component analysis (PCA) of the analytical and other data using three PCs confirmed a good separation between the organically and conventionally produced potatoes when studied in single crop years. However, score-plots (objects) and loading-plots (variables) of pooled results from the consecutive harvests showed that between the years' changes and also variety as well as geographical variations are equally or more important factors determining the quality of potatoes than the farming system. Further studies of various marker compounds of potato quality related to the organic or conventional farming systems should be performed before unbiased information can be given to the consumers.     

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     

GLYCOALKALOID CONTENT OF NEWFOUNDLAND GROWN POTATO TUBERS AND POTATO WART TISSUE

Eight cultivars of potato tubers grown in Newfoundland were examined for total glycoalkaloids (TGA) at harvest and after 3, 6, 9 or 12 days exposure to 150 footcandles light. Freshly harvested tubers had TGA ranging from 0.9 to 15.4 mg/100 g of total tuber tissue. TGA increased as a result of long term light exposure in all cases; however, those cultivars surface-pigmented with red or blue anthocyanins were less responsive to light induction. TGA in light exposed tubers ranged from 52–71 mg/100 g for white cultivars, 26–46 mg/100 g for red varieties, and 23–40 mg/100 g for those pigmented with blue anthocyanins. Healthy tubers from plants afflicted with potato wart did not show abnormally high TGA; however, healthy cankers contained as high as 170 mg/100 g. Greening or decomposition of wart tissue was associated with a decline in TGA. Thin-layer chromatography revealed α-solanine and α-chanconine were the principal components in TGA extracts of both tubers and wart tissue.     

Antioxidant activities of Sideritis congesta Davis et Huber-Morath and Sideritis arguta Boiss et Heldr: Identification of free flavonoids and cinnamic acid derivatives

Different solvent extracts of endemic Sideritis (Labiatae) species, Sideritis congesta Davis et Huber-Morath and Sideritis arguta Boiss et Heldr, were analyzed for free flavonoids (quercetin, apigenin, myricetin and kaempferol) and cinnamic acid derivatives (rosmarinic acid, ferulic acid, caffeic acid, p-coumaric acid and chlorogenic acid) using HPLC-DAD. All the phenolics were quantified in acid-hydrolyzed extracts, except rosmarinic acid, chlorogenic acid and myricetin which were quantified in raw samples. Antioxidant activities of extracts of these two plants and many of their components in pure form were evaluated based on DPPH^. and ABTS^.+ assays. In general, S. arguta extracts displayed higher antioxidant activity than S. congesta extracts possibly due to their richness in antioxidant components of strong activity. Acetone extract of S. arguta, with its strikingly high TEAC value of 3.2 mM trolox and low IC₅₀ value of 38.3 ??g/mL showed the highest antioxidant potency among all extracts. ??-tocopherol, the positive control, displayed IC₅₀ and TEAC values of 33.8 ??g/mL and 2.9 mM trolox, respectively. No direct correlation was found between antioxidant activities and total phenolic contents of the plant extracts studied.     

Phenolic content and antioxidant activities of selected potato varieties and their processing by-products

The total content of free, esterified and bound phenolics of the peel and flesh of four potato varieties (Purple, Innovator, Russet and Yellow) were determined using the Folin–Ciocalteu method. The respective antioxidant activities of these potatoes and/or their skins were evaluated using several in vitro assays. The phenolic profiles of potato peel and flesh samples were determined using high-performance liquid chromatography with photodiode array detection (HPLC-DAD). Bound and esterified phenolics contributed as much or even more than the free phenolics to the antioxidant activity of the peels; extracts from Purple variety showing the highest activity. The peels of all varieties showed significantly (p < 0.05) higher phenolic content and antioxidant activities than their respective flesh. Chromatographic data showed differences in the amounts, but not in types, of phenolic compounds in the potato peel samples. Thus, potato processing discard may be used in food formulations and their extracts could potentially be employed as an effective source of antioxidants in food systems.     

Glycoalkaloids in potatoes

The glycoalkaloids present in the cultivated potato plant might result in their being unacceptable by present-day food standards, if that vegetable were introduced today. The alkaloids are derived biosynthetically from cholesterol. The range of glycoalkaloids found in nature is given. Two main methods of determining these alkaloids have been developed, enabling a general screening procedure to be employed by growers. The advent of protoplast techniques has opened up the possibility of many new species and they present the chemist with new problems. There can be a conflict between the requirement of pest- and disease-resistant potatoes and those with low levels of glycoalkaloids. Damage and microbial infection to potatoes may cause glycoalkaloids to develop. In the end, the consumer must be the final arbiter.     

Anthocyanins from pigmented potato (Solanum tuberosum L.) varieties

Pigmented potato (Solanum tuberosum L.) varieties are a rich source of anthocyanins, in particular acylated derivatives. From potato cultivars “Hermanns Blaue”, “Highland Burgundy Red”, “Shetland Black”, and “Vitelotte” the major anthocyanins were isolated and characterised. Sliced potatoes were blanched to minimise enzymatic reactions which cause degradation of anthocyanins.By means of solid phase extraction, countercurrent chromatography and preparative HPLC, it was possible to separate coumaric acid derivatives (i.e. 3-p-coumaroylrutinoside-5-glucosides of petunidin, pelargonidin, peonidin and malvidin) from non-acylated anthocyanins as well as chlorogenic acids. Identity of the isolated compounds was determined by combination of HPLC-DAD and LC-ESI-MS² measurements.Petunidin derivatives were detected in all varieties except Highland Burgundy Red, where pelargonidin was found to be the only anthocyanidin. Malvidin was the predominant aglycon of the variety Vitelotte. Of the four selected cultivars, Shetland Black was the only one containing minor amounts of peonidin derivatives.     

Health‐beneficial properties of potato and compounds of interest

Potatoes have shown promising health‐promoting properties in human cell culture, experimental animal and human clinical studies, including antioxidant, hypocholesterolemic, anti‐inflammatory, antiobesity, anticancer and antidiabetic effects. Compounds present such as phenolics, fiber, starch and proteins as well as compounds considered antinutritional such as glycoalkaloids, lectins and proteinase inhibitors are believed to contribute to the health benefits of potatoes. However, epidemiological studies exploring the role of potatoes in human health have been inconclusive. Some studies support a protective effect of potato consumption in weight management and diabetes, while other studies demonstrate no effect and a few suggest a negative effect. As there are many biological activities attributed to the compounds present in potato, some of which could be beneficial or detrimental depending on specific circumstances, a long‐term study investigating the association between potato consumption and diabetes, obesity, cardiovascular disease and cancer while controlling for fat intake is needed. © 2016 Society of Chemical Industry     

Antioxidant activity of polyphenol and anthocyanin extracts from fruits of Kadsura coccinea (Lem.) A.C. Smith

Polyphenols and anthocyanins were extracted from Kadsura coccinea fruit. The contents of total phenolics and anthocyanins, influences of pH and temperature on anthocyanins, and antioxidant activities of extracts were further analyzed. The results showed that the total phenolic content of peel extracts was superior to that of pulp extracts. The total anthocyanin content of peel extracts was 180 ± 2.91 mg/100 g of fresh peel tissues. K. coccinea anthocyanins were stable below pH 4, whilst high temperature and extended heating time induced their degradation. Metal-chelating capacity (MCC) assay indicated that no ortho-dihydroxy aromatic moiety existed in the B-ring of the anthocyanin molecules, but there might be a catechol group in the B-ring of the polyphenol molecules. 1,1-Diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging activity and reducing power of extracts decreased in the following order: peel polyphenol extracts > anthocyanin extracts > pulp polyphenol extracts. It would be worthwhile to introduce this rare fruit into more countries.     

Isolation,identification and quantification of unsaturated fatty acids,amides, phenolic compounds and glycoalkaloids from potato peel

Eleven compounds were isolated from potato peels and identified. Their structures were determined by interpretation of UV, MS, 1D, and 2D NMR spectral data and by comparison with reported data. The main components of the potato peels were found to be chlorogenic acid and other phenolic compounds, accompanied by 2 glycoalkaloids, 3 low-molecular-weight amide compounds, and 2 unsaturated fatty acids, including an omega-3 fatty acid. The potato peels showed more potent radical scavenging activity than the flesh. The quantification of the 11 components indicated that the potato peels contained a higher amount of phenolic compounds than the flesh. These results suggest that peel waste from the industry of potato chips and fries may be a source of useful compounds for human health.     

Antioxidant properties of mashua (Tropaeolum tuberosum) phenolic extracts against oxidative damage using biological in vitro assays

Purified mashua extracts (PME) from four different coloured mashua genotypes were assayed for oxidative damage prevention. Three in vitro assays for oxidative damage to biological structures rich in polyunsaturated fatty acids (PUFA), such as LDL and erythrocytes, were tested: AAPH-induced TBARS assay and Cu²⁺-induced conjugated dienes assay for LDL oxidation and AAPH-induced oxidative hemolysis of erythrocytes. Additionally, ORAC antioxidant capacity, total phenolics (TP), total flavanoids (TFA) and total anthocyanins (TA) were evaluated. In the presence of 5 μM of gallic acid equivalents (GAE), inhibitions of LDL oxidation for the PME ranged from 29.1% to 34.8% and from 51.8% to 58.1% when the TBARS and conjugated dienes assays were performed, respectively. PME inhibited the hemolysis of erythrocytes within the range 20.8–25.1%. Thus, mashua phenolic extracts are capable of scavenging peroxyl radicals, as well as chelating redox metal ions in vitro. ORAC and LDL protection (TBARS and conjugated dienes assays) showed good correlations with the TP and TFA, suggesting that these compounds have a good ability to protect LDL molecules under the employed conditions. In contrast, inhibition of hemolysis did not show any correlation with the evaluated phenolic assays (TP, TA, TFA) or with any of the evaluated oxidative LDL assays, suggesting a specific action of some non-evaluated compounds present in the PME. The results of this study indicate that the mashua polyphenol extracts displayed good antioxidant properties against oxidative damage in biological structures rich in PUFA. The displayed antioxidant properties could be applied in the field of food or cosmetic industry.     

Anthocyanin Pigment Composition of Red-fleshed Potatoes

Red potatoes ( Solanum tuberosum and S. stenotomum ) were evaluated as potential sources for natural red colorants. Qualitative anthocyanin composition, pigment content and phenolic composition were screened on 33 cultivars. Monomeric anthocyanin content, determined by pH differential, ranged from 2 to 40 mg/100g tuber fresh weight. Two breeding clones, NDOP5847–1 and NDC4069–4, showed anthocyanin content >35 mg/100g. Anthocyanin composition was characterized by HPLC, spectral analyses and mass spectroscopy (MS). All red potato samples showed similar pigment profiles, with pelargonidin-3-rutinoside-5-glucoside acylated with p -coumaric acid being the major anthocyanin (ca 70%). Anthocyanin content and profiles of epidermal tissue and flesh were compared for NDC4069–4. The presence of glycoalkaloids in color extracts was detected by MS. Some red-fleshed potatoes may be good potential sources of food colorants.     

Safety assessment of genetically engineered potatoes with designed soybean glycinin: compositional analyses of the potato tubers and digestibility of the newly expressed protein in transgenic potatoes

The compositions of transgenic potatoes with intact and modified genes for soybean glycinin were compared with those of control potatoes; non-transgenic or transgenic ones with a vector. The expression levels of glycinin proteins in the transgenic potato tubers were approximately 12–31 mg g⁻¹-total soluble protein. With reference to six major components, moisture, protein, lipid, fiber, ash and carbohydrate, there were no significant differences between transgenic and control potatoes. The levels of glycoalkaloids in transgenic potato tubers, as well as in transgenic controls, increased in comparison with those in non-transgenic ones, though the level was within the permitted limit. The modified glycinin expressed in the transgenic potato tuber was digested under the simulated gastric conditions. From these results, the transgenic potatoes with intact and modified glycinin genes are considered to be as safety utilization for food as non-transgenic potatoes. © 1999 Society of Chemical Industry     

Antioxidative potential of cashew phenolics in food and biological model systems as affected by roasting

The effect of different roasting conditions on antioxidant capacity of phenolics of cashew nuts and their testa was evaluated using several food and biological model systems. Total phenolic content (TPC) of cashew extracts was determined and accelerated oxidative stability of stripped corn oil in the presence of cashew extracts evaluated. In addition, the antioxidant activity of the extracts was assessed in a β-carotene-linoleate and a cooked comminuted pork model system. Inhibition of oxidation of human low density lipoprotein (LDL) cholesterol and stand breaking of supercoiled deoxyribonucleic acid (DNA) was also investigated. The TPC ranged from 5 to 791 mg gallic acid equivalents/g crude extract. In general, whole cashew nuts and testa extracts demonstrated stronger antioxidant activity than that of the cashew kernel. The inhibition percentage of LDL cholesterol oxidation, as evaluated by conjugated dines formation, of cashew kernels was higher than that of testa and was 69% at the end of 24 h incubation. Extracts of roasted cashew nut showed considerable antioxidative efficiency in model systems employed in this study, however, the effect was not significantly (P ? 0.05) different from that of their raw counterparts, except for the accelerated oxidative stability assay. The results suggest that whole cashew nut and testa extracts could be used as a potential source of natural antioxidants in certain food applications and for disease risk reduction.     

Antioxidant potential of barley as affected by alkaline hydrolysis and release of insoluble-bound phenolics

Phenolic constituents of six barley varieties, namely Falcon, AC Metcalfe, Tyto, Tercel, Phoenix and Peregrine were separated into free, soluble conjugate and insoluble-bound fractions. Soluble conjugates and insoluble-bound phenolics were extracted into diethyl ether after consecutive alkaline hydrolysis for 4 h. Total phenolic content of each of the three fractions was determined by using Folin–Ciocalteau method. Total antioxidant capacity of the phenolic fractions was determined by trolox equivalent antioxidant capacity (TEAC) assay. The extracts were evaluated for their efficacy in scavenging of 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical. Oxygen radical scavenging capacity (ORAC_FL) of the extracts was determined using a fluorometric assay. Effectiveness of phenolic extracts in inhibiting oxidation of human LDL cholesterol and radical-induced supercoiled DNA breakage was also evaluated. The contribution of insoluble-bound phenolics toward total phenolic content was significantly (p < 0.05) higher than the soluble phenolics for all barley extracts tested. The ratio of soluble to insoluble phenolics ranged from 1:27 to 1:35. TEAC and ORAC values and DPPH radical scavenging capacity of the insoluble phenolic fraction were significantly (p < 0.05) higher than those of their insoluble counterparts. A similar trend was observed against inhibition of LDL cholesterol oxidation and radical-induced DNA breakage.     

Content of anthocyanins and glycoalkaloids in blue‐fleshed potatoes and changes in the content of α‐solanine and α‐chaconine during manufacture of fried and dried products

In the last ten or so years, potatoes with purple or blue‐flesh and derivative products, for example chips, have appeared on the European markets. The interest in this raw material and these products is increasing among both producers and consumers searching for novel and attractive choices. The anthocyanin content of the analysed potato varieties differed; a higher content of these pigments was determined in Blaue Elise var. potatoes. In blue‐flesh varieties, the prevailing anthocyanins were acylated glycosides: petunidin and malvidin. The production process of French fries, chips and puree caused a decrease in the content of glycoalkaloids in semi‐products and finished products, compared to the raw material. The greatest losses of α‐chaconine and α‐solanine were observed after tuber peeling (ca. 70%) and after frying (ca. 90%). French fries contained 3%, chips 16% and puree 17% of the initial amount of total glycoalkaloids. The losses of α‐chaconine and α‐solanine in the analysed semi‐products and finished products were at the same level, regardless of the processing technology applied.