Rapid detection of freshness of aquatic products based on electronic tongue technology
Aquatic products are delicious and unique in flavor. However, because they are rich in water, protein and unsaturated fatty acids, they are easily oxidized and deteriorated during storage and processing, which leads to their unique taste gradually becoming worse. At present, the main methods of fish freshness test include sensory evaluation, total number of colonies, and physical and chemical index detection (such as K value, total volatile nitrogen, etc.). Among them, sensory evaluation is relatively quick and simple, but it is easily affected by subjective factors and has certain limitations. It is difficult to achieve real-time detection. Therefore, it is of great significance to explore a fast and accurate method to evaluate the freshness of aquatic products.
In order to study the changes of flavor substances of Takifugu binmaculatus during refrigeration and to establish a method for rapid detection of freshness of Takifugu binmaculatus, Fujian Agriculture and Forestry University determined and analyzed flavor substances of Takifugu binmaculatus during different refrigeration periods (0℃ and 4℃), and took the total number of colonies (TVC) as the criterion for determining freshness of fish. The response value of the electronic tongue sensor was the dependent variable. Partial least square method (PLSR) and multiple linear regression method (MLR) were used to establish a TVC prediction model which could be used to distinguish the freshness of Takifugu bifaculatus during different refrigeration periods. The results show that the electronic tongue technique can be used as a rapid method to detect the freshness of Takifugu bifaculatus during refrigeration.
Testing equipment: TS-5000Z electric tongue system, Insent of Japan
Analysis of experimental results
The results of the electronic tongue response to fish taste during storage at 4℃ and 0℃ are shown in the figure. As can be seen from the figure, during the whole refrigeration process, the response profiles of the 8 sensors in the 0℃ group and the 4℃ group are roughly similar, but the response values are significantly different, indicating that different sensors have different sensitivities to fish at different storage periods
As shown in the figure, during storage at 4℃ and 0℃, the signal intensity of umami showed a general downward trend, and at the later stage of Takifugu bimaculatus storage, the signal intensity of umami and bitter were mainly sour and bitter, and the changes of the signal intensity of umami and bitter amino acids were consistent with the changes of umami and bitter amino acids.
The electric tongue response values of Takifugu bimaculatus were analyzed by PCA with PC1 as the horizontal coordinate and PC2 as the vertical coordinate. As can be seen from the figure, the total contribution rates of the first two principal components in the 4℃ and 0℃ groups were 98.30% and 98.90%, respectively, and the taste characteristics of fish in different periods of refrigeration were well distinguished.
According to the factor loading diagram, the fish of the two groups were mainly umami in the early stage of refrigeration (1d). The results showed that the taste and quality of Takifugu bimaculatus changed greatly when refrigerated at 0℃ and 4℃ for 7 and 5 days. The results of TVC showed that the shelf life of Takifugu fish was 7 days and 5 days at 0℃ and 4℃ respectively, which was mutually confirmed with the test results of electronic tongue, indicating that electronic tongue technology can be used to detect and identify the freshness grade of Takifugu fish in the process of refrigeration.
Conclusion: The electronic tongue can effectively distinguish fish with different freshness grades, and the analysis results are consistent with the TVC detection results. The above results indicate that the electronic tongue technology can be used for the rapid detection of the freshness of the refrigerated Takifugu bimaculatus.
