# Correlation between Biogenic Amines and Their Precursors in Stored Chicken Meat
## 3 Results
### Correlations and Principal Component Analysis (PCA)  
PCA was carried out to determine the changes in BA levels and their precursor amino acids over meat storage time. Within the PCA framework, the data from each amino acid and the BA content at every analysis interval were transformed into two new orthogonal variables, denoted as \"principal components\" (PC1 and PC2). The relationships between the parameters and the PCs were interpreted according to the correlations between them. Figure 1 shows the PCA for breast muscles (A) and leg muscles (B). For the breast muscles (Figure 1A), PC1 and PC2 account for 79.73% of the variability in BA levels and their precursors during the evaluated periods, leading to a 20.27% data loss. The primary component (PC1) was positively correlated with spermine, TOTAL BA-2, tyrosine, ornithine, and phenylethylamine levels while showing an inverse relationship with the rest of the BAs and AAs present in the breast muscle. Conversely, the secondary component (PC2) was negatively correlated with TOTAL BA-2, spermine, spermidine, arginine, phenylethylamine, histidine, tryptophan, and the sum of precursors of BAI and positively correlated with the remaining amines and amino acids. In the context of leg muscles (Figure 1B), PC1 and PC2 capture 86.23% of the variance observed in the levels of BAs and their precursors at the measured intervals, resulting in a 13.77% information deficit. Concentrations of spermine, spermidine, TOTAL BA-2, arginine, tyrosine, histidine, phenylethylamine, and the sum of precursors of BAI were positively correlated with PC1. Meanwhile, PC2 is positively correlated with levels of ornithine, putrescine, histidine, and phenylethylamine. Table 3 summarizes the correlations between BAs and precursor AAs. In the breast muscle, a negative correlation was observed between ornithine and putrescine (\(\mathrm{r}=-0.57\)) (\(p<0.05\)) and between ornithine and spermidine (\(\mathrm{r}=-0.73\)) (\(p<0.05\)). A negative correlation was also found for phenylethylamine and its precursor (\(\mathrm{r}=-0.50\)) (\(p<0.05\)). The content of phenylethylamine in the breast muscles negatively correlated with the level of tryptophan (\(\mathrm{r}=-0.90\)) and with the sum of the precursors of BAI (\(\mathrm{r}=-0.92\)) (\(p<0.05\)). In leg muscles, correlations were noted for histamine and its precursor histidine (\(\mathrm{r}=-0.87\)) (\(p<0.05\)) and between putrescine and ornithine (\(\mathrm{r}=-0.96\)) (\(p<0.05\)). Ornithine in leg muscles also correlated with spermine (\(\mathrm{r}=-0.95\)), spermidine (\(\mathrm{r}=-0.95\)), and TOTAL BA-2 (\(\mathrm{r}=-0.90\)) (\(p<0.05\)). A negative correlation was again found for phenylethylamine and its precursor (\(\mathrm{r}=-0.65\)) (\(p<0.05\)). Furthermore, the analysis revealed positive correlations for ornithine with tryptamine (\(\mathrm{r}=0.89\)) and agmatine (\(\mathrm{r}=0.95\)), and for arginine with TOTAL BA-2 levels (\(\mathrm{r}=0.89\)) (\(p<0.05\)). Figure 1: First two components of PCA for biogenic amines and their precursors in breast (A) and leg (B) chicken meat during storage.