Mary Obodai

Evaluation of the chemical and antioxidant properties of wild and cultivated mushrooms of Ghana.

Knowledge of the chemical composition of both wild and cultivated edible mushrooms in Ghana is limited. This study reports their nutritional value, composition in lipophilic and hydrophilic molecules, minerals and antioxidant properties. The samples were found to be nutritionally rich in carbohydrates, ranging from 64.14 ± 0.93 g in Pleurotus ostreatus strain EM-1 to 80.17 ± 0.34 g in Lentinus squarrosulus strain LSF. The highest level of proteins (28.40 ± 0.86 g) was recorded in the mentioned P. ostreatus strain. Low fat contents were registered in the samples, with Auricularia auricula recording the lowest value. High levels of potassium were also observed with the following decreasing order of elements: K > P ~ Na > Mg > Ca. High levels of antioxidants were also observed, thus making mushrooms suitable to be used as functional foods or nutraceutical sources. Furthermore, this study provides new information regarding chemical properties of mushrooms from Ghana, which is very important for the biodiversity characterization of this country.

Evaluating the Effect of Gamma Radiation on the Total Phenolic Content, Flavonoids, and Antioxidant Activity of Dried Pleurotus ostreatus ((Jacq. ex. Fr) Kummer) Stored in Packaging Materials

Dried Pleurotus ostreatus mushrooms stored in polythene and polypropylene packs were exposed to gamma radiation from a cobalt-60 source at doses of 0, 0.5, 1, 1.5, and 2 kGy at a dose rate of 1.7 kGy/hr and stored for a period of 1 month. Total phenolic contents, flavonoids, and free radical scavenging activity DPPH (2,2′-diphenyl-1-picrylhydrazyl) were determined using aqueous, ethanol, and methanol extracts by Folin-Ciocaultaeu method as a source of potential natural antioxidants. Total phenol content ranged 0.56 ± 0.01–10.96 ± 1.7 mg/GAE, flavonoids ranged 1.64 ± 0.05–8.92 ± 0.6 mg/QE, DPPH radical scavenging activity also ranged 7.02 ± 0.10–13.03 ± 0.04%, and IC50 values also ranged 0.08–0.16 mg/mL. Statistical differences (P < 0.05) were recorded for the extracts and the treatment doses of mushrooms stored in polythene and polypropylene packs. A significant linear correlation was confirmed between values for the total phenolic content and antioxidant activity of mushroom extracts. The high contents of phenolic compounds indicated that these compounds contribute to high antioxidant activity. Pleurotus ostreatus can be regarded as a promising candidate for natural mushroom sources of antioxidants with high value. The use of low dose gamma radiation by the local food industry could improve the hygienic quality, extend shelf-life, and preserve nutrients and antinutrients.

Chemical Characterization and Antioxidant Potential of Wild Ganoderma Species from Ghana

The chemical characterization and antioxidant potential of twelve wild strains of Ganoderma sp. from Ghana, nine (LS1–LS9) of which were found growing wild simultaneously on the same dying Delonix regia tree, were evaluated. Parameters evaluated included the nutritional value, composition in sugars, fatty acids, phenolic and other organic compounds and some vitamins and vitamin precursors. Antioxidant potential was evaluated by investigating reducing power, radical scavenging activity and lipid peroxidation inhibition using five in vitro assays. Protein, carbohydrate, fat, ash and energy contents ranged between 15.7–24.5 g/100 g·dw, 73.31–81.90 g/100 g, 0.48–1.40 g/100 g, 0.68–2.12 g/100 g ash and 396.1–402.02 kcal/100 g, respectively. Fatty acids such as linoleic, oleic and palmitic acids were relatively abundant. Free sugars included rhamnose, fructose, mannitol, sucrose and trehalose. Total tocopherols, organic acids and phenolic compounds’ content ranged between 741–3191 µg/100 g, 77–1003 mg/100 g and 7.6–489 µg/100 g, respectively. There were variations in the β-glucans, ergosterol and vitamin D2 contents. The three major minerals in decreasing order were K > P > S. Ganoderma sp. strain AM1 showed the highest antioxidant activity. This study reveals, for the first time, chemical characteristics of Ganoderma spp. which grew simultaneously on the same tree.

Morphological characteristics of mycelia growth of two strains of the indigenous medicinal mushroom, Lentinus squarrosulus Mont. (Singer), on solid media

Morphological characteristics of the mycelia growth of two wild strains of Lentinus squarrosulus Mont. (Singer), Sqw and Lsf, collected from the Volta and Greater Accra regions of Ghana respectively, were studied. Growth characteristics including mycelia growth rate and mycelia density and morphology by the 7 th and 26 th days of incubation on solid media formulated from four lignocellulosic wastes: elephant grass (EG), rice straw (RS), thatch (TH) and sawdust (SD) were classified. Tissue cultures of the fruit bodies were prepared on Malt Extract Agar (MEA). Eight-day old cultures of the subsequently prepared 1 st generation cultures were inoculated on the media and incubated at 25°C. Strain Sqw recorded lower growth rates (between 0.47 and 0.64 cm/day) on the solid media than Lsf (between 0.69 and 0.93 cm/day). The maximum growth rate of strain Sqw was 0.64 cm/day on both SD and TH whereas that of Lsf was 0.93 cm/day on EG. L. squarrosulus mycelia density is not dependent on the growth rate and vise-versa, irrespective of the strain. Although both strains generally had the longitudinally radial morphology with concentric rings, with extended incubation, the culture morphology of both strains changed, usually into thick mats. Mycelia of both strains on all the media were white at the initial stages of incubation. Cultures of strain Sqw largely remained whitish and turned brownish only on EG, whereas strain Lsf turned into different shades of brown on all media with extended incubation. These colour changes were not uniform on the entire plate, appearing in undefined sectors. Mycelia growth characteristics were seen to be substrate and strain-dependent. Futher investigations of these observations could uncover some behavior of L. squarrosulus such as changes in enzyme profile and the phenolic content, which could have applications in biotechnology.

Mycofloral profile and the radiation sensitivity (D10 values) of solar dried and gamma irradiated Pleurotus ostreatus (Jacq.Ex. Fr.) Kummer fruitbodies stored in two different packaging materials

Abstract The presence of fungi in our foods poses serious health risks as some genera of fungi may produce certain mycotoxins which have carcinogenic, mutagenic, teratogenic, and immunosuppressive effect on humans and animals alike. Fruitbodies of Pleurotus ostreatus were solar dried at a moisture content of 12.5 ± 0.2% and stored in polythene and polypropylene packs, gamma irradiated at doses of 0 (control), 1, 2, 3, 4, and 5 kGy at a dose rate of 1.7 kGy/hr from a Cobalt 60 source (SLL, 515, Hungary) and stored at room temperature 28–30°C for a period of 12 months. Mycological analyses were done at intervals of 0, 3, 6, and 12 months. A total of eleven (11) fungi belonging to eight fungal genera were isolated on both Cookes and DRBC media; Aspergillus (A. niger, A. flavus, A. fumigatus, A. tamarii), Rhizopus (R. oligosporus), Mucor (M. racemosus), Fusarium (F. oxysporum), Penicillium (Penicillium sp.), Trichoderma (T. viride), and Rhodotorula sp. were recorded. There was a significant (p < .05) reduction in initial mycofloral population by an average of 2.2 log cycles as well as in species numbers with increasing doses of radiation. Radiation sensitivity (D10 values) also ranged between 1.68–2.78 kGy. Gamma irradiation treatment is one way which can enhance food safety through the reduction in potential pathogens and has been recommended as part of a comprehensive program to enhance food safety.

Bioprospecting of powdered pineapple rind as an organic supplement of composted sawdust for Pleurotus ostreatus mushroom cultivation

Abstract Pineapple rind is a by‐product of the pineapple processing industry and contains nutrients and other compounds which must be utilized as a bioresource for socio‐economic benefits while preventing the potential problems of improper agroindustrial biomass disposal methods. Pleurotus ostreatus is an edible oyster mushroom with medicinal properties and can be cultivated on various agroindustrial biomass, including sawdust containing supplements. Pineapple rind was powdered and used as a supplement of composted sawdust at 2%, 5%, 10%, 12%, 15%, and 20% (w/w) on dry weight basis. A control treatment consisted of composted sawdust supplemented with rice bran at 12% (the most utilized composition in Ghana). P. ostreatus strain EM‐1 was cultivated on these treatments. Factors investigated included the spawn run period, yield, fruiting body weight and size, biological efficiency, and nutritional composition (proximate composition and Copper, Zinc and Lead content) of fruiting bodies harvested from selected high‐yielding treatments and the control treatment. Full colonization of all treatments occurred by the 34th day of incubation. Enhanced yield, fruiting body weight and size, and biological efficiency were generally recorded with supplementation at lower concentrations (2% and 5%) compared to treatments supplemented at higher concentrations. There was also a supplement concentration‐dependent alteration of the nutritional composition of the mushroom. Powdered pineapple rind can be utilized as an organic supplement at relatively low concentrations in composted sawdust for P. ostreatus strain EM‐1 cultivation. The use of lower concentrations of powdered pineapple rind in composted sawdust is advantageous as relatively less input will be required to produce higher P. ostreatus strain EM‐1 yields. Utilization of pineapple rind for mushroom cultivation will extend the pineapple plant value chain, intensify mushroom production in a sustainable way, and minimize agricultural losses.

Nutritional Qualities and Shelf Life Extension of Gamma Irradiated Dried Pleurotus ostreatus (Jacq. Ex. Fr.) Kummer Preserved in Two Different Storage Packs

Pleurotus ostreatus has high nutritional value as an important source of protein, carbohydrates, vitamins, mineral elements and is among most favorite mushrooms of the world. Proximate composition and metabolizable energy of these mushrooms were evaluated for their dietary value. Fruit bodies were solar dried to a moisture content of 12% and exposed to low dose ionizing (gamma) radiations of 0, 0.5, 1, 1.5 and 2 kGy at a dose rate of 1.7kGy/hr and stored in polyethylene and polypropylene packs at room temperature (28- 30℃) for a period of 12 months. Values ranged 14.11- 15.80%, 6.16- 8.31%, 0.65- 1.24%, 13.56- 15.39%, 12.51- 15.25%, 61.16- 65.50% respectively for moisture, ash, fat, fibre, protein and carbohydrate. Metabolizable energy also ranged 247.8- 284.6 Kcal./100g for 12 months storage. Although there were some significant (p<0.05) changes observed for some nutrients due to gamma irradiation and storage, the results obtained showed that the integrity of these nutrients in this mushroom were minimally affected as no adverse effects were observed.

Influence of low dose of gamma radiation and storage on some vitamins and mineral elements of dried oyster mushrooms (Pleurotus ostreatus)

Abstract Mushrooms contain some of the most potent natural medicines on the planet. Vitamins A, C, D, Mineral elements, contents, as well as total soluble solids (Brixo) of dried composition of Pleurotus ostreatus were investigated after exposing to gamma radiation doses of 0 (control), 0.5, 1, 1.5, and 2 kGy at a dose rate of 1.7 kGy per hour in air from a Cobalt 60 source (SLL 515, Hungary) batch irradiator prior to storage (0 month) and after storage (12 months) at room temperature (28 ± 2°C). Results obtained showed some significant (p < .05) differences due to irradiation and storage. Before storage, vitamins A, C, and D contents of dried and irradiated mushrooms ranged 0.003 ± 0.08–0.014 ± 0.08, 0.042 ± 1.06–0.132 ± 1.06, and 0.040 ± 0.76–0.057 ± 0.76 mg/g, respectively. After 12 months, vitamin contents decreased and ranged 0.0029 ± 0.08–0.010 ± 0.08, 0.038 ± 1.06–0.125 ± 1.06, and 0.031 ± 0.76–0.05 ± 0.76 mg/g for vitamins A, C, and D, respectively. Total soluble solids recorded 1.5 Brixo, however, showed no significant difference (p > .05) and did not change in 12 months after gamma irradiation up to 2 kGy. Sodium ranged from 14.00 ± 0.7 to 14.90 ± 0.8 mg/100 g. Potassium content varied from 30.20 ± 0.5 to 33.10 ± 0.6 mg/100 g. Magnesium content ranged 1.27 ± 0.15–3.53 ± 0.04 mg/100 g. Calcium ranged 11.00 ± 0.4–12.53 ± 0.4 ± 0.03 mg/100 g. Phosphorus content ranged 6.11 ± 0.30–6.41 ± 0.35 mg/100 g, whereas Nitrogen content was found to be 3.00 ± 0.03–3.60 ± 0.25 mg/100 g. Microelements or heavy metals included Copper; detected ranged 0.00 ± 0.00–0.02 ± 0.001 mg/100 g, Zinc content ranged 0.01 ± 0.002–0.03 ± 0.001 mg/100 g. Iron content was found to be in the range 0.29 ± 0.01–0.37 ± 0.1 mg/100 g. Manganese content was found to be in the range 0.03 ± 0.001–0.04 ± 0.01 mg/100 g. Lead content was found to be 0.00 ± 0.00–0.03 ± 0.001 mg/100 g. Food processing and storage has the potential to slightly alter the stability of vitamins in foods. Pleurotus ostreatus showed appreciable levels of mineral elemental composition, essential vitamins A, C, and D, and can be endorsed as a natural medicinal food product in the food and pharmaceutical industries. The heavy metals detected were with also below the upper limits permissible by the WHO standards and is thus safe for human consumption.