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Nutritional Properties of Some Edible Wild Mushrooms in Sabah



Chong Kian Shin, Chye Fook Yee , Lee Jau Shya and Markus Atong
 
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ABSTRACT

Ten edible wild mushrooms that were commonly consumed by the native of Sabah were identified as Lentinellus omphallodes, Lentinus cilliatus, Pleurotus sp1, Pleurotus sp2, Schizophyllum commune, Hygrocybe sp., Volvariella sp., Auricularia auricula, Trametes sp. The nutritive value of these wild mushrooms was determined. The protein content of the mushrooms ranged from 5-15% of dry weight, whereas most of the wild species were found to have low fat content (1-5%). Potassium is the most abundant mineral, followed by magnesium and calcium. The sodium concentration was relatively low in all wild mushrooms. However, the calcium content in Pleurotus sp1 is 10 times higher than the cultivated mushrooms. Overall, the trace element concentrations across all wild mushrooms were in the order Fe>Zn>Mn>Cu>Cr. The high protein and low fat characteristic of these wild mushrooms indicating the need to further determine their amino acid and fatty acid profiles.

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  How to cite this article:

Chong Kian Shin, Chye Fook Yee , Lee Jau Shya and Markus Atong , 2007. Nutritional Properties of Some Edible Wild Mushrooms in Sabah. Journal of Applied Sciences, 7: 2216-2221.

DOI: 10.3923/jas.2007.2216.2221

URL: https://scialert.net/abstract/?doi=jas.2007.2216.2221

INTRODUCTION

The acceptance of cultivated mushrooms such as shiitake (Lentinus edodes), oyster mushroom (Pleurotus ostreatus) and button mushroom (Agaricus bisporus) as a delicacy were well-established worldwide. These mushrooms have been used as food and food flavouring material in soups for centuries, due to their unique and subtle flavour. They are highly appreciated for their rich aroma particularly prized for cooking throughout the world. However, wild edible mushrooms have only been traditionally eaten by a specific group of people (local people, enthusiasts and gourmets) seasonally (Diez and Alvarez, 2001).

The consumption of wild mushrooms is increasing even in the developed world due to the good nutritional value of these wild species especially as a source of proteins and trace minerals (Thimmel and Kluthe, 1998). The mineral content in edible wild mushrooms is generally higher than cultivated mushrooms and plants (Aletor, 1995; Mattilla et al., 2001; Rudawska and Leski, 2005). The qualities of protein are good, which is constituted mainly as essential amino acids such as leusine, methionine, tryptophan and valine. (Longvah and Deosthale, 1998; Diez and Alvarez, 2001; Agrahar-Murugkar and Suggulakshmi, 2004). Whereas, their fat fraction is mainly composed of unsaturated fatty acids (Yilmaz et al., 2006; Pedneault et al., 2006; Barros et al., 2007). Dietery fibre is also richly found in edible wild mushrooms and had been widely known for their functional properties (Manzi and Pizzoferrato, 2000).

Borneo Island is a high rainfall area and boasts one of the most diversified rain forests in this region. The high humidity level during the monsoon season provides ideal atmospheric conditions for growth of many wild mushrooms. Mushrooms constitute a traditionally very important vegetable relish, which is passionately enjoyed by many rural village communities in Sabah. Among the indigenous people, they know which mushrooms are fit for human consumption and which should not be touched. They also know which species are medicinally potent and which are fatally poisonous, especially through their experiences and traditional practices. Edible wild mushrooms are collected from the forest for consumption and sale in the various rural and traditional markets for cash income. These mushrooms are consumed fresh and incorporated into the local cuisine. Some of these wild species such as Schizophyllum commune and Trametes sp. are used in fresh as well as in the dry forms during off-season. They are also used by traditional healers in curing ailments such as headache and cold.

Although many studies have be done on the cultivated and wild edible mushrooms in the northern hemisphere (Aletor, 1995; Demirbas, 2000; Manzi et al., 2001), little information is available about the nutritional values of the wild edible tropical fungi from Sabah, east Malaysia. Therefore, the study aimed to examine the proximate and mineral composition of the wild mushrooms. The provision of such information would display the potential of these wild mushrooms to serve as a source of micronutrients for the indigenous people.

MATERIALS AND METHODS

Sample collection: Edible wild mushrooms were obtained from different outskirt traditional markets. The mushrooms were identified based on their morphology, habitats and spore print by the experts. They were washed thoroughly to remove mud, ferns and other extraneous material before oven dried at 45°C. The fruiting bodies were ground into fine powder and stored in tightly stoppered bottles prior to further analysis.

Chemical composition: The proximate composition was determined according to the AOAC method (1990). The protein content of the samples was estimated by the Kjeldhal method (section 954.01) and a conversion factor of 4.38 was used to quantify the nitrogen percentage of the crude protein Fat was determined by Soxhlet extraction with diethyl ether in place of petroleum ether (modified method, section 920.39). Fibre content was analyzed by the ceramic fibre filter method (section 962.09), while the ash content was determined by combusting the plant material in silica crucibles and put into a muffle furnace at 550°C for overnight (modified method, section 942.05).

Mineral determination: The samples were analyzed after wet ashing by method described in AOAC (1990). Two gram of dried and ground samples was accurately weighed into a 250ml Pyrex conical flask and 10 ml of HNO3 were added and soaked for overnight in 3 ml of 60% HClO4. Samples were heated on hot plate slowly until frothing ceases. Each flask was left to cool and the contents were filtered into a 100 mL volumetric flask through a 0.45 μm cellulose membrane filter (Whatman). In the case of magnesium and calcium, 10 mL of 5% lantahum chloride was added. The solution was then transferred into polyethylene plastic bottles, which were left at room temperature before the mineral determination.

The minerals (K, Ca, Mg, Na, Fe, Zn, Cu, Mn and Cr) were determined by flame atomic absorption spectrophotometry, except Cr, which were analyzed by graphite furnace system. Analyses were performed with a GBC Avanta atomic absorption spectrophotometer equipped with a GF3000 automated graphite system,standard air-acetylene flame and single element hollow cathode lamps.

Statistical analysis: Data obtained were evaluated statistically by Statistical Package for the Social Science (SPSS) version 14.01. Analysis of variance (ANOVA) and Tukey’s mean homogeneity test were used to indicate the significant differences between the mean values (p<0.05). Each value was the average with standard deviation of three replicates.

RESULTS AND DISCUSSION

All the wild edible mushrooms obtained in the study are categorized as saprobic (growing on dead organic matter) in nature, except Trametes sp which can be both saprobic and weakly parasitic. The edible mushrooms collected in this study can be sub-divided into two groups; the first six mushrooms in Table 1 are mushrooms with pileus and stipe whereas Schizophyllum commune, Galiella rufa, Auricularia auricular and Trametes sp are mushrooms without both features. Hybrocybe sp can only be obtained during the monsoon season of the year unlike other non-seasonal species. Volvariela sp are rare, either growing on tall tree-trunk or form mycorrhizal with host tree for survival, thus valued at higher prices as compared to other wild mushrooms. Schizophyllum commune and Trametes sp are known by the locals for their medicinal properties to heal some common illness. Indeed, several antitumor compounds and anticarcinorgenic polysacharrides have been extracted for commercial purposes in Japan (Wasser, 2002).

Volvariella sp. has the highest content of ash (10.69%), followed by Lentinellus Omphallodes and Hygrocybe sp. with mean value of 7.11% and 6.56% respectively (Table 2). It is noticeable that mushrooms with pileus and stipe had higher level of ash as compared with those without. This result is agreeable with data collected from the previous study (Latiff et al., 1995; Alofe et al., 1996), The protein level ranged from 3.77% in Trametes sp to 15.58% in Volvariella sp. This concentration is generally lower as compared to than the study by Chang and Buswell (1996), who concluded that cultivated mushrooms normally contain 19-35% protein. However, it is known that the protein contents of mushrooms are affected by a number of factors, namely the type of mushrooms, the stage of development, the part sampled and location (Flegg and Maw, 1997). A great variability can also be observed among the same species of mushrooms in the protein contents, due to the use of 4.38 as the conversion factor (Braaksma and Schaap, 1996). It is known that mushrooms contain a significant amount of non-protein nitrogen, generally in the form of chitin, thus if 6.25 were used as conversion factor, it must minus off the non-protein nitrogen (Diez and Alvarez, 2001).

Table 1: Different species of wild edible fungi and their morphological characteristic used in identification

Table 2: Proximate composition (% dry weight) of edible wild mushrooms
1Values are expressed as fresh weight basis, 2The mean values with different letters within the same column indicate significant different (p<0.05)

A constant factor of 4.38 was preferred as a conversion factor for the determination of protein content in mushrooms to reduce the influence of non-protein based nitrogen source.

The fat content of the wild mushrooms ranged from 1-5%, with the lowest found in Hygrocybe sp. due to it dry and fibrillose nature. The fat contents of the local wild mushrooms are agreeable with the study by Alofe et al. (1995) on edible wild fungi found in Nigeria with the average range of 4.9%. The low fat content of the wild species indicating that the food is suitable to be incorporated as/into a healthy and low fat diet especially for those who are on weight management program.

Table 2 shows the fibre content of Pleurotus sp2 was generally higher than the other wild mushrooms reported elsewhere by many authors (Aletor, 1995; Sanmee et al., 2003). In addition, Pleurotus sp2 was found to have two times higher fibre as compared to the selected cultivated mushrooms (Lentinus edodes) used in the current study. Other Pleurotus species were also reported to be high in dietary fibre (Manzi et al., 2001; Manzi et al., 2004). Carbohydrate content (by subtraction) ranged from 50% to 70%, relatively higher than the ectomycorrhizal fungi reported by Sanmee et al. (2003).

It is obvious that Potassium (K) and Magnesium (Mg) are the main constituents in the ash content as shown in Table 3. The levels of K in all mushroom samples were found to be higher in comparison to Sodium (Na). The present findings seem to be consistent with other researches, which found the similar trend (Manzi et al., 1999; Sanmee et al., 2003; Agrahar-Murugkar et al., 2004). These mushrooms are expected to meet the desires of hypertension and heart diseases patients as a special food for daily consumption.

Calcium was present significantly higher in the wild mushrooms analyzed especially Trametes sp (1,308.77 mg kg–1) and Pleurotus sp1 (1,691.9 mg kg–1) which were found 10 times higher than the calcium content in Lentinus edodes (141 mg kg–1), the cultivated mushroom. The calcium level in wild mushrooms was higher or equivalent to some leafy greens such as Chinese cabbage, cabbage and cauliflower (Kawashima and Valente Soares, 2003; Ekholm et al., 2007). Mg contents of the mushrooms in the current study ranged between 500-2000 mg kg–1. A relatively higher (p<0.05) Mg was observed as compared to the previous published report on Calvatia gigantean, Cantharellus cibarius, Russula integra, Gomphus floccosus and Lactarius quieticolor in India (Agrahar-Murugkar and Subbulakshimi, 2004). Auricularia auricular seems to have the highest Mg (2,014 mg kg–1) among the wild mushrooms analyzed, much higher (p<0.05) than the cultivated counterpart. Nevertheless, the mineral content in the mushrooms are mainly affected by acidic and organic matter content of their ecosystem and soil (Gast et al., 1988).

The mean micro-mineral concentrations in the wild mushrooms across all fungi were in order Fe >Zn>Mn>Cu>Cr. L. Omphallodes has the highest content of ferum (390 mg kg–1), follow by Trametes (251 mg kg–1) and G. Rufa (218 mg kg–1) (Table 3).

Table 3: Mineral cintents (mg kg–1 dry weight) of edible wild mushrooms
*The means with different letters within the same column indicate a significant different (p<0.05)

Since the Recommended Daily Allowances of iron (FAO/WHO) for adult women and men are 35 mg, hence, eating 100 g of dried L. omphallodes is equivalent to the RDA requirement. According to World Health Organization (WHO, 2007), the prevalence of iron deficiency anemia in Sabah was 17-24% for children in rural areas and 33-37% for pregnant women. This indicates that iron deficiency still a major nutritional problem in the country and good nutritional advices on dietary intake based on the locally available food sources play important role in the eradication of nutrient deficiency. Most fresh and cooked lean meat contains 20-30 mg kg–1 of ferum (Tee et al., 1997). However, due to the cholesterol and portion size, human can normally consumed only 200-300g of meat per serving. Thus, Lentinellus omphallodes can be a substitution of meat for their iron source especially for those hardcore poor in the rural area of Sabah, where meat intake are almost impossible.

The mushrooms investigated in the current study were also quite good sources of Zn, Mn and Cu as compared to the cultivated mushroom. Zinc concentrations ranged from 25.5 mg kg–1 in Trametes to 61.58 mg kg–1 in S. commune, which was in paralleled with the results reported previously elsewhere (Mattila et al., 2001; Longvah and Deosthale, 1998). The highest Mn content was found in Trametes sp (114.4 mg kg–1), while Volvariella sp. has the highest Cu content. (70.97 mg kg–1). The findings of the current study are in agreement with those of Işıloğlu et al. (2001) on Volvariella speciosa found in Turkey. The extreme difference between Mn, ranged from 7.7 to 114.4 mg kg–1 is not rare as it was also previously reported by Mendil et al. (2005) on various wild mushrooms collected from the forest of Turkey, which ranged from 21.2 to 103 mg kg–1.

Hygrocybe (4.13 mg kg–1), Volvariella (3.57 mg kg–1) and Galiella rufa (3.60 mg kg–1) were relatively high in Cr contents compared to the cultivated species (0.41 mg kg–1). Chromium contents of mushroom samples have been reported in the range of 0.34-1.05 mg kg–1 (Soylak et al., 2005) and 1.1-4.4 mg kg–1 (Mendil et al., 2005). Nevertheless, the concentrations of the elements in fruiting bodies of mushrooms are generally species-dependent. Substrate composition is also an important factor besides the great differences exist in uptake of individual trace elements by the fruiting body of mushrooms (Nikkarinen and Mertanen, 2004; Kalac and Svoboda, 2000).

CONCLUSION

The edible wild mushrooms found in Sabah are of high nutritional quality, comparable to the commercially cultivated mushroom in particular their protein, fibre and mineral contents. Therefore, further study on the amino acids and anti-nutritional factors should be carried out to establish a complete nutritional database on these unique species, which could be used in the nutrition intervention program.

ACKNOWLEDGMENTS

This study was supported by the Fundamental Research Grant No B-0201-03-PR-/U032 of University Malaysia Sabah.

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