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Composition and health benefits of potato peel

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Abstract

Potatoes are one of the most commonly consumed vegetables throughout the world. The global consumption of potatoes as food is shifting from fresh potatoes to value added processed products such as French fries, chips and puree. Peels are the major byproducts of potato processing industries, which represent a waste disposal problem for the industry concerned. However, these waste peels are also promising source of compounds, which may be used because of their valuable technological or nutritional properties. Peel contains about 40-50% dietary fiber and has been considered as a new source of dietary fiber in bread making. In addition to these, peels are rich source of phenolics and fair source of vitamins like riboflavin, ascorbic acid, folic acid and vitamins B6. The phenolic compounds extracted from the potato peel have been shown to prevent lipid oxidation in bulk oils and in muscle model systems. Phenolic compounds from potato peels were shown to bound carcinogens and reported to have anti-carcinogenic properties. In experiment animals potato peel power was shown to have hyperglycemic and cholesterol lowering properties. Furthermore, potato peel powder in the diet also appeared to attenuate the eye lens damage associated with the diabetic condition. This chapter will deal in detail the composition of potato peel, its different health benefits and safety aspects of potato peel glycoalkaloids.

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Chapter
In plants, primary products such as carbohydrates, lipids, proteins, photosynthetic components, and nucleic acids are common to all; they are involved in the primary metabolic processes of building and maintaining cells. In contrast, secondary metabolites do not appear to have such a vital biochemical role, but studies have indicated a role of these chemicals in defense and stress response of plants. Some of the most abundant stress induced secondary metabolites synthesized by plants are phenolics and their derivatives. Phenolic compounds include a large array of chemical compounds possessing an aromatic ring bearing one or more hydroxyl groups, together with a number of other side groups. Plant phenolics are a chemically heterogeneous group (1-3). These phenolics usually occur in conjugated or esterified form as glycosides (1,2,4). The diverse arrays of plant phenolics have many roles in plant growth and development. Therefore, emergence of dietary and medicinal applications for phenolic phytochemicals, harnessing especially their antioxidant and antimicrobial properties, for the benefit of human health and wellness is not altogether surprising. As stress damage at the cellular level appears similar among eukrayotes, it is logical to suspect that there may be similarities in the mechanism for cellular stress mediation between eukaryotic species. Plant adaptation to biotic and abiotic stress involves the stimulation of protective secondary metabolite pathways (5-7), resulting in the biosynthesis of phenolic antioxidants. Studies indicate that plants exposed to ozone responded with increased transcript levels of enzymes in the phenylpropanoid and lignin pathways (8). Increase in plant thermotolerance is related to the accumulation of phenolic metabolites and heat shock proteins that act as chaperones during hyperthermia (9). Phenolics and specific phenolic like salicyclic acid levels increase in response to infection, acting as defense compounds or serving as precursors for the synthesis of lignin, suberin, and other polyphenolic barriers (10). Antimicrobial phenolics, called phytoalexins, are synthesized around the site of infection during pathogen attack and, along with other simple phenolic metabolites, are believed to be part of a signaling process that results in systemic acquired resistance (5-7). Many phenylpropanoid compounds such as flavonoids, isoflavonoids, anthocyanins, simple phenolics, and polyphenols are induced in response to wounding (11), nutritional stress (12), cold stress (13), and high visible light (14). Ultraviolet (UV) irradiation induces lightabsorbing flavonoids and sinapate esters in Arabidopsis to block radiation and protect DeoxyriboNucleic Acid (DNA) from dimerization and cleavage (15). In general, the initiation of the stress response arises from certain changes in the intracellular medium (16) that transmits the stress induced signal to cellular modulating systems, resulting in changes in cytosolic calcium levels, proton potential as a long distance signal (17), and low molecular weight proteins (18). Stress can also initiate free radical generating processes and shift the cellular equilibrium toward lipid peroxidation (19). It is believed that the shift in prooxidant antioxidant equilibrium is a primary nonspecific event in the development of the general stress response (20). Therefore, phenolic compounds are ubiquitous and have important roles in all vascular plants, and as a result are integral part of the human diet (21-23). These phenolic secondary metabolites that are synthesized through the shikimic acid pathway vary from simple phenolics such as the hydroxy benzoic acids and levodopa (l-DOPA) to biphenyls such as resveratrol and rosmarinic acid to large condensed tannins and hydrolysable tannins with high molecular weights (23,24). The polymers formed from plant phenolics in the cell wall provide structural support and form barriers to prevent moisture loss diffusion and pathogen encroachment. The phenolics also function in defense mechanisms with UV protectant, antifungal, antibacterial, antifeedant, and antimitotic properties, and in morphogenesis (25,26). When exposed to air, most phenolics readily undergo oxidation to colored quinone containing products. This response is frequently observed as a browning reaction of plant tissues as a part of a healing response. The oxidation of these compounds by polyphenoloxidase (PPO) has been suggested to be the main cause of apple browning (27). Therefore, protective phenolic metabolites involved in such secondary metabolite linked stress responses in food plant species can be targeted as a source of therapeutic and diseasepreventing functional ingredients, especially in oxidation disease linked diets (diets containing foods with a high glycemic index and saturated fats) and environmentally (physically, chemically, and biologically) influenced chronic disease problems (23).
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The distribution of anthocyanins, flavonoids and phenolic acids in the tubers (skin and flesh), flowers and leaves of eight wild Solanum species has been compared to that found in coloured, cultivated, S tuberosum. Principal component analysis (PCA) of these results revealed a strong association between the various coloured S tuberosum cultivars with distinct differences from the other wild Solanum species. Similarly, PCA-showed that there were close correlations between the tuber skin and flesh components. Diseased tubers of S sanctae-rosae showed large increases in levels of flavonoids and phenolic acids. (C) 1998 SCI.
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The major anthocyanins, flavonoids and phenolic acids in the tubers (skin and flesh), flowers and leaves of 26 cultivars of Solanum tuberosum L with coloured skins and/or flesh have been identified and quantified using analytical HPLC. Red tubers contained mostly pelagonidin-3-(p-coumaroyl-rutinoside)-5-glucoside (200-2000 mu g g(-1) FW) plus lesser amounts of peonidin-3-(p-coumaroyl-rutinoside)-5-glucoside (20-400 mu g g(-1) FW). Light to medium purple tubers contained petunidin-3-(p-coumaroyl-rutinoside)-5-glucoside (1000-2000 mu g g(-1) FW) plus small amounts of malvidin-3-(p-coumaroyl-rutinoside)-5-glucoside (20-200 mu g g(-1) FW) whilst dark purple-black tubers contained similar levels of petunidin-3-(p-coumaroyl-rutinoside)-5-glucoside together with much higher concentrations of malvidin-3-(p-coumaroyl-rutinoside)-5-glucoside (2000-5000 mu g g(-1) FW). Tuber flesh also contained chlorogenic acid (30-900 mu g g(-1) FW) and other phenolic acids plus low concentrations of flavonoids (0-30 mu g g(-1) FW). Tuber skins showed much higher levels (1000-4000 mu g g(-1) FW) of chlorogenic acid. The major anthocyanins in flowers were present as the rutinosides or other glycosides of pelargonidin, petunidin and malvidin whilst glycosides of cyanidin and delphinidin were found in some flowers, together with many of the same phenolic acids as found in tubers. The commonest flavonoids included rutin, kaempferol-3-rutinoside and two quercetin-rhamnose-glucosides. Flowers and leaves contained higher concentrations of flavonoids which fell into two patterns, with some cultivars containing high concentrations of quercetin-3-glycosides, whilst others had much lower concentrations. (C) 1998 SCI.
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Tubers of all 31 Czech varieties listed in the National Book of Varieties of the Czech Republic in 1996 and three Slovakian varieties after harvest were exposed to the light (one week and 14 days) during the years 1996 and 1998 and the content of the two most important glycoalkaloids (α-chaconine and α-solanine) in them was measured. The reaction to light and to the effect of different duration of continuous lighting (one week and 14 days) differed among the varieties. In this way we simulated the conditions in many stores or supermarkets. High-performance liquid chromatography (HPLC) was used to determine α-chaconine and α-solanine in samples of tubers harvested after physiological maturation. Comparisons of the reaction of groups of varieties (early, medium early and medium late to late) showed that after exposure to one week of lighting (expressed in per cent), the increment in the content of SGAs decreased from the group of early to the medium late to late varieties. This was obviously associated with the total content of SGAs at the beginning of the experiment (prior to lighting). After leaving the tubers in the light for one week, the average content of α-solanine increased more than the content of α-chaconine in all the groups of varieties. After 14 days in light the average percentual growth of SGAs was the highest in the group of early varieties, then gradually lower from the medium early, and medium late to late varieties, to the lowest in the very early varieties. The different duration of lighting had a highly significant influence on the SGAs content in the respective groups divided according to the duration of the vegetative period. In all the 34 varieties the increase in the SGAs content in tubers after 14 days of lighting was approximately double (68.6 mg.kg-1) the content in tubers kept in light for one week (33.1 mg.kg-1). The effect of the conditions of the year of cultivation was also highly significant. The differences in the response of the varieties to light in terms of the increased SGAs content were significant (> 50 mg.kg-1 fresh matter after one week and > 80 mg.kg-1 after 14 days of light). The α-solamne:α-chaconine ratio in control tubers (kept in darkness) was 1:1.48, after one week in the light this ratio dropped to 1:1.44 and after another week of lighting it increased to 1:1.47.
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This study was undertaken to determine whether potato peels, as a source of dietary fibre, exert a hypocholesterolaemic effect on rats fed cholesterol-rich diet. Male rats were fed diets containing 1% cholesterol and 0.2% cholic acid with either 6% cellulose or potato peels as the fibre source. The present study demonstrates for the first time the in vivo hypocholesterolaemic influence of potato peels. After 4 weeks, rats fed potato peels showed a 40% decrease in plasma cholesterol content and a reduction of 30% in hepatic fat cholesterol levels as compared with rats fed cellulose. Our data indicate that potato peels might be considered as a source of dietary fibres for human consumption.
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Potato peel is discarded as a by-product from the potato industries. In the current study the chemical composition of potato peel and commercial Rusk was determined. Seven blends were obtained by mixing potato peel powder (PPP) and Rusk at different ratios, namely 0:100, 5:95, 10:90, 25:75, 50:50, 75:25 and 100:0(w/w g/100g). Sensory properties of fried chicken coated with potato peel blends were evaluated as well as quality assurance tests to indicate the stability of potato peel blends during storage period. The results showed that protein content, crude fat, crude fiber and ash content of PPP were 13.51, ND, 12.70 and 8.6 %, respectively. Mixing Rusk with various levels of potato peel powder controlled the increase in acid value and peroxide value as well as the formation of secondary oxidation products as measured by TBA value during storage period . The results indicate that the mixtures of potato peel powder and Rusk at ratios 25 :75 and 50 : 50 (w/w) can be successfully used as coating agents during frying process.
Article
The decrease in α-chaconine (CHA) and a-solanine (SOL), toxic glycoalkaloids in potatoes, during cooking by three procedures was investigated. Raw or cooked potato samples (2 g) were extracted twice with 5% acetic acid solution. The extract was purified on Sep-pak C18and CHA and SOL contents were determined by high performance liquid chromatography. Recoveries of CHA and SOL from raw potatoes were 96.5% and 98.2%, respectively and those from cooked potatoes were 96.2% and 96.7%, respectively. It was found that 93.9% of CHA and 95.9% of SOL remained in potatoes after boiling. These values indicate that boiling is ineffective as a means to decrease the alkaloids. Alkaloid content was reduced by microwaving by 15% in each case. In the case of deep-frying, their contents varied according to the temperature. At 150°, both alkaloids showed no decrease, and at 170°, the potatoes showed a large variation in residual alkaloids. At 210°, however, the alkaloids were partially decomposed; after 10 minutes’ heating, 64.9% of CHA and 59.7% of SOL remained. It was suggested that the critical temperature for the decomposition of both alkaloids in potatoes may be around 170°C. In this study, relatively high stability of CHA and SOL in potatoes under normal home cooking conditions was confirmed. © 1990, Japanese Society for Food Hygiene and Safety. All rights reserved.
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Article
The present work was undertaken to examine the utilisation of potato peel, a waste material, as a source of natural antioxidants for retarding lipid and protein oxidation in minced mackerel. Mackerel mince with two different concentrations (2.4 or 4.8 g/kg) of water or ethanol extracts of potato peel and a control with no added extracts were prepared. The samples were stored at 5 °C for 96 h and the sampling was done at time points 0, 24, 48 and 96 h. The ethanol extracts, which contained high amounts of phenolic compounds, was found to be very effective in retarding lipid and protein oxidation as it resulted in low levels of peroxide value, volatiles, carbonyl compounds and protected against the loss of α-tocopherol and tryptophan and tyrosine residues. Water extracts was less efficient especially at higher concentrations, which might be due to lower phenolic content or due to the pro-oxidative nature of some of the phenolic acids/co-extracted compounds.
Article
The cholesterol-lowering and hypoglycemic effect of dietary fiber are commonly attributed to soluble fiber fractions. By enzymatic treatment of potato pulp, which is rich in cellulose and pectin, we prepared 3 fractions with different chemical composition and solubility, and compared their effects with commercially available crystalline cellulose (negative control) on central parameters related to risk factors of diabetes mellitus and cardiovascular disease in diabetic prone Goto-Kakizaki rats. Forty male rats were fed a semisynthetic Western-type diet containing 5% dietary fiber in the form of concentrated potato fiber (CF), insoluble potato fiber (IF), soluble fiber (SF), or cellulose (CEL) ad libitum for 4.5 weeks to study weight change and induce diabetic conditions. This was followed by 16 days of slightly restricted feeding, for the measurement of fecal organic matter digestibility, fecal dry matter, urinary glucose excretion, and fasting blood glucose. Finally, the rats were euthanized 2 hours postprandial for measurement of postprandial glucose, triacylglycerol and cholesterol levels, and cecal fermentation pattern to assess any relation between digestion processes and hematological risk markers. Diet SF had higher fecal organic matter digestibility and led to a significantly larger pool of organic acids with a higher proportion of propionate than the other diets. There was no difference in hematological parameters except for a small but significant reduction in postprandial plasma triacylglycerol concentration of rats fed diet SF compared to diet CEL and diet CF. In conclusion, increased fermentation and production of propionate with diet SF did not reduce plasma cholesterol or glycemic response.
Article
Glycoalkaloid and chlorophyll concentrations within tuber tissue of three potato cultivars (Desiree, King Edward and Kerrs Pink) were measured following 15 days continuous illumination (250 μmol m−2 s−1 photosynthetically active radiation). Comparisons were made of the influence of four light sources: fluorescent tube type warm white, high pressure sodium, and high and low pressure mercury light. There were significant differences between cultivars in their rates of glycoalkaloid and chlorophyll accumulation. Glycoalkaloid and chlorophyll accumulation were markedly influenced by light source, with exposure to sodium and fluorescent light promoting higher glycoalkaloid and chlorophyll accumulation compared with exposure to high and low pressure mercury light. In virtually all cases, glycoalkaloid and chlorophyll concentrations within tuber tissue increased steadily over time with no indication of cessation when exposed to light. Exposure to light altered ratios of α-chaconine:α-solanine but did not significantly influence ratios of chlorophyll a:chlorophyll b. Results demonstrated a strong relation between glycoalkaloid and chlorophyll accumulation in response to light.
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Host pathogen interactions between potato tubers and soft rot bacteria Erwinia carotovora ssp. atroseptica respectively dry rot fungi Fusarium spp. were investigated by a special descending paper chromatographic technique for the eluation of soluble compounds from the infected tissue region. The continuously formed sugars, phenolics and phytoalexins determined by thin layer or gas chromatography after diffusing into the eluate. As fresh harvested as stored potato turners produced phenolics and phytoalexins after infection. The uninfected controls produced only low levels of these compounds.
Article
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.
Article
Both the steroidal glycoalkaloid mixture from potato (α-solanine and α-chaconine) and pure α-tomatine are able to complex with the sterols cholesterol, sitosterol, stigmasterol, campesterol and ergosterol in vitro. The sterol-complexing ability of tomatine was greater than that of the potato alkaloids and more akin to that of the steroidal saponin, digitonin. With all three compounds, cholesterol was the least-readily bound sterol while binding to other sterols was of a similar order. Complex formation with tomatine was not markedly influenced by temperature, and with the aglycone tomatidine did not appear to occur at all.
Article
Potatoes, members of the Solanaceae plant family, serve as a major, inexpensive food source for both energy (starch) and good-quality protein, with worldwide production of about 350 million tons per year. U.S. per capita consumption of potatoes is about 61 kg/year. Potatoes also produce potentially toxic glycoalkaloids, both during growth and after harvest. Glycoalkaloids appear to be more toxic to man than to other animals. The toxicity may be due to anticholinesterase activity of the glycoalkaloids on the central nervous system and to disruptions of cell membranes affecting the digestive system and other organs. The possible contribution of glycoalkaloids to the multifactorial aspects of teratogenicity is inconclusive. Possible safe levels are controversial; guidelines limiting glycoalkaloid content of potato cultivars are currently being debated. This review presents an integrated, critical assessment of the multifaceted aspects of the role glycoalkaloids play in nutrition and food safety; chemistry and analysis; plant physiology, including biosynthesis, distribution, inheritance, host-plant resistance, and molecular biology; preharvest conditions such as soil composition and climate; and postharvest events such as effects of light, temperature, storage time, humidity, mechanical injury, sprouting inhibition, and processing. Further research needs are suggested for each of these categories in order to minimize pre- and postharvest glycoalkaloid synthesis. The overlapping aspects are discussed in terms of general concepts for a better understanding of the impact of glycoalkaloids in plants and in the human diet. Such an understanding can lead to the development of potato varieties with a low content of undesirable compounds and will further promote the utilization of potatoes as a premier food source for animals and humans.
Article
Japanese radish (Raphanus sativus) juice effectively decreased nitrite at acidic ranges. Nitrite-consuming activity was due to dialyzable, negatively charged, and unstable substances showing characteristic ultraviolet absorption maxima at 270 and 332 nm (pH 12). The major nitrite-reacting substance(s), obtained from partial purification by dialysis and subsequent column chromatography through a diethylaminoethylcellulose column, was (were) assumed to be a phenolic compound(s). The nitrite-reacting substances were transformed into other compounds showing absorption maximum at 288 nm (pH 12) by reaction with nitrite. Japanese radish juice effectively inhibited the formation of N-nitrosodimethylamine and N-nitrosodiethylamine from reaction between nitrite and the corresponding secondary amines.
Article
To test the effect of glycoalkaloids on sodium ion active transport, frog skin was exposed to the potato glycoalkaloids alpha-chaconine and alpha-solanine in a glass Ussing chamber. It was found that the short-circuit current (ISC), the measure of transepithelial active transport of sodium, decreased up to 30% at an alpha-chaconine concentration of 10 mg/L. alpha-Solanine had a similar but smaller effect, decreasing short-circuit current by 16%. The data suggest that (a) frog skin is a useful experimental model to evaluate effects of glycoalkaloids at the cellular level and (b) the mechanism of action of the two glycoalkaloids is to modify the active transport of sodium. The possible significance of these findings to food safety is discussed.
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Potato peel extract, as natural antioxidant was evaluated during 60 days storage of refined soy bean oil at 25 and 45 °C. Free fatty acids (FFA), peroxide values (POV) and iodine values (IV) were used as a criteria to assess the antioxidant activity of potato peel extract. Different organic solvents, including ethanol, methanol, acetone, hexane, petroleum ether and diethyl ether, were used to prepare extracts of potato peels. Maximum amount of extract (21%) was obtained with petroleum ether, followed by diethyl ether (15.25%) and methanol (14.75%). After 60 days’ storage at 45 °C, soy bean oil, containing 1600 and 2400 ppm of petroleum ether extract of potato peels, showed lower values of FFA (0.120, 0.109%) and POVs (10.0, 9.0 meq/kg) than the control samples (FFA 0.320%, POV 59 meq/kg). Soy bean oil containing 200 ppm of BHA and BHT showed FFA values of 0.102 and 0.078%, whereas POVs were 8.0 and 6.0 meq/kg, respectively, after 60 days, storage at 45 °C. Similarly, after 60 days, storage at 45 °C, iodine values of soy bean oil containing 1600 and 2400 ppm of potato peel extract were 71 and 77, respectively, which were higher than the control samples of oil (58). However, iodine values for soy bean oil treated with 200 ppm of BHA and BHT were 80 and 84, respectively, after 60 days’ storage at 45 °C. These results illustrate that potato peel extract, at various concentrations exhibited very strong antioxidant activity which was almost equal to synthetic antioxidants (BHA & BHT). Therefore, potato peel extract in oils, fats and other food products can safely be used as natural antioxidant to suppress lipid oxidation.
Article
To demonstrate whether folic acid can protect Xenopus embryos against reported adverse effects of the potato glycoalkaloid α-chaconine, the frog embryos were exposed simultaneously to the glycoalkaloid, folic acid (pteroylglutamic acid), and an electrochromic fluorescent dye, Di-4-ANEPPS, in a specially designed instrument that measures embryonic membrane potential. Folic acid decreased the chaconine-induced fluorescence, with a maximum decrease occurring at about 10 mg/L of both folic acid and the glycoalkaloid dissolved in solution. The protective effect was also operative in the frog embryo teratogenesis assayXenopus (FETAX), in which survival and teratogenicity of the whole embryos were the endpoints. Possible mechanisms of the protective effect and the possible significance of the results to food safety and health are discussed. Keywords: α-Chaconine; folic acid; food safety; frog embryos; glycoalkaloids; membrane potential; potatoes; teratogenicity
Article
Potato peels are a potential source of dietary fiber. The abrasion peeling method used by chip manufacturers results in more starch and less dietary fiber than the steam peeling procedure used for production of dehydrated potatoes. The objective of this study was to identify differences in dietary fiber composition between these types of peels and the effects of extrusion on fiber. Peels were extruded in a twin screw extruder at barrel temperatures of 110 or 150 °C and feed moistures of 30% or 35%. Extrusion cooking reduced starch content and increased total dietary fiber in steam peels. Total dietary fiber in abrasion peels was not affected by extrusion. Extrusion increased soluble nonstarch polysaccharides in both types of peels. More glucose was recovered from insoluble fiber of extruded steam peels than from abrasion peels, suggesting that resistant starch may have been formed. Lignin increased in extruded steam peels but decreased in extruded abrasion peels. Keywords: Dietary fiber; starch; peeling; potato; extrusion
Article
Enzymatic and nonenzymatic browning reactions of amino acids and proteins with carbohydrates, oxidized lipids, and oxidized phenols cause deterioration of food during storage and processing. The loss in nutritional quality and potentially in safety is attributed to destruction of essential amino acids, decrease in digestibility, inhibition of proteolytic and glycolytic enzymes, interaction with metal ions, and formation of antinutritional and toxic compounds. Studies in this area include influence of damage to essential amino acids on nutrition and food safety, nutritional damage as a function of processing conditions, and simultaneous formation of deleterious and beneficial compounds. These compounds include kidney-damaging Maillard reaction products, mutagens, carcinogens, antimutagens, antioxidants, antibiotics, and antiallergens. This overview covers the formation, nutrition, and safety of glycated proteins, characterized browning products, and heterocyclic amines. Possible approaches to inhibiting browning reactions and preventing adverse effects of browning during food processing and food consumption, including protection against adverse effects of heterocyclic amines by N-acetylcysteine, caffeine, chlorophyll, conjugated linoleic acid, lignin, and tea extracts, are also described. This research subject covers a complex relationship of the chemistry, biology, and pathology of browning products and the impact on human nutrition and health. Future study should differentiate antinutritional and toxicological relationships, define individual and combined potencies of browning products, and develop means to prevent the formation and to minimize the adverse manifestations of the most antinutritional and toxic compounds. Such studies should lead to better and safer foods and improved human health. Keywords: Browning prevention; food browning; food safety; glycated proteins; glycosylation; heterocyclic amines; human health; Maillard products; nutrition
Article
Chlorogenic acid was isolated from two varieties of potatoes by column chromatographic methods, and identified by paper chromatography and by ultraviolet and infrared absorption spectral analyses. Chlorogenic acid was the principal phenolic compound in the inner tissue of tubers and the only compound which increased significantly during the storage of the potatoes at 40° F. No increase in the chlorogenic acid content was observed, however, in potatoes stored at 60° F. It was postulated that the increase in chlorogenic acid during cold storage is due to the accumulation of sugars.
Article
Severed commercial potato products were analyzed for their α-chaconine and á-solanine content by using high-performance liquid chromatography (HPLC). The α-chaconine content ranged from 0.04 to 97.9 mg/100 g of product while the quantity of α-solanine varied from 0.04 to 48.0 mg/100 g of product. Percent recoveries for α-chaconine ranged from 98 to 101% while those for α-solanine were 93-98%. Glycoalkaloid stability during four cooking procedures-frying, baking, microwaving, and boiling-was investigated, and it was determined that they were stable for all except frying where a slight loss of glycoalkaloids was shown. α-Chaconine and α-solanine were confirmed as the major glycoalkaloids in each product by thin-layer chromatography (TLC).
Article
Chlorogenic acid has been determined in potato tubers by HPLC and GLC and the results were compared with the results of a spectrophotometric method. The HPLC analysis was performed by reversed-phase chromatography on C18 μBondapak column. For GLC, the chlorogenic acid or the quinic acid obtained by enzymatic hydrolysis was silylated. The methods have been applied to the peel and peeled tubers of six varieties of potato. The results establish that the chromatographic methods (HPLC or GLC) provide the most reliable determination of chlorogenic acid in potato extracts. Spectrophotometric measurements gave higher levels of the acid than HPLC and GLC analysis in a majority of the potato samples. The indirect determination by enzymatic hydrolysis and analysis of the increase in quinic acid content was not found to give reliable results.
Article
The effects of extrusion conditions on binding of the dietary carcinogen benzo[a]pyrene [B(a)P] were determined using an in vitro digestion model followed by HPLC with fluorescence detection. Extrusion at 110 degrees C and 30% feed moisture resulted in significantly less binding than did nonextruded peels (77% vs 84%), but other conditions did not affect binding. Peels bound more B(a)P than did wheat bran, cellulose, or arabinogalactan. B(a)P dosage was inversely related to the percentage bound. A model system containing cellulose with chlorogenic acid bound all B(a)P added, compared with only 66% by cellulose alone and 32% by a cellulose-quercetin mixture.
Article
Potato plants (Solanum tuberosum), cultivar Superior, were subjected to insect damage by Colorado potato beetles (Leptinotarsa decemlineata) and potato leafhoppers (Empoasca fabae) to assess the influence of pest-related stresses on glycoalkaloid content in tubers. Detection and quantification of the glycoalkaloids, solanine and chaconine, were achieved using a C-18 reversed phase HPLC computer integrated system equipped with a UV photodiode array detector at 208 nm. Field and growth room studies indicated that the tuber glycoalkaloid concentrations of potatoes subjected to defoliation damage by Colorado potato beetles were consistently greater than those concentrations found in tubers from undamaged plants. Damage to plants by potato leafhoppers did not have any apparent effect on tuber glycoalkaloid content. These results indicate that a food crop not protected from common pests may produce elevated levels of natural toxins, possibly affecting the degree of food safety.
Article
Exposure of commercial White Rose potatoes to fluorescent light for 20 days induced a time-dependent greening of potato surfaces; an increase in chlorophyll, chlorogenic acid, and glycoalkaloid content (alpha-chaconine and alpha-solanine); and no changes in the content of inhibitors of the digestive enzymes trypsin, chymotrypsin, and carboxypeptidase A. The maximum chlorophyll level of the light-stored potatoes was 0.5 mg/100 g of fresh potato weight. Unstored potatoes contained no chlorophyll. Storing potatoes in the dark did not result in greening or chlorophyll formation. Chlorogenic acid and glycoalkaloid levels of dark-stored potatoes did increase but less than in the light-stored potatoes. In the light, chlorogenic acid concentration increased from 7.1 mg/100 g of fresh potato weight to a maximum of 15.8 mg after greening. The corresponding values for alpha-chaconine are 0.66 and 2.03 mg and for alpha-solanine 0.58 and 1.71, respectively, or an approximately 300% increase for each glycoalkaloid. The trypsin, chymotrypsin, and carboxypeptidase A concentrations, respectively, of about 1000, 375, and 100 units/g of dehydrated potato powder were not changed. Experiments on delay of greening by immersion in water suggest that (a) chlorophyll formation and glycoalkaloid synthesis are unrelated physiological processes and (b) the concentration of chlorophyll is 26 times greater, of chlorogenic acid and glycoalkaloids 7-8 times greater, and of protease inhibitors about 2-3 times lower in the peel of the green potatoes than in the whole tuber. The described compositional changes should help define consequences of potato greening for plant physiology, food quality, and food safety.
Article
The content of phenolic acids formed during wound healing of gamma-irradiated and nonirradiated potato tubers was determined by HPLC. Chlorogenic acid, caffeic acid, p-coumaric acid, and ferulic acid were detected in small quantities in resting whole tubers of irradiated and nonirradiated potatoes. During wound healing their content increased many fold, and in addition, the neo and crypto isomers of chlorogenic acid accumulated in the wound healing 'tissue. The increased formation of phenolics was accompanied by a parallel rise in phenylalanine ammonia-lyase activity. Chlorogenic acid contributed about 56% and together with the neo and crypto isomers accounted for 88% of the phenolics formed. Tubers irradiated to 100 Gy for sprout inhibition showed significantly lower levels of chlorogenic acid and its isomers during the first 8 days of wound healing. The results point to an impairment of wound-induced biosynthesis of phenolics in general and chlorogenic acid and its isomers in particular by irradiation.
Article
As part of a program to control the biosynthesis of Solanum glycoalkaloids in potatoes, we used a modified extraction-HPLC assay to measure the α-chaconine and α-solanine content of commercial and new potato varieties, different parts of the potato plant, and commercial potato products. The improved assay was accomplished by extracting, precipitating, and filtering the hot methanol extract through a 0.45-μm membrane before HPLC analysis. Recoveries of spiked samples ranged from 89 to 95%. The combined α-chaconine and α-solanine contents of different parts of the new NDA 1725 potato cultivar (in milligrams per 100 g of fresh weight) were as follows: tubers, 14.7; main stems, 32.0; small stems, 45.6; roots, 86; leaves, 145; and sprouts, 997. The α-chaconine content of several other potato cultivars ranged from 1.17 to 13.5 mg/100 g of fresh weight and the corresponding α-solanine content from 0.58 to 5.9 mg/100 g of fresh weight. The corresponding values for potato berries were 22.1 and 15.9 mg/100 g of fresh weight, respectively. The total glycoalkaloid content determined by titration with bromophenol blue was 12-30% greater than the sum of α-chaconine and α-solanine determined by HPLC. The extraction-HPLC method was adapted to measure the glycoalkaloids in freeze-dried french fries (0.08-0.84 mg/100 g of product), skins (3.1-20.3 mg/100 g of product), potato chips (2.4-10.9 mg/100 g of product), and potato pancake powders (4.5-6.5 mg/100 g of product). The presence of the two glycoalkaloids in commercial foods was also confirmed by thin-layer chromatography. The possible significance of these findings to food safety and plant physiology is discussed.
Article
The chemical interaction of lipids and lipid-containing foods with nitrite in a mild acidic aqueous system was investigated. Methyl linoleate-coated silica gel, Intralipid, cow's milk, mayonnaise, yolk and miso reduced a considerable amount of nitrite. Methyl linoleate-coated silica gel and cow's milk extensively prevented the formation of carcinogenic N-nitrosamines. It seemed likely that the unsaturated fatty acid residues were responsible for the interaction of lipids with nitrite. Methyl linoleate was changed into two or more unidentified products, neither of which was the hydroperoxides of the ester.
Article
The reduced efficiency of antibiotics, caused as a consequence of acquired drug resistance, necessitates the development of new approaches to deal effectively with infectious diseases. Intervention strategies which enhance innate defence mechanisms offer one such possibility. This report demonstrates that mice prophylactically treated with low doses of an extract derived from Solanum species containing both solanine and chaconine were rendered resistant to challenge with lethal doses of Salmonella typhimurium. Single or multiple treatment(s) with low doses of purified glycoalkaloids also provided mice with significant protection against infection. Treated animals were found to rapidly clear bacteria from various target organs. An enhancement of innate defences by glycoalkaloid administration offers an alternative to antigen-specific vaccines and prophylactic antibiotic treatment. © 1998 John Wiley & Sons, Ltd.
Article
The effect of peeling on the total phenols, total glycoalkaloids (TGA), discoloration, and flavor of 50–80g sized cooked potatoes was studied. Three methods of cooking were studied; (1) boiling in distilled water; (2) boiling in 16% NaCl solution; and (3) steaming. In all three methods, potatoes cooked without the peel were lower in phenolic and TGA content, discolored less, and were less bitter than potatoes cooked with the peel. During cooking phenols migrated from the peel into both the cortex and internal tissues of the potato. Glycoalkaloids were less mobile than phenols and migrated only into the cortex. The movement of phenols and TGA into the cortex increased both discoloration and bitterness in potatoes cooked with the peel.