In order to improve the fermentation process of the emerging commercial low-salt shrimp paste, this study systematically analyzed the changes in the major quality indicators during the fermentation process. High-throughput sequencing technology was used to analyze the microbial community diversity and composition. The results showed that during the fermentation of shrimp paste, the pH, malondialdehyde (MDA) content, total volatile basic nitrogen (TVBN) content, amino acid nitrogen content, moisture content, salt content and biogenic amine content fluctuated in the range of 7.19–6.90, 3.09–5.56 mg/kg, 44.81–175.05 mg/100 g, 1.42–1.63 g/100 g, 59.19%–62.40%, 11.02%–12.04% and 0–113.29 mg/kg, respectively. The MDA content increased and then subsequently decreased. The contents of amino acid nitrogen, TVBN and biogenic amines all showed an increasing trend. At the middle and late stages of fermentation, the bacterial diversity indexes decreased significantly, and the fungal diversity indexes decreased slowly. At the early stage of fermentation (0–7 days), Streptococcus and Lactobacillus were the dominant bacterial genera. During the middle and late periods (34–145 days), Tetragenococcus was the dominant bacterial genus and was differential between the three stages of fermentation. Trichosporon was the dominant fungal genus at the early stage of fermentation. At the middle stage, Candida and Alternaria became the dominant genera. At the late stage, Candida became the dominant genus, and no significantly differential fungal genera were found between the three fermentation stages. The Spearman correlation heat map showed that compared with the fungus genera, the bacterial genera had a higher correlation with the physiochemical indicators, indicating that the bacterial community was dominant in the fermentation process. Tetragenococcus was positively correlated with the TVBN, amino acid nitrogen, and MDA contents; Streptococcus was significantly negatively correlated with the content of biogenic amines. Starting from the 64^th day, the quality indicators and microbial community of the shrimp paste remained basically stable, suggesting that shortening the fermentation time can be considered as an option to improve the fermentation process. These results provide a theoretical basis for improving the fermentation process of low-salt shrimp paste.

In order to develop new shrimp paste products and expand the shrimp paste market, ginger, cinnamon or perilla was added before fermentation of low-salt shrimp paste in this study. The physicochemical indexes of low-salt shrimp paste were determined, and the effect of spice addition on the microbial community composition and diversity of shrimp paste was explored by high-throughput sequencing technology. The results showed that the contents of moisture and salt in shrimp paste were 51.34%–61.77% and 15.61%–17.71%, respectively. The addition of spices decreased the pH and amino nitrogen content of shrimp paste. The addition of cinnamon and ginger reduced the total volatile basic nitrogen (TVB-N) content by 30.41% and 10.28%, respectively, while the addition of perilla increased the TVB-N content by 9.98%. Compared with the control shrimp paste, the diversity of fungi and bacteria in shrimp paste added with perilla was higher. The addition of cinnamon and ginger decreased the richness of bacterial community and increased the richness of fungal community in shrimp paste. The analysis of differential flora showed that the addition of ginger and cinnamon increased the relative abundance of Tetragenococcus and Wallemia, but reduced the relative abundance of Staphylococcus by 99.32% and 98.14%, respectively. The relative abundance of Penicillium and Aspergillus in shrimp paste added with perilla was higher. Pearson correlation analysis showed that Staphylococcus, Wallemia, Rhodotorula and Penicillium had significant correlations with physicochemical indicators, indicating that these microorganisms play an important role in shrimp paste. To sum up, the addition of spices can change the microbial community composition of shrimp paste, enrich the types of shrimp paste and improve the safety of shrimp paste.