Effect of Metal Salts on the Immersion Method for the Preparation of Preserved Eggs
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Abstract:
Using duck eggs as raw material, the effects of the type and amount of added metal salts on the quality of preserved eggs were studied by comparing the safety performance and sensory quality of preserved eggs prepared by the immersion method, using different metal salt solutions. The experimental results showed that good sensory quality was obtained in preserved eggs prepared by the addition of CuSO4, ,CuSO4:ZnSO4 = 1:1, or ZnSO4:FeSO4 = 1:1, with evaluation scores of 90.6 ± 2.4, 89.8 ± 3.2, or 88.2 ± 2.7, respectively. The sensory quality of the preserved egg prepared by the addition of ZnSO4 was slightly lower, with an evaluation score of 85.80 ± 3.80. Low sensory quality was obtained in preserved eggs prepared by the addition of FeSO4 or MgSO4. For the preserved eggs prepared by the addition of CuSO4: ZnSO4 = 1:1, the concentrations of residual zinc and copper ions (Cu2+: 4.12±0.11 mg/kg, Zn2+: 8.32±0.19 mg/kg) were significantly lower than those of preserved eggs prepared by the addition of zinc salt (Zn2+: 12.96 ± 0.22 mg/kg) or copper salt (Cu2+: 8.55 ± 0.28 mg/kg). The impacts of different zinc salts on the sensory quality of the preserved eggs were different. The concentration of residual zinc ions (Zn2+: 9.27 ± 0.09 mg/kg) and sensory evaluation score of preserved eggs prepared by adding zinc oxide were significantly lower than those of preserved eggs prepared by adding other zinc salts. Based on this comprehensive evaluation, ZnSO4 was found to be a suitable zinc salt for the preparation of preserved eggs. For preserved eggs prepared by the addition of CuSO4 or CuSO4:ZnSO4=1:1, the runny-yolk index was high (0.66 or 0.57, respectively), with good elasticity, hardness, and chewiness. Therefore, considering the sensory quality and the level of metal residues, the qualities of preserved eggs prepared by the immersion method, using CuSO4 and ZnSO4 solutions, were relatively good, while the addition of FeSO4 alone was not suitable for the preparation of preserved eggs.
