Two cultivated mushroom species, namely,
Mushrooms are important in the ecosystem because they are able to biodegrade the substrate and therefore use the wastes of agricultural production. Fruiting bodies of mushrooms are appreciated, not only for texture and flavor [
Organisms require trace amounts of some heavy metals, including iron, cobalt, copper, manganese, chromium, and zinc. Excessive levels of these metals, however, can be detrimental to organisms. Other heavy metals such as cadmium and lead have no known beneficial effect on organisms [
In this context, it is worthwhile to evaluate (a) the metal content in mushrooms grown on any substrate, (artificially/natural occurrence), (b) to assess the contribution of mushrooms to the daily intake of several toxic elements, and (c) to compare the results with the norms for these toxic elements in food stuff, so that it would help to adjudicate the mushrooms for their nutritional value in terms of minerals and also to define the limits of safety [
Thus, the present paper is focused on the analysis of four species of mushrooms namely
Fruiting bodies (3 kg fresh or equivalent) of
One gram of dry powdered sample was placed in a porcelain crucible and ashed at 450°C for 5-6 h; then the ash was dissolved in 2 mL concentrated HNO3 (Merck), and heated on a low heat for 1 min. Then, it was cooled and filtered through Whatman No. 42 filter paper to a 50 mL volumetric flask and was made to volume with triple distilled water. A blank was also prepared using similar experimental procedure [
The mineral contents were determined employing Atomic Absorption Spectrometer (AAS), [Analyst 700 Perkin Elmer, USA] with air-acetylene burner for flame and Inductively Coupled Plasma Atomic Emission Spectrometer (ICP-AES) [ACTIVIA-M, Horiba Jobin yvon] with Argon plasma.
Aliquot of the ash solution was aspirated to the instrument (AAS/ICP-AES) for the determination of metals/minerals
Calibration of AAS was done using the working standard prepared from commercially available metal/mineral standard solutions (1000
Working conditions of AAS were as follows: instrument: AAS (Perkin Elmer A Analyst 700), flame temperature: 2800°C, acetylene pressure: 0.9–1.0 bar, air pressure: 4.5–5 bar, reading time: 1–10 sec (max 60 sec), flow time: 3-4 sec (max 10 sec).
Calibration of ICP-AES was done using the working standard prepared from commercially available multielement standard solution (100 mg/L, Merck, Germany). The most appropriate wave length, Argon gas flow, Plasma stabilization, and other ICP-AES instrument parameters for metals/minerals were selected, and measurements were made within linear range of working standards used for calibration [
Working conditions of ICP-AES were as follows: instrument: ICP-AES (ACTIVIA-M, Horiba Jobin-yvon), power: 1000 W–1200 W, plasma gas flow: 12–16 L/min, auxillary gas flow: 0.8 L/min, plasma burning height: 5–22 mm, reading time: 1–10 sec (max 60 s), flow time: 2-3 sec (max 10 s).
Phosphorus was determined by spectrophotometric method, wherein phosphorus reacts with molybdic acid to form phosphomolybdate complex, which was then reduced with amino naphthol sulfonic acid to complex molybdenum blue that was measured spectrophotometrically [
The concentrations of all the minerals were expressed as mg/100 g dry weight of the sample. The limit of detection for Pb was 0.05 mg/100 g and for Cd was 0.01 mg/100 g on dry weight basis. Each value is the mean of three replicate determination ± standard deviation.
Minerals represent the ash left behind after complete incineration of the dry mushroom. The mineral composition reflects on the growth conditions of the mushroom. Minerals such as potassium, calcium are said to be major because they are in high concentrations of the mushroom, as well as phosphorus and magnesium. However, sodium is relatively less in mushroom species; thus, mushrooms are said to be good for patients with hypertension [
To overcome the inaccuracies borne in differences in moisture contents from different authors from different parts of the world, on fresh weight basis, and to ensure universal comparison of data, all the values obtained were expressed here on moisture free basis. Amongst the four mushroom species studied (
Major element concentrations (mg/100 g on dry weight basis) in four species of mushrooms.
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Potassium |
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Phosphorus |
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Calcium |
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Sodium |
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Magnesium |
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Each value is the mean of three replicate determinations ± standard deviation.
Iron, zinc, copper, manganese, and selenium are dealt with under minor/trace elements.
Trace element concentrations (mg/100 g on dry weight basis) in four species of mushrooms.
Elements |
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Iron |
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Zinc |
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Copper |
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Manganese |
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Selenium |
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Each value is the mean of three replicate determinations ± standard deviation.
Toxic metal concentrations (mg/100 g on dry weight basis) in four species of mushrooms.
Metals |
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Nickel |
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Lead | BDLa | BDLa |
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Cadmium | BDLa | BDLa | BDLa | BDLa |
Each value is the mean of three replicate determinations ± standard deviation.
aBDL: Below detectable level.
Thus, the minerals analyzed in the four mushroom species were quite comparable with reported literature values (Table
Range of reported literature values (mg/100 g dry weight basis) in mushroom.
Mineral elements | Range of literature value |
Reference |
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Potassium | 2500–4100 | [ |
Phosphorus | 120.0–2000 | [ |
Calcium | 1.8–59.0 | [ |
Sodium | 6.0–92 | [ |
Magnesium | 60–250 | [ |
Iron | 1.46–83.5 | [ |
Zinc | 2.98–15.8 | [ |
Copper | 7.1–9.5 | [ |
Manganese | 1.81–10.3 | [ |
Selenium | 1–5 | [ |
Nickel | 0.118–0.514 | [ |
Lead | 0.286–0.688 | [ |
Cadmium | 0.271–0.75 | [ |
Recommended Daily Intake (RDI) of trace elements.
Element | RDI | Reference |
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Cu | 2.2 mg/day | [ |
Fe | 28–30 mg/day | [ |
Zn | 15.5 mg/day | [ |
Mn | 5.5 mg/day | [ |
The four mushroom species analyzed for their mineral contents conform as sources of calcium, potassium, iron, and zinc and less in sodium.
Accordingly, these species are good supplementary health foods from the angle of human nutrition. More importantly, it is vital to always relate the mushroom mineral contents with specificities of growth substrates on which the species under study is grown, further based on their nonstarchy carbohydrates [
Atomic Absorption Spectra
Inductively Coupled Plasma Atomic Emission Spectrometer.
The authors are grateful to the Director of CFTRI, Mysore. This study was funded by Department of Biotechnology, Government of India, New Delhi.