Glycoalkaloids in potato tubers: the effect of variety and drought stress on the α‐solanine and α‐chaconine contents of potatoes

Six varieties of Solanum tuberosum L potato grown in the Bolivian highlands under drought stress, with and without irrigation, were analysed for their content of glycoalkaloids (GAs). The plant material consisted of three drought‐tolerant varieties from a local breeding programme (PROINPA), Potosina, Chapaquita and Pampeña, and three control cultivated varieties, Malcacho, Sani Imilla and Desiree, either susceptible or relatively tolerant to drought. α‐Solanine and α‐chaconine were quantified in both the peel and flesh of the tubers. A significant increase in GA concentration (α‐solanine + α‐chaconine) was observed under drought stress conditions in most varieties; average concentration increases of 43 and 50% were registered in the improved and control cultivars respectively. In all tested cultivars, however, the GA concentration remained lower than the recommended food safety level (200 mg kg⁻¹ fresh tubers). It ranged from 52.4 to 100 mg kg⁻¹ fresh tubers in the improved cultivars and from 55.6 to 122.3 mg kg⁻¹ fresh tubers in the controls. In the improved and control varieties the α‐solanine content averaged 42.6 and 35.4% of the total potato GAs respectively and was not significantly affected by drought stress, except in Desiree. In all conditions the peel contained the greatest proportion of total GAs. The hybrid variety Pampeña (new drought‐tolerant variety) contained the lowest amounts of GAs, which were lower than those of the control varieties, with and without irrigation. © 2000 Society of Chemical Industry     

Light‐induced glycoalkaloid accumulation of potato tubers (Solanum tuberosum L)

The total glycoalkaloid concentration of non‐sprouted potato tubers, cvs Marfona, Fianna, Maris Piper, Kestrel and Golden Wonder, was measured following 15 days of continuous illumination (250 µmol m⁻² s⁻¹ photosynthetically active radiation) using high‐performance liquid chromatography. Comparisons were made of the influence of four sources of illumination: fluorescent tube‐type warm white, high‐pressure sodium, high‐pressure mercury types MB/U and MBFR/U. Irrespective of cultivar, glycoalkaloid concentrations of tubers placed in the dark remained relatively constant from day 0 to day 15 and did not exceed food safety values of 200 mg kg⁻¹ FW. A highly significant cultivar, light and cultivar × light (P < 0.01) interaction was recorded. Cultivar Kestrel was shown to be light‐sensitive with high rates of glycoalkaloid accumulation irrespective of light source, and cv Maris Piper was demonstrated to be light‐insensitive. In the majority of cultivars tested, maximal rates of glycoalkaloid accumulation were recorded following exposure of tubers to sodium or fluorescent light, and minimal rates of accumulation were recorded following exposure of tubers to mercury (MB/U and MBFR/U) illumination. In virtually all cases glycoalkaloid concentrations steadily increased with time during light exposure with no indication of cessation. In some instances the α‐chaconine/α‐solanine ratio decreased over 15 days of illumination (P < 0.05), indicating enhanced α‐solanine synthesis over that of α‐chaconine. The implications of these results in terms of consumer safety are discussed. © 1999 Society of Chemical Industry     

Effect of bruising on the total glycoalkaloid and chlorogenic acid content of potato (Solanum tuberosum) tubers of five cultivars

Tubers from five potato cultivars were selected on the basis of their low, intermediate or high rates of glycoalkaloid synthesis in response to stresses such as light or cold storage temperatures. The tubers were subjected to a standard degree of damage sufficient to cause bruising but not severe damage such as cracking or splitting. Increases in glycoalkaloid levels in response to damage were observed in all cultivars. Importantly, the rates of glycoalkaloid synthesis in response to damage were in good agreement with cultivar response to light and cold temperature stress. The cultivars, Ailsa and Eden, exhibited a slower response than the higher synthesis rates observed in Pentland Dell or Brodick. The cultivar Torridon exhibited severe internal damage symptoms throughout the tuber as opposed to localised bruising observed in the other cultivars. The extensive cell death observed in the tubers of the cultivar Torridon severely curtailed glycoalkaloid and chlorogenic acid synthesis. The increased levels of glycoalkaloids in response to bruising damage ranged from approximately 27% (Ailsa, Torridon) to 130% for the cultivar Brodick. Chlorogenic acid levels increased in two cultivars (Brodick and Torridon) but not in the others, Ailsa, Eden and Pentland Dell. The α-chaconine/α-solanine ratios observed within the five cultivars were in good agreement with previous research. The consistency across years is notable, indicating a strong relationship in the synthesis of the two glycoalkaloids. The results are discussed in terms of implications for the potato industry, for the retail trade and also for selection within potato breeding programmes. © 1998 SCI.     

Effect of environmental stress during tuber development on accumulation of glycoalkaloids in potato (Solanum tuberosum L)

The effects of low temperature and of combined stresses, cool temperature and waterlogging and also warm temperature and drought, on potato tuber glycoalkaloid levels were investigated, with emphasis on comparison of tubers of similar size. The early maturing cultivars Home Guard, Rocket and British Queen were grown under favourable controlled environment conditions (18/14 °C day/night temperature, 14 h photoperiod) until the imposition of treatments after the start of tuber initiation. Transfer to low temperature (12/9 °C) did not increase total glycoalkaloid concentration in any of the three cultivars. However, waterlogging at 12/9 °C increased total glycoalkaloid concentration during the later stages of development of British Queen. Drought stress at 24/18 °C also increased total glycoalkaloid concentration in British Queen, although the response varied between individual tubers of similar size. Total glycoalkaloid concentrations in tubers of Rocket were not affected by the combined stress treatments, and any effects on Home Guard were very much less than on British Queen. © 1999 Society of Chemical Industry     

Is there a link between greening and light-enhanced glycoalkaloid accumulation in potato (Solanum tuberosumL) tubers?

Potato (Solanum tuberosum L) tubers (cvs Pentland Dell and Record) were treated with the chlorophyll biosynthesis inhibitors 4-amino-5-fluoropentanoic acid (AFPA) and 3-amino-2,3-dihydrobenzoic acid (gabaculine), and subsequently exposed to daylight for up to 10 days prior to pigment and glyco-alkaloid analysis. AFPA inhibited the accumulation of total chlorophyll (Chl) by between 50 and 70% in both cultivars throughout the duration of light exposure. The synthesis of Chl b was inhibited by over 80% in both cultivars. Neither inhibitor had a significant effect on light-enhanced glycoalkaloid accumulation. It is concluded that there is no direct metabolic link between Chl and glycoalkaloid biosynthesis. © 1998 SCI.     

Glycoalkaloid Concentrations in Aerial Tubers of Potato ( Solanum tuberosumL)

The total glycoalkaloid concentrations in aerial and subterranean tubers of 14 potato genotypes were measured using high-performance liquid chromatography immediately after harvest. Post-harvest, aerial tubers from all genotypes were exposed to 144 h continuous fluorescent light; additionally three genotypes (cvs Home Guard, Kerrs Pink and Desiree) were subjected to mechanical wounding prior to glycoalkaloid analysis. Variations in glycoalkaloid concentrations between aerial tubers taken from a single genotype (cv Kerrs Pink) were determined by analysis of eight aerial tubers formed in the second leaf axil, selected from separate individual plants. Irrespective of genotype, total and individual glycoalkaloid concentrations were higher in aerial than in subterranean tubers. The highest glycoalkaloid concentrations were found in aerial tubers of cv Kerrs Pink (1343·0 mg kg⁻¹ FW) and lowest in cv Lindsey (301·0 mg kg⁻¹ FW). Ratios of α-chaconine: α-solanine in aerial tubers differed significantly ( P< 0·05) from those in subterranean tubers of cv Cara, Golden Wonder, Home Guard, Lindsey, Maris Piper, Record and 8859 indicating that exposure to light during aerial tuber growth enhanced the synthesis of one glycoalkaloid to a greater degree than the other. In all cultivars except cv Maris Piper, exposure of aerial tubers to 144 h continuous fluorescent light post-harvest increased total and individual glycoalkaloids compared with dark-treated controls. However, the ratios of α-chaconine: α-solanine in all genotypes except cv Golden Wonder (decreased α-chaconine: α-solanine, P< 0·05) were not significantly altered in comparison with dark controls, indicating that light exposure of aerial tubers post-harvest fails to enhance selectively synthesis of individual glycoalkaloids in the majority of cultivars. Regardless of cultivar, total glycoalkaloid, α-solanine and α-chaconine concentrations were higher in wounded than unwounded aerial tubers. Wounding stimulated synthesis of α-solanine more than α-chaconine ( P< 0·05) in cv Home Guard and Desiree. Glycoalkaloid concentrations in aerial tubers varied widely from a minimum of 1010 mg kg⁻¹ to a maximum of 2520 mg kg⁻¹ FW when harvested from individual plants of cv Kerrs Pink but selected from equivalent positions on the plant. Throughout the experiments large, non-significant increases in total and individual glycoalkaloid concentrations were recorded following light and wounding treatments. The scientific implications of aerial tuber formation are discussed.     

Glycoalkaloid Concentration of Potato Tubers Following Exposure to Daylight

The total glycoalkaloid concentrations in white- (cv Pentland Hawk), pink- (cv Kerrs Pink) and red- (cv Desiree) skinned potato tubers were measured following 21 days exposure to daylight using high-performance liquid chromatography. Average daytime irradiance during this period was 232 μmol m⁻² s⁻¹. Regardless of cultivar, glycoalkaloid concentrations were increased after light exposure compared with initial concentrations. Glycoalkaloid concentrations fluctuated with time and continuous accumulation of glycoalkaloids with time was not demonstrated. Glycoalkaloid synthesis was maximal in the sequence cv Kerrs Pink<cv Pentland Hawk<cv Desiree. Exposure to daylight altered the ratio of α-chaconine: α-solanine in tubers of cv Desiree but not those in cv Pentland Hawk and Kerrs Pink. Glycoalkaloid concentrations in all cultivars were higher than the recommended food safety level, this was reached after 8 days in cv Kerrs Pink and Desiree and at 13 days in Pentland Hawk. The implications of these results in terms of food safety are discussed.     

Glycoalkaloid concentration of potato tubers following continuous illumination

The total glycoalkaloid concentration of dormant (non-sprouted) and sprouted potato tubers cv Pentland Hawk was measured following 13 days continuous illumination (250 μmol m^?2 s^?2 photosynthetically active radiation) using high-performance liquid chromatography. Comparisons were made of the influence of three sources of illumination: high-pressure mercury, high-pressure sodium and fluorescent tube type warm white. Glycoalkaloid concentrations in both dormant and sprouted tubers increased over 13 days illumination regardless of the form of illumination used. Glycoalkaloid concentrations accumulated with time in dormant and sprouted tubers exposed to sodium and fluorescent light but fluctuated in those exposed to mercury light. Dormant tubers were more sensitive to illumination than sprouted tubers regardless of light souce. Fluorescent light was associated with maximum glycoalkaloid synthesis in dormant tubers; while sodium light enhanced glycoalkaloid synthesis in sprouted tubers to the greatest extent. Mercury light weakly elicited glycoalkaloid synthesis in both sets of tubers. Exposure of dormant tubers to continuous light altered the ratio of α-chaconine to α-solanine irrespective of illumination source.     

The Effect of Low-Temperature Storage on the Glycoalkaloid Content of Potato (Solanum tuberosum) Tubers

Tubers from six cultivars selected on the basis of their rates of glycoalkaloid accumulation in response to light exposure were stored at 10, 7 and 4°C. After 9 weeks at 10°C a subset from each cultivar was removed and subsequently stored at lower temperatures. Samples were removed after 9, 18 and 24 weeks storage and analysed for their glycoalkaloid content. At all temperatures the rate of glycoalkaloid accumulation was independent of the level found at harvest and significant interactions were found between cultivar and temperature. The highest rates of accumulation were seen in tubers from the cultivars Brodick and Pentland Crown stored at 4°C. During the first 9 weeks of storage at this temperature the glycoalkaloid content of these two cultivars increased by 7·4 and 19·1 mg per 100 g fresh weight respectively and thereafter remained constant. At 7°C glycoalkaloid content tended to increase more rapidly than at 10°C with again the greatest increases being found for Brodick and Pentland Crown. In the case of the former glycoalkaloid content increased linearly during the 24 weeks of the experiment but the glycoalkaloid content of Pentland Crown tubers stored at 7°C increased rapidly in the first 9 weeks and thereafter increased more slowly, reaching a final value which exceeded the recommended maximum glycoalkaloid concentration for human consumption by 50%. Cultivars which did not accumulate glycoalkaloids rapidly in response to light exposure were the most stable and least sensitive to storage temperature. Tubers transferred to colder conditions nine weeks after storage at 10°C did not accumulate glycoalkaloids at a similar rate to those placed in similar conditions soon after harvest. © 1997 SCI     

The effect of prior storage on the potential of potato tubers (Solanum tuberosum L) to accumulate glycoalkaloids and chlorophylls during light exposure,including artificial neural network modelling

Potato tubers of four varieties (Brodick, King Edward, Pentland Dell and Record) were stored under commercial conditions and exposed to light for up to 10 days after 0, 10, 20 and 30 weeks. These were analysed for photosynthetic pigment and glycoalkaloid content. There was no significant alteration in either tuber chlorophyll or glycoalkaloid content during dark storage. All four varieties greened in response to light exposure, but only three exhibited a significant increase in glycoalkaloid concentrations during this exposure. Storage duration did not significantly affect pigment accumulation. However, there was a marked effect of storage on the extent of glycoalkaloid accumulation. Tubers of all four varieties stored for more than 10 weeks did not accumulate glycoalkaloids to the same extent as fresh tubers. Indeed, Brodick and Record did not accumulate any glycoalkaloids in response to light after 30 weeks of storage. A number of artificial neural network models of the results were produced. These accurately modelled cultivars individually, but a model encompassing all the data was not successful at predicting cultivar differences. © 1999 Society of Chemical Industry     

Potato glycoalkaloids: formation and strategies for mitigation

With the increasing production and consumption of potato and its products, glycoalkaloid (GA) formation and toxicity are likely to become an important focus for food safety researchers and public health agencies. Not only the presence of GA, particularly in the form of α‐solanine and α‐chaconine, but also the changes occurring as a result of various post‐harvest handling practices and storage, are critical issues influencing the quality of stored potatoes. Studies on various factors (pre‐harvest, during harvest and post‐harvest) affecting GA have been carried out from time to time, but it is difficult to compare the results of one study with another due to wide variation in the parameters chosen. This review aims to develop a clear understanding of these issues. Published information on the types of GA, their effects on health, their typical concentrations in potatoes, their formation mechanisms, and how their levels can be controlled by following appropriate post harvest practices and storage regimes are critically analysed. The levels of GA in potato can be controlled effectively by adopting appropriate post‐harvest practices. Further studies are necessary, however, to investigate best practices, which either check completely or retard substantially their formation. Copyright © 2008 Society of Chemical Industry     

A simplified procedure for quantification of potato glycoalkaloids in tuber extracts by H.p.l.c.; comparison with ELISA and a colorimetric method

An improved high-performance liquid chromatography (h.p.l.c.) procedure for determination of glycoalkaloid levels in potato tubers has been developed in which Sep-Pak cartridges replace the commonly used alkaline precipitation for clean-up of tuber extracts. Glycoalkaloids are extracted from fresh tuber tissue into an aqueous medium, the extract is submitted to clean-up and α-solanine and α-chaconine are quantitatively separated on a reversed phase column with ethanolamine modifier added to the mobile phase. Potato tubers were comparatively analysed for their glycoalkaloid content by this and two other methods: a recently developed immunoassay (ELISA) and a colorimetric procedure representing the traditional chemical approach. Agreement between the h.p.l.c. and the other methods was good.     

High levels of glycoalkaloids in the established swedish potato variety magnum bonum

In 1986, potentially toxic levels of the glycoalkaloids α-solanine and α-chaconine were unexpectedly found in tubers of the established Swedish consumer potato variety Magnum Bonum, leading to the imposition of a conditional sales ban on such potatoes. The combined amounts of α-solanine and α-chaconine in more than 300 commercial lots of Magnum Bonum potatoes analysed as a consequence of the ban ranged from 61 to 665 mg kg^?1 fresh weight with an average of 254 mg kg^?1. Sixty-six percent of the samples exceeded a temporary maximum residue limit of 200 mg kg^?1, 8% were above 400 mg kg^?1. Peeling did not significantly remove the glycoalkaloids in tubers with a high content. The occasional glycoalkaloid elevation was initially attributed to the unusually cold and rainy conditions during the late part of the season in 1986, but subsequent investigations have failed to confirm this hypothesis. Varietal characteristics are likely to have been involved since most other common Swedish varieties seemed to have had normal glycoalkaloid levels in 1986. There were no indications of serious or widespread adverse health effects in consumers due to the high glycoalkaloid levels, although there was circumstantial evidence that a few cases of temporary gastrointestinal disturbances were caused by consumption of Magnum Bonum potatoes with glycoalkaloid concentrations in the range 310–1000 mg kg^?1.     

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.     

GLYCOALKALOID CONCENTRATION IN BY-PRODUCTS of POTATO STARCH EXTRACTION AS MEASURED BY MATRIX-ASSISTED LASER DESORPTIONIIONIZATION MASS SPECTROMETRY

Starch, potato protein concentrate, and potato pulp were produced in order to determine the fate of endogenous toxic glycoalkaloids during potato processing. Potato protein concentrate was precipitated from potato fruit water using acid and heat. Glycoalkaloid concentrations were determined using matrix- assisted laser desorption/ionization mass spectrometry. No correlation was observed between tuber protein concentration and yield of potato protein concentrate (r = 0.257). Glycoalkaloids could not be detected in starch extracted from tubers with a glycoalkaloid concentration of 6.6 mg/i 00 g (fwb). Dry potato protein concentrate and dry potato pulp produced from the same tubers contained 60 and 50 mg glycoalkaloid/100 g, respectively. the apparent partitioning of glycoalkaloids into the protein concentrate and pulp indicates toxicity might be a concern for these products, given that a maximum acceptable level of 20 mg glycoalkaloid/100 g is often cited for tubers.     

A rapid screening method for the estimation of total glycoalkaloids in potato tubers

A rapid method for estimating the total glycoalkaloid (TGA) content of potato tubers is described which allows TGA content to be classified into three groups: (i) low TGA containing (< 15 mg TGA 100 g^?1 fresh weight); (ii) high TGA containing (< 15-35 mg TGA 100 g^?1 fresh weight); and (iii) very high TGA (> 35 mg TGA 100 g^?1 fresh weight). The method is intended for use by plant breeders, particularly when high TGA content might be expected in hybrid clones where one or both parents is derived from a wild species. The TGA concentration in juice expressed from potato periderm and cortex tissue was assayed by thin layer chromatography. The method utilises a direct relationship which was established between the glycoalkaloid concentration in expressed juice and the TGA content of the whole tuber and enables up to 50 analyses to be completed in 1 day by one operator without the need for expensive equipment.     

Glycoalkaloids (α-chaconine and α-solanine) contents of selected Pakistani potato cultivars and their dietary intake assessment

Glycoalkaloids (α-solanine and α-chaconine) are naturally occurring toxic compounds in potato tuber (Solanum tuberosum L.) that cause acute intoxication in humans after their consumption. Present research was conducted to evaluate α-chaconine, α-solanine, and total glycoalkaloids (TGAs) contents in the peel and flesh portions by high-performance liquid chromatography method in selected Pakistani potato cultivars. The α-solanine content varies 45.98 ± 1.63 to 2742.60 ± 92.97 mg/100 g of dry weight (DW) in peel and from 4.01 ± 0.14 to 2466.56 ± 87.21 mg/100 g of DW in flesh. Similarly, α-chaconine content varied from 4.42 ± 0.16 to 6818.40 ± 211.07 mg/100 g of DW in potato peel and from 3.94 ± 0.14 to 475.33 ± 16.81 mg/100 g DW in flesh portion. The TGA concentration varied from 177.20 ± 6.26 to 5449.90 ± 192.68 mg/100 g of DW in peel and from 3.08 ± 0.11 to 14.69 ± 0.52 mg/100 g of DW in flesh portion of all the potato cultivars tested. All the potato cultivars contained lower concentration of TGA than the limits recommended as safe, except 2 cultivars, that is FD8-3 (2539.18 ± 89.77 mg/100 g of DW) and Cardinal (506.16 ± 17.90 mg/kg). The dietary intake assessment of potato cultivars revealed that Cardinal, FD 35-36, FD 8-3, and FD 3-9 contained higher amount of TGA in whole potato, although FD 8-3 only possessed higher content of TGA (154.93 ± 7.75) in its flesh portion rendering it unfit for human consumption. Practical Application: This paper was based on the research conducted on toxic compounds present in all possible potato cultivars in Pakistan. Actually, we quantify the toxic compounds (glycoalkaloids) of potato cultivars through HPLC and their dietary assessment. This paper revealed safety assessment and their application in food industries especially potato processing.     

Glycoalkaloid content of early potato varieties

Samples of Swedish domestic early potatoes were collected from wholesalers and analysed for their content of glycoalkaloids (GA), α-solanine and α- chaconine, using a modified HPLC procedure. The varieties included were, in order of increasing GA content; Maris Bard, Ukama, Pro vita, Evergood Eldorado, Maria, Early Puritan, Silla and Ulster Chieftain. The average total GA content (α-solanine and α-chaconine combined) for the different varieties ranged from 51 to 221 mg kg^?1 fresh weight. α-Solanine constituted on average between 35 and 41% of the GA detected. The GA concentrations in individual samples were in the range 31-344 mg kg^?1. The variety Ulster Chieftain accounted for 88% of the samples above 200 mg kg ^?1. The results obtained with tubers grown experimentally in field trials in two different years were consistent with the findings for commercially grown potatoes in terms of GA content rank among varieties.     

Provitamin‐A and xanthophyll carotenoids in vegetables and food grains of nutritional and medicinal importance

This study reports carotenoid composition of vegetables (n = 56), cereals (n = 12), pulses and legumes (n = 12), analysed by HPLC. It was hypothesised that food grains, like vegetables may be good sources of carotenoids. Amongst vegetables, higher level (mg/100 g dry weight) of lutein (210–419) was detected in green/red/capsicum and yellow zucchini, whilst zeaxanthin was dominant in kenaf (4.59). β‐Carotene (mg/100 g dry weight) was higher in green capsicum and kenaf (48,159) whilst carrot, ivy gourd and green capsicum contain α‐carotene (22–110). Amongst food grains, chickpea, split red gram and flaxseed contain higher levels (μg/100 g dry weight) of lutein (185–200) whilst zeaxanthin level was highest in puffed chickpea (1.8). Red unpolished parboiled rice was richest (μg/100 g dry weight) in β‐carotene (67.6) whilst whole black gram contained higher levels of α‐carotene (52.7). Thus, results indicate that chickpea and red unpolished parboiled rice are good sources of carotenoids. These carotenoid‐rich vegetables and grains may be exploited to meet the lutein and β‐carotene requirement.     

Effect of exposure to light on the solanine content of two varieties of potato (Solanum tuberosum) popular in Jordan

An analysis of random samples of potatoes (Solanum tuberosum) from local markets in Jordan showed that many whole tubers had solanine contents above the recommended level of 20 mg/100 g (fresh weight) of potato, while the maximum level in the skins was 128 mg/100 g. Exposure of two local varieties, Draga and Sponta, to direct or diffuse sunlight generated comparable levels over a 3-week period, but differences between the varieties were significant. It is suggested that growers in countries with Mediterranean climates should select varieties that generate low levels of solanine, remove the tubers from the field immediately after harvest and store the crop in the dark.