Change in physicochemical properties, aroma components, and potentially beneficial compounds during the stir-frying of Massa Medicata Fermentata

Massa Medicata Fermentata (MMF) is widely applied in feed additives and human medicine. The stir-frying is a commonly used method for process of MMF, which will improve its efficacy in invigorating the spleen. However, the dynamic change of physical properties and ingredients during stir-frying remain un-elucidated. Here, the appearance color, pH values, UV–visible and fluorescence spectroscopy, content of volatile and non-volatile compounds of MMF at different process stage of stir-frying were measured. The results indicated that with increasing stir-frying time, the appearance color deepened, and pH value decreased, while the UV absorbance and fluorescence exhibited rising trends. Additionally, we identified four non-volatile compounds from MMF, and three of them showed gradual increase in content during stir-frying (from 0 to 30 min). Regarding the volatile compounds, the content of alcohols decreased, while aldehydes increased evidently after 30 min. These results demonstrated that the physicochemical properties, types of compounds and their content all significantly changed during stir-frying. The study provides insights regarding the change in substance and appearance, which will provide a guidance for the judgment of the degree of stir-frying MMF.