Archive for January, 2014

Grad Student Developing Pigment Extract From Lobster Shells to Color Fish

Thursday, January 9th, 2014

A University of Maine graduate student is researching ways to use lobster shell waste to create a pigment extract as a green alternative to synthetic versions found in fish food.

Beth Fulton, a Ph.D. student in food science, is working with other researchers on the project that aims to use environmentally friendly solvents and methods to develop a carotenoid pigment extract from lobster shell waste generated by processing facilities. The extract would be used in food for farmed salmonid fish, such as salmon and trout.

“I feel this project could lead to a really simple answer to a lot of problems that we have in Maine at the same time,” Fulton says, noting that decreasing waste and disposal costs by recycling secondary processing resources could have a positive effect on the fishing industry and communities.

Lobster shells are rich in carotenoid pigments — yellow to red pigments found in plants and animals — that can’t be synthesized in salmonid fish but can be used as a natural colorant in food. Farmed salmonid fish get their color from their diet, which contains commercial pigments that may include synthetic carotenoids from petroleum products, dried copepods, whole yeast and algae, or oil extracts from krill. Fulton says 15 percent of salmon feed cost comes from the commercial pigment alone.

“This pigment can potentially replace artificial color in common food products like farmed salmon feeds, and increase the value of whole lobsters,” Fulton says.

Fulton of Lee, N.H., has been working on the project since 2011, primarily with her faculty adviser Denise Skonberg, an associate professor of food science at UMaine. After citing Skonberg’s research in her master’s thesis at the University of New Hampshire, Fulton decided she wanted to attend UMaine to earn her Ph.D. under Skonberg’s guidance. Fulton also has a bachelor’s degree in food science from Cornell University.

When Fulton first came to UMaine, Skonberg suggested she look at what seafood byproducts are getting thrown away in the state and determine usable and efficient food uses for them.

“When we process lobsters — which are 70 percent of this state’s fishing income — we throw away almost 80 percent of the animal, including shell and organs,” Fulton says.

Fulton took Skonberg’s advice and related it to what she had learned while completing her master’s work on green crabs. During that research, she was fascinated by the adult crabs’ ability to change color from orange to green-blue every year.

“That color change is not very well understood, but has been attributed to interactions between proteins and carotenoids in the shell,” Fulton says. “So I started reading a lot about the pigments in lobster shell because they are similar to the ones seen in green crabs.”

In lobster shell, the main pigment is a red-colored carotenoid called astaxanthin, which when bound to a protein called crustacyanin is a blue-green color, she says.

“I started reading a lot about astaxanthin and found there is a very large market for this pigment, and most of the stuff we use in our salmon food is made artificially from petroleum products that are not extracted from natural sources. Consumers are becoming aware of that and are demanding natural colors,” Fulton says.

Fulton is currently examining different methods of removing minerals from lobster shells. She studies a variety of factors, such as how fine the shell needs to be ground, what type of food-grade chemicals should be used, how the shell should be exposed to the chemicals and what type of agitation should be used to maximize the removal of minerals.

She plans to determine the best treatment for pressurized liquid extraction and then look at the effect removing the minerals has on both cooked and high-pressure shucked waste.

Once the extract is developed, it will be assessed for total carotenoid content, carotenoid profile and antioxidant activity. The researchers also propose the extract will then be added to food for rainbow trout, and the effectiveness of the extract in coloring the fish will be studied in comparison to a conventional synthetic pigment.

After Fulton graduates in 2016, she plans to work in the seafood industry.

The project has received a $4,800 Maine Agricultural Center grant, and Fulton has received a $3,000 graduate student award from the Northeast Section of the Institute of Food Technologists for related research. The group recently applied for a grant to fund the project titled “Green production methods for a high-value product from lobster shell waste.” The proposed study would last two years starting in June 2014.

Contact: Elyse Kahl, 207.581.3747

Sexual Selection May Result in Bigger-Billed Male Birds, says UMaine Researcher

Thursday, January 9th, 2014

To female coastal plain swamp sparrows, male bill size matters.

When looking for a mate outside of their pair bond, female coastal plain swamp sparrows (Melospiza georgiana nigrescens) choose males with large bills, according to a University of Maine-led study conducted along Delaware Bay.

Small-billed males are more at risk of being cheated on by their mates. Males with larger bills than their avian neighbors, on the other hand, sire a greater percentage of young birds in their territory, says Brian Olsen, assistant professor in UMaine’s School of Biology and Ecology and Climate Change Institute.

Thus, Olsen says, sexual selection may explain why males have larger bills than females along the Delaware coast.

“Conventionally, bird bills have been considered one of the premier examples of how diet shapes morphology: the right tool for the right job,” he says.

For the past 40 years, researchers have explained differences between the shapes of male and female bills by differences in diet. But Olsen and his colleagues say their research suggests that female mating preferences alone could do it.

“It really makes me wonder how much of bill shape, or the shape of any other structure for that matter, is due to mating preferences instead of better survival,” Olsen says.

Olsen and his fellow researchers also found that bill size increases with age. So, by selecting males with larger bills, females are picking a mate that has the right stuff to survive and successfully defend a territory over multiple years.

“In other words,” says Olsen, “the genes of older males have been tested and proven worthy, and females who prefer to mate with the largest-billed males can then pass these good survivor genes on to their offspring.”

Since the difference in large and small bills is only a few millimeters, Olsen says he doesn’t know how female swamp sparrows make the distinction. He suspects song may play a role, since male bill shape can greatly influence singing.

Russell Greenberg of the Smithsonian Migratory Bird Center at the National Zoological Park; Jeffrey Walters of Virginia Tech’s Department of Biological Sciences; and Robert Fleischer of the Center for Conservation and Evolutionary Genetics at the National Zoological Park also participated in the study.

The team’s research article, “Sexual dimorphism in a feeding apparatus is driven by mate choice and not niche partitioning,” was published in the November 2013 issue of Behavioral Ecology.

Contact: Beth Staples, 207.581.3777