Developing Value-Added Products from Green Crab
The overall goal of this project is to develop value-added products from invasive green crabs. Researchers are working on identifying and extracting functional ingredients and/or bioactive proteins and compounds from green crab biomass that would identify the crab as a useful species.
Specific goals for green crab research:
- To develop appropriate methods to fractionate green crab biomass into multiple processing streams (shell component, soft tissue mass).
- To isolate functional proteins from green crab biomass using isoelectric solubilization.
- To assess the composition, protein size distribution, and functional properties (solubility, emulsifying capacity, gelation capacity) of crab protein isolate for use as a food ingredient.
- To identify if the green crab has bioactive proteins with health benefits.
- To determine the impact of enzymatic hydrolysis on the functional and bioactive properties of crab protein isolate for food and/or nutraceutical application.
- To examine if there are extracts from green crab that can inhibit α-amylase and α-glucosidase.
- To determine carotenoid content of the fractionated green crab shell processing stream.
- To determine the impact of thermal processing on the stability of carotenoids in crab shell.
- To determine an appropriate food grade method to extract carotenoids from crab shell.
- To develop new products employing green crab (soup base that is low sodium).
Results and Accomplishments
In 2017-2018, the primary objective of the study has been to investigate the development of bioactive proteins and their derivatives (peptides) through enzyme hydrolysis. Graduate student Bouhee Kang has begun evaluation of the effects of commercially available proteases on green crab mince extracted using the mechanical deboner. Bouhee has started screening the anti-oxidant and anti-hyperglycemic effects of green crab hydrolysates based on the degree of hydrolysis and commercial enzyme source applied.
The mechanically separated green crab mince was homogenized with water (1:1), then hydrolyzed by 1% of Alcalase (AL), Protamex (PR), or the combination of both enzymes (CB) for 0, 30, 60, 120 min. The freeze-dried supernatant (powder) was analyzed for degree of hydrolysis (DH) and antioxidant activity (free radical scavenging activity). Based on antioxidant activity, select samples from each enzyme treatment were chosen to evaluate their anti-hyperglycemic properties, including inhibition of α-glucosidase and α-amylase, and DPP IV were investigated.
Results indicated the enzymes were effective in hydrolyzing the mince from 6.2% to 22.7% at 120 min and that there was no significant effect of hydrolysis time (eg the 30 min hydrolysis was as effective as the 120 min hydrolysis). However, with regard to antioxidant activity, the AL, PR, and CB treatments showed the highest activity at 30 (AL30, EC50 3.6 mg/mL), 120 (PR120, EC50 2.2 mg/mL), and 120 (CB120, EC50 2.2 mg/mL) min, indicating that antioxidant activity of the hydrolysates was affected by time and enzyme type. Anti-diabetic activity (alpha-amylase inhibitory activity and alpha-amylase inhibitory activity) was also impacted by hydrolysis time and enzyme source; however none of the activities measured were impacted by degree of hydrolysis.
There have been some preliminary investigations on the potential use of whole green crabs as a pet treat. Dr. Myracle has worked with an undergraduate student (Anna Smasted) to evaluate the effects of high pressure cooking on shell hardness and nutrient composition of the whole green crab. Results indicate that high pressure cooking softens the crab shell, likely by demineralizing the carapace. Research is ongoing to assess extent of demineralization and nutrient composition of the potential pet treat.
These results indicate that green crab hydrolysates have the potential for antioxidant and type 2 diabetes management, and these bioactivities are not dependent on the degree of hydrolysis. The study suggests green crab hydrolysate could be applied in food products and dietary supplement as a
Summary of Data Collected
|Processing (fractionating yield)||Lab||Several ~20-50lb batches of green crab||Food pilot plant, UMaine|
|Protein solubility, emulsifying capacity, gelation capacity||Lab||50+ protein isolate samples||Seafood analytical laboratory, UMaine|
|Protein molecular weight determination||Lab||20-30 protein isolate samples||Phytochemical laboratory, UMaine|
|Nutrient content (protein, fat, minerals)||Lab||20-30 crab meat and protein isolate samples||Various laboratory on campus, UMaine|
|Carotenoid content||Lab||50+ crab shell samples||Seafood analytical laboratory, UMaine|
|Hydrolytic efficiency and protein size distribution||Lab||Multiple batches of fractionated green crab soft tissue||Seafood analytical laboratory, UMaine|