Evaluation of Sufu Fermented Using Mucor racemosus M2: Biochemical, Textural, Structural and Microbiological
Yuan Xie1,2, Ziyu Guan1,2, Shitong Zhang1,2
1State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi 214122, China.
Abstract:
The quality and safety of sufu fermented using Mucor racemosa M2 was studied and compared with naturally fermented sufu. After 90 days post-fermentation, both naturally fermented and inoculated fermented sufu reached the maturity standard of sufu, and the degree of protein hydrolysis of natural sufu (WP/TP: 34% ± 1%; AAN/TN: 33% ± 1%) was slightly higher than that of the inoculated sufu (WP/TP: 28.2% ± 0.4%; AAN/TN: 27% ± 1%). The hardness and adhesiveness of inoculated sufu (Hadness: 1063 g ± 211 g; Adhesiveness: -80 g ± 47 g) were significantly greater than those of natural sufu (Hadness: 790 g ± 57 g; Adhesiveness: -23 g ± 28 g), and the internal structure of natural sufu was denser and more uniform than that of inoculated sufu. A total of 50 aroma compounds were detected in natural and inoculated sufu. The total number of bacterial colonies in naturally fermented sufu was significantly higher than that in inoculated sufu, and the pathogenic bacteria in both types of fermented sufu were lower than the limit of pathogenic bacteria required in fermented soybean products. The content of biogenic amines in sufu was determined by high performance liquid chromatography (HPLC), and the results showed that the content of biogenic amines (Putrescine, Cadaverine, Histamine, Tyramine, etc.) in naturally fermented sufu was significantly higher than that in inoculated fermented sufu. Especially the histamine content, after 90 days of fermentation, was found to be 64.95 ± 4.55 for inoculated fertilization and 44.24 ± 0.71 for natural fertilization. Overall, the quality of inoculated sufu was somewhat better than that of natural sufu, and the M2 strain can be used to ferment sufu.
Insights
Fermenting sufu with Mucor racemosa M2 enhances its quality, resulting in better texture and lower biogenic amine content compared to natural fermentation. This study confirms M2 strain
Area of Science:
- Food Science and Technology
- Microbiology
- Fermentation Technology
Background:
- Sufu, a fermented soybean product, relies on microbial fermentation for its characteristic flavor and texture.
- Traditional sufu production involves natural fermentation, which can lead to variations in quality and safety.
- The use of specific starter cultures, like Mucor racemosa M2, offers potential for controlled and improved sufu fermentation.
Purpose of the Study:
- To evaluate and compare the quality and safety of sufu fermented using Mucor racemosa M2 with naturally fermented sufu.
- To assess the impact of M2 strain inoculation on key fermentation parameters, including protein hydrolysis, texture, aroma, microbial load, and biogenic amine content.
- To determine the suitability of Mucor racemosa M2 as a starter culture for sufu production.
Main Methods:
- Comparative analysis of sufu fermented with Mucor racemosa M2 and naturally fermented sufu after 90 days.
- Measurement of protein hydrolysis (WP/TP, AAN/TN) and texture properties (hardness, adhesiveness).
- Detection of aroma compounds, enumeration of bacterial colonies, and quantification of pathogenic bacteria.
- High-performance liquid chromatography (HPLC) analysis for biogenic amine content (Putrescine, Cadaverine, Histamine, Tyramine).
Main Results:
- Both fermentation methods yielded mature sufu, but inoculated sufu exhibited higher hardness and adhesiveness.
- Natural sufu showed slightly higher protein hydrolysis, denser internal structure, and a more uniform texture.
- Inoculated sufu had significantly lower biogenic amine content, particularly histamine, compared to naturally fermented sufu.
- Pathogenic bacteria levels in both types of sufu were below safety limits.
Conclusions:
- Fermentation with Mucor racemosa M2 improves certain quality attributes of sufu, notably texture and safety by reducing biogenic amines.
- While natural fermentation resulted in slightly higher protein hydrolysis, the M2 strain offers a viable alternative for controlled sufu production.
- The M2 strain of Mucor racemosa is suitable for sufu fermentation, leading to a product with potentially enhanced safety and desirable textural characteristics.
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