JP2008541756A - Feed for farmed fish and fish stored under living conditions, and method for producing such feed - Google Patents

Abstract

The present invention relates to a soft feed for fish, wherein the soft feed is made from a mixture of at least one blended dry feed and liquid, the mixture being essentially absorbed by the dry feed and then kneaded. It becomes a paste-like cohesive lump, and the lump is formed into a piece of feed having a size and shape suitable for the type and size of fish. The present invention also relates to a method for producing a soft feed.
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Description

  The present invention provides a soft feed for fish, eg, farmed fish, and fish that are captured live and stored live in netpens or closing nets or other suitable devices. About. Furthermore, the present invention, among other things, loses its structure when soaked in water and when subjected to mechanical action, and forms extruded and pelletized soft lumps (pelled and coherent). pelletized) feed. This pasty mass may be divided into the desired size for the fish, either manually or by extruding the mass through a suitable opening.

  In various types of fishing techniques, fish have been caught alive and have long been surrounded by nets until they are returned to the sea or river. An example of this is the fishing method for splats (Splattus splattus) in the Norwegian fjords. In this fishing method, the fish is protected with a net and stored alive in a pulling net until it is recovered from the sea by a receiving vessel. Such protection of the fish, or alive storage, is necessary to empty the fish intestines, thereby improving quality protection until the processing stage.

  It has also become customary to store other species of fish under live conditions. An advantage of this is thought to be the ability to adjust the market so that captured wild fish can be provided with a more stable supply, thereby obtaining fish at a better price. Another advantage is that smaller fish with lower market prices can be fed as bait to obtain larger fish with higher market prices. This can be combined with achieving higher prices by providing out-of-season fish. This type of habit is alive captured cod (Gadus morhua), Seis (Pollachius virens), southern blue-finned tuna (Thynus McCoy (Thynus) ) And northern blue-finned tuna (Thynnus synnus).

  After catching the fish alive, salmon (Salmo salar), rainbow trout (Oncorhynchus mykis), grouper (Dicentrchus labrax) and European sea bream (axillarly) ) (Sparus auratus) is transferred to the same type of net or pen as used for aquaculture. Thus, this technique is well known and has been tried.

  Farmed fish (including cultured cod and halibut (Hippoglossus hippogrossus)) when they run out of yolk sac nutrition or possibly after a short period of feeding on algae, rotifers and possibly brine shrimp (Artemia) And accustomed to dry formulated feed. Such fish are therefore considered to accept dry formula feed as food and grow well with this type of feed. Since only a small amount of feed introduced is sinking through the net pen and is thought to be wasted, the degree of availability of the feed is high.

  Formulated fish feed means feed consisting of one or more protein sources, including protein from the sea (eg fish meal and krill meal), plant protein (eg soybean meal, rapeseed meal, wheat gluten, Corn gluten, lupine flour, pea flour, sunflower flour and rice flour) and slaughterhouse waste (eg, blood flour, bone flour, feather flour and chicken flour). Mixing different protein sources (each with a different amino acid composition) allows for the achievement of the desired amino acid profile for a feed suitable for the fish species to which it is fed. Formula feeds further comprise an energy source, for example in the form of fish oil and / or vegetable oil (eg rapeseed oil and soybean oil). Formula feeds are also usually made of flour-based (starchy) ingredients (eg wheat or wheat flour, potato starch or tapioca flour, peas or beans) to give the feed the solidity and stability required. In the form of a binder. In addition, the formula feed will contain the minerals and vitamins necessary to ensure good growth and good health of the fish. In addition, the feed may contain additional additives such as colorants to achieve a specific effect. Thus, mixed fish feeds are complex feeds where the quantitative proportions of protein, fat, carbohydrates, vitamins, minerals and other additives are calculated based on the age of the fish to suit the nutrient requirements of the species. It is. Usually only one type of feed is used, so each piece of feed has sufficient nutritional value.

  By dry blended feed is meant here a compressed or extruded type of feed. Compressed feed will usually contain less than about 10% water after compression and possibly after application of oil. The extruded feed will contain 18 to 28% water after extrusion. After extrusion, the feed is subjected to a drying process and a subsequent oil application process. Similar to compressed feed, the final product is believed to contain about 10% or less water and as a result is considered highly storable. This is because the water activity of these feeds is low, thus preventing mold and fungal growth and avoiding bacterial corrosion.

  The dried and compressed or extruded feed may be of different shapes and sizes. A common shape is a cylindrical feed piece, the ratio of length to diameter usually being between 1 and 1.5. Such feed fragments are referred to as pellets. The size of the pellet is proportional to the size of the fish, so the pellet diameter can be between 1 and 30 mm. In practice, it has proven difficult in the fish feed industry to produce feed pellets with diameters greater than 30 mm. The difficulty with drying such pellets within a reasonable time is cited as one problem. Another problem is the lack of solidity, which causes a lot of dust and breakage.

  Dry compressed or extruded fish feeds retain their shape in water for hours and days unless subjected to external mechanical action. This is because the pellets contain a binder in the form of starch. For example, to provide pellets with sufficient strength to be able to be stored and transported in large bags that hold 500 to 1000 kg of feed, or to withstand storage in a feed silo, and for loading and unloading Binders have been added to withstand pneumatic transport through the production plant, and between the feed plant and individual net pens. Dimensional stability in water is also due in part to covering the pellets with fat, leaving the outer oil film, and possibly filling the pores and cavities with oil, inhibiting water ingress. .

  The pellets break into the water after a period of time forming an unstable granular mass. This process can be facilitated by subjecting the pellet to an external mechanical load. On a laboratory scale, this may be done by stirring the water or directly crushing or poking the pellets. Water and pellets will form a granular thin paste consisting of large and small particles.

  A conventional pelletized feed that is simply moistened looses its shape when crushed, but it remains split into individual pellets when the pressure is stopped. When subjected to a stronger mechanical treatment, it will split into large and small pieces, but no cohesive mass will form.

  Live catch fish are fed various types of prey and are not fed dry formula feed. Dry formula feeds differ from prey in shape, color, consistency, smell, taste and motility. Therefore, it was found that live fish require a transition period or an adaptation period before accepting dry blended feed as food. In some cases, attempts to adapt fish to such feed have completely failed. An example of this is southern bluefin tuna. The fish weighs approximately 15 kg when captured and is sold between 30 and 60 kg. Conventional feed pellets with a diameter of 10 to 20 mm are too small for fish to care about, and such feed pellets do not have an appetizing texture.

  During the period until the live fish accepts the feed, it does not grow and the fish loses weight. This means that a longer period of time is required before slaughter, and an increase in maintenance costs is also expected. This is because the lost weight must be compensated with purchased feed resources.

  It has been found that if the feed has a soft viscosity, it will be easier for a live fish to accept. Soft viscosities are achieved with water content much higher than about 10% (found in dry feed). A soft feed is basically a paste that can contain all the essential nutrients and that is formed into a piece of feed, either manually or by its extrusion through an opening (eg a sieve plate). . Perhaps it has a softer texture that is more acceptable to fish than dry feed. After the fish gets used to the soft feed, the use of this feed can be continued until the fish reaches the desired size. Alternatively, the fish can adapt to the dry blended feed after the fish recognizes the soft feed as food.

  Soft feed (also called semi-wet feed) is generally used in aquaculture. In particular, it is common for farmers to prepare their own feed at the early stage of cultivation. Such feed typically contains 40% or more water. As the aquaculture changes to a more industrialized form, soft feed is replaced with compressed or extruded industrial feed.

  Soft feed is made from whole fish, minced fish or fish scraps. This is done in a grinder with a binder (often in the form of starch but also in the form of alginate) and possibly fish oil or other cooking oil, and possibly vitamins, minerals and other Necessary additives are mixed and formed into a piece of feed by extruding it through a sieve plate. The size of the feed piece is generally determined by the diameter of the opening. The volume of the feed piece is usually determined by the diameter of the opening. Alternatively, the paste may be manually formed into feed fragments.

  Raw fish materials are obtained in a frozen or fresh state. Frozen raw fish material may be thawed before grinding with a grinder, although some types of grinders can handle frozen fish. Dry raw materials such as binders, vitamins and minerals can be premixed and can be so-called premixes. It is also possible to mix in dry protein materials such as fish meal and wet protein materials such as fish ensilage.

  An alternative to soft feed is to give live fish a whole fish or a small piece of fish. This may be fresh fish or frozen fish that is thawed just before feeding. Some farmers raise the entire frozen fish block to the surface. As the chunks thaw, the fish or fish fragments fall and become available for food.

  In Japan, it is known to extrude live tail (Yellow tail) (Seriola lanlandi) and get used to soft feed. This feed is an extruded feed with a relatively low fat content. This feed is soaked in water before feeding to allow the pellets to absorb the water. The pellet can absorb 50% to 150% of water compared to its own weight. Immersion can be from 5 minutes to 1 hour. After soaking, the pellets become soft and elastic, but are still sharp pellets and are given to fish as normal pellets.

  When producing fish feed with an extruder, the extrudate contains up to 30% water. Prior to drying, the extrudate is soft and elastic. This extrudate is known to be stored by freezing instead of drying. The farmer will then thaw the feed before feeding.

  It is also known to produce fish feed by partially adding various water binders and various softeners. Glycerin is an example of such an additive.

  In the case of dry formulated feed, it is a problem if the captured fish does not recognize the feed as food. A conventional feed supply can take a long time. During this time, they do not grow and the fish may lose weight. Most of the feed used to adapt fish to dry feed is lost. This is detrimental to farmers and is harmful to the environment. This is because the feed that has not been consumed settles on the seabed and causes environmental degradation.

  The use of soft feed, whole fish or fish fragments does not cause the same inconvenience as using dry feed in terms of time spent by fish to get used to them. On the other hand, these require more labor because they must be made on site and have a short shelf life. Soft feed requires a stable supply of fresh ingredients or access to frozen ingredients. Stable supply of fresh raw materials can be difficult due to seasonally constrained fishing techniques. Deteriorating weather conditions will also affect availability. Alternatively, frozen raw materials that require the use of a freezer can be used. The same applies to the availability of whole fish or fish fragments. A further disadvantage of soft feed is the fact that it is not formulated. In particular, it is difficult to adjust the ratio of fat to amino acid, and the amino acid profile is determined by the raw material. The same applies when using whole fish or fish fragments.

  Soft feed is compact and it is difficult to adjust the density of the feed. Soft feeds sink into water very quickly compared to extruded dry formula feeds. This means that in the situation where fish are accustomed to each feed, the soft feed is more wasted than the dry extruded feed.

  Frozen extruded feed requires a complete chain of frozen transport from producer to farmer. This requires more expensive and complex logistics than transporting dry feed. The simplest and cheapest way to freeze feed pellets is to package the feed in a bag (eg, a 25 kg bag). The bag is then placed in the freezer. Since fish feed has good thermal insulation properties, it takes time to freeze bags. In some cases, the center will not freeze and many fungi, molds and bacteria will grow in the middle of the bag during storage and transport. When the damaged feed is mixed with the rest of the feed, this will not become apparent until the bag is thawed and opened. An alternative to freezing is the freezing of the pellets prior to packaging, for example by using a tunnel freezer. This technology increases product prices.

  Adding water to the binding and softening ingredients (eg glycerol) makes the product more expensive. Known mold inhibitors and bacterial inhibitors (eg, propionic acid and benzoate) can also be added to give the pellets better storage stability at room temperature. All such additions make the product more expensive. It is also important that such additives should not reduce the palatability of the product. Thus, it is known that fish reacts rejected to feed containing propionic acid.

  A known method for increasing the shelf life of wet products is to package them under modified air or in vacuum packaging. This creates specific requirements in packaging and requires dedicated packaging equipment.

  The object of the present invention is to ameliorate or reduce the disadvantages of at least one prior art.

  This object is achieved by the features described in the following description and the appended claims.

  The object of the present invention is a fish feed that is soft when fed to fish, in particular captured fish, and at the same time the beneficial properties of extruded dry feed in terms of formulation with respect to the specific requirements of the fish And to achieve a fish feed that maintains simple logistics on extruded dry feed from producers to fish farms.

  It is also an object of the present invention that the soft feed can be adapted to fish of different sizes, conveniently forming a larger piece of feed than is possible by conventional fish feed production based on extrusion technology. Is possible.

  Soft feed means feed containing more than 15% water. In particular, it means a feed containing more than 20% water and a moisture content of more than 30% is even more beneficial for a soft texture. Feed containing more than 30% water cannot be produced using conventional extrusion techniques. Such soft feeds have a texture that is beneficial when adapting formulated feeds to live catch fish.

  Surprisingly, known raw material protein substances such as fish meal, krill meal, soybean meal, rapeseed meal, wheat gluten, corn gluten, lupine meal, pea meal, sunflower meal, rice flour and slaughterhouse waste (eg blood meal, bone meal) , Feather flour and chicken flour), and using starch-containing binders (eg wheat, peas, beans, potato starch or tapioca flour) and using fats (eg fish oil or rapeseed oil) Made it possible to produce pelleted fish feed with new technical properties, and feed pellets that form a soft cohesive paste after immersion and simple mechanical kneading. . For this reason, pressure and temperature conditions as well as thermal and mechanical energy are required to give the starch in the extruded material the properties required for the feed pellets to exhibit the desirable new properties of forming a soft cohesive paste. Extruders set from the viewpoint of the ratio between and are used. This paste may be formed into a piece of feed of the desired size, for example by compressing it through a suitable opening by means of a sieve plate or by manual shaping. Such shaping can result in larger feed pieces than can be achieved with dry extruded pellet production.

  Feed is produced by comminuting dried raw protein material and binder and mixing with vitamins and minerals and other desired ingredients. This mixture is passed through a known preconditioner before being transferred to a known extruder (eg single screw or double screw extruder) where steam, possibly water, possibly oil and possibly fish ensilage are added to the mixture. The Here, the mixture is kneaded and any additional steam, water, oil or fish ensilage is added here to impart the intended properties to the starch fraction, after which the mass is extruded. Extrude through base) and cut the extrudate to the desired length with a rotary blade. The hole in the extrusion-type table may be 1 mm to 25 mm. The desired length may be shorter than the diameter of the pellet and up to twice the length of the pellet, or longer if convenient. The water content of the extrudate may be between 18 and 28%.

  After cutting, the extrudate is passed through a known dryer (eg vertical drying tower or horizontal belt dryer) and dried to a moisture content of less than 10%. Following dewatering, if necessary, further oil may be applied to the pellets using known techniques (eg, a vacuum coating machine). Following dehydration and application of any oil, the pellets may be cooled in a known manner, scraping off the debris and particles and packaging.

  Prior to feeding, the desired amount of dry extruded feed according to the present invention is placed in a suitable container and the liquid is added to the pellets. The term suitable container also means, for example, a bag or other packaging (eg packaging for the delivery of feed).

  Preferably, the amount of liquid added to the dried pellets is less than or equal to the amount that the pellets can absorb and at the same time is sufficient to impart a pasty viscosity. Preferably, the amount of liquid added comprises 20 to 200% by weight of the pellet. More preferably, the amount of liquid added comprises 25 to 100% by weight of the pellet. More preferably, the amount of liquid added comprises 30 to 80% by weight of the pellet. Most preferably, the amount of liquid added comprises 30 to 60% by weight of the pellet.

  The liquid may be fresh water, sea water, fish ensilage, size water or other protein-containing liquid (eg, a mixture of water and fish viscera), or a mixture of two or more such liquids. It's okay. The temperature of the liquid may be as high as the ambient temperature or may deviate from that temperature.

  Hereinafter, the term “liquid” means a liquid composition of one or more such liquids and substances.

  Preferably, the immersion time is between 1 minute and 24 hours. More preferably, the immersion time is between 1 minute and 12 hours. More preferably, the immersion time is between 1 minute and 6 hours. Most preferably, the immersion time is between 1 minute and 90 minutes.

  After soaking, the soaked feed is worked into a cohesive soft paste. The kneading operation may be performed by a rotating arm or screw installed in the container, or by lowering an appropriate device to the container. When the paste has the desired viscosity, it may be removed and transferred to a suitable apparatus for shaping the feed fragments. A suitable such device may be a simple grinder in which an auger carries the paste through one or more openings suitably placed and shaped in the sieve plate. The length of the piece of feed can be determined by a rotating blade or by breakage of the string due to its own weight.

  Alternatively, the soaked but still defined pellets may be transferred to a suitable apparatus for kneading and agglomerating. Such a device may be a grinder. Next, kneading and kneading the feed into pieces would be done in one operation.

  Alternatively, they may be associated with a mixing vessel, a device having one or more suitably arranged and shaped openings. The paste in the mixing container can be compressed towards the opening device by means of a suitable device, for example a rotating arm that compresses the paste towards the wall of the container. Outside the container, the paste may be cut to an appropriate length, or the paste string will break due to its own weight. Furthermore, other devices can be envisaged that achieve the desired mechanical kneading operation of the soaked feed according to the invention.

  An alternative method is to mix the whole fish or fish pieces into a dry pellet before soaking, or mix or screen whole fish or fish pieces after soaking and before kneading or kneading to form a paste. This involves mixing the whole fish or fish pieces into the prepared paste prior to shaping the food pieces through the plate.

  The person skilled in the art can prepare the paste and form the feed pieces on the shore or in the floating structure, and the feed pieces can be transported to the net pen in a known manner and You will see that it can be distributed to net pens in a known way. Alternatively, those skilled in the art can prepare the paste and form the feed pieces directly on the net pen, for example, drop the formed feed piece directly onto the net pen or by a simple device It will be appreciated that it can be distributed across the surface of the net pen or to several nearby net pens. Alternatively, those skilled in the art will recognize that depending on the most favorable conditions, the paste may be produced in one place and the feed pieces may be shaped in another place.

  In the following, non-limiting examples of preferred embodiments are described.

Example 1
The feed according to the present invention was prepared according to the following recipe.

  After grinding and mixing the dry raw materials, they are pretreated with a Wenger DDC preconditioner and preconditioned at a feed rate of 140 kg per hour (dry matter) in a double screw extruder (Wenger TX-57). Extruded to. Steam (13.8 kg / hr) and water (26.1 kg / hr) were added to the preconditioner mass. The mass was at a temperature of 87 ° C. as it exited the preconditioner. Water (7.7 kg / hour) and fish oil (17.0 kg / hour) were added to the extruder. The specific mechanical energy was 26.9 kWh / ton and the specific thermal energy was 43.0 kWh / ton. The pellet diameter was 3 mm. The pellets were dried with a three-compartment belt dryer (air temperatures in each section were 80 ° C., 80 ° C. and 70 ° C., respectively). Total drying time was 13 minutes.

  The dry feed contained 54% protein, 17% fat and 5% water.

  The prepared feed was soaked for about 20 minutes at a ratio of 6 kg of water to 10 kg of feed. A mesh-like space was created between loose pellets so that water could easily spread and all the pellets were immersed. After soaking, it was easy to form a soft paste by kneading the feed by hand. The feed paste contained about 40% water, about 34% protein and about 11% fat. The prepared feed was immersed for about 30 minutes at a ratio of 9 kg of water to 10 kg of feed. The feed paste contained about 50% water, about 28% protein and about 9% fat.

  Wet feed pellets were also kneaded with a normal mincer. When passed through the Mincer sieve plate, a soft spaghetti string was formed. The formed piece of feed showed good properties for submerging in water and was stable in water for a period exceeding the time required to submerge in the net pen during feeding.

Example 2
The feed according to the present invention was prepared according to the following recipe.

  After the dry raw materials were crushed and mixed, they were pre-treated with a Clexral preconditioner and extruded into a (dry matter) preconditioner with a double screw extruder (Wenger TX-57) at a feed rate of 3 tons per hour. 6% steam, 10% water and 5% ensilage were added to the preconditioner mass. 9% water was added to the extruder. The pellet diameter was 3 mm. The pellets were dried with a belt dryer. After drying in a vacuum coater, oil (10.7%) was added.

  The dry feed contained 47.6% protein, 17.7% fat and 10.6% water.

  After soaking, the feed was kneaded into a paste, and the pieces of the feed were formed into pieces having the size of golf balls and tennis balls by rolling the paste by hand. These feed fragments were fed to Seis that were stored live. The chase weighed between 300 and 400 g. Compared to conventional dry extruded feed, Seis showed a strong appetite. The whole piece of golf ball size feed was ingested, but the piece of tennis ball size feed was ingested little by little.

  The soft feed according to the present invention can be used for feeding cultured fish that grow under controlled conditions throughout its lifetime.

  Another application is recreational fishing in which pasty feed can be used as fishhook bait. It may also be used as bait for attracting wild fish to bait hooks by sprinkling small pieces of feed into the water around the fishing point.

  The pasty feed may further be used by professional fishermen as bait for fishhook fishing equipment and as bait for fishpots, fish traps and other fixed fishing gear.

  Consists of standard feed ingredients in the form of proteins, fats, carbohydrates, vitamins and minerals, and when immersed in water, the pellets are simply mechanically kneaded to produce a cohesive soft paste (of feed with the desired cross-section and size) The production of extruded pelleted fish feed, which shows the quality that can result in (which can be formed into pieces) is a new idea. Molding can be accomplished by known methods of compressing the paste through a sieve plate having one or more suitable openings, or by manual molding. The produced feed fragments are suitable for adapting the formulated feed to stored live fish.

Claims (25)

  A soft feed for fish, wherein the soft feed is made from a mixture of at least one blended dry feed and liquid, the mixture being essentially pasty by allowing the dry feed to absorb the liquid and then kneading. A soft feed for fish characterized in that it becomes a cohesive lump, said lump being formed into a piece of feed of a size and shape suitable for the type and size of fish.   Soft feed for fish according to claim 1, characterized in that whole fish, minced fish, fish internal organs or fish scraps are added to the dry feed and liquid mixture. feed.   Soft feed for fish according to claim 1, characterized in that the liquid is constituted by fresh water, sea water, size water or other protein-containing liquid, or a mixture of two or more such liquids. Soft feed for fish to fish.   A soft feed for fish according to claim 1, wherein the liquid is freshwater, seawater, size water or other protein-containing liquid, or two or more such liquids, along with fish internal organs and / or crushed fish A soft feed for fish characterized in that it is composed of a mixture of   Soft feed for fish according to claim 1, characterized in that the liquid constitutes between 20% and 200% by weight of the dry feed.   Soft feed for fish according to claim 1, characterized in that the liquid constitutes between 25% and 100% by weight of the dry feed.   Soft feed for fish according to claim 1, characterized in that the liquid constitutes between 30% and 80% by weight of the dry feed.   Soft feed for fish according to claim 1, characterized in that the liquid constitutes between 30% and 60% by weight of the dry feed.   The soft feed for fish according to claim 1, wherein the dry feed is pelletized. A method for producing a blended soft fish feed based on a blended dry feed for fish comprising the following steps:
a) preparing the blended dry feed;
b) transferring said blended dry feed into a container;
c) introducing into the container a liquid adjusted to wet the dry feed and mixing the dry feed and the liquid;
d) absorbing the liquid into the dry feed;
e) Kneading the wet dried feed into a paste-like cohesive mass;
f) shaping the pasty mass into a piece of feed; and g) distributing the feed piece to a place where fish is fed.   11. The method of claim 10, wherein raw fish material is added to the dry feed in the form of whole fish, minced fish, fish internal organs or fish scraps prior to mixing the dry feed and liquid. And mixed.   11. The method of claim 10, wherein raw fish material is added to and mixed with the moist and dry feed in the form of whole fish, minced fish, fish internal organs or fish scraps. And how to.   11. The method of claim 10, wherein raw fish material is added to and mixed with the pasty mass in the form of whole fish, minced fish, fish offal or fish scraps. Method.   14. A method according to any one of claims 10 to 13, characterized in that the mixture of wet dried feed and raw fish material is kneaded in a crusher.   11. A method according to claim 10, wherein the liquid is constituted by fresh water, sea water, size water or other protein-containing liquid, or a mixture of two or more such liquids.   11. The method according to claim 10, wherein the liquid is composed of fresh water, seawater, size water or other protein-containing liquid, or a mixture of two or more such liquids, along with fish viscera and / or fish litter. A method characterized by being made.   11. The method of claim 10, wherein the liquid comprises between 20% and 200% by weight of the dry feed.   11. The method of claim 10, wherein the liquid comprises between 25% and 100% by weight of the dry feed.   11. The method of claim 10, wherein the liquid comprises between 30% and 80% by weight of the dry feed.   11. The method of claim 10, wherein the liquid comprises between 30% and 60% by weight of the dry feed.   11. The method according to claim 10, wherein the immersion time is 1 minute to 24 hours.   The method according to claim 10, wherein the immersion time is 1 minute to 12 hours.   The method according to claim 10, wherein the immersion time is 1 minute to 6 hours.   The method according to claim 10, wherein the immersion time is 1 minute to 90 minutes.   11. A method according to claim 10, characterized in that the feed fragments are formed by compressing the pasty mass through openings or sieve plates.