*3.5. Textural Profile Analysis*

TPA is an important indicator to evaluate the quality and acceptability of comminuted meat products, which is expressed as hardness, springiness, gumminess, chewiness, and cohesiveness [25]. The results of TPA of sausages is listed in Table 3, and significant differences (*p* < 0.05) were observed among the sausages. With the improve of AC content, the hardness, gumminess, and cohesiveness of sausages were decreased, but the springiness and chewiness were increased. Compared with the control, hardness, gumminess, and cohesiveness of replacement group decreased by 9.29%–33.91%, 36.25%–72.51%, and 29.09%–58.18%, indicating that these sausages had a softer texture. This downtrend was similar to low-fat burger with high beta-glucans and oat-hull-based ingredient as fat replacer [27]. By contrast, the springiness and chewiness of replacement group increased by 2.29%–20.86%, and 1.87%–8.09% in comparison with the control, suggesting that these sausages required more energy to be compressed and the work during chewing will be slightly greater. It could be attributed to the highest amount of AC. The moisture and fat content also could influence TPA parameters [30]. These results may be attributed to the fiber and the rich and elastic properties of AC. This result complies with the report by dos Santos Alves [31] where animal fat was replaced with pork skin-based emulsion gels. Similar observations were also made by [11] who reported that using *Pleaurotus eryngii* as replacements for pork back fat in sausages.

### *3.6. Free Amino Acids*

Amino acids are important for the nutritional value and sensory properties of sausages [4]. The amino acids of sausages formulated with AC replaced pork fat are shown in Table 4. The main essential amino acids in the control group were valine, lysine, and leucine, and the main non-essential amino acids were glutamate, aspartic, and arginine. By contrast, the main essential amino acids in the replacement group were leucine, valine, and lysine, and the main non-essential amino acids were glutamate, proline, and aspartate. Compared with the control group, the contents of isoleucine, leucine, and proline in the replacement group increased by 18.87%–49.06%, 17.20%–48.39%, and 3.41%–43.18%, respectively. It may be due to the AC being abundant in these amino acids. Amino acids were linked with multiple health benefits. In the literature, isoleucine was a potent plasma glucose-lowering amino acid [32]. Zhang and Guo et al. [33] found that increasing dietary leucine intake could reduce diet-induced obesity and improve glucose and cholesterol metabolism in mice via multi mechanisms. Proline is critically essential for nutrition, antioxidative reactions, and immune responses [34]. In addition, the control was higher than other amino acids of replacement group. These results could be explained by the fact that the difference of amino acid content between AC and pork fat.
