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Nitrate content in a collection of higher mushrooms

Authors:
  • Plant Protection Institute, Center for Agricultural Research, Budapest

Abstract

Background Data of mushroom nitrate content from scientific studies is limited. There have been two such recent investigations (mainly regarding certain cultivated species). To obtain comparable analytical data, we analyzed 134 samples of 54 taxa gathered and prepared by our Department.ResultsThe mushroom species were evaluated according to their nutritional types: saprotrophic, mycorrhizal and wood-decaying groups. Low and relative invariable contents were found in the mycorrhizal (216.5 mg kg−1 dry matter [D.M.] and wood-decaying groups (228.6 mg kg−1 D.M.), but in the saprotrophic group we observed wide variability (151.4 – 12715 mg kg−1 D.M.).Conclusion Considerable nitrate contents were found in samples of seven “accumulator” species (Clitocybe nebularis, C. odora, Lepista nuda, L. personata, L. irina, Macrolepiota rachodes and M. procera). Toxicological relevance of daily uptake of acceptable nitrate content via mushrooms only is not presumable, but the “accumulator” saprotrophic species can be “contributors” of our nitrate intake by foods.
Nitrate content in a collection of higher mushrooms
RENÁTA BÓBICS, DÁNIEL KRÜZSELYI, AND JÁNOS VETTER*
Department of Botany, Faculty of Veterinary Science, Szent István University, Rottenbiller 50, 1077
Budapest, Hungary
*Corresponding author [telephone +36 1 4584238; fax: +361 4584238; e-mail
vetter.janos@aotk.szie.hu]
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ABSTRACT
BACKGROUND. Data of mushroom nitrate content from scientific studies is limited. There
have been two such recent investigations (mainly regarding certain cultivated species). To
obtain comparable analytical data, we analyzed 134 samples of 54 taxa gathered and prepared
by our Department.
RESULTS. The mushroom species were evaluated according to their nutritional types:
saprotrophic, mycorrhizal and wood-decaying groups. Low and relative invariable contents
were found in the mycorrhizal (216.5 mg kg-1 dry matter [D.M.] and wood-decaying groups
(228.6 mg kg-1 D.M.), but in the saprotrophic group we observed wide variability (151.4
12715 mg kg-1 D.M.).
CONCLUSION. Considerable nitrate contents were found in samples of seven “accumulator”
species (Clitocybe nebularis, C. odora, Lepista nuda, L. personata, L. irina, Macrolepiota
rachodes and M. procera). Toxicological relevance of daily uptake of acceptable nitrate
content via mushrooms only is not presumable, but the “accumulator” saprotrophic species
can be “contributors” of our nitrate intake by foods.
KEYWORDS: Food, human nutrition, edible mushrooms, fruiting bodies, nitrate content,
accumulator species
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INTRODUCTION
Nitrate (NO3-) is one of several soluble nitrogen sources found in livings (e.g., bacteria,
fungi, and plants), and it is an important member of the nitrogen-cycle. The uptake, content,
and accumulation of nitrate (and of nitrite [NO2-] originating from its reduction) can be the
beginning of ecotoxicological problems, such as animal and/or human poisonings
(methemoglobinemia). In toxicological damages, ingestion by plants (as foods) and drinking
of water are the two main possible factors. Recently there has been evidence that nitrate’s
metabolic transformation into nitrite and nitric oxide(s) can have some useful properties, as
prevention of vascular damages and protection of the stomach. 1
Nitrate intake into plants is carried out by root system, and transported via xylem system. It
can be stored in the vacuolar system of roots, shoots, and storage organs. Acquired nitrate can
be transformed by a reductase system (located partly in cytoplasm and in chloroplasts) and
has important role in the plant nitrogen cycle. Actual nitrate concentration depends on its
absorption and assimilation. Increased accumulation can be caused by different internal and
external factors (e.g. nutritional, environmental and physiological ones, but primarily by
activity of the reductase enzyme system).2 Some plant species of the Chenopodiaceae
(Chenopodium album, C. hybridum) and Amarantaceae (Amaranthus retroflexus) families as
well as some vegetables (Lactuca species, Spinacia oleracea) can accumulate higher nitrate
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levels. These plants can contain 2000-5000 mg kg-1 nitrate concentration on a fresh matter
(F.M.) basis. 3 The so-called nitrophile character of certain plants describes not only the
essential and required role of nitrogenous compounds in their life but that these plants often
exhibit a higher rate of nitrate accumulation (taxa from the Solanaceae family including
Datura stramonium, Atropa belladonna, Hyoscyamus niger, Scopolia carniolica or some
Solanum species).
Nitrate is a nitrogen source for certain fungi (mushrooms). For example, nitrate is an
essential nitrogen form for Rhizoctonia solani, Trichoderma lignorum microscopic fungal
taxa as well as for the mushrooms Armillaria mellea, Collybia velutipes, Lentinus tigrinus and
others.4 Efficient nitrate use requires an active enzyme system (composed of nitrate reductase,
nitrite reductase and hydroxyl-amine reductase), which can catalyze the following metabolic
processes: NO3- NO2- NH2OH glutamate. Therefore, uptake and use of nitrate is
essential for amino acid synthesis and for other metabolic changes (i.e. proteins, nucleic acids,
vitamins, and chitin).
Actual nitrate content of higher mushrooms appears to be poorly studied.5-6 Determinations
of inorganic anions (including nitrate) were carried out for eight wild growing higher
mushroom taxa: Agaricus bisporus, Lepista nuda, Marasmius oreades, Coprinus comatus,
Verpa conica, Morchella elata, M. esculenta and Pleurotus ostreatus.5 Chung and coworkers
analyzed nitrate contents of some vegetables consumed in Hong-Kong, including fruiting
bodies of six commonly cultivated taxa (Coprinus comatus, Flammulina velutipes, Pleurotus
ostreatus, Lentinula edodes, Volvariella volvacea and Agaricus bisporus).6 Iammarino and
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coworkers,7 published data on nitrate level of 1785 samples, but, unfortunately, this data has
no samples of mushroom origin.
Nitrate as toxicological agent has numerous implications for animals, including humans. The
main problems include clinical and subclinical poisoning caused by high nitrate intake, which
can originate from different “accumulator” plant taxa and/or by agricultural/environmental
(pollution) factors (i.e., fertilization, drinking waters etc.). The possible consequences can be
methemoglobinemia (a rapid and intensive poisoning) and/or production of nitrosamines
(from the secondary amines); their carcinogenic character seems to be doubtless.
Nitrate intoxications (poisonings) are known for ruminants and monogastric animal
species (including humans) and this problem has been widely studied in recent literature. 8-11
Certain environmental aspects such as soil quality, drinking water, nitrogen fertilizers etc. are
contributing to these problems. 12
The fact different types of food can have higher nitrate (and nitrite) content generates
the need of regulation (i.e., limitation) of the permissible (and/or recommended) nitrate
contents of foods. The European Commission’s Scientific Committee for Food established the
Acceptable Daily Intake for nitrate as 3.65 mg kg-1 body weight. 2,13 In 2005, the European
Commission (EC) adopted EC regulation No. 1822 14 and regulated the maximum nitrate
level for certain plant species (i.e. lettuce, spinach) and types of food i.e., (baby foods). These
limited levels depend on the season; for instance, levels are 3000 mg kg-1 F.M. for spinach
during winter but only 2500 mg kg-1 F.M. during summer. There are no specific limitations
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for mushrooms. Control and monitoring of nitrate levels of different foodstuffs is an essential
question.
Goals of this investigation were:
1. to produce a comparative data bank of nitrate contents regarding the fruiting bodies
both wild growing and cultivated species (including different varieties);
2. to describe any “accumulator” species (taxa), to find the probable factors involved in
regulation of nitrate level in mushrooms;
3. and to investigate if nitrate levels found in common edible mushrooms can be
dangerous or hazardous to consumers.
EXPERIMENTAL
Biological samples. The fruiting bodies of higher edible mushrooms (mainly for
basidiomycetous taxa) analyzed in this study were obtained from a sample collection from the
Botanical Department, Faculty of Veterinary Science, Szent István University, Hungary.
Samples of wild growing species were gathered from different habitats in Hungary. The
cultivated species (varieties) were produced by Hungarian and German growers or scientific
Institutes. For sample preparation, the cleaned fruiting bodies (carpophores) were sliced, dried
carefully (at 35 °C) and grounded. All nitrate determinations were performed from these
homogenous, fine mushroom powders in triplicates.
Nitrate determination. Extraction of mushroom samples was performed in bi-distilled
water (2 hours on a rotary shaker at 175 rpm) in triplicates; the filtrated homogenate was
deproteinased (according to methods of Bintoro15) and centrifuged (10000 rpm, for 20 min).
Nitrate concentration was determined from the supernatant16; the optical density was
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measured at 540 nm (Spectrophotometer Metertech SP-880). The nitrate content of mushroom
samples was calculated with potassium nitrate (KNO3) calibration and was given in mg nitrate
kg-1 D.M. (dry matter).
Statistical evaluation. The nitrate data of samples were characterized by the
arithmetical mean and standard deviation (±SD) using the software Origin 8.5.
RESULTS AND DISCUSSION
Nitrate contents of saprotrophic mushroom samples (54 samples of 19 taxa) are
summarized in Table 1. The found nitrate contents vary widely in concentration. The lowest
nitrate level occurred in a Craterellus cornucopioides sample from the Bakony Mountains
(151.4 mg kg-1 D.M.), and the highest concentration was in a sample of Clitocybe nebularis
from the same habitat and from same season with 12715 mg kg-1 D.M. This range is very
large (approximately 85 fold). Averaged by mushroom species: high levels of nitrates were
found in seven species: Clitocybe nebularis (average 6983 mg kg-1 D.M.), Clitocybe odora
(1766 mg kg-1 D.M.); Lepista irina (7238 mg kg-1 D.M.), L. nuda (5844 mg kg-1 D.M.). L.
personata (5558 mg kg-1D.M.), Macrolepiota rhacodes (1877 mg kg-1 D.M.) and M. procera
(627 mg kg-1 D.M.). Samples of all other species from different habitats had significantly
lower nitrate contents: in general, 200-300 mg kg-1 D.M. (Table 1).
Table 2 contains our data of edible mushrooms of mycorrhizal type. We analyzed 27
samples of 13 taxa. The data regarding this mushroom group have a relatively homogenous
nitrate level. The lowest content was in a Suillus grevillei fruiting body (137 mg kg-1 D.M.),
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whereas the highest one was achieved in a Tricholoma terreum sample (507.8 mg kg-1 D.M.)
the range is only about four fold. For the species with more samples also within species,
standard deviation is relatively unimportant. For example, Lactarius deliciosus, Suillus
grevillei and Boletus aereus samples from different habitats have the following coeffeicients
of variation 30.9 %; 16.7 % and 21.5 %, respectively. In groups of mycorrhizal species for
which we did not detect nitrate accumulation, the average nitrate level was 216.2 mg kg-1
D.M.
Twenty-two samples of 13 taxa represent the group of wood-decaying mushrooms (Table
3). The range between the lowest (Hericium clathroides from Mt. Börzsöny with 131.4 mg
kg-1 D.M.) and highest nitrate level (Armillaria mellea from Mt. Bakony with 342.7 mg kg-1
D.M.) is only about three fold. The average of the entire group is 228.6 mg kg-1 D.M., which
is similar to the average of mycorrhizal mushroom group. Differences between the samples of
the same species are restricted; the nitrate data comprise a homogenous group, and nitrate
“accumulator” species were not found in this group.
Regarding cultivated mushrooms, only three species were analyzed; just three species
(Agaricus bisporus, Lentinula edodes and Pleurotus ostreatus) but they represent the majority
of world mushroom cultivation. We had 31 samples of nine species (produced by different
growers and/or research Institutes); six varieties for A. bisporus, and five varieties of P.
ostreatus species were analyzed. In some cases, we had distinct cap and stipe samples.
Regarding Lentinula edodes, we analyzed a series of samples from different parts of fruiting
bodies (i.e. whole fruiting body, cap skin, gills, stipe and the primordium) for investigation of
nitrate distribution in the carpophores. Data of analyses are given in Table 4. The lowest one
level was measured in gills of Lentinula edodes at 140 mg kg-1 D.M. The highest nitrate
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content was found in stipes of Agaricus subrufescens (1011 mg kg-1 D.M.). Therefore, the
highest content is about seven-fold greater than the lowest. The calculated average nitrate
level of cultivated mushroom samples is 333.6 mg kg-1 D.M., but a lot of our samples had
nitrate contents less than 250 mg kg-1 D.M. Accumulation of nitrate was not found in fruiting
bodies of cultivated mushrooms.
Moreover, for some other species, we had samples from different morphological parts
of fruiting bodies, mainly cap and stipe. Different distributions were detected: Agaricus
subrufescens stipe had a higher content (compared to caps), but caps had the higher nitrate
level in Pleurotus ostreatus. The distribution of nitrate through the mushroom was
investigated in particular for of Lentinula edodes. Data in Table 4 indicate a very balanced
distribution in nitrate content with no accumulation in some fruit body parts.
Finally, we analyzed some conserved products of four mushroom species (Table 5). The
found nitrate contents were low. No essential differences were found between the various
species or between samples produced by different conservation technologies (i.e., mushrooms
in own juice, natural or marinated products).
This investigation is likely the first whose goals involve the nitrate content of wild-growing
and of cultivated, edible mushroom species. We analyzed the fruiting bodies altogether of 134
samples of 54 taxa and five canned products were also included. Data from our analyses were
grouped according to mushroom nutrition type: saprotrophic, mycorrhizal and wood-decaying
groups.
1. In the saprotrophic mushroom group (Table 1) the different, changing nitrate levels were
identified in. The majority of taxa had relatively low (200-300 mg kg-1 D.M.) nitrate levels,
but seven taxa (independently, from their habitat) had high nitrate levels: two Clitocybe
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species (C. nebularis and C. odora), three Lepista species (L. nuda, L. personata and L.
irina) and two Macrolepiota species (M. rachodes and M. procera). These species can be
classified as “accumulator” species. Because a possible cause of the high nitrate
concentrations (accumulation) may be the high nitrate content of environment (i.e., soil, or
water), nitrate pollution could be a major factor. However, support for this hypothesis is very
low because different samples from the same habitat had extremely different nitrate
concentrations. For instance, from the ‘Farkasgyepű” habitat we measured the following
nitrate contents: 12715 mg kg-1 D.M. in Clitocybe nebularis; 2568 in Macrolepiota rachodes;
358.3 in Laccaria laccata; 151.4 in Craterellus cornucopioides; 358.3 in Laccaria laccata;
313 in Armillaria mellea; and 285 in Lactarius deliciosus). The “accumulator” taxa are in
two families: mainly in the Tricholomataceae (Clitocybe and Lepista species) and
Agaricaceae families (Macrolepiota species). It seems most likely that the capacity of the
nitrate reductase enzyme system, which is responsible for further transformation of nitrate, is
not enough for the reduction of nitrate ions and/or the intensity of nitrate uptake is to high for
subsequent reduction. The saprotrophic mode of nutrition includes very intensive metabolic
changes in and from the environment.
2. Groups of mycorrhizal and wood decaying mushroom taxa had balanced; low nitrate
levels with averages of 216.2 and 229.3 mg kg-1 D.M., respectively, without relevant
differences. All samples (and taxa) of these groups can use (metabolize) nitrate ions without
accumulation.
3. Thirty-one samples of nine species (including the three most important Agaricus bisporus,
Pleurotus ostreatus, and Lentinula edodes species) were in the group of cultivated
mushrooms. The nitrate levels of these cultivated species and varieties were in general low,
and no nitrate accumulation occurred. The Agaricus bisporus levels, however, were slightly
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higher (562.8 mg kg-1 D.M.), than those of other cultivated species. A realistic explanation,
that the nitrogen (including nitrate) level of this cultivated species is significantly higher
because the substrate of cultivation included some components of animal origin.
4. Nitrate contents of the analyzed canned products were low or very low, without health
hazards. Conservation of Agaricus bisporus (comparison of Table 4 and 5) yields a decrease
of the original nitrate content because the conservation can cause partial dissolving of nitrate.
5. Lastly but very importantly, the discovered “accumulator” species are (or can be)
problematic from a toxicological point of view. A calculation was made (see Table 6). For a
of 70-kg person, 255 mg nitrate is the acceptable daily intake. Table 6 shows the amount (per
cent) of ADI (Acceptable Daily Intake) for mean ingestion of 100 g fresh mushroom based on
an estimated 10% of dry matter content (from the seven edible “accumulator” species). The
data suggest that daily uptake of acceptable nitrate content via mushrooms is not presumable
because ingestion of 350 g of fresh mushroom can provide 100% of the acceptable daily
nitrate quantity. Daily uptake of such quantities pro day is too much for the majority of the
human population (the average uptake can be 100-150 g for fresh matter pro meal). The
possible daily nitrate ingestion for humans is the sum of the obtained nitrates from different
sources (primarily from some foods of plant origin, especially certain vegetables and from
drinking water). The possible contribution of so called “accumulator” mushroom species for
the daily nitrate intake is (or can be) important. Use and ingestion of other, wild-growing (not
“accumulator” species) and cultivated mushroom species, however, seems to be safe.
More extensive investigations are required for better understanding of nitrate relations
(uptake, content, accumulation etc.) of common edible and frequent mushroom species. Our
presented work is only one moderate step of this project.
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183-189 (2008).
Table 1. Nitrate content of wild-growing saprotrophic mushroom species
Mushroom species Location in Hungary Nitrate content
(mg kg-1
D.M.)
± SD
Agaricus abruptibulbus Peck Mátraszentistván (Mt.
Mátra)
366.2 ± 4.7
Nagykovácsi (Ördögárok)
near to Budapest
343.9 ± 4.8
Agaricus benesii (Pilát) Singer Hárskút (Mt. Bakony) 421.7 ± 15.0
Agaricus sylvaticus Schaeff. Hárskút (Mt. Bakony) 539.6 ± 38.2
Calvatia gigantea (Batsch)
Lloyd
Domony 330.98 ± 22
Clitocybe nebularis (Batsch) P.
Kumm.
Farkasgyepű (Mt. Bakony) 12715 ± 1045
Karancs 10164 ± 525
Domonyvölgy 7819 ± 349
Pilisszentkereszt (Mt. Pilis) 2311 ± 102
Pilisszentkereszt (Mt. Pilis) 1018 ± 23.6
Bakonybél (Mt. Bakony) 3356 ± 223
Karancs 11504 ± 506
Mean ± SD (CV%) 6983 ± 4737
(67%)
Clitocybe geotropa (Bull.:Fr.)
Quél.
Nagykovácsi (near to
Budapest)
173.7 ± 4.9
Clitocybe odora (Bull.) P.
Kumm.
Herend (Mt. Bakony) 1766 ± 93.5
Craterellus cornucopioides (L.)
Pers.
Mátraszentistván (Mt.
Mátra)
181.9 ± 4.5
Farkasgyepű (Mt. Bakony) 151.4 ± 7.2
Pilisszentkereszt (Mt. Pilis) 188.9 ± 7.5
Mean ± SD (CV%) 174.1 ± 19.9
(11.4%)
Lepista irina (Fr.) H.E. Bigelow Hárskút (Mt. Bakony) 3386 ± 23.4
Hárskút (Mt. Bakony) 11091 ± 307.2
Mean ± SD (CV%) 7238 ± 5444
(75.2%)
Lepista nuda (Bull.) Cooke Herend (Mt. Bakony) 8363 ± 268
Farkasgyepű (Mt. Bakony) 7117 ± 68
Farkasgyepű (Mt. Bakony) 12577 ± 582
Pilisszentkereszt (Mt. Pilis) 3217 ± 91.4
Karancs 5396 ± 285
(5.3%)
Pilisszentkereszt (Mt. Pilis) 2414 ± 141
Pilisszentkereszt (Mt. Pilis) 1830 ± 109
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292
293
Mean ± SD (CV%) 5844 ± 3835
(65.6%)
Lepista personata (Fr.) Cooke Nyíregyháza 5558.6 ± 389
Laccaria laccata (Scop.) Cooke Hárskút (Mt. Bakony) 358.3 ± 11.9
Herend (Mt. Bakony) 237.5 ± 22.9
Domony 309.5 ± 8.4
Mean ± SD (CV%) 301.7 ± 60.7
(20.1%)
Lycoperdon perlatum Pers. Mátraszentistván 391.7 ± 31.3
Herend (Mt. Bakony) 392.0 ± 10.3
Pilisszentkereszt (Mt. Pilis) 352.1 ± 20.6
Pilisszentkereszt (Mt. Pilis) 265.6 ± 68
Mean ± SD(CV%) 350.4 ± 59.5
(17%)
Lyophyllum decastes (Fr.)
Singer
Budapest 233.2 ± 5.07
Macrolepiota procera (Scop.)
Singer
Pilisszentkereszt (Mt. Pilis) 296.9 ± 24.1
Mátra 2113.5 ± 308
Domony 399.3 ± 32.2
Domony 443.1 ± 11.3
Soroksári Botanikus Kert 334.9 ± 19.7
Normafa (Mt. Budai) 259.8 ± 13.8
Pilisszentkereszt (Mt. Pilis) 544.9 ± 11.4
Mean ± SD (CV%) 627.4 ± 662
(105%)
Macrolepiota rachodes (Vittad.)
Singer (=Chlorophyllum
rachodes (Vittad.) Vellinga
Normafa (Mt. Budai) 1666.6 ± 62
Mátraszentistván (Mt.
Mátra)
1059. 6 ±168.5
Macrolepiota rachodes var.
hortensis (Pilát) Wasser
Domonyvölgy 3262.6 ± 40.4
Macrolepiota rachodes var.
hortensis (Pilát) Wasser
Domonyvölgy 2814.8 ± 141
Farkasgyepű (Mt. Bakony) 1028.6 ± 94.8
Farkasgyepű (Mt. Bakony) 2564.2 ± 140.6
Börzsöny (Mt. Börzsöny) 1339.6 ± 159.2
Domony 3192.1 ± 347
Pilisszentkereszt (Mt. Pilis) 1837.2 ± 48.14
Mean ± SD (CV%) 1877 ± 1065
(57%)
Stropharia aeruginosa (Curtis)
Quél.
Hárskút (Mt. Bakony) 305.45 ± 27.6
Herend (Mt. Bakony) 247.9 ± 11.2
Karancs 169.8 ± 10.0
Pilisszentkereszt (Mt. Pilis) 215.9 ± 112.9
Mean ± SD (CV%) 234.8 ±56.9
Table 2. Nitrate content of mycorrhizal species
Mushroom species Location Nitrate content
(mg kg-1 D.M.)
± SD
Amanita rubescens Pers. Pilisszentkereszt (Mt.
Pilis)
210.5 ± 10.2
15
18
294
295
296
Törökmező (Mt.
Börzsöny)
269.5 ± 25.3
Mean ± SD (CV%) 239.9 ± 41
Boletus aereus Bull. Szilvásvárad (Mt. Bükk) 209.3 ± 6.2
Mikófalva (Mt. Bükk) 217.5 ± 13.7
Egercsehi (Mt. Bükk) 303.6 ± 14.4
Mean ± SD (CV%) 243.7 ± 52.2
(21.5%)
Boletus reticulatus
Schaeff.
Szilvásvárad (Mt. Bükk) 217.1 ± 13.6
Cantharellus cibarius Fr. Szilvásvárad (Mt. Bükk) 194.0 ± 8.3
Gyroporus castaneus
(Bull.) Quél.
Börzsöny 158.4 ± 10.8
Hydnum repandum (L.) Mátraszentistván (Mt.
Mátra)
179.9 ± 25.4
Pilisszentkereszt (Mt.
Pilis)
236.3 ± 21.4
Mean ± SD (CV%) 208.1 ± 23.4
(11.25%)
Lactarius deliciosus (L.)
Gray
Herend (Mt. Bakony) 244.6 ± 43
Farkasgyepű (Mt.
Bakony)
284.8 ± 15.0
Mátra 151.0 ± 12.5
Bátor (Mt. Bükk) 152.2 ± 18.5
Mean ± SD (CV%) 206.6 ± 64.0
(31.0%)
Leccinum scabrum (Bull.)
Gray
Monor 180.7 ± 12.3
Suillus grevillei (Klotzsch)
Singer
Pilisszentkereszt (Mt.
Pilis)
194.0 ± 17.8
Pilisszentkereszt (Mt.
Pilis)
160.8 ± 14.4
Pilisszentkereszt (Mt.
Pilis)
137.0 ± 8.2
Mean ± SD (CV%) 163.9±27.4
(16.8%)
Tricholoma terreum
(Schaeff.) P. Kumm.
Herend (Mt. Bakony) 371.7 ± 27.1
Karancs 507.8 ± 41.9
Mean ± SD (CV%) 439.7 ± 78.7
(17.8%)
Tuber aestivum Vittad. Mecsek 165.9 ± 5.8
Tápiógyörgye 172.5 ± 13.8
Bükk (Horvölgy) 152.9 ± 6.0
Aggtelek (Szőlősardó) 227.1 ± 20.8
Aggtelek (Jablonca) 137.5 ± 3.2
Mecsek 165.8 ± 5.9
Mean ± SD (CV%) 165. 3± 5.8
(3.5%)
Xerocomellus
chrysentheron (Bull.)
Sutara
Pilisszentkereszt (Mt.
Pilis)
235.9 ± 16.8
Table 3. Nitrate concentration of some wood-decaying mushrooms
Mushroom species Location Nitrate content
16
19
297
298
(mg kg-1 D.M.)
± SD
Armillaria mellea
(Vahl) P. Kumm.
Herend (Mt. Bakony) 290.3 ± 6.58
Hárskút (Mt. Bakony) 342.7 ± 20.9
Farkasgyepű (Mt.
Bakony)
313.9 ± 21.4
Bakonyszentkirály (Mt.
Bakony)
281.7 ± 10.6
Normafa (Mt. Budai) 244.9 ± 24
Karancs 234.7 ± 3.9
Mean ± SD (CV%) 288.0 ± 42.8 (14.9%)
Auricularia auricula-
judae
Monor 155.5 ± 12.8
Daedalea quercina
(L.) Pers.
Pilisszentkereszt (Mt.
Pilis)
224.9 ± 15.9
Pilisszentkereszt (Mt.
Pilis)
226.1 ± 6.4
Mean ± SD (CV%) 225.5 ± 11.6 (5.2%)
Fistulina hepatica
(Schaeff.) With.
Mátraszentistván (Mt.
Mátra)
161.2 ± 3.2
Budapest (Budakeszi u) 142.8 ± 3.8
Mean ± SD (CV%) 152 ± 10.2 (6.7%)
Grifola frondosa
(Dicks.) Gray
Nyíregyháza (Woods of
Sóstó)
322.8 ± 25.9
Budakeszi (Mt. Budai) 232.0 ± 6.7
Mean ± SD (CV%) 277.4 ±50.7 (18.3%)
Hericium chlathroides Normafa (Mt. Budai) 268.2 ± 20.6
Hericium cirrhatum
(Pers.) Nikol.
Börzsöny 131.4 ± 7.6
Hypsizygus ulmarius
(Bull.) Redhead
Budapest (Újpest) 150.6 ± 3.2
Laetiporus sulphureus
(Bull.) Murrill
Normafa (Mt. Budai) 179.2 ± 12.4
Budapest (Városmajor) 162.4 ± 8.0
Mean ± SD(CV%) 170.8 ± 11.9 (7.0%)
Pleurotus ostreatus
(Jacq.) P. Kumm.
Szarvaskút (Mt.
Bakony)
279.8 ± 15.8
Trametes versicolor
(L.) Lloyd
Bakony 235.9 ± 17.4
Trametes gibbosa
(Pers.) Fr.
Bakony 264.1 ± 17.4
Volvariella bombycina
(Schaeff.) Singer
Gyál 199.1 ± 10.5
Table 4. Nitrate level in cultivated mushrooms
Mushroom species (variety) Grower Nitrate content
(mg kg-1 D.M.)
± SD
Agaricus bisporus (J. E. Lange) Imbach
,A15’
GAMU, Germany 660.0 ± 36.7
A. bisporus (J. E. Lange) Imbach ,A15’ GAMU, Germany 430.3 ± 6.7
A. bisporus (J. E. Lange) Imbach ’Sylvan
A15’
GAMU, Germany 539.9 ± 114
A. bisporus (J. E. Lange) Imbach, ’LeLion GAMU, Germany 484.9 ± 41.3
17
20
299
300
301
C-9’
A. bisporus (J. E. Lange) Imbach ,A15’ János Szarka, Hungary 682.5 ± 22.3
A. bisporus (J. E. Lange) Imbach ,K 145’ „Korona gomba”
Hungary
579.3 ± 6.51
Mean ± SD (CV%) 562.8 ± 98.2
(17.5%)
A. subrufescens Peck ,2603’ Corvinus University,
Budapest
387.3 ± 28.9
A. subrufescens Peck ,2603’ Corvinus University,
Budapest
1010 ± 43
Mean ± SD (CV%) 699.1 ± 440.9
(63%)
Agrocybe cylindracea (DC.) Maire „Korona gomba”,
Hungary
205.7 ± 6.4
Ganoderma lucidum (Curtis) P. Karst. GAMU, Germany 165.9 ± 4.6
Pleurotus cornucopiae (Paulet) Rolland „Korona gomba”,
Hungary
227.7 ± 10.5
P. eryngii (DC.) Quél. „Korona gomba”
Hungary
259.4 ± 11.9
Corvinus University,
Budapest
247.3 ± 5.9
Corvinus University,
Budapest
213.6 ± 8.9
„Korona gomba”,
Hungary
246.5 ± 18.1
Mean ± SD (CV%) 241.7 ± 19.6
(8.1%)
P. ostreatus (Jacq.) P. Kumm. ,HK-35’ Corvinus University,
Budapest
210.1 ± 12.3
P. ostreatus (Jacq.) P. Kumm. ,HK-35’ Corvinus University,
Budapest
176.8 ± 3.5
P. ostreatus (Jacq.) P. Kumm. ,Amycel
3015’
GAMU, Germany 229.3 ± 16.3
P. ostreatus (Jacq.) P. Kumm. ,Somycel
HK-35’
GAMU, Germany 314.5 ± 19.7
P. ostreatus (Jacq.) P. Kumm. GAMU, Germany 260.5 ± 17.2
P. ostreatus (Jacq.) P. Kumm. GAMU, Germany 202.6 ± 3.8
P. ostreatus (Jacq.) P. Kumm. ,P80’ László Kelemen,
Hungary
183.4 ± 16.0
P. ostreatus (Jacq.) P. Kumm. ,BL’ László Kelemen,
Hungary
188.6 ± 7.9
Mean ± SD (CV%) 220.7 ± 46.7
Lentinula edodes (Berk.) Pegler „Korona gomba”,
Hungary
184.7 ± 11.6
GAMU, Germany 224.9 ± 27.7
L. edodes (Berk.) Pegler ,KST 70’ „Korona gomba”,
Hungary
151.4 ± 2.5
Mean ± SD (CV%) 187.1 ± 36.8
(19.7%)
Lentinula edodes, KST 70’ whole fruiting
body
L. edodes, KST 70’, capskin
L. edodes, KST 70’, gills
„Korona gomba”
Hungary
162.7 ± 6.24
„Korona gomba”
Hungary
145.6 ± 5.0
„Korona gomba” 140.1 ± 2.1
18
21
L. edodes, KST 70’, stipe
L. edodes, KST 70’, primordium
Hungary
„Korona gomba”
Hungary
156.5 ± 5.1
„Korona gomba”
Hungary
167.2 ± 5.5
Mean ± SD (CV%) 154.4 ± 11.4
(7.4%)
Table 5. Nitrate content of mushroom conserves
Mushrooms Character of sample Nitrate
content
(mg kg-1
D.M.)
± SD
Agaricus bisporus (J.E. Lange)
Imbach
Conserved whole caps 231.9 ± 3.9
Conserved sliced fruit
bodies
178.0 ± 5.4
Mean ± SD (CV%) 205.4 ± 38.7
Boletus aereus Bull. Conserved in own juice 160.8 ± 11.6
Boletus badius (Fr.) Fr. Conserve, natural 176.4 ± 3.1
Conserve, marinated 144.6 ± 27
Mean ± SD (CV%) 160.5 ± 22.5
Cantharellus cibarius Fr. Conserve, natural 183.9 ± 19.5
Table 6. Calculated quantity of possible nitrate ingestion by eating of 100 g fresh fruit bodies of the
“accumulator” species on the basis of estimated 10% dry matter content
Species Nitrate quantity of 100 g
fresh mushrooms
(mg)
Nitrate quantity
in per cent of
ADI value
Macrolepiota procera 6.27 2.45
Macrolepiota rachodes 18.77 7.36
Lepista nuda 58.44 22.91
Lepista irina 72.38 28.4
Lepista personata 55.58 21.8
Clitocybe nebularis 69.83 27.4
Clitocybe odora 17.66 6.92
19
22
302
303
304
305
306
307
308
309
310
311
20
23
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
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The massive introduction of nitrogen fertilisers, necessary to maximise the global food production, has brought about an increase of the residual amounts of nitrites and nitrates in the products. Notoriously, these compounds may exercise toxic effects. In this work the results obtained from 5years of official controls and monitoring focused on tracing quantifiable amounts of nitrites and nitrates in 1785 samples of meat, dairy, fish products and leafy vegetables are reported. A widespread presence of nitrates at low concentrations in foodstuffs was verified. High concentrations of nitrates were registered in some leafy vegetables and mussels samples, while high nitrites concentrations were registered in some spinach samples. The results confirmed the necessity to develop most controls and suggest the introduction of new legal limits related to some combinations contaminant/matrix. Such new limits may fill legislative gaps that may cause wrong interpretations of the results obtained during official controls.
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Levels of nitrate and nitrite in 73 different vegetables, a total of 708 individual samples grouped into leafy, legumes, root and tuber, and fruiting vegetables, which are traded mainly in Hong Kong, were measured. Where available, five samples of each vegetable type were purchased from different commercial outlets during the winter of 2008 and summer of 2009. Levels of nitrate and nitrite were determined by ion chromatography and flow injection analysis, respectively. Nitrate and nitrite levels of all samples ranged <4–6300 and <0.8–9.0  mg kg−1, respectively. Nitrate concentrations for the different groups, in descending order, were leafy > root and tuber > fruiting and legume vegetables. More than 80% of vegetables had mean nitrate concentrations less than 2000 mg kg−1, but mean nitrate concentrations of three types of leafy vegetables, namely Chinese spinach, Shanghai cabbage and Chinese white cabbage, were >3500 mg kg−1. On the other hand, nitrite concentrations were generally low – <1 mg kg−1 on average. Nitrate in vegetables (i.e. Chinese flowering cabbage, Chinese spinach and celery) can be reduced significantly (12–31%) after blanching for 1–3 min, but not after soaking.
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There has now been a great deal written about inorganic nitrate in both the popular press and in scientific journals. Papers in the 1970s warned us that inorganic nitrate could theoretically be metabolised in the human body to N-nitroso compounds, many of which are undoubtedly carcinogenic. More recently there is evidence that nitrate can undergo metabolic conversion to nitrite and nitric oxide and perform a useful protective function to prevent infection, protect our stomach, improve exercise performance and prevent vascular disease.
Article
In this paper, a rapid and simple enzymic method is described for the determination of nitrate in 32 fresh and five dry Indonesian milk samples, deproteinized by Carrez reagents. Interference from albumin, casein, lactose and chloride ions was controlled. The calibration graph was linear over the range l-12.5 micrograms/ml NO3-; r = 0.9998. The limits of detection and quantification were found to be 0.45 micrograms/ml NO3- and 1 microgram/ml NO3- respectively. Standard nitrate solutions (10 micrograms/ml NO3-) were used to evaluate the precision. The results showed an average of 10.1 micrograms/ml, a standard deviation of 0.3 and a relative standard deviation of 3.4%. Adequate agreement was found between results obtained by the enzymic method and those of the French official reduction/photometric reference method (AFNor). Good recoveries (100% +/- 5%) were found for nitrate added to milk. The nitrate levels were in the range 1-2.6 mg/kg NO3- for fresh milk and 1.1-18 mg/kg NO3- for dry milk. All the results are in good agreement with those previously published for UK and American milk.