Mixing Science Into Mayo

Mayo may be a commonly used condiment, but it’s not simple to manufacture at a commercial scale. Some even say that making stable mayonnaise is more of an art than a science.

That includes a group of researchers in the Department of Food Science at the University of Tennessee, who teamed with two engineering students to explore the mysteries of mayonnaise making. They did the work at the request of a food industry partner who was having difficulty producing a consistent product, says Tao Wu, associate professor in the university’s Department of Food Science and coauthor of an article on the research that appeared in LWT—Food Science and Technology.

The company had a problem with the quality and stability of its mayo, which varied from batch to batch, and the team there didn’t know why, Wu explains. “This was actually really a surprise for me,” says Wu. “Oh, mayonnaise? Just blend all the ingredients together. What else do we need to do?”

The project was also part of the U.S. Department of Agriculture’s Research and Extension Experiences for Undergraduates program, which provides food science experience to engineering students.

Adding Acid

The key to consistent, stable mayo, the researchers found, is the acid. Vinegar is used in mayo to prevent microbial spoilage of the sauce, explains Tao, and it also provides unique sensory properties and taste. (Sometimes lemon juice is used instead.)

The researchers blended a simple recipe of soybean oil, water, frozen egg yolk, vinegar, salt, and sugar, explains University of Tennessee postdoctoral student and coauthor Min Li. The vinegar was separated into two amounts, one added pre-emulsification and the other afterward. The amounts ranged from no vinegar before emulsification and all of it post-emulsification down a scale of 20%:80%, 40%:60%, 60%:40%, 80%:20%, and 100% and none.

They then analyzed the resulting sauce, including its viscosity, microstructure, and stability. They found that adding more vinegar after the mix was emulsified resulted in firmer and more stable mayo, compared with adding it pre-emulsion. Most commercial mayonnaise production adds vinegar twice, once at the beginning and once at the end of the process.

Their lab mayo samples led the researchers to conjecture that the vinegar was changing the structure of the egg yolks. Egg yolk has the most important function because it acts as an emulsifier to stabilize the mix. “If you don’t have egg yolk, the emulsion will break,” Wu says.

So in a second trial, they mixed water, salt, and egg yolks with five varying amounts of vinegar and then examined what happened to the yolks. One effect of the vinegar was that it enlarged the size of the egg yolk particles; the more vinegar added, the larger the particle clusters that formed.

“The stability of the mayonnaise was associated with the structure of the egg yolk,” Li explains. “And the structure of the egg yolk can be affected by the amount of vinegar added before the emulsification.”

Li says she had not, in fact, tasted mayonnaise before this experiment. “I’m not a big fan of mayonnaise,” she admits.

The results are “really surprising,” adds Wu. “But in this way, we get a good firm and stable mayonnaise. The secret is we should add the vinegar at the end of the process.”

Continuing their mayo investigation, the researchers plan to work with their department’s sensory center. Sensory assessments are important to see if changing the vinegar step will impact consumer acceptance, says Wu. “We don’t know exactly how it will affect the sensory quality,” he says.

The paper has been shared with industry partners, says Wu, and the researchers are working with them to see if the lab results can be replicated in an industrial setting. “We are going to see if our data can really help them to improve the production process of mayonnaise,” he notes.