This research investigates the dynamic changes of free amino acids in beef cooked to different doneness levels and develops a qualitative framework to predict doneness based on chemical attributes. During the frying process, beef proteins and free amino acids exhibit recognizable patterns that correspond to the central temperature. Myosin, being less thermally stable, exhibited a decreasing tendency at the first degree of doneness, while actin showed a distinct change at the fourth degree of doneness. The logarithmic curves adeptly fit hydrophilic and aromatic amino acids. Recognizing the nonlinear relationship between free amino acids and central temperature, Fisher's discriminant analysis was applied, achieving an 89.7% classification rate for non-enzymatic hydrolysis beef beef and 62.1% for enzymatically hydrolyzed beef. Therefore, the discriminatory accuracy for enzymatically hydrolyzed beef was deemed insufficient. By incorporating mean and covariance matrix parameters of beef doneness into a mathematical discriminative model, the discrimination accuracy could be enhanced to 96.55%.

Medium-milled rice is increasingly valued for its health benefits and distinctive aroma, which differs from that of white rice because differences in milling degree modify the content of lipids and other aroma precursors. However, its aroma profile remains underexplored. This study aimed to systematically analyze aroma differences among four Simiao rice cultivars after medium milling (8% degree of milling) and to elucidate the chemical basis underlying consumer preference. Odor sensory evaluation identified Xiangzhuxiang as the cultivar with the highest aroma acceptance. Subsequently, gas chromatography–olfactometry–mass spectrometry and odor activity value analysis characterized the volatile profile, identifying 45 volatile compounds across the four cultivars, including 17 key odor-active components. Multivariate statistical analysis pinpointed the discriminating key odor-active compounds responsible for the superior aroma quality of Xiangzhuxiang. The results showed that (E,E)-2,4-decadienal and indole (VIP > 1.0, FDR-adjusted q < 0.05, FC > 1.2, OAV > 1.0, confirmed by GC-O) significantly increased the aroma scores of Xiangzhuxiang; imparted nutty, fatty, and sweet notes; and thus played a decisive role in shaping its characteristic aroma. Moreover, the moderate levels of hexanal and octanal in Xiangzhuxiang facilitated its characteristic aroma expression. These findings provide a basis for developing premium fragrant Simiao rice cultivars optimized for medium milling.