Effectiveness of Infrared Heating for Drying Edible Mushrooms

Edible mushrooms such as black fungus, shiitake, and oyster mushrooms are delicious and nutritious, often referred to as healthy foods. For instance, shiitake mushrooms contain various amino acids, some of which are essential for the body’s proper functioning. Research has also found that shiitake, button mushrooms, enoki, and lion’s mane mushrooms contain substances that enhance human immunity. Some mushroom species even have compounds that can improve the body’s anti-cancer capabilities.

China has abundant resources of edible mushrooms and is one of the earliest countries to cultivate and use them. However, Chinese dried mushroom products lack competitiveness in the international market. The main reason is that early-stage manufacturers have not conducted in-depth research on the drying processes and techniques, resulting in low drying efficiency and poor product quality. Below, we introduce a method of drying edible mushrooms using infrared radiation.

It is well known that each substance has its unique infrared absorption spectrum. When the spectrum of the radiation source matches the absorption band of the substance being heated, the energy carried by the infrared radiation causes the molecules to resonate and absorb energy, leading to a rapid temperature rise. Edible mushrooms have a high water content—an average of 78.3%, meaning that one kilogram of fresh shiitake mushrooms will only weigh 0.2-0.3 kilograms after drying. This indicates a significant match between the infrared absorption band of fresh mushrooms and that of water molecules, which is in the 2-18um range. So, what infrared heating source product matches this band?

An agricultural university verified that the drying effects of microwave heating, infrared heating, and traditional hot air heating decrease in that order. Microwaves are not suitable for widespread use due to various reasons. Today, we will verify the drying effect of shiitake mushrooms using infrared heating. The university conducted this experiment using an industrial infrared oven measuring 45cm45cm60cm to dry shiitake mushrooms.

The results showed that the entire drying process of shiitake mushrooms can be divided into three stages: accelerated dehumidification, constant-rate evaporation, and decelerated air drying. In the first stage, the mushrooms have high moisture content, and the surface is relatively moist, making water evaporation easy. As time progresses, the evaporation rate of the mushroom’s moisture stabilizes, entering the second stage—constant temperature evaporation. In this stage, the mushrooms begin to absorb the heat carried by infrared electromagnetic waves, causing the internal temperature to rise. The heat diffuses from the inside out, bringing the internal moisture to the mushroom’s surface. In the third stage, the internal moisture content of the mushrooms becomes very low and gradually dries out.

Which drying method yields the best results for drying shiitake mushrooms? Let’s look at the laboratory comparison test results. Specific data related to patents are not listed here.

• Color Change: Shiitake mushrooms dried by infrared heating show less color change compared to those dried by hot air.
• Shrinkage Rate: Shiitake mushrooms dried by infrared heating have a lower shrinkage rate than those dried by hot air.
• Amino Acid Content: The amino acid content in shiitake mushrooms dried by infrared heating is higher than that in those dried by hot air.

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