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What is Fish Meal ? How is it manufactured? – Part 2

Fish meal, or fishmeal, is a commercial product made from fish and the bones and offal from processed fish. It is a brown powder or cake obtained by drying the fish or fish trimmings which are left often after cooking, and then by grinding it.

What are the main methods to manufacture it?

1. Cooking
• A commercial cooker is a long steam jacketed cylinder through which the fish are moved by a screw conveyor.
• This is a critical stage in preparing the fishmeal.
• Incomplete cooking means that the liquor from the fish cannot be pressed out satisfactorily.
• Overcooking of fish makes the material too soft for pressing.
• No drying occurs in the cooking stage.

2. Pressing
• A perforated tube with increasing pressure is used for this process.
• This stage involves removing some of the oil and water from the material.
• The solid obtained is known as Press cake.
• The water content in pressing is reduced from 70% to about 50% and oil is reduced to 4%.

3. Drying
• It is essential to get this stage of the process right.
• If the meal is under-dried, moulds or bacteria may grow.
• If it is over-dried, scorching may occur and this reduces the nutritional value of the meal.

There are two main types of dryer: Direct and Indirect
Direct drying
• This is the quicker method. Very hot air at a temperature of 500 °C (932 °F) is passed over the material as it is tumbled rapidly in a cylindrical drum. The heat damage is much more likely if the process is not carefully controlled.

Indirect drying
• Cylinder containing steam heated discs which also tumble the meal.

4. Grinding
• This is the last step in processing.
• This process involves the breakdown of any lumps or particles of bone are involved in this stage.

Nutrient composition of Fish Meal

• Any complete diet must contain some protein.
• The nutritional value of the protein relates directly to its amino acid composition and digestibility.
• The amino acid profile of fishmeal is what makes this feed ingredient as attractive as a protein supplement.
• High-quality fishmeal normally contains between 60% and 72% crude protein by weight.
• Typical diets for fish may contain from 32% to 45% total protein by weight.
• The other important reason why fishmeal is sought after as an ingredient in aquaculture diets.
• It is because it contains certain compounds that make the feed more acceptable and agreeable to the taste.
• This property allows for the feed to be ingested rapidly.
• This will reduce nutrient leaching.
• Fish lipids are also highly digestible by all species of animals.
• They are excellent sources of the essential polyunsaturated fatty acids (PUFA) in both the omega-3 and omega-6 families of fatty acids.
The predominant omega-3 fatty acids in fishmeal and fish oil are:
– linolenic acid
– docosahexaenoic acid (DHA)
– eicosapentaenoic acid (EPA)
• Essential fatty acids are necessary for normal larval development, fish growth, and reproduction.
• They are important in normal development of the skin, nervous system, brain, and visual acuity.
• PUFAs appear to assist the immune system in defense of disease agents and reduce the stress response.

What does fish meal contains?

• Valuable phospholipids
• Fat-soluble vitamins
• Steroid hormones
Fishmeal is considered to be a moderately rich source of vitamins of
• B-complex especially cobalamine (B12)
• Niacin
• Choline
• Pantothenic acid
• Riboflavin

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