# Effect of Different Drying Methods on the Quality of _Oudemansiella raphanipes_
## 3 Results and Analysis  
### Effects of Different Drying Methods on the Appearance Quality of O. raphanipes  
With reference to Section 2.3.1, the appearance quality of _O. raphanipes_ treated with different drying methods was evaluated in terms of gill color, aroma, and degree of shrinkage, and the scoring results are shown in Table 3.  
As can be seen from Table 3, VD scored the highest in terms of gill color, which allows the samples to be kept under vacuum and non-high-temperature conditions, reducing the possibility of enzymatic as well as non-enzymatic browning of _O. raphanipes_ and, therefore, maintaining the original color of the gills to the maximum extent possible. On the contrary, HD drying temperatures were high and prolonged, and the samples underwent severe browning, hence the darkest color of the gill. The effect of ID on the color of the gills is in between, probably due to the low energy of infrared photons, which can keep the components of the raw material stable during the heating process, so the degree of influence on its chemical properties is small. [PERSON] et al. [37] performed a similar drying treatment on _F. velutipes_ and showed that the VD treatment had the least effect on the color change in _F. velutipes_. _O. raphanipes_ treated with HD had a more intense flavor compared to ID and VD. This is similar to the findings of [PERSON] et al. [38] that HD creates a high-temperature environmental condition under which chemical components such as fatty acids in _O. raphanipes_ may undergo decomposition reactions to produce volatiles with distinctive aromas, and, thus, \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Drying Method**} & \multicolumn{4}{c}{**Scoring Indicators**} \\ \cline{2-5}  & **Gill Color** & **Flavor** & **Degree of Shrinkage** & **Totals** \\ \hline HD & 8.4 & 11.9 & 4.8 & 25.1 \\ \hline ID & 10.2 & 9.8 & 5.7 & 25.7 \\ \hline VD & 12.9 & 8.8 & 10.5 & 32.2 \\ \hline \hline \end{tabular} HD: hot air drying; ID: infrared radiation drying VD: vacuum freeze drying.  
\end{table} 
Table 3: Effect of different drying methods on appearance quality evaluation. HD may increase the aroma of dried products. In a certain sense, ID can also increase the amount of volatiles, and VD does not adversely affect the aroma after drying. After HD and ID drying, the surface of _O. raphanipes_ showed an obvious wrinkling phenomenon; the stipe was thinned, and the cap was narrowed. And after drying by VD, its volume did not change significantly from fresh, so it scored the highest for this indicator of shrinkage. The degree of wrinkling is closely related to the internal structure of the _O. raphanipes_ VD drying. The moisture in the fruiting body forms ice crystals at low temperatures, sublimates into water vapor, and forms a microporous structure, so it has little effect on the appearance of the mushroom body. HD and ID samples, under prolonged heating and drying conditions, destroy the original spatial structure, shrink in volume, harden on the surface, and crumple severely. Based on the above analysis, among these three drying methods, vacuum freeze drying scored the highest in terms of appearance quality, and this method maximizes the preservation of the original color, aroma, and appearance of the gills of the _O. raphanipes_. Hot air drying, infrared drying, and vacuum freeze drying were used to dry to constant weight (\(\pm\)0.02 g), after 10 h, 10 h, and 24 h, respectively, until the moisture content of the sample was reduced to about 6%. According to Table 4, it can be seen that the rehydration rate of _O. raphanipes_ dried by vacuum freeze drying is the highest, and the rehydration rate of dried products dried by infrared radiation is slightly higher than that of hot air drying. The high rehydration ability of VD dried products may be related to the principle of freeze drying. Vacuum freeze drying can directly sublimate the water in the fruiting body, maintaining the original voids inside the _O. raphanipes_.