Yingtai: Application of Vacuum Freeze-Drying Technology in Edible Fungi
The industrialization of the edible fungi industry is a crucial foundation for ensuring stable yield and quality, as well as a key driver for industrial upgrading amid rapid socio-economic development. However, constrained by the predominance of primary processing in China's edible fungi sector, the industry still faces certain challenges despite abundant upstream raw material supply. Thanks to the recent application of food freeze-drying technology in edible fungi processing, the industry has been able to develop health-oriented products that align with market trends while extending the industrial chain.
Trends in Freeze-Dried Edible Fungi
China is a major producer of edible fungi. In recent years, advancements in superior strains, diversified varieties, large-scale production, and growing market demand have further propelled the industry to cultivate over 60 types of artificially grown edible fungi, including shiitake mushrooms, white fungus, matsutake, termitomyces, boletus, and morel. Both output and production value have shown an overall upward trend.
According to data released by the China Edible Fungi Association, by 2019, China's edible fungi output had reached nearly 39.34 million tons, with the total industry output value exceeding 300 billion yuan. However, for a long time, edible fungi have primarily been sold fresh or dried, while derived snack products are mostly processed through methods such as pickling, puff drying, or frying to produce snacks or crisps. Overall, post-harvest processing categories remain limited, with most products undergoing primary processing for culinary use.
Whether considering the rich protein, amino acids, and other nutrients in edible fungi or the growing consumer demand for healthy and convenient foods, the industry is driven to expand production scale while enhancing product value by exploring development potential and extending the industrial chain.
Notably, with the widespread application of vacuum freeze-drying technology in the food industry, products such as freeze-dried fruits and vegetables, freeze-dried yogurt bites, freeze-dried instant porridge, and freeze-dried seafood have emerged. These products not only better preserve the color, aroma, and nutrition of raw materials but have also established a market presence, pointing the way for the deep processing of edible fungi.
Advantages of Freeze-Dried Edible Fungi
In recent years, while expanding its industrial chain, the edible fungi industry has vigorously developed processing sectors such as freeze-dried edible fungi crisps, instant soups, and freeze-dried mushroom products. The introduction of corresponding freeze-drying equipment has become a driving force for industrial development.
Currently, edible fungi freeze-dryers consist of a drying chamber, condenser, heating system, vacuum system, refrigeration system, and electrical control system. In terms of production technology, the process involves freezing materials into a solid state at low temperatures and then sublimating the water content under vacuum to achieve dehydration. Compared to earlier methods like hot-air drying or frying, this technology offers distinct advantages.
For example, freeze-dried foods exhibit excellent rehydration properties. Products such as white fungus soup, processed through washing, boiling, freeze-drying, and packaging, can be quickly rehydrated with hot water for immediate consumption. The final product's form and flavor are widely regarded as comparable to freshly stewed white fungus soup. Additionally, freeze-dried edible fungi, whether sliced or whole depending on the mushroom structure, retain their shape and nutritional content well. Without the need for preservatives, this method extends shelf life and ensures stable quality.
Overall, the active integration of advanced food processing technologies into the edible fungi industry and the development of products that meet contemporary health-conscious consumer demands are essential for industrial upgrading. Extending the industrial chain in this way will create new economic growth opportunities.
Freeze-Drying Process for Edible Fungi
The freeze-drying technology for edible fungi involves the following key steps:
1. Pre-Treatment Process
This includes raw material selection, cleaning, slicing, blanching, sterilization, and the addition of agents or antioxidants. The goal is to remove spoiled materials and impurities, prevent chemical changes caused by fat oxidation or yeast, and facilitate sublimation drying. Excessive heating should be avoided during pre-treatment.
For edible fungi with thick and dense tissue structures—such as button mushrooms, king oyster mushrooms, shiitake mushrooms, and lion's mane mushrooms—slicing is generally required to accelerate freeze-drying due to their slow drying speed and long processing time. In contrast, varieties with thin and loose structures—such as cordyceps, bamboo fungus, wood ear, and enoki mushrooms—can typically be freeze-dried whole without slicing.
Research shows that some edible fungi, like shiitake mushrooms, dry more easily when blanched, though this may cause greater deformation and nutrient loss. Thus, fresh shiitake mushrooms are often preferred without blanching. On the other hand, blanched enoki mushrooms dry more efficiently, while unblanched ones are harder to process, making heat-treated enoki mushrooms the better choice.
Morel mushrooms are valuable both medicinally and as food. In one study, the aroma and lipophilic extracts of black morels grown in China were analyzed using gas chromatography/mass spectrometry, and the antioxidant and antimicrobial activities of the lipophilic extracts were evaluated. The drying method significantly influenced the chemical characteristics of black morels, with freeze-drying better preserving nutrients and the distinctive morel aroma. This study marks the first report on the aroma and lipophilic extracts of black morels cultivated in China.
Fresh mushrooms have high water content and enzymatic activity, making them highly perishable. Thus, dehydration is necessary for preservation. In most cases, drying is used in food processing. However, the drying process alters the composition and content of mushroom metabolites, thereby affecting their nutritional value, taste, and aroma.
