1. Amino acid nitrogen (calculated as nitrogen)/(g/100mL): first grade ≥ 0.7, special grade ≥ 1.0; 2. Total acid (calculated as lactic acid) / (g/100mL): first grade ≤ 2.5, special grade ≤ 2.2 ; 3. Total nitrogen (calculated as nitrogen)/g/100mL): first grade ≥ 1.35, special grade ≥ 1.6; 4. Soluble salt-free solids / (g/100mL): first grade ≥ 20.00, special grade ≥ 22.00