Computer vision online measurement of shiitake mushroom (Lentinus edodes) surface wrinkling and shrinkage during hot air drying with humidity control

Abstract A new image processing method based on region segmentation was established for on-line measurement of surface wrinkling of shiitake mushrooms (Lentinus edodes) during hot air drying with four RH control methods. The relationship between RH change and the surface wrinkling and radial shrinkage of shiitake mushrooms during the drying process, as well as the effect on drying time and rehydration ratio (RR) were investigated. Compared with continuous dehumidification, maintaining relatively high RH can inhibit the case hardening of materials, while with prolonged drying time, resulting in more surface wrinkles, larger radial shrinkage, and lower RR. The optimized RH control method reduced the shrinkage, surface wrinkling, and drying time by continuous fanning in the later drying stage, but did not improve RR. For better rehydration characteristics in the meantime obtaining better appearance quality and shorter drying time, lower initial RH or its retention time in the early drying stage might be adopted.