Many people enjoy a tender piece of beef, but few know what makes the meat tender.

ISU researchers are working to find ways to increase the tenderness for meat-loving consumers.

The tenderness of a cut of beef is directly related to the breakdown of the muscle cells, said Richard Robson, professor of animal science and biochemistry, biophysics and molecular bio-agriculture.

Calcium present in the cells activates enzymes, called calpaines, that begin the breakdown process, he said.

“The question is, `How can we capture more value by refining the system and by being able to better classify and understand the mechanisms?'” said Steven Lonergan, assistant professor of animal science.

The research is being conducted from both ends of the cattle industry.

Researchers are looking at how to increase tenderness at the cellular level and during the butchering process.

When the cell breaks down, it loses ordered structure, Robson said, and the samples with more degradation perform better in taste tests.

“We are looking at what specific proteins are broken down in this process to cause this destruction [in the cell] and at what rate it is occurring,” said Elisabeth Lonergan, assistant professor of animal science and Steven’s wife.

A natural inhibitor called calpastatin holds up the process of the calpaines breaking down the cells.

This acts like the brakes in the cell-degradation process. When calpastatin is found in high levels, the cells don’t break down to become tender, Steven Lonergan said.

The research could lead to testing of breeding stocks for traits that signify increased tenderness in their offspring during the butchering process.

“Ultimately, we could find genetic markers that would tell us which cattle have a high probability” of having offspring that would grade out a high tenderness, Steven Lonergan said.

Breeders could then select breeding stock that are genetically predisposed to tenderness in the same way they select stock on birth weight, Elisabeth Lonergan said.

“There is more variation within a breed than among the breeds when it comes to tenderness,” Steven Lonergan said.

The rate at which the cell breaks down affects the development of the tenderness, he said. This rate is what plays a role in the meat-processing industry.

“If we could speed up the process, the meat wouldn’t have to hang for two weeks,” Elisabeth Lonergan said. “It might only be two or three days. This would be a big advantage to the [meat] packers.”

Other components that affect the tenderness are the postmortem procedures, she said. Elements such as environment, temperature and time until freezing all affect tenderness, Elisabeth Lonergan said.

There has been a great deal of industry interest in this research. The U.S. Department of Agriculture’s National Research Initiative Competitive Grants Program has several different subdivisions.

Two of these divisions, growth and nutrient utilization and production, are used at Iowa State, Elisabeth Lonergan said.

The research conducted at Iowa State is done with a large group of people, Robson said. There are many graduate and undergraduate students and faculty members who work in the labs on the research, he said.

“We want to produce a quality product,” Steven Lonergan said, “but we also want to produce it efficiently.”