When thinking about what makes different foods pleasurable to eat, taste and texture will always come to mind. But the noise a morsel makes between one’s teeth can be just as important to the experience. What’s a potato chip without that characteristic crispiness? Or a pickle without the soft snap? And, as many Wisconsinites will assert, a cheese curd is not truly a curd (or at least not a fresh one) unless it squeaks.

Unfortunately, curds typically lose their signature squeak within a few days to a couple of weeks, depending on how they’re stored (room temperature or refrigerated) and served (warmed or cold). That’s why a Center for Dairy Research (CDR) team, led by scientist Rani Govindasamy-Lucey, is looking to extend the shelf life of the squeak that consumers have come to expect.

First, the researchers needed a way to gauge squeakiness. They collaborated with professor Nike Gnanateja from UW’s Speech Processing and Auditory Neuroscience Laboratory (SPAN Lab) to develop a method for measuring the acoustic properties of cheese squeaks. The method is based on analysis of roughly 5,200 recordings of people chewing fresh or aged curds, which revealed clear auditory distinctions between squeaky and non-squeaky samples. Using these recordings, the researchers created a squeakiness metric, and they trained sensory panel participants to characterize squeakiness.

The team also explored different manufacturing treatments for cheese curds. They suspected that acidification caused by starter cultures may quickly weaken the protein structure of traditional cheddar-based curds and eliminate their squeak. Another process, called proteolysis, was thought to weaken the protein matrix through the actions of native milk enzymes and residual rennet (an enzyme used in cheesemaking because it curdles milk).

“So, instead, we took inspiration from a Finnish cheese that has a long-lasting squeak — Juustoleipä, sometimes called ‘bread cheese’,” says recent food science graduate Maggie Becher PhD’24, who helped lead the study. “Juustoleipä does not include any form of acidification, and it’s baked at high temps after it’s made.”

The team used this cheesemaking style for their research on cheese curds. But Juustoleipä can still be susceptible to proteolysis, so the team focused on the potential relation of that process to squeakiness. Their analysis of Juustoleipä curds found that proteolysis increased during storage, but it occurred much more slowly in samples that were baked at high temperatures. The team also found that increases in proteolysis detracted from measured squeakiness levels.

“Now we know how to quantify squeakiness, and we understand what causes the loss of squeakiness,” Govindasamy-Lucey says. “This is valuable data for cheese manufacturers looking to keep consumers happy with squeaky cheese that lasts longer.”

This project was supported with funding from the Dairy Innovation Hub, Dairy Farmers of Wisconsin, and Dairy Management Inc.