Shrimp shells: A ressource
Special Symposium - Innovations in Food Technology (LMC Congress)
Innovations in Food Technology - Poster Session (Food - P2)
Keywords: resources, environment, sustainability
The production of seafood is increasing and so is the production of individually cooked and frozen shrimps (Pandalus borealis). In Greenland the quota is around 120,000 t per year and half of this is processed in factories at shore. Only 1/3 of the caught shrimps end up as eatable product. The rest is disposed of in various ways, e.g. dumped on the bottom of a fiord. This causes problems with anaerobic conditions, production of bad smelling gasses. The purpose of this project is to identify utilization of this waste material. The composition of the shrimp shells is approximately (in g per kg drained waste): 73 g chitin, 70 g protein, 125 g CaCO3 and minor amounts of lipids. The utilization begins with an extensive wash at pH 5 for 15 min. The wash water is drained off and a red sediment composed mainly of proteins forms beneath a clear supernatant. Duration max. 2 h. The sediment is harvested and astaxanthin is extracted from the insoluble protein with oil (fish or vegetable) either directly or after an enzymatic treatment. The products are protein usefull for feeding purposes and astaxanthin in oil suited for feed to aquaculture.
The washed shells are either freed from protein (by enzymes or alkali treatment) or decalcified (by acid) and then protein is removed. The shells only treated for protein are washed to near neutrality and dried. The product is suitable for insulation purposes (h around 40 mW/(mK)) as loose filling. The shells decalcified and deproteinized are washed to near neutrality, pressed and dried. The material consists mainly of chitin. The pressed material exhibits mechanical strength comparable to cardboard and are useful for applications where papermasses is used today. The material is charring (selfextinguising to some extend), but not combusting, the water absorption in humid atmosphere is moderate and it is not supporting the majority of moulds that causes problems in housing.
It is important that the shells are not crushed to smaller dimensions if the material is to be used as insulation. If the extraction of protein is the most important a size reduction and multiple washing is an advantage.
The net result is products that are directly useful or are suited for further production (e.g. of chitosan) plus a clear solution of soluble protein and some calcium containing slump. A much lower pollution load should be the result.
