The oxidative degradation of lipids in food is a key factor that limits their shelf life and acceptability [24]. Therefore, after incubation at 50 °C for 0, 48, and 96 h, the effects of EGCG on the primary (lipid hydrogen peroxide) and secondary (TBARS) oxidation products of the lipid oxidation resistance of the emulsion were studied. The amount of lipid hydrogen peroxide gradually increased with increasing storage time, indicating the oxidative degradation of unsaturated lipids (Figure 6A). The addition of EGCG indicates the excellent antioxidant properties of EGCG. The efficacy of the highest dose used (0.04%) was lower than that of the lower doses (0.01%, 0.02%, and 0.03%). After being treated with 0%, 0.01%, 0.02%, 0.03%, and 0.04% EGCG for 96 h, the content of lipid hydrogen peroxide is 369.95 ± 5.47 mmol/kg oil, 93.78 ± 2.97 mmol/kg oil, 104.89 ± 3.88 mmol/kg oil, 107.48 ± 2.47 mmol/kg oil, and 145.89 ± 4.12 mmol/kg oil, respectively. This result indicates that the addition of polyphenols must be optimized to be as effective as possible. This is advantageous because fewer antioxidants are added to the system. The active groups in EGCG can scavenge free radicals by contributing their hydrogen atoms to form reactive phenoxy groups [44]. More importantly, the complex formed between protein and EGCG can enhance the antioxidant activity of WBMP and significantly improve its ability to scavenge free radicals [45]. However, we found that excess EGCG caused it to change from an antioxidant to an oxidative factor. This has also been confirmed in previous studies [46]. This could be due to endogenous iron increasing in the form of Fe2+ [47]. The effect of EGCG addition on TBARS formation (Figure 6B) was similar to that of lipid hydrogen peroxide (Figure 6A). The addition of EGCG significantly reduced the production of secondary reaction products during storage (p7]. The antioxidant activity of EGCG decreased with increasing concentration. Taking the emulsions with EGCG contents of 0%, 0.01%, 0.02%, 0.03%, and 0.04% as examples, the TBARS concentrations after 96 h were 2.18 ± 0.17 μmol/kg oil, 0.37 ± 0.07 μmol/kg oil, 0.38 ± 0.07 μmol/kg oil, 0.38 ± 0.05 μmol/kg oil, and 0.79 ± 0.07 μmol/kg oil, respectively. We demonstrated that EGCG could effectively inhibit lipid oxidation in the WBMP emulsion system. Therefore, an excessive concentration of EGCG promotes lipid oxidation and affects the storage properties of emulsions.The chemical reaction substances produced by lipid oxidation may promote the oxidation of proteins. Polyphenols (EGCG) can combine with proteins to change their structure and surface chemistry properties to change their oxidation sensitivity [26]. We determined the effect of EGCG on protein oxidation in emulsions. The two most significant modifications of carbonyl and sulfhydryl derivatives after protein oxidation are the acquisition of carbonyl groups and the loss of sulfhydryl groups [48]. However, the addition of EGCG changed the degree of protein oxidation in the emulsions. The addition of 0.03% EGCG significantly reduced carbonyl formation (pFigure 6C), indicating that this level inhibited protein and lipid oxidation. The inhibitory effect of EGCG on protein carbonylation might be related to its ability to scavenge free radicals and chelate transition metal ions [49]. They can bind to protein molecules and produce phenolic protein complexes. However, increasing the concentration of EGCG in the emulsion will lead to increased carbonyl formation, indicating that higher concentrations promote protein oxidation. Taking 0%, 0.01%, 0.02%, 0.03%, and 0.04% EGCG as examples, the carbonyl contents in the emulsion after 96 h storage were 19.69 ± 1.78 nmol/mg of protein, 18.46 ± 1.88 nmol/mg of protein, 13.78 ± 1.78 nmol/mg of protein, 9.03 ± 0.96 nmol/mg of protein, and 23.48 ± 1.22 nmol/mg of protein, respectively. Protein oxidation is promoted at high doses (e.g., 200 μM) [50]. The EGCG concentration also affected the degree of sulfhydryl consumption in the emulsion (Figure 6D). The sulfhydryl contents in the emulsions of 0%, 0.01%, 0.02%, 0.03%, and 0.04% EGCG were 20.11 ± 1.06 μmol/g of protein, 32.15 ± 1.99 μmol/g of protein, 38.96 ± 2.78 μmol/g of protein, 59.12 ± 2.98 μmol/g of protein, and 17.69 ± 1.98 μmol/g of protein, respectively. This result showed that appropriate doses of EGCG (0.03%) had the highest antioxidant capacity, which was consistent with the measurement of carbonyl formation (Figure 6C). EGCG inhibits lipid oxidation more effectively than protein oxidation [16]. Among them, 0.03% EGCG had a more advantageous effect on fat and protein oxidation. However, when the addition of EGCG increased to 0.04%, the antioxidant effect was greatly decreased and further promoted oxidation. This could be due to the presence of high concentrations of polyphenols enhancing the binding of transition metals to the protein surface [51].