## 3 Results and Discussion  
### Mass Yield, pH and Salt Concentration  
The mass of herring marinated by the German method (G-) decreased by day 14 (Figure 2A), which was caused by a decrease in meat pH close to the isoelectric point and in the resulting loss of water (Figure 2B). The mass of German marinades significantly correlated with marinating time, most strongly for G-whole r = \(-\)0.987 (Figure 3A). In the case of the Danish (D-) method, the yield increased after 2 days due to protein salting and moisture increase, but when acetic acid was added, fish mass and moisture significantly decreased (Figure 2A,B). The mass of Danish marinates also significantly correlated with marinating time, but the correlation was lower than that of German marinates. After 4-7 days of marinating, the mass yield of G-fillets marinades averaged 78.7%, while G-headed and G-whole marinades had higher yields of 4.1 and 15.0 percentage points, respectively (Figure 2A). At the same time, D-fillets marinades had an average mass yield of 83.3%, while D-headed and D-whole marinades were 4.7 and 9.1 percentage points higher, respectively. Thus, the advantage of higher mass yield of the Danish method over the German method when marinating fillets [9] was not present in the case of marinating whole herring.  
G-fillets marinades after 4-7 days of marinating had an average meat pH value of 3.91, while G-headed and G-whole had 4.16 and 4.26, respectively (Figure 4A). The pH value significantly correlated with the decreasing mass of German marinades: G-whole (0.973), G-fillets (0.891) and G-headed (0.871) (Figure 3A,C,E). The D-fillets marinades had a meat pH of 3.88, while the D-headed and D-whole marinades had a pH of 4.22 and 4.38, respectively. The pH values of D-filleds, D-headed and D-whole marinades significantly correlated with a mass yield of 0.991, 0.877 and 0.750, respectively (Figure 3B,D,F). The content of table salt after 4-7 days of marinating in the meat of G-fillets marinades was 2.96% and was 0.07-0.17% higher than in G-whole and G-headed marinades (Figure 4B). For marinating using the Danish method, the differences in salt content between D-fillets marinades (2.80%) and D-headed (2.38%) and D-whole (2.16%) marinades were higher than that of the German method (Figure 4B). PCA analysis showed that the higher the degree of primary processing of the herring (whole \(<\) headed \(<\) filllets), salt concentration correlated less strongly with the mass yield of marinades performed by the German method (G-whole \(-\)0.820, G-headed \(-\)0.801, G-fillets \(-\)0.469) (Figure 3A,C,E), in contrast to Danish  
Figure 2: Effect of marinating method and degree of primary processing of Baltic herring (whole, headed, filllets) on (**A**) mass yield and (**B**) moisture during marinating. G—German method, D—Danish method. \({}^{\text{a,b,c}}\) Results marked with the same lower case letter do not statistically differ by the influence of marinating time; \({}^{\text{A,B,C}}\) Results marked with the same capital letter do not statistically differ by the influence of the marinating method.  
method (D-whole 0.750, D-headed 0.877 and D-fillets 0.991) (Figure 3B,D,F). Therefore, in marinades made of whole herring, the skin reduced the loss of water and protein from the meat [30], and also reduced the diffusion of acetic acid and salt into the meat (Figure 4A,B), which synergistically reduced the water holding capacity of the marinated meat [31].  
Figure 3: PCA biplot for correlations between protease activity, physicochemical parameters and sensory analyses of marinades depending on marinating methods: (**A**,**C**,**E**) German method (G-), (**B**,**D**,**F**) Danish method (D-) and depending on degree of primary processing of Baltic herring: (**A**,**B**), fillets of herring, (**C**,**D**) headed herring and (**E**,**F**) whole herring.