Abstract

Major (Na, K, Ca, Mg, P), minor (Mn, Cu, Fe, Zn) and toxic (Pb, Cd) minerals composition of twelve edible mushrooms (Pleurotus ostreatus, Lentinula edodes, Agaricus bisporus #1 (fresh), Agaricus bisporus #2 (canned), Agaricus campestris, Laetiporus sulphureus, Termitomyces clypeatus, Termitomyces microcarpus #1, Termitomyces microcarpus #2, Termitomyces aurantiacus, Termitomyces letestui and Termitomyces species) collected from three regions of Ethiopia were analyzed. The samples were further investigated for their antinutrients (phytate and condensed tannin) to determine bioavailability of minerals. All the results are expressed in dry basis (db). The major minerals concentration (mg/g) ranged: Na (0.41-34.8), K (3.66-42.4), Ca (0.29-6.45), Mg (0.57-2.12) and P (0.71-2.82). The minor (mg/kg) ranged: Fe (32.5-6835.9), Zn (26.6-87.6), Cu (5.69-45.9) and Mn (0.96-138.6). The toxic metal lead was detected (1.52-18.0 mg/kg), indicating most of the mushrooms samples exceeded the weekly tolerance limit set for Pb with more proportion in wild than cultivated mushrooms. Cadmium was detected only in A.campestris (4.08 mg/kg). The anti-nutrients (mg/100 g) were significantly varied with phytate ranged from 31.3 to 242.8 and condensed tannin from 4.81 to 31.7. The calculated molar ratio between phytate and Fe, Zn and Ca was above the suggested critical values indicating the bioavailability of Fe, Zn and Ca to be high. In conclusion, the results imply that the edible mushrooms have high concentrations of essential minerals with lower anti-nutrients that make them bioavailable to the human body. Although, the consumption of some contaminated mushrooms should be avoided.

Highlights

  • The wide variety and abundance of minerals is the most valuable part of mushrooms as food which is related to species of mushroom, collecting area of the sample, age of fruiting bodies and mycelium, and distance from any source of pollution [1]

  • Some mushrooms tend to collect any minerals from their surroundings, even the toxic heavy metals such as lead, cadmium and mercury that are present in polluted areas [2]

  • The results clearly show that method detection limits and the calibration curves were in good range for the analysis of metals in the mushroom samples

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Summary

Introduction

The wide variety and abundance of minerals is the most valuable part of mushrooms as food which is related to species of mushroom, collecting area of the sample, age of fruiting bodies and mycelium, and distance from any source of pollution [1]. Bioavailability is a general term that refers to how well a nutrient can be absorbed and used by the body It can be affected by many factors such as the presence of anti-nutrients, for example, phytates, oxalates, tannins and polyphenols in foods, a person’s need, fibre, competition with other nutrients and acidity of intestinal environment [5]. The respective [Phy]: [Fe], [Phy]: [Zn], [Phy]: [Ca], [Phy]*[Ca]: [Zn] molar ratios and the proportion of phytate phosphorus and non phytate phosphorus were calculated and compared to the critical values to predict the bioavailability of Fe, Zn, Ca and P obtained from these edible mushrooms to the human body

Materials and Methods
Method detection limits and quality assurance
Conclusions
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