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Agriculture & Foods - You Want a Piece of Me?

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Joseph Galletti

University of Maine graduate student Joseph Galetti completed his master’s thesis last December on the mechanical processing of the European green crab and the potential use of the mince in a value-added product — crab patties. Galetti, a graduate of Johnson & Wales University, is now pursuing a Ph.D. at UMaine in food and nutrition sciences.

Consider an industry that uses only 20 percent of its raw materials and throws the rest away. Not a very economically and environmentally efficient business model, but one that is employed out of necessity by Maine’s crab processing industry, which thrives by steaming or boiling the raw crustaceans and handpicking the sweet, succulent meat from the legs, body and claws.

While the cooked crabmeat is destined for the consumer market, the rest of the crab — approximately four-fifths of its body weight — is bound for the nearest landfill or compost pile.

For food scientist Denise Skonberg, those numbers don’t add up. That’s why she’s been exploring other options for that 80 percent of cast-off crab deemed unusable and undesirable by the food processing industry.

Skonberg, an associate professor in the University of Maine Department of Food Science and Human Nutrition, focuses her research on seafood quality evaluation and the utilization of crustacean processing by-products. In particular, she has looked at ways to utilize a chemical derived from crab shells for use as a food coating to extend the refrigerated and frozen shelf life of seafood. She also is using a mechanical process to extract bits of meat from shells to produce crab mince or paste, which is typically used as a filler or flavor enhancer in the restaurant industry.

But Skonberg’s crab research doesn’t end with the Jonah crab (Cancer borealis). In addition, she has turned her attention to the European green crab (Carcinus maenas), an invasive species that pesters the lobster industry by eating bait out of traps, but one for which there is currently no commercial fishing industry. Green crabs are about a third the size of Jonah crabs and, therefore, make for even more difficult meat extraction.

That’s something Skonberg hopes to change by taking the same mechanical process that harvests mince from Jonah crabs and applying it to the smaller species. Together, her two areas of crab research could one day be used to improve the efficiency of the state’s processing industry, as well as create an entirely new fishing industry while alleviating a nuisance to lobster fisherman.

Talk about nothing to crab about.

“There are a lot of potential opportunities,” says Skonberg. “The crab industry focuses on the 20 percent of the body weight of the crab that is the easily extractable meat. It’s the highest value portion and the whole reason the industry exists.” But there is other stuff inside the crab that is useful.

“The green crab opportunity is really exciting. They are easy to catch, but for the lobstermen they are a nuisance. If there was a market for them, they could easily be targeted.”

Skonberg has been doing crustacean by-products research since 1998. Her crab experiments are the latest in a long line of by-products research at UMaine where, in the last three decades alone, food scientists have explored potential uses for Maine-based by-products such as potato peels, salmon and lobster mince, and unripe (red and green) blueberries. The goal of the department’s by-products research is to probe areas that might be of benefit to industries and specialty food producers that play a significant role in the state’s economy.

“We’re creating opportunities for businesses to make profits on something that may have been a waste disposal issue,” says Mary Ellen Camire, a UMaine professor of food science and human nutrition, and a fellow of the Institute of Food Technologists. “We’re not getting things ready to be sold in stores. We develop concepts, then it’s up to the industry to take the next steps.”

But finding a business willing to make a significant financial commitment to implement one of the university’s food by-products concepts can be difficult, especially in current economic times when profitability is more critical than ever.

“Trying to get things picked up by industry is always a challenge,” Camire says. “The trick is, if a company wants to use a by-product concept, it has to make economic sense for them.”

The economics of by-products research also extends to supply and demand. Take the department’s research on potato peels in conjunction with the McCain Foods potato facility in Easton, Maine. More than two decades ago, peels from Aroostook County’s cash crop were used as cattle feed before interest spiked in their antioxidant value, as demonstrated by researchers such as Camire.

But there is only a finite number of potato peels to go around and the availability of them is directly tied to the production of the main product, which is the challenge with all food by-products.

Skonberg has little doubt there is enough Jonah crab by-product and whole green crabs to support new or expanded industries in Maine and beyond, and her research focuses on making that possible.

“Here we have this invasive species that is eating clams and oysters, and bait out of lobster traps. It’s not good for our fishing industry,” says Skonberg. “But if we can use them as a food resource, we could develop an industry.”

Freeing meat from these small, pesky crab shells requires mechanical extraction equipment originally developed for the poultry industry. The cooked green crabs are tossed into a giant hopper and the extractor grinds them under high pressure, separating the meat from the shell.

The result is what Skonberg describes as a crabmeat mince or paste that, while visually unappealing, has the same taste, fat content and nutrient values as the pre-extracted cooked crabmeat.

In UMaine’s Consumer Testing Center, Skonberg and graduate student Joseph Galetti have conducted consumer taste tests to determine a viable use for the crab mince. The winner was a crab empanada using the mince as a filling, similar to the traditional South American variety with a spicy beef mixture. More than half of the taste test participants indicated they would purchase the value-added product if sold in stores.

But don’t go running to the nearest supermarket just yet. The crab empanadas proved there could be a food product use for the invasive green crab, but there’s got to be a market if there is ever going to be an industry based on the species.

“Fishermen can catch the crab, but they need to have someone willing to buy them,” Skonberg says. “In order to buy them, people need to have an end market established.”


In Maine, the European green crab (Carcinus maenas) is an invasive predator that threatens the health of marine ecosystems. It also is a by-catch species of the lobster industry. As part of her research on seafood quality evaluation and the utilization of crustacean processing by-products, University of Maine food scientist Denise Skonberg is investigating ways to use the meat from cooked green crabs to make a mince or paste for use in value-added food products. Photos by Joseph Galetti, Denise Skonberg and Michael Mardosa

The value-added potential of Jonah crabs — the 80 percent of the crustacean traditionally tossed by the processing industry — holds even more promise for the right entrepreneurial food producer. Using the mechanical extracting process, bits of meat deemed too time consuming to extract are ground up and used to make a crab appetizer in the testing center.

The crab appetizer features crab mince preformed into nuggets, seasoned with different flavorings, then battered or breaded. In taste tests, the Italian flavor was most popular, and again more than 50 percent of taste test participants indicated they would buy the appetizer in stores.

Skonberg also has experimented with food-related uses for crustacean shells and chitin, a carbohydrate biopolymer similar to cellulose found in the protective covering. Chitin can be converted to chitosan, a compound used in weight loss supplements because it can bind to dietary fat, preventing absorption in the body.

Skonberg isn’t interested in the diet fad, but rather what chitosan can do as an antioxidant and antimicrobial when applied to fresh seafood. Chitosan can be made into a powder for coating fish filets or salmon steaks.

Skonberg found that the antimicrobial properties of chitosan coatings slow bacteria growth on refrigerated seafood, extending its life at premium quality for several days.

She also discovered the coating can extend the freezer life of seafood because its antioxidant properties slow the oxidation of the fat in fish. Skonberg says the chitosan coating has the potential to make a significant impact on the industry by extending the shelf life of seafood.

But like much of the food products developed in the testing center, the chitosan coating won’t be available on fresh seafood in the United States anytime soon. The reason: It requires Food and Drug Administration approval, even though countries in Asia and the European Union have signed off on the use of chitosan in food products.

“We hope a company will come along, look at the research that’s been done and take it from there,” she says.

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