Effect of Fermentation with Coffee Powder on the Flavor Quality and Antioxidant Activity of Glutinous Rice Sweet Wine: A Combined GC-MS and GC-IMS Study

To explore coffee’s effect on sweet rice wine quality, this study developed a novel fermented beverage using round glutinous rice and coffee powder as raw materials. The fermentation process was optimized using an orthogonal array design combined with fuzzy comprehensive evaluation. Flavor, physicochemical properties, and antioxidant activities were systematically evaluated via electronic tongue (E-tongue), gas chromatography–mass spectrometry (GC-MS), and gas chromatography–ion mobility spectrometry (GC-IMS). The optimal fermentation parameters were 0.6% fermentation starter (Jiuqu), 10% coffee powder, a fermentation time of 56 h, and a temperature of 28 °C. Adding coffee powder significantly increased total flavonoid content. Compared to the control group, the scavenging activities against 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS+), as well as hydroxyl radicals, increased by 18.36%, 7.40%, and 10.96%, respectively, compared to the control group. Flavor analysis identified 173 volatile organic compounds, demonstrating strong complementarity between GC-MS and GC-IMS. The addition of coffee powder preserved traditional sweet rice wine components while introducing roasted heterocyclic compounds, such as 2-methylpyrazine and 2-ethylfuran, thereby imparting nutty and roasted characteristics. E-tongue analysis revealed enhanced sensor responses for sweetness, bitterness, and saltiness, along with decreased umami. In conclusion, the addition of coffee powder is an effective strategy to enhance the in vitro antioxidant activity and enrich the flavor profile of sweet rice wine. This study provides a scientific basis for the application of coffee in traditional fermented foods.