Cili (Rosa roxburghii Tratt.) Fruit and Its Co-Culture Fermentation with Bacillus subtilis and Lactiplantibacillus plantarum Improves the Nutritional, Functional and Bioactive Quality of White–Black Wheat Composite Bread

Whole black wheat increases the dietary fiber and anthocyanin content of bread, but reduces loaf-specific volume and increases crumb firmness. This study evaluated Cili (Rosa roxburghii Tratt.) fruit co-culture fermented with Bacillus subtilis and Lactiplantibacillus plantarum, as an ingredient (30%, flour weight) in white wheat (BsLp) and white–black wheat (50:50) (WWBW-BsLp) composite bread, and compared with the breads without Cili (white wheat: WB; white–black wheat: WWBW). In dough, β-glucosidase, feruloyl esterase, and α-amylase activities were elevated in BsLp and WWBW-BsLp after proofing. In bread, compared with WB, WWBW-BsLp contained more GABA (312.2 vs. 5.7 mg/kg DW), total phenolics (484.8 vs. 70.7 mg GAE/100 g DW), total flavonoids (58.0 vs. 17.0 mg QE/100 g DW), and total dietary fiber (9.46 vs. 3.01 g/100 g DW), including more soluble fiber (2.29 vs. 0.30 g/100 g DW) (all p < 0.05). DPPH and ABTS radical-scavenging activities increased from 11.9% to 72.9% and from 28.8% to 80.0%, respectively. Compared with WWBW, inclusion of fermented Cili reduced crumb firmness (410 vs. 493 g; p < 0.05) but did not significantly change specific volume (4.17 vs. 3.94 mL/g). Co-fermented Cili is thus a promising ingredient for increasing GABA, phenolics, and soluble fiber in composite bread.