Abstract: In this study, pneumatic stirring method was used instead of manual stirring for the production of Zhejiang rosy vinegar, and the effects of stirring method and frequency on the fermentation process and vinegar flavor were explored as well. The optimal airflow rate and ventilation time were determined to be 0.73 m3/min and 53 s, respectively. Excessively low stirring frequency could affect substance exchange in acetic acid bacteria, while excessively high stirring frequency was detrimental to the growth of acetic acid bacteria. Under both conditions, the fermentation speed and the final yield of vinegar were reduced. The concentrations of organic acids and non-volatile acids in rosy vinegar produced by pneumatic stirring were increased compared with the traditional method. The volatile component concentrations of rosy vinegar produced by pneumatic stirring method with stirring frequency of once every 5 and 7 d were 6 344.59 and 6 062.63 mg/L, respectively, higher compared to 5 505.83 mg/L for the traditional method. Principal component analysis (PCA) was performed on the volatile components. Rosy vinegar produced by pneumatic stirring was significantly different from that produced by the traditional method and rice vinegar produced using a self-priming fermentor.

Key words: rosy vinegar, mechanization, pneumatic stirring, flavor substances, sensory evaluation