Quality improvement of sweet rice wine fermented with Rhizopus delemar on key aroma compounds content, phenolic composition, and antioxidant capacity compared to Rhizopus oryzae

The pure culture fermentation has led to less flavorful rice wine and relatively lower bioactive substance level compared to traditional mixed culture fermentation; however, a pure strain is easily controlled by industrialized producers. The purpose of the present research was to screen a species of Rhizopus for improving the flavor deficiency and antioxidant function of sweet rice wine. Seven rice wine samples fermented with isolated strains were analyzed for their total phenolics, total flavonoids, peptide and antioxidant activity using spectrophotometry, as well as ethanol, ethyl acetate, β-phenethyl alcohol, and volatile alcohol contents measured by headspace gas chromatography (HS-GC), the further principal component analysis determined Rhizopus delemar rice wine better on aroma and antioxidant capacity. A comparison of phenolics profile between R. delemar and R. oryzae rice wines was made based on the measurement data of ultrahigh-performance liquid chromatography coupled with Q-exactive orbitrap mass spectrometry (UHPLC-QE-MS) data. Thirty-two phenolics were identified in sweet rice wine. Overall, the results presented in this study showed that a strain of R. delemar is available for the improvement of flavor and antioxidant activity in sweet rice wine, which has the great potential to be applied to industrialized products.