Seafood Flashcards
Composition and nature of Lean Fish.
What are Lean Fish?
Lean fish are ‘ground fish’ that live on the sea floor and contain little fat in the muscle -fat is stored on the liver (e.g. Cod liver oil)
Lean fish tend to toughen in frozen storage through protein cross linking
Spoils faster due to bacterial degradation (the bacteria are used to very cold water temps and can survive in cold storage)
Composition and Nature of Flat Fish
Flat fish have intermediate fat levels. Their flesh is valued more commercially than lean ground fish
E.g. Flounder
Important features of Salmon
Fat levels depend on diet,season,wild vs. cultured,exercise etc
Carotenoid pigment comes from the feed (crustations)
Has a long shelf life in frozen storage
Most imp fish in aquaculture
Composition of Pelagics fish
Pelagics live near the surface (e.g. Herring, mackerel, tuna, swordfish)
Have high levels of muscle fat because travel long distances to find food
Will spoil through oxidation if not properly stored
Good smoked
Scombroid fish may produce toxins
Do not toughen in frozen storage
Stores heavy metals (Mercury and cadmium and lead)
Mercury contamination
Heavy metals will bioaccumulate in fish.
Is a problem in large, long lived conivorous fish e.g shark,tuna,and swordfish
The health Canada limit for Mercury is 0.5 ppm concentration. Higher is shark, swordfish and tuna
Dioxins
Polycholrinated dibenzodioxins (PCDD)
Is higher in farmed fish but still well below health Canada limits.
Highest in beef
Muscle proteins
Sarcoplasmic- enzymes responsible for muscle degradation
Myofibrillar
Stroma - connective tissue. Not much diff between fish and beef. But fish muscle structure is unique (myotome -flakiness)
Differences of beef vs fish muscle
Beef: Fish:
Long fibers Short fibers
More connective tissue. Less connect tissue
Age to tenderize. Ageing results in spoilage
Cook long to soften Cook less collagen soft easy
Protein stable to freezing protein not stable freezing
Saturated fats. Unsaturated fats
Warm blooded. Cold tolerant bacteria
“Production” process for fresh fish
- Landing - catching
- Bleeding out - blood will brown, may catalyze due to lipid oxidation and bacterial spoilage
- Gutting - to remove digestive enzymes
- Icing - prevent and slow spoilage
- Filleting - skinning and deboning
- Retail
“Production” process of frozen fish
- landing - catch method
- Iced storage - to prevent/slow spoilage
- Filleting/gutting/bleeding
- Packaging
- Plate freezing
- Cold storage - up to 6-8 months for most fish
- Thawing
- Breading/ battering
- Refreezing and packaging for sale
Note: the quality changes in frozen fish cause the protein changes (denaturation) resulting in the loss of solubility (loss of water holding capacity - thaw drip and water loss during cooking)
Also loss of gelation capacity.
How to prevent denaturation caused by freezing process in fish
Low temp storage - -30 degrees C
Constant temp
Prevent entry of oxygen through proper packaging and glazing
Temper asap - water contact not air
Use of cryoprotectants (sugar,amino acids etc)
Processing production of Restructured Fish (Surimi)
- Landing/bleeding/gutting
- Filleting/mechanical deboning/mincing - minced fish gels to produce elastic, chewy texture that can be used as fish and shellfish substitutes
- Washing
- Refining - remove any connective tissue, bone, skin,scale
- Dewatering - screw press to add moisture (82% moisture)
- Cryoprotectants - fish is mixed with cryoprotectants such as sucrose, sorbitol, polyphosphate
- Freezing
- Frozen storage
- Tempering/shaping/flavouring and colouring
- Heating and packaging to form gel
