## 3 Results and Discussion
### Manufacturing the Mushroom-Based Meat Sausage Analogue  
Egg white powder is commonly used in sausage production because it can improve texture by retaining moisture and stabilizing the product, without adding any unpleasant flavors. Meat flavor powder is a well-known flavor enhancer, but its excessive use can result in the scent of spices becoming unacceptable. Red yeast rice was produced by _Monascus purpureus_, which has been reported to reduce cholesterol levels, affect texture properties, give sausages their characteristic meat-like appearance, improve color stability, enhance flavor and stimulate the appetite [21; 22]. Plant oils also act as an excellent lipid ingredient and can be included in a formulation to enhance the tenderness, mouthfeel, juiciness and flavor release of the meat product [6]. Therefore, the contents of egg white powder, red yeast rice, and oil were selected as key factors for optimization. To obtain a holistic view of the acceptability and preference of the products, the sensory attributes of the different sausage analogue samples were assessed comprehensively by sensory evaluation. Before steaming, the physicochemical properties, pH and \(a_{w}\), of the sausage analogues were measured and compared. The \(a_{w}\) and pH of the sausages ranged from 0.96 to 0.98 and from 5.0 to 5.8, respectively (Figure S4), values slightly lower than those of traditionally made animal meat sausages but might improve shelf-life [23]. The color of different groups was measured with a colorimeter. The results in Table S1 shown the strong relationship between the lightness and redness values with the amount of red yeast rice. When red yeast rice was added in high levels, the color value of sausage analogues exhibited a lower level. The sensory evaluation focused on color, flavor, mouthfeel and structural condition, which assessed the acceptability of sausage analogue with different formulations more directly (Table S2). Based on the scores of different treatment groups from 32 panelists, the most significant factor is red yeast rice and followed by egg white powder, oil, and meat flavor powder. The optimized formulation of the sausage analogue (MMSA, Figure S5) was as follows: red yeast rice at level II (0.02%), egg white powder at level III (5%), oil at level II (19%), and meat flavor powder at level I (0.1%). As well as sensory evaluation, texture profile is one of the most important properties of sausage products from both animal and plant sources. A principal component analysis (PCA), which is a multivariate statistical method, can highlight differences between the samples [24]. The PCA plot (Figure 4A) reflected statistically significant differences in the core information to allow a comparison of the textural characteristic of sausage samples from the control, treatments (G1-9), and optimal (MMSA) groups on the main component plane. Based on the analysis of hardness, springiness, adhesiveness and fracture properties, the data were clustered into the following three groups: MMSA and the commercial products (CP1 and CP2) overlapped and interwove, indicating that they cannot be completely discriminated and exhibited similar textural characteristics. Meanwhile, they were separated from the interlaced treatment groups and the control group thoroughly, which displayed a significant discrepancy in texture profile. The cluster dendrogram (Figure 4B) further shows the hierarchical relationship between the sausage samples more directly. The cook yield test was carried out and the results were shown in Table S3. After being steamed, the yields were between 101.22% to 106.89%. The increased weight of all the sausage analogues was attributed to the vapor they absorbed. Overall, the evaluation showed that MMSA might be an ideal and feasible formulation for producing sausages made from plants and edible mushrooms to replace those made using animal resources. While it is might not be suitable for vegetarians who do not eat any meat products and consume eggs due to the existence of egg powder and meat flavor powder.