## 3 Results and Discussion
### The Results of Chemical Analyses
They were used as indicators of quality degradation and spoilage of fish burgers due to bacterial activity and amino acid decarboxylation. The initial TVB-N of the control burger was 14.71 \(\pm\) 0.10 mg/100 g, while burgers with extracts had significantly lower initial TVB-N, ranging from 13.64 \(\pm\) 0.02 to 14.35 \(\pm\) 0.14 mg/100 g. A slight increase was recorded in all burgers at the end of the storage period. However, the control burger had the highest values, 22.77 \(\pm\) 0.19 mg/100 g, while JB and BCV burgers had lower final values than the initial values for the control burger, at 16.89 \(\pm\) 0.21 mg/100 g and 15.38 \(\pm\) 0.45 mg/100 g, respectively. A similar trend was also observed for the TMA values. The control burger's initial TMA (8.37 \(\pm\) 0.15 mg/100 g) was insignificantly higher than the initial TMA for burgers with extracts. These values are also higher than those once reported for high-quality fresh fish of <2 mg/100 g [49]. TVB-N and TMA were previously reported to be <60 mgTVB-N/100 g and <40 mg TMA/kg in hake with high initial microbial loads and during storage at 4 \({}^{\circ}\)C [50]. On the other hand, the shelf life of whole unguttted hake in ice was established at 8 to 10 days, and TMA values of 5 mg/100 g were proposed for an unacceptable grade of quality [49]. The difference from our results could be because of the mix of two different species and the addition of salt to the minced meat. At the end of the storage period, the control burger had the highest TMA value, 18.37 \(\pm\) 0.38 mg/100 g, while the lowest TMA was recorded for the BCV burger. The BCV burger had a lower final TMA value (10.64 \(\pm\) 0.28 mg/100 g) than the initial TMA value for the control burger. Figure 3: The results of thiobarbituric acid reactive substances (TBARS) analyses of burgers over 13 days of storage at 0 \(\pm\) 2 \({}^{\circ}\)C. CON—burger without extracts; JB—burger with 2% of 1:2 common juniper by-product/blackberry leaves extract; PCJ—burger with 2% of 1:1. _Padina paponica_/prickly juniper needles extract; BCV—burger with 2% of 2:1:1 blackberry leaves extract/catechin/vanillic acid. Typically, TVB-N and TMA values vary depending on the size of the fish, its microbiological quality, as well as handling and storage conditions [16; 40]. The results showed that these natural extracts slow the accumulation of TVB-N and TMA in fish, preserving the fish muscle's nitrogenous compounds from degradation. There are a limited number of studies that investigated these particular extracts. In MAP-packed sea bass fillets treated with the Padina extract, TVB-N and TMA values were significantly lower compared to untreated controls [16]. [PERSON] [46] reported that juniper oil and vacuum packaging kept  
Figure 4: The results of total volatile base nitrogen analyses of burgers over 13 days of storage at 0 \(\pm\) 2 \({}^{\circ}\)C. CON—burger without extracts; JB—burger with 2% of 1:2 common juniper by-product/blackberry leaves extract; PCJ—burger with 2% of 1:1 _Padina provonica_/prickly juniper needles extract; BCV—burger with 2% of 2:1:1 blackberry leaves extract/catechin/vanillic acid. Figure 5: The results of trimethylamine nitrogen analyses of burgers over 13 days of storage at 0 \(\pm\) 2 \({}^{\circ}\)C. CON—burger without extracts; JB—burger with 2% of 1:2 common juniper by-product/blackberry leaves extract; PCJ—burger with 2% of 1:1 _Padina provonica_/prickly juniper needles extract; BCV—burger with 2% of 2:1:1 blackberry leaves extract/catechin/vanillic acid. TVB-N and TMA below spoilage limits far longer than in untreated fish. Initial TVB-N in trout fillets was 12 mg/100 g, and juniper-treated samples stayed under the acceptable spoilage limit of 25-30 mg/100 g for the entire 28-day storage, whereas controls exceeded this limit much earlier and treated fillets did not reach the typical spoilage odor, correlated with TMA. Additionally, tea polyphenols significantly delayed the formation of volatile bases in carp fillets [47].