When sourcing mayonnaise, the oil content is the primary indicator of quality; standard mayonnaise typically contains 70-80% vegetable oil (soybean, sunflower, or canola). You must verify the emulsification stability to ensure the product does not separate during transit. Additionally, check the pH levels (usually between 3.3 and 4.5) to ensure microbial safety and the viscosity (measured in centipoise) to match your specific application, whether it is for dipping, spreading, or industrial food processing.