Sensory Evaluation Workshops Train Industry to Assess Tuna, Mahi and Shrimp Quality

March 8, 2005

Contact: Marsha Gear, Communications Director, mgear@ucsd.edu, 858-534-0581

On Nov. 3-4, 2004, California Sea Grant, in partnership with the National Fisheries Institute, Department of Commerce Seafood Inspection Program and the FDA, offered two sensory evaluation workshops for U.S. seafood importers, processors, overseas exporters and third-party seafood inspectors. The workshops, held at the Seafood Inspection Program’s Western Inspection Office in Bell, Calif., focused on teaching attendees how to assess the quality of three popular seafoods – tuna, mahi and shrimp.

Tuna on Plate. Credit: Christina Johnson

Sensory evaluation is a technical term for a simple idea: A person’s senses – sight, smell, taste and touch – can be trained to detect properties of seafood indicating freshness or, on the other side of the spectrum, spoilage and improper handling. Traditional meat and poultry inspections also employ sensory evaluation, as USDA inspectors visually examine, touch, and smell animal parts to detect signs of disease or contamination.

Each plate on the table (above) has a piece of fish on it of varying quality. Based on odor, color and

Tuna. Credit: Christina Johnson

texture, workshop attendees assigned a numerical score to each sample, indicating whether it would pass FDA standards. All seafood sold in America, including imports, must meet FDA standards.

One of the main food quality issues that can be evaluated organoleptically (with the senses) is decomposition. Decomposition may occur if seafood sits too long before being frozen or refrigerated and may pose health hazards to seafood consumers. Sensory evaluation courses are designed to teach industry professionals how to tell whether a shipment of seafood will pass or fail FDA standards on decomposition.

In the first workshop, participants focused on evaluating fresh-frozen tuna and mahi steaks. The second workshop was dedicated to evaluating the quality of shrimp products.

High-quality tuna steaks typically have a uniform color and texture, a translucent or glassy appearance and are firm and moist. Looks, however, can be deceiving. Take for example, the tuna steak you see here (above). Although this particular sample looks attractive, it smells strongly of burnt plastic and would be deemed unfit for human consumption by FDA standards. In this particular case, the plastic odor is not associated with decomposition but may be a result of improper filtering of smoke used to treat tuna and mahi.

Tuna steaks are often treated with carbon monoxide, a gas and component of smoke that reacts with heme proteins in fish meat, imparting a bright cherry color to flesh. Most of the samples that attendees inspected during the course of the workshop were treated with carbon monoxide, including the sample in the photo above.

After attendees tried their hand at scoring fish samples, James Barnett, the FDA’s national sensory expert, discussed how he would have scored each sample. “P” denotes pass while “F” denotes fail. The most difficult samples to score correctly were the borderline ones, the “F/P” and “P/F” samples. Group discussions addressed how to score and think about these borderline cases, which can result in discarding “good” fish or passing “bad” fish.

“You cannot get this kind of training from a book,” said Seafood Extension Program Manager Ms. Pamela Tom of California Sea Grant Extension at UC Davis. “You have to be trained by a master or an expert.” And that is what these classes do. They provide one-on-one training with experts: “nose-on” experience.

Shrimp. Credit: NOAA

The sensory evaluation course on shrimp focused on teaching participants how to evaluate three species of shrimp sold in the United States – black tiger shrimp, Mexican white shrimp and Mexican brown shrimp.

According to NOAA Fisheries, Americans ate a record 16.3 pounds of fish and shellfish per person in 2003, compared with 14.9 pounds in 1998. The single most popular seafood item in 2003, and in recent years, was shrimp. Per capita shrimp consumption was 4 pounds in 2003, compared with 2.8 pounds in 1998. Canned tuna was the second most commonly eaten seafood at 3.4 pounds per person per year.

More than 80 percent of the seafood that Americans consume is imported. About 160 countries export seafood to the United States.

Seafood Extension Program Manager Ms. Pamela Tom of the California Sea Grant Extension Program

Pam Tom: Christina Johnson

at UC Davis helped organize the sensory workshops. She stands beside Leonard Shanks, US Department of Commerce, Seafood Inspection Program, who led group discussions on evaluating seafood quality.

Ms. Tom is currently coordinating a shrimp sensory evaluation course to be held in January in Thailand. The Vietnamese Association of Shrimp Exporters and Producers has asked her to help organize a short-course on sensory evaluation in Vietnam next year.

The National Fisheries Institute in McLean, Va., was the lead organizer of the sensory evaluation workshops.