# Optimization of Vacuum Freeze-Drying Process and Quality Evaluation of _Stropharia rugosanmulata_
###### Abstract  
_Stropharia rugosanmulata_ is a valuable medicinal and food fungus with high nutritive value. Freeze-drying addresses the storage and transportation challenges of fresh _Stropharia rugosanmulata_, expanding its market while preserving its flavor and quality more effectively than other drying methods. This study optimizes the vacuum freeze-drying process for _Stropharia rugosanmulata_ using an orthogonal experiment method. The process parameters were optimized to determine their effects on the quality of the vacuum freeze-dried product, including pre-freezing temperature, pre-freezing time, and freeze-drying time. The optimal conditions were identified as a pre-freezing time of 60 h, a pre-freezing temperature of \(-\)80 \({}^{\circ}\)C, and a freeze-drying time of 72 h. The optimal product exhibited a bright color close to its natural state, with minimal browning and its natural white color maintained post-drying. During the drying process, the internal structure of the raw materials remained intact. After drying, the finished product retained its natural form, making it suitable for sale on the market. The soluble protein content of the vacuum freeze-dried _Stropharia rugosanmulata_ reached 68 mg/g. Optimizing the freeze-drying process can better preserve the tissue structure and bioactive substances of _Stropharia rugosanmulata_, providing a reference for high-quality food processing and showing potential for sustainable development. Stropharia rugosanmulata; vacuum freeze-drying; process optimization; texture;  
strengthen the heart and blood, enhance brain function, improve skin health, and alleviate mental fatigue. In vitro test results indicate that the extracellular polysaccharides of _Stropharia rugosoannulata_ possess strong antioxidant, anti-tumor, lipid-lowering, and blood-sugar-lowering effects, with these effects positively correlated with its concentration [4]. In addition, it has immunomodulatory and anti-tumor effects and is rich in nutrients, with over 65% of its composition containing high-quality carbohydrates [5]. It can improve the immune system and effectively enhance physical strength. Vacuum freeze-drying can maximally preserve the shape and nutritional functions of _Stropharia rugosoannulata_, which is a healthy and safe processing method suitable for the treatment of health food ingredients. Freeze-drying is an important drying process for products that need to preserve their flavor, bioactivity, and other characteristics [6]. Freeze-drying technology addresses issues such as high bacterial content, nutrient loss, and low sensory quality in dried products, ensuring the safety and durability of the finished product and increasing the added value of _Stropharia rugosoannulata_ sales. [PERSON] et al. [7] discovered that the retention rate of umami-providing amino acids in freeze-dried Flammulina veluipes could reach 70%, and that the retention rate of soluble sugars and alcohols could reach 98%. [PERSON] et al. [8] found that vacuum freeze-drying can effectively preserve the nutritional components of matsutake mushrooms, with a total phenol retention rate of up to 80% and a protein retention rate as high as 93%. Currently, the market mainly sells fresh _Stropharia rugosoannulata_, which has a short shelf life and cannot meet the requirements for long-term storage. Dried _Stropharia rugosoannulata_ products are relatively rare. Traditional drying methods for _Stropharia rugosoannulata_, in addition to natural drying, include hot-air drying and microwave drying. Both hot-air drying and microwave drying involve high processing temperatures, which can lead to browning of the material and significant loss of the active components [9]. Naturally dried _Stropharia rugosoannulata_ experiences significant nutrient loss and low product quality, failing to achieve increased sales value.