Quality Analysis and Evaluation of Shrimp paste in China

Shrimp paste, a traditional aquatic fermented product, is more prevalent in Southeast Asia and the coastal areas of China. The traditional shrimp paste production process is straightforward. Usually, small economic shrimp species, such as grasshopper and sesame shrimp, are used as raw materials. Microorganisms and a series of endogenous enzymes are relied upon to create a condiment with a distinct flavor and aroma via natural fermentation. The quality of shrimp paste is influenced by various factors, including the type of raw shrimp used, the freshness of raw materials, fermentation duration, fermentation temperature, salt addition, and storage time. There are several brands of shrimp paste in the market, but their quality varies significantly. There are no studies on the quality evaluation system for commercially available shrimp paste. In this study, a comprehensive evaluation of shrimp paste samples was conducted to investigate the quality differences among commercially available shrimp pastes. 32 brands of shrimp paste were collected from six provinces, namely Shandong, Guangdong, Hebei, Tianjin, Liaoning, and Jiangsu. The color and histomorphology of these samples were assessed via sensory evaluation, whereas their physicochemical indicators, such as moisture, salt, protein, and amino acid nitrogen, were determined. Principal component analysis was utilized to create a comprehensive ranking of 32 commercially available shrimp pastes. The results showed that the odor score of commercially available shrimp paste had the highest coefficient of variation value at 37.64%, indicating that the odor of different brands of shrimp paste varied significantly. The SC/T 3602-2016 "Shrimp paste" standard states that the moisture content of shrimp paste should be ≤ 60%, ash content should be ≤ 35%, salt content should be ≤ 25%, protein content should be ≥ 10.0 g/100 g, and amino acid nitrogen content should be ≥ 0.6 g/100 g. The minimum variation value for the moisture content of shrimp paste products was 12.17%, but the overall moisture content was high, with seven samples exceeding the standard limit by a significant margin. In the shrimp paste production process, with the extension of the fermentation time, the moisture content gradually reduced, and the water activity decreased. The high moisture content of individual samples could be related to the production process that shortens the fermentation cycle of shrimp paste. A total of 32 samples had ash content ≤ 35%, in accordance with the standard requirements of "shrimp paste". Fifty percent of commercially available shrimp paste samples had salt content values greater than 20%, indicating that most commercially available shrimp pastes were high in salt concentrations. Since a diet high in salt may lead to a series of health problems, such as increased blood pressure, reducing the salt content of traditional shrimp paste is more in line with modern consumer values. The protein content of 28 samples met the requirements, and the amino acid nitrogen content of 31 samples met the requirements. The maximum variation value of amino acid nitrogen content was 33.91%, indicating a large difference in amino acid nitrogen content between samples. The amino acid nitrogen content of 78.13% of the shrimp paste samples was greater than 1.0 g/100 g, and a few shrimp paste samples even exceeded 2.0 g/100 g, which was significantly higher than the amino acid nitrogen content of fish sauce and comparable to that of commercially available oyster sauce. Through principal component analysis, three principal components representing eight quality indicators of 32 commercially available shrimp pastes were extracted based on the principle of principal component eigenvalues greater than 1, and the cumulative variance contribution reached 82.32%, indicating that the majority of the information regarding shrimp paste quality indicators could be covered. Through further analysis, it was determined that moisture, amino acid nitrogen, and odor were important indicators affecting the overall quality of shrimp paste, and a comprehensive evaluation model was established as follows: Fsynthesize= 0.497F1 + 0.318F2 + 0.185F3, in order to investigate the differences in the odor composition of different shrimp pastes in greater detail. The samples were subjected to an e-nose analysis, and an e-nose clustering heat map was developed; the results showed that 32 shrimp sauces were clustered into four categories at a Euclidean distance of 4.03, with the main distinction lying in the W1S, W2S, and W3S sensors, and clustering occurred between the sea silver shrimp sauce and grasshopper shrimp sauce. Gas-ion mobility spectrometry (GC-IMS) analysis of shrimp paste derived from three raw materials (i.e., sea silver shrimp, grasshopper shrimp, and white shrimp) showed the presence of 63 volatile components, mainly different alcohols. The high content of alcohol contained in the flavor substances is consistent with the findings of several previous studies. The results indicated that the quality of commercially available shrimp paste differed significantly, with odor, moisture, and amino acid nitrogen being the most influential factors affecting quality. The results of the study provide a benchmark for the quality assessment and production process enhancement of shrimp paste.