Effect of vacuum and oven drying on the radical scavenging activity and nutritional contents of submerged fermented Maitake (Grifola frondosa) mycelia

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.

The effect of drying temperature on bioactive compounds and antioxidant activity of Leccinum scabrum (Bull.) Gray and Hericium erinaceus (Bull.) Pers.

“…For H. erinaceus it was a 17% reduction of TP (from 3.79 to 3.14 mg/g DW), while for L. scabrum it was a 40% reduction of TP (from 1.89 to 1.14 mg/g DW) at 70°C in comparison to fresh. The results were in agreement with some studies on mushrooms, fruits and seeds, which contradict the reduction of TP under high-temperature drying (Juhaimi et al 2018;Sim et al 2017). The loss of TP (up to 25%) during drying at high-temperature was also confirmed for edible mushroom Phlebopus colossus (Liaotrakoon and Liaotrakoon 2018).…”

“…The loss of TP (up to 25%) during drying at high-temperature was also confirmed for edible mushroom Phlebopus colossus (Liaotrakoon and Liaotrakoon 2018). Phenolics are molecules sensitive to temperature, and the changes of the content (both reduction and increase) with different drying temperature was indicated (Jaworska et al 2014;Jiang et al 2017;Sim et al 2017;Yang et al 2017). The oxygen atmosphere was responsible for their oxidation (Hamrouni-Sellami et al 2012).…”

“…The oxygen atmosphere was responsible for their oxidation (Hamrouni-Sellami et al 2012). In Grifola frondosa mycelia the drying in an oven at 70°C reduced the TP content only from 17.0 to 16.6 mg GAE/g (Sim et al 2017). In Lentinula edodes an increase of TP was observed under hot air drying (Yang et al 2017), because the phenolic compounds are substrates of lignin, whose more intense accumulation was observed as a result of high temperature drying.…”

“…The ability to scavenge free radicals is connected with phenolic compounds (Š umić et al 2017). Additionally, Sim et al (2017) suggested that heating of the mycelium interrupts its ability to donate hydrogen.…”

Bioactive Ingredients and Medicinal Values of Grifola frondosa (Maitake)

“…Generally, proximate composition is determined by the methods suggested by the Association of Official Analytical Chemists (AOAC). The total carbohydrate content can be calculated by subtracting the percentages of ash, crude fat and protein [ 7 , 40 ]. For the determination of crude protein, the nitrogen conversion factor is 4.38 instead of the usual 6.25, due to the large amount of chitin that is usually contained within the fungus, a component that may interfere with the correct calculation of the result of total nitrogen [ 41 ].…”