*3.7. Principal Component Analysis*

To further analyze the relationships among antibacterial activity, antioxidant activity, and TPC of spice extracts and to select suitable spice extracts with good antioxidant and antibacterial activities as food preservative candidates, principal component analysis (PCA) was performed to cluster factors, including TPC, FRAP, TEAC, and DIZ values against both *S. aureus* ATCC 25923 and *S. aureus* SJTUF 20978 (Figure 2). According to the results of Kaiser–Meyer–Olkin (KMO) and Bartlett's test (KMO value = 0.725, *p* < 0.05), as well as the communalities of factors with extraction >0.94, the data met the requirements of PCA. In addition, the cumulative variance contribution rate of the two main components (C1 and C2) extracted was 96.3%, with C1 counting for 55.6% and C2 being 40.7%. According to the rotated component matrix, C1 included the factors TPC, FRAP, and TEAC, suggesting that TPC was closely related to the antioxidant capacity. On the other hand, C2 contained DIZ values of *S. aureus* ATCC 25923 (DIZ1) and drug-resistant *S. aureus* SJTUF 20978 (DIZ2). More interestingly, C1 and C2 were clearly divided into two separate clusters (Figure 2), indicating there was no evident relationship of antibacterial capacity with antioxidant ability and TPC. These results were generally in agreement with those of the correlation analysis.

**Figure 2.** The results of principal component analysis (PCA). C1 included the factors total phenolic content (TPC), ferric-reducing antioxidant power (FRAP), and trolox equivalent antioxidant capacity (TEAC), suggesting that TPC was closely related to the antioxidant capacity. C2 contained DIZ values of *S. aureus* ATCC 25923 (DIZ1) and drug resistant *S. aureus* SJTUF 20978 (DIZ2). C1 and C2 were clearly divided into two separate clusters, suggesting that there was no evident relationship of antibacterial capacity with antioxidant ability and TPC.

Next, the general score (GS) of each sample was calculated based on the factor scores of the two principal components, following the equation GS = (C1 × 0.556 + C2 × 0.407)/0.963, and the results are shown in Table S1. Spice extracts with higher GS usually exhibited higher phenolic contents, antioxidant, and antibacterial activity. Based on the results listed in Table S1, clove extracts, prepared from both fruit and flower of clove, as well as cinnamon showed the highest GS values, indicating that they could be used as potential promising food preservatives by means of reducing microbial contamination and lipid spoilage oxidation simultaneously.
