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Application of Heat Pump Dryer in Edible Mushroom Production

I. Energy-saving Effect of Heat Pump Dryer

A heat pump is a high-efficiency heating device whose heat output exceeds 100% of its energy consumption. The heat pump drying unit integrates heat pump technology with a dryer, allowing waste gas to be recycled through the heat pump system.With 100 units of fuel or electric energy consumed, the heat pump can generate 140 to 800 units of heat energy, achieving high efficiency and energy conservation. The heat pump evaporator cools the dryer exhaust gas, controls the moisture content and temperature of the inlet air, and is suitable for atmospheric low-temperature drying.

II. Features of the Dryer

The air-source heat pump dryer can realize fully automatic digital drying of Velvet Antler Mushrooms, shiitake mushrooms, tremella and other products by adjusting parameters, realizing multi-purpose use of one machine.The machine is energy-saving and power-efficient, with uniform and excellent drying performance. It operates intelligently without special personnel on duty, is environmentally friendly, easy to operate and simple to maintain.After drying, the products have better taste and flavor, are convenient for storage, with improved color, aroma and quality, higher solid content and long shelf life, and the mushroom caps curl naturally.The moisture content of dried mushrooms should be lower than 13%. The baking ratio is about 4.5–5 kg of fresh mushrooms to 0.75 kg of dried mushrooms, which is widely recognized by the market.

III. Market Requirements for Drying Quality of Fresh Mushrooms

1. Drying Process of Velvet Antler Mushrooms

With the vigorous development of the edible mushroom industry, many Velvet Antler Mushroom factories have emerged across the country. However, the downturn in the market economy has hindered the circulation of fresh Velvet Antler Mushrooms, prompting manufacturers to seek reliable drying technologies.Traditional boiler steam drying has many shortcomings, such as inaccurate temperature and humidity control, lack of automation, poor drying uniformity and low qualification rate.

(1) Initial Heating Stage: Set temperature at 40℃, load materials, and dry for 4–5 hours. Keep the dehumidification fully open at the early stage to prevent moisture accumulation and material discoloration.

(2) Shaping Stage: Raise the temperature slowly to 50℃. During this stage, the mushrooms soften first, then moisture evaporates and hardening proceeds from the edge of the cap toward the thick center. The mushroom cap is shaped while the core still contains moisture. At 50℃, the gills will not turn light yellow. Drying duration: 2 hours.

(3) Dehumidification Stage: Set temperature at 55–58℃ and dry for 2 hours. The internal and external temperatures of the mushrooms tend to be consistent, the color turns light yellow, and a characteristic aroma is produced.

(4) High-temperature Drying Stage: Set temperature at 65℃ and dry for 2 hours. The mushrooms are thoroughly dried with natural color.

(5) Cooling & Conditioning Stage: Immediately bagging is not recommended for freshly dried mushrooms. To ensure quality and integrity, transfer them to a conditioning room for 30 minutes of moisture reconditioning.This process properly softens the surface, avoiding brittleness and breakage during bagging. Following this process can guarantee the quality of Velvet Antler Mushrooms.