What is fish protein concentrate?

Introduction

This note describes what fish protein concentrate is, how it can be made, and the principal technical problems encountered in making it. The manufacture and use of fish protein concentrate raise a number of economic and social questions and these also are briefly discussed in the note.

The term fish protein concentrate is often shortened to FPC, and this abbreviation is used frequently in this note.

The idea of producing a fish protein concentrate is by no means new. A vase found in the ruins of Pompeii bore an inscription claiming that the best liquamen in the world was made in the factories of Umbricus Agathopus, and liquamen is a kind of FPC. In more recent times the Norwegians exhibited biscuits containing fish flour at an international exhibition in 1876.

However, it is only in the last twenty-five years that extensive endeavours have been made to produce fish protein concentrate, and only in the last few years that most of the technical problems of making FPC on a large scale have been solved.

What is fish protein concentrate?

Fish protein concentrate is any stable fish preparation, intended for human consumption, in which the protein is more concentrated than in the original fish.

What are the principal types of FPC?

The Food and Agriculture Organization of the United Nations defines three types:

Type A:	a virtually odourless and tasteless powder having a maximum total fat content of 0·75 per cent.
Type B:	a powder having no specific limits as to odour or flavour, but definitely having a fishy flavour and a maximum fat content of 3 per cent.
Type C:	normal fish meal produced under satisfactorily hygienic conditions.

These three types, all of which in a sense resemble fish meal, are the subject of this note, but there are other fish protein concentrates which are totally unlike fish meal. These are typically made by hydrolysing fish protein by means of enzymes or other chemicals and then concentrating the product into a paste or extract. Hydrolysed products have received much less technological attention than the variants of fish meal, and they are not discussed further here.

The fat content is specified when defining types of FPC because fat when oxidised can produce a strong, often rancid, taste in the product. The protein content of FPC depends on the raw material used and the extent to which water has been removed, but the products normally contain at least 65 per cent protein and, in type A, up to 80 per cent.

How does FPC differ from fish meal?

Fish meal as produced throughout the world is a very cheap potential FPC, but it is not intended for human consumption; it is used for making pig and poultry feeds for farming. Ordinary fish meal is unsuitable for human consumption for three main reasons:

1. It is not normally made under sufficiently hygienic conditions to rule out the risk of occasional contamination by disease-causing bacteria.

2. It usually contains rancid fat which destroys certain vitamins and may lower the nutritive value of the protein; a fish meal diet might precipitate vitamin deficiency in poorly nourished people. Moreover the flavour of the rancid fat is unacceptable in many societies, though not in all.

3. There is a slight risk that the rancid fat may have a cumulative toxic effect if consumed over a long period.

The first of these reasons is the most important; thus fish meal made under hygienic conditions is called FPC type C.

Is FPC the same as fish flour?

Fish flour is not a precise term, and causes confusion in some languages, but is the name sometimes given to a product such as FPC type A which, when ground to a fine powder, can be used as an unobtrusive additive to prepared foods.

What raw material is used to make FPC?

The raw material can be fresh fish of almost any kind or size, or fish meal. The care taken of the fish on the fishing vessel should at least equal that given to fish for ordinary consumption; it should normally be stored in ice immediately after capture, and the factory should start processing it within at the most 48 hours and preferably within 12 hours of landing. Storage of the raw fish in ice for up to 8 days after capture does not affect the nutritive value of the FPC.

In some areas of the world’s oceans there are large stocks of unexploited fish, and these might well be used to make FPC. In any large-scale operation, FPC would be in direct competition with the fish meal industry for its raw material. Biologists estimate that the annual world harvest of marine fish could be doubled or tripled; much of the additional catch would consist of species not normally eaten but which could be used to make FPC.

How is FPC made?

The manufacture of types A and B is described here, since type C is simply hygienically prepared fish meal.

Water and fat together constitute about 80 per cent of the whole fish, with the fat itself in some species accounting for up to about 20 per cent at times. The manufacture of FPC involves removal of most of the water and some or all of the fat. Methods developed so far are based mainly on the use of chemical solvents to remove the water, fat and fishy-tasting components, either from raw fish or from fish meal. The solvents most successfully used to make FPC type A are the alcohols, for example ethanol or propanol; ethylene dichloride is also used. The choice between ethanol and propanol is based on cost, but since propanol is usually free of excise tax it has tended to replace ethanol. Normally the solvent is recovered and used again and again.

The manufacturing process is quite complicated, but an outline of a typical process is shown in the figure. The sequence of operations is:

Diagram of an FPC production plant

1. Fresh whole fish are rinsed with fresh water soon after landing, weighed and fed to a mincer by conveyor.

2. First extraction: the minced fish are fed to extractor 1 which dehydrates the fish; it is an unheated vessel in which the mince is agitated for about 50 minutes together with the liquid recovered from extractor 2, which contains some isopropanol.

3. Centrifuging: the contents of extractor 1 are fed to a continuous centrifuge, where the slurry separates into a solid known as wet cake, and a liquid. The wet cake is conveyed to extractor 2, and the liquid to a still for recovery of solvent and fat.

4. Second extraction: extractor 2 is jacketed, and the temperature is about 75°C. Here the liquid recovered from extractor 3 is added to the wet cake from extractor 1 and the mixture is agitated for 90 minutes. At the beginning of this stage the cake is almost completely dehydrated, but has a fat content of about 5 per cent, which is reduced to about 1 per cent during the extraction.

5. Centrifuging: the contents of extractor 2 are centrifuged, the wet cake is conveyed to extractor 3, and the liquid is returned to extractor 1 for the next batch of raw material.

6. Third extraction: extractor 3 is jacketed, and the temperature is again about 75°C. Fresh isopropanol is added to the wet cake and agitated for about 70 minutes. During this stage the fat content is reduced to about 0·3 per cent.

7. Centrifuging: the contents of extractor 3 are centrifuged and the wet cake is washed with pure isopropanol for about 50 minutes. The liquid is returned to extractor 2 for the next batch.

8. Solvent removal: the wet cake is heated in a rotating vacuum dryer to evaporate the solvent; the vapours are drawn off, condensed and used again.

9. Grinding and packing: the dried material is conveyed to a hammer mill, where it is ground to a fine powder and sieved. The FPC is typically packed in 50-lb fibreboard containers and sent to store ready for shipment.

The important point to note is that the solid FPC material and the solvent move through the extractors in opposite directions. Thus the solvent becomes more contaminated with water and fat as it moves from extractor 3 to extractor 1, while the FPC loses water and fat as it moves the other way. The fat can be recovered from the solvent, and the solvent can be used again; solvent losses are said to be only about 1 per cent of the amount used for a batch.

How is FPC used?

Fish protein concentrate type A is an odourless, tasteless powder which is unattractive to eat by itself; there is therefore a real problem in finding ways to make most use of it. It has to be incorporated in other foods such as bread, biscuits, soups and stews at a level that does not affect their normal properties. Good results have been obtained with macaroni products, a milk shake drink, spaghetti sauce, infant foods, dietetic foods and breakfast cereals.

There is less of a problem with other FPC products which have some flavour. A fishy flavour, even if a rancid one, is acceptable in food in some societies; thus the FPC can be eaten more or less as it is, or used as a flavouring in soups or stews.

However, it is true to say that this highly nutritious, concentrated, stable foodstuff is now available without as yet any clear demands appearing for its use.

How long does FPC keep?

Fish protein concentrate is described in its definition as stable; the term stable here has been tentatively defined as showing no significant deterioration in 6 months at 27°C when packed in a hermetically sealed container. Some FPC now being made can certainly reach this standard of stability.

Is FPC made commercially?

Although it has been made in Canada, USA, Norway, Sweden, Morocco, South Africa, Chile, Peru and the UK, FPC is not yet an article of commerce in the usual sense. Plants capable of producing about 15 tons a day of FPC type A have recently been completed in the USA, but their output is sold to the government for use in aid programmes. Since there is no established market, it cannot yet be claimed that FPC is made commercially. The process, however, is a commercial one, and not merely experimental.

How much does FPC cost?

It is difficult to obtain a firm idea of its likely commercial price; this will depend obviously on the cost of the raw material and the process used. Estimates vary between 15 and 50 U.S. cents a pound; a commercial price for type A would probably be close to the latter. These prices compare very favourably with those for proteins from other sources. Fish protein concentrate is for example about half the price of non-fat dried milk and about one-twentieth that of meat for a unit weight of protein.

Introduction

This note briefly describes the manufacture, storage, composition and use of fish meal, and also touches on the problem of air pollution from fish meal plant.

The use of fish byproducts for feeding animals is not a new idea; a primitive form of fish meal is mentioned in the Travels of Marco Polo at the beginning of the fourteenth century: ‘... they accustom their cattle, cows, sheep, camels and horses to feed upon dried fish, which being regularly served to them, they eat without any sign of dislike.’ The utilization of herring as an industrial raw material actually started as early as about 800 AD in Norway. A very primitive process of pressing the oil out of herring by means of wooden boards and stones was employed.

What is fish meal?

In the UK the term fish meal means a product obtained by drying and grinding or otherwise treating fish or fish waste to which no other matter has been added. The term white fish meal is reserved for a product containing not more than 6 per cent oil and not more than 4 per cent salt, obtained from white fish or white fish waste such as filleting offal.

These are semilegal definitions, and for convenience fish meal can be defined as a solid product obtained by removing most of the water and some or all of the oil from fish or fish waste. Fish meal is generally sold as a powder, and is used mostly in compound foods for poultry, pigs and farmed fish; it is far too valuable to be used as a fertilizer.

What raw material is used?

Virtually any fish or shellfish in the sea can be used to make fish meal, although there may be a few rare unexploited species which would produce a poisonous meal. The nutritional value of proteins from vertebrate fish differs little from one species to another; whole shellfish would however give a nutritionally poorer meal because of the low protein content of the shell. Most of the world’s fish meal is made from whole fish; the pelagic species are used most for this purpose. Where a fishery catches solely for the fish meal industry, it is known as an industrial fishery.

Countries with major industrial fisheries are Peru,Norway and South Africa. Some countries like the UK make fish meal from unsold fish and from offal, that is the heads, skeletons and trimmings left over when the edible portions are cut off. Other countries like Denmark and Iceland use both industrial fish and processing waste. Fish meal made mainly from filleting offal usually has a slightly lower protein content and a higher mineral content than meal made from whole fish, but a high proportion of small whole fish in the raw material can have the same effect.

The following points are important when selecting species for an industrial fishery:

1. The species must be in large concentrations to give a high catching rate; this is essential because the value of industrial fish is less than that of fish for direct human consumption.

2. The fishery should preferably be based on more than one species in order to reduce the effect of fluctuations in supply of any one species.

3. The total abundance of long lived species varies less from year to year, and

4. Species with a high fat content are more profitable, because the fat in fish is held at the expense of water and not at the expense of protein.

Manufacturing fish meal

There are several ways of making fish meal from raw fish; the simplest is to let the fish dry in the sun. This method is still used, in some parts of the world where processing plants are not available, but the product is poor in comparison with ones made by modern methods. Almost all fish meal is made by cooking, pressing, drying and grinding the fish in machinery designed for the purpose. Although the process is simple in principle, considerable skill and experience are necessary to obtain a high yield of high quality product, and to make the plant efficient. A typical process is shown diagrammatically in figure 1:

COOKING

When fish are cooked and the protein is coagulated, much of the water and oil runs off, or can be removed by pressing, whereas raw fish lose very little liquor even under very high mechanical pressure. A commercial cooker consists essentially of a long steam jacketed cylinder through which the fish are moved by a screw conveyor. Some cookers also have the facility for injecting steam into the cooking material. The cooking operation is critical; if the fish are incompletely cooked, the liquor cannot be pressed out satisfactorily, and if overcooked the material becomes too soft for pressing. No drying occurs during the cooking stage.

PRESSING

This stage of the process removes some of the oil and water. The fish are conveyed through a perforated tube whilst being subjected to increasing pressure, normally by means of a tapered shaft on the screw conveyor. A mixture of water and oil is squeezed out through the perforations and the solid, known as press cake, emerges from the end of the press. During the pressing process the water content may be reduced from about 70 per cent to about 50 per cent, and the oil content reduced to about 4 per cent.

PRESS LIQUOR

After screening to remove coarse pieces of solid material, the liquor from the presses is continuously centrifuged to remove the oil. The oil is sometimes further refined in a final centrifuge, a process known as polishing, before being pumped to storage tanks. The refined oil is valuable and is used in the manufacture of edible oils and fats, for example margarine.

The water portion of the liquor, known as stickwater, contains dissolved material and fine solids in suspension which may amount to about 9 per cent by weight. The solids are mostly protein and stickwater can contain as much as 20 per cent of the total solids in the fish so that it is normally well worth recovering. The material is recovered by evaporating the stickwater to a thick syrup containing 30-50 per cent solids, and sometimes marketed separately and known as condensed fish solubles. More usually however the concentrated product is added back to the press cake and dried along with it to make what is known as whole meal.

DRYING

Although basically a simple operation, considerable skill is required to get the drying conditions just right. If the meal is underdried, moulds or bacteria may be able to grow; if it is overdried, scorching may occur and the nutritional value of the meal will be reduced.

There are two main types of dryer, direct and indirect. In the direct dryer very hot air at a temperature of up to 500°C is passed over the material as it is tumbled rapidly in a cylindrical drum; this is the quicker method, but heat damage is much more likely if the process is not carefully controlled. The meal does not reach the temperature of the hot air, because rapid evaporation of water from the surface of each particle of fish causes cooling; normally the product temperature remains at about 100°C.

The most usual type of indirect dryer consists either of a steam jacketed cylinder or a cylinder containing steam heated discs which also tumble the meal.

Much of the unpleasant odour from fish meal plants originates from the dryers; indirect dryers, which are normally used in the UK, cause less nuisance because they use less air.

In the UK, where white fish offal are the main raw materials, the pressing stage is not essential, since the material contains only very small amounts of oil. White fish meal can be produced by a simpler process of cooking and drying only. However the use of a pressing stage is increaseingly favoured and there are two main reasons for this:

The plant has greater flexibility in that it may be used for white and oily fish, or a mixture of both.

The removal of water by pressing, and evaporation of the stickwater obtained, is less expensive because the triple effect evaporators used are more efficient in terms of use of steam than are dryers.

GRINDING AND BAGGING

The final operations are grinding to break down any lumps and particles of bone, and packing the meal into bags or storing it in silos for bulk delivery. From the fish meal factory the meal is transported to the animal food compounder, and from there to the farm. The problems of storage and transport are discussed below.

HYGIENE IN THE FACTORY

Contamination of the material during processing may seriously affect quality; microorganisms like Salmonella that may ultimately cause disease in man have to be kept out. Much can be done by good housekeeping in the plant, for example by keeping floors, walls and conveyors clean and by separating ‘wet’ and ‘dry’ areas of the plant, but the processing machinery itself is often less readily accessible for cleaning. Contaminated water, from a dock for example, should not be used for cooling or other purposes if it can come in contact with the fish or the fish meal.

The temperature during processing is normally high enough to kill any Salmonella present, but when a plant is restarted after a stoppage there is likely to be moist meal standing in the plant that will not reach a high enough temperature; for this reason it is now USA practice to recirculate the meal produced in the first 45 minutes after starting again.

How is fish meal used?

Fish meal in the UK was used mainly as a fertilizer until about 1910, but since then its high nutritional value has been far better utilized in animal feeding. The demand in the UK for fish as fish meal is far greater than the demand for fish for direct human consumption; therefore imports of fish meal to the UK are high. The pig and poultry industries producing large amounts of bacon and eggs, pork and chicken, at relatively low prices could not survive without large scale use of high protein animal foods like fish meal. Usually about 10 per cent of the diet of pigs and poultry consists of fish meal; 10 per cent is the upper limit for meal containing 10 per cent fat, because more than about 1 per cent of fish oil in the diet of the animal may taint the taste of its flesh. Much of the UK production is of white fish meal with a fat content low enough to eliminate any risk of taint. Fish meals with an extremely low fat content are sometimes made for certain specialized purposes.

Other uses of fish meal include the feeding of mink, farmed fish, dogs, cats and cattle. Very small amounts of specially processed meals have been used in prepared foods for humans, and fish meal is also used in the preparation of certain antibiotics for the pharmaceutical industry.

How are fish oils used?

Fish oils are produced whenever fatty fish are processed into meal. In Europe they are widely used in the manufacture of edible oils and fats, for example margarine. Other uses include the paint and varnish industry. In addition, there are several other specialized uses for small quantities of fish OILS. Fish oils usually have to be low in free fatty acids, less than 2 per cent, to obtain the best price; production of high quality fish oils depends on the use of fresh raw material, proper purification and good storage.

Introduction

This note describes what fish protein concentrate is, how it can be made, and the principal technical problems encountered in making it. The manufacture and use of fish protein concentrate raise a number of economic and social questions and these also are briefly discussed in the note.

The term fish protein concentrate is often shortened to FPC, and this abbreviation is used frequently in this note.

The idea of producing a fish protein concentrate is by no means new. A vase found in the ruins of Pompeii bore an inscription claiming that the best liquamen in the world was made in the factories of Umbricus Agathopus, and liquamen is a kind of FPC. In more recent times the Norwegians exhibited biscuits containing fish flour at an international exhibition in 1876.

However, it is only in the last twenty-five years that extensive endeavours have been made to produce fish protein concentrate, and only in the last few years that most of the technical problems of making FPC on a large scale have been solved.

What is fish protein concentrate?

Fish protein concentrate is any stable fish preparation, intended for human consumption, in which the protein is more concentrated than in the original fish.