Preparing Ganoderma lucidum slices by improved steam explosion enhances their apparent, functional and structural properties

Ganoderma lucidum slices exhibit antioxidant and enzyme inhibitory activity, enhancing vitality and longevity. However, untreated Ganoderma lucidum slices fail to meet specific physical and chemical requirements for consumption and processing because their bioactive compounds must be released before intake through effective pretreatment. We proposed developing a novel preparation method for Ganoderma lucidum slices through improved steam explosion (ISE). The effect of ISE (at 0.4-1.2 MPa for 5 min) on their chemical compounds, apparent properties, biological activity, sensory quality and structural characteristics was assessed. The results showed that ISE (0.8-1.2 MPa) increased the content of flavonoids (by 32.29 %-126.57 %), phenolics (by 31.79 %-96.28 %), triterpenes (by 1.74-5.24 times) and polysaccharides (by 6.27-18.03 times) in Ganoderma lucidum slices. Additionally, ISE improved the color saturation and hue of their infusions while reducing the color values of these slices. Under all conditions, ISE significantly increased the soluble solids content (by 1.31-11.44 times) and the inhibitory activity of tyrosinase and xanthine oxidase when compared to infusions of untreated slices. At 0.8-1.2 MPa, the radical scavenging activity of 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2 '-azino-bis(3-eth- '-azino-bis(3-eth- ylbenzothiazoline-6-sulfonic acid) (ABTS) was also significantly higher in steam-exploded slices than in untreated slices. In the sensory evaluation, steam-exploded slices outperformed untreated slices in terms of color, taste, form attributes, and overall score. ISE disrupted the microstructure of Ganoderma lucidum slices, whose microscopic structure was broken into fragments, thereby promoting the dissolution of bioactive compounds and enhancing their biological functions, as shown in this study. Therefore, ISE improved the nutritional and medicinal effects of the fruiting body of Ganoderma lucidum by facilitating nutritional retention and resource utilization efficiency.