Date of Award

Summer 8-20-2021

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Food Science and Human Nutrition

Advisor

Jennifer J. Perry

Second Committee Member

Denise I. Skonberg

Third Committee Member

L. Brian Perkins

Abstract

The European green crab, Carcinus maenas, is an aggressive invasive species of green crab that has had severe ecological and economic effects to the North American East Coast since the early 1800s. The green crab has disrupted entire ecosystems, particularly in the Gulf of Maine, due to its eating and uprooting of eel grass. The disruption of this plant reduces coastal habitats for bivalves and other coastal marine life. The green crabs have also been found to prey on juvenile lobsters and bivalve mollusks, disrupting both the ecosystem in the Gulf of Maine and the seafood economy dependent on lobsters and soft-shell clams. With the changing climate and consistent increases in the ocean temperature, the number of crabs killed by the cold, winter temperatures has been steadily decreasing. The establishment of a green crab fishery for the sale of soft-shell crabs has been identified as a method to control the growing population since the crabs are too small for hard-shell culinary use. However, most crabs fished cannot be sold as soft-shell, creating a large amount of biomass. The biomass can currently only be sold to lowvalorization waste streams such as compost, bait, or animal feed. In order to sustain green crab fisheries, a high-value waste stream valorization needs to be established. Fish sauce is a clear, brown, fish-flavored condiment that is traditionally spontaneously fermented from under-utilized fish species and salt. Fish sauce originated in Asia, but has been fermented in many places throughout the world including Rome, South America, and Africa with slight variations to the formulation depending on location and starting material. Since this fermentation is spontaneous it relies on the proteolytic activity of endogenous enzymes and proteolytic bacteria to break down proteins into amino acids. One of the most common fish species used for the fermentation of fish sauce is the anchovy, which has a protein content of about 20%. Green crabs have a protein content of about 17%, indicating that green crabs could be used instead of anchovies to produce a similar condiment. The data from this work showed that when fermented at a temperature of 24°C at a salt content of 20-30%, a green crab fermented condiment can be produced that is chemically comparable to commercially available fish sauce products. Fermentation temperatures of 30°C, 37°C, and 50°C were investigated to provide guidance for temperature control. A temperature of 30-37°C with a salt content of 20% and a 90 day fermentation time was suggested based on this data, but a temperature of 24°C or 50°C will still produce a viable product. The most abundant families of bacteria throughout the course of the fermentation, regardless of fermentation temperature or time, were Rhodobacteracea, Saprospiraceae, and Hyphomonadaceae, all of which contain salt-tolerant proteolytic genera isolated from marine sources. The creation of a viable fermented crab sauce product creates a high-value waste stream for green crab fishers, thus opening the doors to start economical large-scale fishing of green crabs on the North American East Coast.

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