Driven by the increasing
consumption of fish meat due to world population boom and the limitation of
wild catch, volume growth rate of global aquaculture has been sustained at about
8% over the last 10 years, and must continuously undergo a tremendous development
in order to fill the huge gap between supply and demand for the premier protein
sources. This represents a divine opportunity and a promising future for the
aqua-feed industry.
The unique physiology of
aquatic animal is asking for special requirements in aqua-feed manufacturing
technology. This article will discuss the complete solution for aqua-feed
manufacturing based on Muyang's years of experience as an aqua-feed mill
supplier and builder in such aquaculture regions.
1.
Requirements
of aqua-feed
1) Grinding fineness:
Proper particle size of ground materials can contribute to lower energy
consumption of a feed mill, facilitate the subsequent conditioning process,
increase the water stability of aqua-feed pellets, and eventually obtain
nutritional aqua-feed that benefits the digestibility of aquatic animals.
2) Size of feed pellet: It
is depending on the size of aquatic animal to be fed and its feeding habits.
3) Water stability: 45~90
min for shrimp feed and 5~30 min for common fish feed.
4) Floating / sinking
ability: Different aquatic animal species live in different depths of water
(shallow water, middle water and deep water) and different habitats. Therefore,
the feed for different aquatic animals should be sustainable in corresponding
depths.
5) Palatability: Most of
aquatic animals favor feed of special color, scent and flavor.
2.
Aqua-feed
processing technology and equipment
Both pelleting process and
extrusion process are adaptable to aqua feed production. As the development of
aquaculture, however, feed extrusion technology is more and more popular in the
aqua-feed production because of its balanced nutrition, the excellent water
stability, and most of all, the environment friendliness.
Raw material receiving and
cleaning
The designed capacity for
raw material intake in an aqua-feed mill shall be 2~3 times of its production
capacity. For materials of different properties, special cleaning operation
should be carried out where it is received. For instance, granular materials
can be cleaned with a Muyang Drum Pre-cleaner and the powdery materials with a
Muyang Conical Pre-cleaner, under the assistant of an aspiration system.
Primary grinding
As the pretreatment of fine
- grinding or ultra-fine grinding in aqua-feed production, primary grinding (or
coarse grinding) is designed to diminish the difference in and the variation of
material particle size, to improve the working performance and working
efficiency of the pulverizer thereof, and to ensure constant quality of
finished products.
Primary proportioning and
batch mixing
In such processing section,
the major ingredients, i.e. the ingredients of larger proportion in aqua-feed
formulation, are batched by an electronically controlled proportioning system,
and then sent to the mixer for primary mixing. Primary proportioning and batch
mixing are designed to limit the variation of material particle size before
ultra-fine grinding, so as to further ensure constant quality of finished
product. The proportioning bins in this process section should be designed to
have a storage capacity to sustain the 4~6 hours' uninterrupted production of
subsequent process.
Secondary grinding
Eating little, short
digestive tract as well as bad digestibility of the aquatic animals require
finely ground feed particles.
Secondary grinding usually
is executed by a specialized pulverizer (ultra-fine grinding) or a
fine-grinding hammer mill in Muyang solutions.
Secondary proportioning and
batch mixing
The finely ground
ingredients are fed into the other mixer for secondary batch mixing after
proportioning. Usually, a manual feeding inlet is provided for adding micro
ingredients into the secondary mixing mixer. And also two liquid application
devices are furnished for adding water and oil respectively.
Extrusion and drying
Extrusion process is mainly
executed by an extruder that is basically composed of a stationary barrel
housing in which such elements as segmented screws and shear locks rotates,
fulfilling extrusion operation together with a disc and knife assembly. There are
two kinds of extruders that might be used in aqua-feed production: the
single-screw extruder and the twin-screw extruder.
Coating and cooling
If necessary, liquid fats,
flavors, and vitamins can be added externally to extruded feeds after drying.
Post liquid application by coating will not only avoid the risk of damaging
heat sensitive ingredients, but also improve the palatability and reduce powder
generation of the finished product. After coating, extruded aqua-feed is cooled
as required.
Bagging
When bagging aqua-feed, the
amount of air entrained in the bag or that penetrating into the bag should be
controlled to a minimum, so as to prevent feed from oxidation and
deterioration. Therefore, it is recommended to close the bag through sewing
plus heat sealing (plastic film lining), which can prolong the shelf life of
finished product by 50~100%.
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