Wheat variety dominates Nong-flavor Daqu functionality over compression parameters: A quantitative framework linking crop traits to fermentation starter quality

Wheat variety and compression parameters critically determine Nong-flavor (NF) Daqu functionality, yet their relative contributions remain poorly understood. This study investigated how wheat biochemical traits and processing parameters influence microbial assembly and enzymatic functionality in this traditional Chinese liquor starter. Three wheat varieties with different end-use quality were processed into Daqu bricks under 33 combinations of compression pressure, duration, and loading weight, with full replication enabling rigorous statistical analysis. Variance partitioning revealed that wheat variety exerted a stronger influence (partial η 2 = 0.890) than compression parameters on Daqu functionality. Weak-gluten Chuanmai93 (CM93) yielded Daqu with superior sensory scores (38.9 vs. 26.2 for CM39) and approximately 17 % higher saccharifying power (724 vs 618 mg/g·h), concomitant with enrichment of the functional fungus Thermomyces (44.6 % relative abundance). This was likely attributed to higher native enzyme activities (e.g., α-galactosidase, α-amylase, arabinanase, β-1,3-glucanase), starch content, and farinograph quality. Conversely, strong-gluten CM39 promoted protein-degrading microbes, possibly correlating with inferior sensory. Hierarchical clustering revealed that bacterial communities exhibited strong variety-dependent segregation, whereas fungal communities were more influenced by processing parameters. Critical compression thresholds were identified at 6.0 kN (approximately ∼47 – 87 % below peak hydrolase activities at other pressures) and 5.0 kg loading (∼37 – 169 % above minima at other loadings), revealing non-linear microbial responses to physical processing parameters. Network analysis ( p < 0.001) suggested that starch/farinograph promoted beneficial microbes ( Thermomyces , Pantoea ) and sensory outcomes, whereas protein/hardness drove detrimental proteolysis. Weak-gluten CM93 enabled stable, high-quality Daqu production at lower energy input (6 kN/ 5 s/ 4.5 kg). Among all two-way interactions tested, only the variety × pressure term reached significance, affecting merely 11.5 % of properties and indicating largely independent effects of variety and compression parameters. These findings establish a quantitative framework linking wheat biochemical traits to fermentation starter functionality, providing data-driven guidance for optimizing Daqu quality.