Mining the Impact of Mechanical-Stamping Heterogeneity on the Macro- and Micro-Levels of Nongxiangxing daqu

In the production of modern <i>nongxiangxing daqu</i>, mechanical stamping is utilized to compact raw materials into <i>daqu</i> bricks. Nevertheless, variations in stamping frequencies may modify the initial physicochemical properties of <i>daqu</i>, which in turn influence its physicochemical and biochemical parameters, and ultimately affect the quality of <i>baijiu</i>. This study systematically evaluated <i>daqu</i> samples prepared with different stamping frequencies (2 to 5 cycles) in terms of (1) physicochemical and biochemical parameters, (2) volatile compound profiles, (3) microbial community dynamics, and (4) interspecific interactions. The results showed that with the increase in stamping frequency, the moisture content, fermentative power, esterifying power, and liquefying power of daqu were all enhanced, with respective increases of 20.11%, 67.16%, 12.24-fold, and 36.27%. Specifically, the relative abundances of <i>Weissella</i>, <i>Lactobacillus</i>, <i>Aspergillus</i>, and <i>Rasamsonia</i> in <i>daqu</i> exhibited a significant increase with the elevation of pressing cycles. With the reduction in stamping frequency, the primary producers of flavor compounds shifted gradually from bacteria to fungi. These findings verify that stamping frequency exert a substantial regulatory impact on the physicochemical and biochemical parameters, microbial community dynamics, accumulation of flavor substances, and abundance of functional enzymes in <i>daqu</i>. Through a systematic elucidation of the mechanistic links between stamping parameters and <i>daqu</i> functionalities, this research offers actionable insights for optimizing industrial pressing processes and establishes a scientific basis for modern <i>daqu</i> production.