Freeze Drying vs. Hot Air Drying for Mushroom Preservation

Freeze drying and hot air drying are two common techniques for preserving mushrooms, each with specific benefits and cons. Freeze drying, which is renowned for its ability to preserve the physicochemical characteristics and antioxidant functions of substances obtained from mushrooms, is particularly effective at retaining the rehydration capabilities and natural texture of mushrooms. This is accomplished by preserving the porous structure, which leads to higher rehydration ratios and better texture retention than hot air drying which requires higher temperatures. Furthermore, freeze drying outperforms hot air drying in terms of nutrient retention, protecting proteins, vitamins, and minerals, whereas hot air drying can cause nutritional destruction, particularly in the case of heat-sensitive components like vitamin C.

By reducing enzymatic browning and Maillard reactions, freeze drying surpasses hot air drying in terms of aesthetics, producing freeze-dried mushrooms that nearly match their fresh counterparts in color. In contrast, the breakdown of the pigment during hot air drying can result in substantial color shifts. The capacity of freeze drying to prevent oxidative stress and maintain antioxidant activity is a major additional benefit. When mushrooms are freeze-dried, phenolic compounds and other antioxidants are better preserved, but hot air drying can reduce the bioactivity of antioxidants owing to heat exposure.

Economically, freeze-drying has higher expenses because it requires specialized equipment and takes longer to complete. The greater quality of the finished product, which makes it appropriate for premium items or those with certain dietary requirements, frequently justifies the investment. However, hot air drying is a feasible option for large-scale operations when cost-effectiveness and punctuality are crucial since it is time and money-efficient. By using freeze drying to preserve the microstructure and porosity of mushrooms, a light, porous product that rehydrates quickly is produced. On the other hand, hot air drying might result in less porous, denser dried mushrooms. This discrepancy in texture and rehydration draws attention to another benefit of freeze drying.

For applications that stress quality preservation, such as gourmet foods and pharmaceuticals, freeze-drying is recommended from a commercial standpoint. The ability to preserve quality and distinctive characteristics makes freeze-dried items premium options. Hot air drying, in contrast, is a popular option for contexts involving mass manufacturing since it is appropriate in situations where efficacy and cost-effectiveness take precedence above maximum quality retention.

Studies on Inonotus obliquus (chaga mushroom)  polysaccharides (IOPS) indicate that freeze-dried IOPS exhibit enhanced antioxidant capabilities, showcasing superior DPPH radical scavenging, ferric- reducing power, and lipid peroxidation inhibition, implying its superior retention of necessary antioxidants compared to hot air drying. Furthermore, freeze-drying preserves molecular weight distribution, and particular structural configurations such as the triple helix configuration, and creates a porous microstructure, all of which support improved rehydration and textural properties as well as increased bioactivity. Despite its benefits, freeze-drying is known to be more expensive, slower, and technically challenging, which restricts its applicability for smaller enterprises. In contrast, hot air drying is less expensive and takes less time to process, but there is a chance that bioactive chemicals and antioxidant capabilities will be compromised, lowering the quality of the final product [1].