Effect of Vacuum and Oven Drying on the Radical Scavenging Activity And
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a Food Science and Technology ISSN 0101-2061 DDOI http://dx.doi.org/10.1590/1678-457X.28816 Effect of vacuum and oven drying on the radical scavenging activity and nutritional contents of submerged fermented Maitake (Grifola frondosa) mycelia Kheng Yuen SIM1*, Jeng Young LIEW2, Xin Yi DING2, Wan Shin CHOONG2, Seri INTAN2 Abstract Maitake (Grifola frondosa) mycelia contain high dietary and medicinal values that have gained great attentions from consumers. Proper drying can preserve their bio-availabilities prior to subsequent processing or consumption. Pure Maitake (Grifola frondosa) strain was cultivated in Mushroom Complete Medium (MCM) using submerged fermentation for 14 days. Maitake mycelia were harvested and treated respectively by vacuum, oven drying treatments while the fresh mycelia were assigned as control. All the samples were tested for Total Phenolic Content, DPPH radical scavenging assays and nutritional contents. Submerged fermentation produced mycelia biomass (1.3 ± 0.1 g/L) within 14 days of fermentation. Both the pH and reduced sugar content had decreased (P < 0.05) throughout fermentation. Vacuum dried mycelia had shown higher (P < 0.05) total phenolic (20.0 ± 0.4 mg GAE/g), DPPH radical scavenging activity (84.7 ± 0.1%), and soluble protein content (283.6 ± 7.1 µg/mL) as compared to other treated samples. The crude protein (39.1 ± 0.2), fat (5.7 ± 0.7), ash (11.1 ± 0.3%) of mycelia were well preserved using vacuum drying as compared to oven dried samples. The study has suggested that vacuum drying at 70 °C, 1000mBar has the advantage to preserve the nutritional and radical scavenging activity of high value maitake mycelia effectively at lower cost. Keywords: DPPH radical scavenging; maitake mycelia; submerged fermentation; total soluble protein; vacuum drying. Practical Application: Cultivation of high value maitake biomass via submerged fermentation within shorter time at desirable yield. The use of vacuum drying at 70 °C, 1000 mBar to preserve its bioactive and nutritional compositions of maitake mycelia which can be considered as cost efficient dehydration unit for subsequent post-harvest or downstream process. 1 Introduction Edible mushrooms are popular macro fungi that have been enhance one’s immune system, limits or reverse tumour growth, consumed for millennia as part of our dietary source. They are delaying cell ageing and cancer development (Gregori et al., 2011). high in nutritional compositions especially protein, essential Various downstream of maitake products are available ranging amino acids, carbohydrate, fatty acid, vitamins and minerals. from the maitake mushroom tea, mycelia biomass and capsule Some of them even possess bioactive components namely of maitake extract with potent bioactivities (Wu et al., 2016). polysaccharides, glycoproteins, antioxidants and polyphenolic Commercial mushroom cultivation relies on the complete compounds that exert great medicinal effects which include fruiting body development which is time consuming (approximately anticancer, antibiotic, antiviral activities, immunity blood 2 months) and labour intensive. The quality of the mushroom is lipid lowering effect (Toledo et al., 2013; Bhattacharya et al., inconsistent as it relies on the successful rate for each cultivation 2014). Therefore, large varieties of mushrooms have gained batch. An extra cost will be incurred if the solid cultivation great attentions from consumers in different cultures who substrate is contaminated. Hence, the submerged fermentation wish to maintain their health as well as to boost up their has been used as alternative to accelerate the production of immuno- modulatory systems. mushroom biomass and valuable metabolites. A liquid complete Maitake or Grifola frondosa is a Basidiomycete fungus that medium will be used to cultivate respective mushroom species grows in small and overlapping-tongue or fan shaped caps with under controlled environment and condition. The method has stalks. Maitake is considered as a newly cultivated species with the potential to obtain higher mushroom biomass or mycelia accelerating market consumption and demand similar to other within shorter time of consistent quality (Kim et al., 2007). Some cultivated ones, especially the Pleurotus, Agaricus, Lentinus, researchers discovered that the nutritional value of mushroom Volvariella and Shiitake sp (Zhang et al., 2014). In fact, maitake biomass cultivated via submerged fermentation is comparable has been used as medicinal source in Asia for a very long time to to those found in fruiting body (Ulziijargal & Mau, 2011). treat high blood pressure, elevated serum cholesterol, improving Besides, the texture is also unique as compared to fruiting immunity and anti-ageing (Deng at al., 2009; Yeh et al., 2011). body. This actually encourages more mushroom growers to opt The Maitake-D fraction or specifically the β-glucans group is for submerged cultivation on mushroom biomass especially the important active compounds available in maitake which can growing mycelia to meet the market demand. Received 07 Dec, 2016 Accepted 13 July, 2017 1 Faculty of Science, Universiti Tunku Abdul Rahman, Kampar Campus, Kampar, Perak, Malaysia 2 Faculty of Agro-Based Industry, Universiti Malaysia Kelantan, Jeli Campus, Jeli Kelantan, Malaysia *Corresponding author: [email protected] Food Sci. Technol, Campinas, 37(Suppl. 1): 131-135, Dec. 2017 131 Study on the feasibility of vacuum drying in preserving submerged fermented Maitake mycelia Mushrooms are highly perishable upon harvest, as they 2.4 Determination of chemical analysis of maitake mycelia need appropriate postharvest treatments to prolong their storage time and to preserve the nutritional and chemical Maitake mycelia were extracted overnight with methanol compositions. Generally, dehydration using heat is the most solvent at room temperature on a shaker at 150 rpm and common practice to preserve the mushroom from getting spoil. filtered via Whatman no. 4 filter paper. The filtrate was further For instance, the use of hot air, sun and microwave oven that extracted by rotary evaporator (Buchi R210, US). The dried aims to reduce the excessive moisture within mushrooms prior extract was used for analysis and re-dissolved in methanol to a other processes (Manaa et al., 2013). As far as the nutritional concentration of 10 mg / mL. The total phenolic content of the and chemical compositions are concerned, the use of direct maitake mycelia extract was determined using Folin-Ciocalteu thermal processing is detrimental to the valuable properties method as described by Wong & Chye (2009). A total of as well as the sensory attributes of mushrooms. However, little 0.1mL extract prepared earlier was added with 0.75 mL of information is available on the suitability of drying approaches Folin-Ciocalteu reagent (Sigma). The resulting mixture was in preserving the chemical and the proximate compositions then measured at 725 nm after incubated for 90 minutes of the high commercial value of maitake mycelia that was and the data was calculated by comparing to the gallic acid derived from submerged fermentation. Therefore, the present standard curve. The results were expressed as mg of Gallic study aims to compare the influence of vacuum and oven Acid Equivalents (GAE) per gram of maitake mycelia extract. drying methods on the antioxidant capacity and nutritional Then, the DPPH radical scavenging activity of themaitake compositions of fermented maitake mycelia. mycelia was tested for DPPH radical scavenging activity using 1, 1-diphenyl-2-picrylhydrazyl (DPPH) method as 2 Materials and methods reported by Wong & Chye (2009). The procedure involved the 2.1 Maitake stock culture preparation measurement of test solution at 515 nm and the percentage of DPPH radical scavenging activity was calculated according The stock cultures ofmaitake (Grifola frondosa) were to Formula 1 given: obtained from Mushroom Research Centre (MRC), University of Malaya and maintained on malt extract agar (MEA). The stock culture was prepared by cutting 10 plugs (approximately Radical Scavenging A – = control × (1) 5mm each) aseptically prior to transferring into a 250mL / Acontrol 100% (A : absorbance) Activity (%) Asample Erlenmeyer flask containing Mushroom Complete Medium (MCM) as basal medium and incubated at 25 °C using orbital shaker at 150 rpm for 7 days. The determination of total soluble protein content was done using Bradford method and the Bovine Serum Albumin (BSA) 2.2 Submerged fermentation and harvest of mycelia as a standard procedure. The standard procedure was done with biomass reference to Tripathy et al. (2014) procedure. The amount of A total of 10% (v/v) of the seed culture was transferred soluble protein in maitake mycelia was calculated and expressed aseptically into a new 100 mL conical flask containing 100mL as µg protein / mL. MCM solution. The flask was then sealed with cotton plug and allowed to incubate at 25 °C using orbital shaker at 150 rpm for 2.5 Determination of nutritional compositions of maitake 7 to 14 days. The biomass obtained was rinsed with distilled mycelia water and filtered by Whatman no. 1 filter paper. The filtrate was recovered from the liquid medium and centrifuged twice The nutritional composition analyses were done according to at 6000 rpm, 15 minutes. The mycelia pellet was collected the Association of Dfficials Analytical Association (Association and left to dry to remove excessive moisture before stored in of Dfficial Analytical Chemists, 1995). The moisture content