Selenium contents of Portuguese commercial and wild edible mushrooms

The selenium contents of 66 mushroom samples, wild growing or commercially available in Portugal, fresh, canned or dried, were determined. The samples consisted of 18 mushroom species, mainly selected in accordance with their availability and consumer preference. The selenium contents varied considerably between different mushroom species. The highest selenium contents were found in the wild species Boletus aestivalis (48.5 mg/kg dry weight, DW), Boletus pinophilus (19.9 mg/kg DW), Boletus edulis (14.9 mg/kg DW), Boletus aereus (12.3 mg/kg DW), Boletus fragans and Boletus spretus (∼2 mg/kg DW). Other mushrooms having considerable selenium contents included Marasmius oreades (1.5 mg/kg DW), Agaricus bisporus “Portobello” (1.25 mg/kg DW), A. bisporus (1.0 mg/kg DW) and Russula cyanoxantha (0.72 mg/kg DW). The selenium contents of these mushrooms are sufficient to provide nutritionally significant amounts in relation to the total daily intake of selenium. Other edible mushrooms, such as Lentinula edodes, Pleurotus ostreatus, Cantharellus cibarius,Craterellus cornucopioides and Lepista nuda, contained only small amounts of selenium. The importance of these mushrooms as a source of selenium is therefore marginal.     

Ultraviolet irradiation: The generator of Vitamin D2 in edible mushrooms

Fresh Shiitake mushrooms (Lentinula edodes), Oyster mushrooms (Pleurotus ostreatus), Button mushrooms (Agaricus bisporus), and Abalone mushrooms (Pleurotus cystidus) were irradiated with Ultraviolet-A (UV-A; wavelength 315–400 nm), Ultraviolet-B (UV-B; wavelength 290–315 nm), and Ultraviolet-C (UV-C; wavelength 190–290 nm). Irradiation of each side of the mushrooms for 1 h, was found to be the optimum period of irradiation in this conversion. The conversions of ergosterol to vitamin D₂ under UV-A, UV-B, and UV-C were shown to be significantly different (p < 0.01). The highest vitamin D₂ content (184 ± 5.71 μg/g DM) was observed in Oyster mushrooms irradiated with UV-B at 35 °C and around 80% moisture. On the other hand, under the same conditions of irradiation, the lowest vitamin D₂ content (22.9 ± 2.68 μg/g DM) was observed in Button mushrooms.     

Mercury and its bioconcentration factors in Brown Birch Scaber Stalk (Leccinum scabrum) from various sites in Poland

The total mercury contents were determined in the carpophores of Brown Birch Scaber Stalk (Leccinum scabrum) and topsoil (0–10 cm) collected from 12 spatially distant sites across Poland. Mercury was measured by cold-vapour atomic absorption spectroscopy (CV-AAS) after nitric acid (mushrooms) or aqua regia (soil) digestion of the samples. The caps, depending on the site, had total mercury concentrations from 0.38 ± 0.23 to 1.2 ± 0.4 μg/g dm (median 0.36–1.2 μg/g dm), and stalks from 0.17 ± 0.08 to 0.72 ± 0.20 μg/g dm (median 0.17–0.72 μg/g dm). Overall-mean mercury contents for 240 caps and stalks were 0.63 ± 0.38 (0.072–2.0 μg/g dm) and 0.32 ± 0.20 (0.028–1.2 μg/g dm), respectively. The total mercury content in top soil layer (0–10 cm) at 12 sites, after hot aqua regia extraction, averaged 0.026 ± 0.010–0.066 ± 0.018 μg/g dm. The BCF values of total mercury in caps of Brown Birch Scaber Stalk from the particular sites ranged from 14 ± 5 to 20 ± 4 (total mean was 16 ± 5, and median 18), in stalks from 6.0 ± 4.0 to 11 ± 1 (total mean was 8.3 ± 3.1, and median 8.1). In human feeding, wild mushrooms are usually only a small part of the total diet, so consumption of Brown Birch Scaber Stalk collected from the background sites in Poland, or elsewhere in Europe, as regards mercury content, could be considered safe.     

Quantification of polyphenols and ergothioneine in cultivated mushrooms and correlation to total antioxidant capacity

Agaricus bisporus, Lentinula edodes, Pleurotus ostreatus, Pleurotus eryngii and Grifola frondosa were analyzed for antioxidant capacity, as measured by oxygen radical absorbance capacity (lipophilic and hydrophilic) (ORAC_total), hydroxyl radical averting capacity (HORAC), peroxynitrite radical averting capacity (NORAC), superoxide radical averting capacity (SORAC) assays, Folin-Ciocalteu reagent and ergothioneine (ERG) content. ORAC_totalvalues ranged from 39 to 138 μmol of Trolox equivalents (TE)/g dry weight (dw). HORAC values ranged from 3.0 to 13.6 μmol of caffeic acid equivalents/g dw. NORAC values ranged from 2.0 to 9.0 μmol TE/g dw. SORAC values ranged from 0.37 to 2.6 kunit superoxide dismutate equivalents/g dw. Polyphenols ranged from 4.2 to 10.6 mg gallic acid equivalents/g dw. A. bisporus mushrooms, especially portabellas, had higher antioxidant capacity relative to the specialty mushrooms tested. ERG ranged from 0.21–2.6 mg/g dw with L. edodes, P. ostreatus, G. frondosa containing a statistically significant greater amount compared to A. bisporus. A good correlation was found between ORAC_total and polyphenols (R² = 0.86).     

Preparation and characterisation of selenium-enriched mushroom aqueous enzymatic extracts (MAEE) obtained from the white button mushroom (Agaricus bisporus)

Selenium-enriched mushroom aqueous enzymatic extracts (MAEE) were obtained from the white button mushroom (Agaricus bisporus) by a procedure based on enzyme and membrane technology. MAEE, with a selenium concentration of 51.8 ± 5.58 μg/g is a product suitable for achieving the recommended daily dose (RDD) of 55 μg with a small amount of around 1 g of product, which can be incorporated into any type of solid or liquid food without modifying its organoleptic properties. Chemical characterisation and selenium speciation are also reported; more than 86% of the selenium-containing products are organic in nature. The utilisation of this product would help in the treatment and/or prevention of diseases associated with low selenium concentrations, such as ageing, and neurodegenerative, cardiovascular and immunological diseases, while avoiding the risk of reaching high plasma selenium concentrations which has recently been associated with deleterious effects.     

Silver uptake byAgaricus bisporus from an artificially enriched substrate

The champignon mushroomAgaricus bisporus was cultivated on compost (wheat and rye straw, hens' manure, gypsum, urea and peat) artificially fortified with silver nitrate added at four different concentrations (0.01, 0.1, 1.0 and 10.3 mg/kg) and 0 mg/kg (control) on a dry weight basis. The method of measurement was flame atomic absorption spectrophotometry after dry ashing of the samples at 420° C and dissolving the residue in 1M nitric acid. The highest concentration of silver, reaching between 120±30–150±36 mg/kg on a dry weight basis, was observed in fruit bodies grown on the most contaminated substrate containing 10.3 mg added Ag/kg dry weight. The silver concentration in caps/stalks/whole fruit bodies ofA. bisporus was positively correlated (r=0.72; P<0.001) with an increasing level of fortification of the substrate. The bioconcentration factor (BCF) of silver in caps/stalks/whole fruit bodies ofA. bisporus was inversely correlated (?0.44<r<?0.36; 0.001<p<0.01) with the silver concentration of the contaminated substrate. The highest silver BCF value of 120–230 has been observed in caps and stalks of mushrooms grown on a substrate enriched with 0.01 mg Ag/kg dry weight. Silver ion added to the substrate in concentrations up to 10.3 mg/kg on a dry weight basis exhibited no observable toxic effect against the mycelial growth and fruiting of A.bisporus.     

Non-volatile taste components of Agaricus blazei, Agrocybe cylindracea and Boletus edulis

Three species of dried mushrooms are commercially available in Taiwan, namely Agaricus blazei (Brazilian mushroom), Agrocybe cylindracea (black popular mushroom) and Boletus edulis (king bolete), and their non-volatile taste components were studied. All mushrooms were high in contents of carbohydrate, crude fiber and protein but low in contents of crude ash and fat. Arabitol, myo-inositol, mannitol and trehalose were detected in these three mushrooms, whereas glucose was not found in B. edulis. Contents of total soluble sugars and polyols ranged from 150.33 to 225.08 mg/g. Total free amino acid contents were low in these three mushrooms and ranged from 8.97 to 14.91 mg/g. The contents of MSG-like components ranged from 1.24 to 4.40 mg/g were in the descending order of the A. blazei, A. cylindracea and B. edulis. Total 5′-nucleotides contents of A. blazei and A. cylindracea were higher than that of B. edulis whereas flavor 5′-nucleotides content of A. blazei was higher than those of A. cylindracea and B. edulis. Equivalent umami concentrations values in three mushrooms ranged from 10.46 to 135.90 g per 100 g. Overall, these three mushrooms possessed highly umami taste.     

Folate composition of 10 types of mushrooms determined by liquid chromatography–mass spectrometry

White button, crimini, shiitake, maitake, enoki, oyster, chanterelle, morel, portabella, and uv-treated portabella mushrooms were sampled from U.S. retail outlets and major producers. Folate [5-methyltetrahydrofolate (5-CH₃-H₄folate), 10-formyl folate (10-HCO-folate), 5-formyltetrahydrofolate (5-HCO-H₄folate)] was analysed using a validated LC–MS method in four composites of each product, including an in-house mushroom control composite and a reference material (BCR 485 Lyophilised Mixed Vegetables). Chanterelle and morel had the lowest total folate (2–6 μg/100 g), oyster had the highest (mean, 44.2 μg/100 g); other types contained 12.4 μg/100 g (shiitake) to 29.8 μg/100 g (vitamin D-enhanced portabella). Enoki and oyster had almost exclusively 5-CH₃-H₄folate. Morel and chanterelle contained predominately formyl folates. Other species had similar amounts of 5-CH₃-H₄folate and formyl folates. Enoki, oyster, and shiitake, unlike all others, had low to non-detectable 10-HCO-folate (<1 μg/100 g). These precise data on the composition of folate vitamers in different types of mushrooms will facilitate assessment of the dietary contribution of naturally occurring folate.     

Chemical,biochemical and electrochemical assays to evaluate phytochemicals and antioxidant activity of wild plants

Plants are a source of compounds that may be used as pharmacologically active products. Cytisus multiflorus, Filipendula ulmaria and Sambucus nigra have been used as important medicinal plants in the Iberian Peninsula for many years, and are claimed to have various health benefits. Herein, the phytochemical composition and antioxidant activity of the mentioned wild medicinal plants were evaluated in vitro, based on chemical, biochemical and electrochemical methods. F. ulmaria was found to be richest in antioxidant phytochemicals, such as phenolics (228 mg GAE/g DW), flavonoids (62 mg CE/g DW), ascorbic acid (2700 μg/g DW) and tocopherols (497 μg/g DW). The antioxidant activity was found to vary in the order: F. ulmaria > S. nigra > C. multiflorus, irrespective of the analysis method. Electrochemical methods have proven to be rapid and inexpensive techniques to characterise the antioxidant activity of plant extracts.     

Heat stability of agaritine in water extracts from Agaricus blazei and other edible fungi,and removal of agaritine by ethanol fractionation

An analytical system to quantify agaritine present in Agaricus blazei,Agaricus bisporus, and other food mushrooms was established using high pressure liquid chromatography combined with mass-spectroscopy (HPLC–MS). Water extracts from dried, homogenised mushrooms were kept at differing temperatures for defined periods to investigate the heat-stability of agaritine. Homogenates were then freeze-dried, and agaritine was extracted using methanol. After evaporation of methanol, agaritine levels were analysed by HPLC–MS. A. bisporus contained 341 ± 32 μg/g agaritine, and A. blazei contained 22–57 μg/g agaritine. While pure agaritine in H₂O solution was heat-unstable and decomposed exponentially at 120 °C, agaritine in Agaricus water extracts was partially heat stable, and 20–50% of agaritine remained after 120 min at 120 °C. Thus agaritine, a known carcinogen, is likely to be present in Agaricus extracts sold as nutritional supplements. Therefore, a method was developed that can be used to remove agaritine from water extracts in order to prevent health risk. Agaritine was successfully removed from Agaricus water extracts by ethanol fractionation.     

Antioxidant activity and phenolic content of 16 raisin grape (Vitis vinifera L.) cultivars and selections

Six raisin grape cultivars and 10 new raisin grape selections were analyzed for antioxidant activity (ABTS assay) and for total and individual phenolic compounds. Samples were freeze–dried and values are reported on a dry weight basis. Antioxidant activity across the 16 samples ranged from 7.7 to 60.9 μmol Trolox/g DW, with A95-27 exhibiting the greatest activity. Total phenolic content, determined in gallic acid equivalents using the Folin–Ciocalteau assay, ranged from 316.3 to 1141.3 mg gallic acid/100 g DW and was strongly correlated (r = 0.990) with antioxidant results. Concentrations of individual phenolics were determined by HPLC. trans-Caftaric acid was the predominant compound in all samples. A95-15 contained the lowest concentration (153.5 μg/g DW) of caftaric acid, while Fiesta contained the highest concentration (598.7 μg/g DW). Selections A56-66, A95-15, and A95-27 had much higher levels of catechin (86.5–209.1 μg/g DW) and epicatechin (126.5–365.7 μg/g DW) than the other samples.     

Mercury content and bio-concentration potential of Slippery Jack, Suillus luteus, mushroom

This study aimed to assess the total Hg intake due to the meals made of fruit bodies of wild-grown Slippery Jack (Suillus luteus) fungus, which is popular and numerous species in young the common pine tree (Pinus sylvestris) forests of the northern chemosphere with temporal climate. Total mercury content has been determined separately in 120 composite samples of 383 caps and stipes of Slippery Jack and in surface soil layer (0–10 cm; <2 mm fraction) underneath to fruit bodies. The material originated from eight spatially distant background (unpolluted) areas across of Poland and was collected in 2002–2007. Determination of mercury was by cold-vapour atomic absorption (CV-AAS) after direct sample matrix pyrolysis and further released mercury amalgamation and desorption from gold wool. Slippery Jack effectively accumulated Hg in fruit bodies. Depending on the area of mushrooms collection, the median values of Hg bio-concentration factor varied between 2.5 and 14 for caps and between 1.0 and 8.8 for stipes. For well-developed fruit bodies of Slippery Jack a majority of Hg occurs in caps, when compared to much smaller in size stipes. The means of Hg content varied between 0.095 ± 0.082 and 0.28 ± 0.07 μg/g in caps and between 0.045 ± 0.018 and 0.13 ± 0.03 μg/g dry weight in stipes. A meal consisting of 300 g caps (fresh weight) of Slippery Jack mushroom collected from unpolluted sites could constitute up to 14–40% of daily reference dose (RfD) value of mercury.     

Vitamins B1 and B2 contents in cultivated mushrooms

Mushrooms have long been treated as a delicacy. Nowadays however, many researchers consider them to be nutraceutical foods, which has stimulated new and existing Brazilian producers to search for more productive techniques and to introduce other species. The objective of this study was to determine the vitamin B₁ and B₂ contents in mushrooms. The main species of mushroom cultivated in Brazil and analysed in this study are: Agaricus bisporus (white button mushroom and portobello), Lentinula edodes (shiitake) and Pleorotus spp. (shimeji and oyster mushroom). The methodology employed used acid hydrolysis followed by enzymatic hydrolysis and separation of the vitamins by high performance liquid chromatography using a C₁₈ reverse phase column and fluorescence detector. The results obtained for thiamine (vitamin B₁) were from 0.004 to 0.08 mg/100 g and for riboflavin (vitamin B₂), from 0.04 to 0.3 mg/100 g.     

Mycobial enhancement of ergothioneine by submerged cultivation of edible mushroom mycelia and its application as an antioxidative compound

Ergothioneine (2-mercaptohistidine trimethylbetaine, ESH) in mushroom is one of bioactive and functional components. In the present study, a method of producing ESH within a short period and with high productivity was established by applying submerged fermentation of edible Shiitake mushroom (Lentinula edodes) mycelia. High-resolution mass spectrometry and online flow injection analysis of 2,2-diphenyl-1-picrylhydrazyl scavenging activity clearly confirmed that ESH was the most potent antioxidant in the mycelial extract. Among several mushroom mycelia, Shiitake produced the highest amount of ESH (0.60 mg/g dry weight (DW)). Optimisation of the culture medium was performed to achieve higher ESH production. The monosaccharide content in the medium, particularly fructose in combination with aspartic acid, was one of the factors that enhanced ESH production by 3.15-fold (1.89 mg/g DW). Individual supplementation of 2 mM methionine as an amino acid precursor yielded a significantly higher amount of ESH (3.45 mg/g DW) compared to that of the control medium (1.85 mg/g DW). The mycelial extracts containing ESH were effective in retarding the formation of secondary lipid oxidation products in the yellowtail red meat model during chilled storage as well as in the oxidation of linoleate and bleaching of beta-carotene in an oil-in-water emulsion system.     

Comparison of the antioxidant activity of two Spanish onion varieties

Phenol content and antioxidant activity of two Spanish onion varieties, namely white onion and Calçot de Valls, have been studied. White onions contained higher phenol content than Calçot onions, with values which ranged from 2.57 ± 0.51 to 6.53 ± 0.16 mg gallic acid equivalents/g dry weight (GAE/g DW) and 0.51 ± 0.22 to 2.58 ± 0.16 mg GAE/g DW, respectively, depending on the solvent used. Higher phenol content was associated with higher antioxidant capacity. White onion extracts had the highest antioxidant activity at 86.6 ± 2.97 and 29.9 ± 2.49 μmol Trolox/g DW for TEAC and FRAP assays, respectively, while the values for the Calçot variety were 17.5 ± 0.46 and 16.1 ± 0.10 μmol Trolox/g DW.     

Effect of modified atmosphere packaging on the shelf-life of coated, whole and sliced mushrooms

Whole and sliced fresh mushrooms (Agaricus bisporus) were packaged with PVC wrap or two polyolefins (PD-941 and PD-961) films after coating with CaCl₂ and chitosan. Package gas composition, color, weight loss and maturity were measured during storage at 12 °C and 80%RH. For PD-961, the highest in-package concentration occurred during the first day of storage regardless of treatments, while wrap and PD-941 showed varying degrees in-package concentration with different processes and coatings. The whiteness of whole mushrooms varied significantly with the type of coating, but not with the type of films. The extent of darkening was greater in coated whole mushrooms than in sliced ones. Weight loss occurred in all packages and varied from 3 (g/100 g) to about 7 (g/100 g) after 6 days of storage. Due to a lower permeability, PD-961 packages had the lowest weight loss. The type of packaging films significantly affected the maturity index, where PD-961 most effectively lowered maturity index for both whole and sliced mushrooms, thus extending the shelf-life. The type of coating did not appear to affect maturity index except for the wrap package where chitosan coating markedly lowered the maturity index of sliced mushrooms.     

Moisture adsorption isotherms for mushroom

The moisture adsorption isotherms of Agaricus bisporus and Pleurotus florida mushrooms were determined at temperatures (30-70°C) typically found in drying and storage. The samples were equilibrated above saturated salt solutions. Equilibrium moisture content of mushroom decreased with an increase in temperature at constant water activity. The data was adjusted to 11 sorption models to ascertain the best fit. Comparisons were based on mean relative error, standard deviation and coefficient of determination. Of the models tested, the Chung and Pfost model showed the best fit. The net isosteric heat of sorption was determined using the Clausius-Clapeyron equation. The net isosteric heat of sorption decreased from 13 to about 1 kJ/mol when the moisture content increased from 5 to 50 g /100 g dry matter.     

Isolation and quantitative determination of ergosterol peroxide in various edible mushroom species

Ergosterol peroxide, the steroidal derivative with cytotoxic activity, has been isolated for the first time from the mycelium of edible and medicinal mushroom Hericiumerinaceum (lion’s mane mushroom) together with erinacine A. The new densitometric method was applied for the quantitative determination of ergosterol peroxide in n-hexane extracts of H. erinaceum, Laetiporus sulfureus (chicken mushroom), and Morchella esculenta (common morel) mycelia, as well as in Boletus edulis (king bolete), Suillus bovinus (Jersey cow mushroom), and B. badius (bay bolete) fruiting bodies. The ergosterol peroxide content reached 15.98 ± 0.78, 10.07 ± 0.75, 13.37 ± 0.56, 29.32 ± 1.43, 17.27 ± 0.84, and 12.60 ± 0.59 mg per 100 g, respectively. What is significant was that ergosterol peroxide was identified for the first time, to the best of our knowledge, in edible mushrooms mentioned above.     

Antioxidant and antimicrobial activities of Laetiporus sulphureus (Bull.) Murrill

Antioxidant capacity and antimicrobial activities of Laetiporus sulphureus (Bull.) Murrill. extracts obtained with ethanol were investigated in this study. The study was aimed at determining the antioxidant activity (DPPH free radical-scavenging, β-carotene/linoleic acid systems), total phenolic content and total flavonoid concentration of L. sulphureus. Inhibition values both of L. sulphureus ethanol and the standards increased parallel with the elevation of concentration in the linoleic acid system. Inhibition values of L. sulphureus (LS) extract, BHA and α-tocopherol standards were found to be 82.2%, 96.4% and 98.6%, respectively, at a concentration of 160 μg/ml. DPPH free radical-scavenging activity was found to exhibit 14%, 26%, 55% and 86% inhibition, respectively, at concentrations of 100, 200, 400 and 800 μg/ml. Total flavanoids were 14.2 ± 0.12 μg mg⁻¹ (quercetin equivalent) while the phenolics were 63.8 ± 0.25 μg mg⁻¹ (pyrocatechol equivalent) in the extract. Positive correlations were found between total phenolic content in the mushroom extracts and their antioxidant activities. Edible mushrooms may have potential as natural antioxidants. L. sulphureus showed narrow antibacterial activity against Gram-negative bacteria and strongly inhibited the growth of the Gram-positive bacteria tested. The crude extract exhibited high anticandidal activity on Candida albicans. Therefore, the extracts could be suitable as antimicrobial and antioxidative agents in the food industry.     

Chitin content of cultivated mushrooms Agaricus bisporus, Pleurotus ostreatus and Lentinula edodes

The chitin contents of pileus and stipes of fruit bodies of Agaricus bisporus, Pleurotus ostreatus and Lentinula edodes (shii take) were determined and compared. The fruit bodies of different, common varieties of the cultivated mushroom species were taken from Hungarian and German large-scale farming. The analytical procedure was carried out on the powder of cleaned, dried and milled pileus and stipes. The pileus of A. bisporus variety ‘K-23’ showed a significant decrease (p < 0.05) during the cultivation’s flushes (breaks), 1–3, while the chitin level of stipes seemed to be constant. The other analysed A. bisporus varieties (var. ‘158’, ‘K-7’, ‘Sylvan A-15’, ‘Sylvan 608’, and Le Lion C-9) had practically the same chitin levels. This indicates that the chitin content is a stable characteristic of the species and there are no significant differences between the different varieties. The chitin levels of pileus and stipes were not significantly different (for A. bisporus, 6.68 and 7.25) but showed significant differences for P. ostreatus (p < 0.05) and L. edodes (p < 0.001). In the case of the latter two species, the pileus had the higher and the stipe the lower chitin content. The presented data confirm that a mushroom saprotrophic (A. bisporus) had higher chitin level than had the wood-rotting ones (P. ostreatus, L. edodes).