In the wake of the food scares that have alarmed consumers, enthralled the popular press and concerned the food sector in recent years, safety and hygiene have become the main focus of the feed industry today. Feed equipment suppliers are scrambling to offer models with improved hygiene features and new process solutions (see "Bigger, Better, Hotter," World Grain, January 2002) while feed associations and governments require ever higher standards and more rigorous accountability.
How is the feed manufacturer to go about finding possible solutions in the production process that can contribute to a system that is safer and can be controlled more easily?
A team from Tebodin CCE (Cebeco Consulting Engineers B.V.), of Deventer, the Netherlands, one of Europe’s most experienced feed mill builders and milling consultants, shared its thoughts with World Grain and offered some possible solutions.
To be completely sure that the entire feed production process and feed mill management procedures are kept under control, certain key conditions must be fulfilled:
•An optimal tracking and tracing system (fig. 1) must be in place.
•Prevention of the introduction of noxious contaminants into the feed mill, such as from the surrounding environment.
•The ability to ensure that critical or suspected raw materials and finished products can be isolated for a longer period (kept in quarantine) and be removed from the feed mill in the event they fail to meet quality criteria.
•No superfluous areas in silos and machinery that could provide conditions for contamination, condensation, growth of bacteria, etc.
•Strict control of hygiene and process conditions.
TRACKING AND TRACING.
According to Tebodin CCE, tracking means "to follow the product during the flow in the total process, with the result that in each stage the information about the condition of the product can be checked."
Tracing means "to investigate at the end of the process, with the purpose of recovering the origin, the production processes undergone and the delivery of the end products with any deviations — upstream for the received materials and downstream for the delivered products."
RAW MATERIALS PROCUREMENT.
All incoming deliveries of raw materials must be sampled in order to establish and judge the product quality and to be able to demonstrate due diligence in the event of legal liability. This sample could already have been taken and analyzed at the point of origin of the goods (at the supplier’s facility). If the quality is acceptable, nothing further needs to be done when the goods are received, and there will be no delay.
The analysis method used for sampling will depend on the suppliers’ certificates: i.e. ISO, GMP and HACCP. Sampling for quality control may be combined with that for the composition of the material, which is required for the nutritionist’s production recipes. Quality sampling should take place to determine possible deviations such as micro-bacterial pollution; noxious substances, such as pesticides; mold and mycotoxins; and physical pollution, such as stones, metals and other foreign objects.
Special attention must always be given to smaller deliveries from local suppliers and farmers because these companies usually don’t have a professional quality assurance system or certification program. Furthermore, be careful not to put price before quality. In the past, problems in the feed sector often appear to have been related to inferior raw material supply.
RAW MATERIALS RECEPTION.
A typical intake system is not generally optimal with respect to hygiene and contamination prevention. Intake pits nowadays are used for more than one type of product and in general are not cleaned before each delivery. Mud and dirt as well as rainwater on the bed of the truck can become part of the delivered goods.
In contrast to this open system, a docking system will be a major improvement because it is completely closed (figure 2). However, trucks will have to be of a suitable design for this system. Although the intake points must be closed, there must be accessibility for cleaning.
Raw materials with conflicting properties can only follow each other after "flush-batches" and careful cleaning, or must be received at another intake. This last concept can be realized more easily with pneumatic transport (figure 3). Consideration should be given to using this type of system more often, despite the restricted capacity and higher energy consumption.
Tebodin CCE also suggests that the raw material be stored on the truck in a separate (clean) container (figure 4). This container is filled by the supplier and delivered to the feed plant. The container with product is then placed in the dosing section and will operate as a dosing bin. The truck will deliver full containers and collect empty ones; refilling takes place at the supplier after cleaning.
This procedure is not cheap, however. Regular cleaning, driving around with empty containers, storage of the containers and so on costs money. Nevertheless, the container system is already used in special feed plants and human food installations. The same procedure can also be applied for liquids.
Tools for sampling analysis and registration, such as NIR/NIT, laser scanning and barcodes, are already in general use. Weighing all received batches of products is an important step in order to keep the tracing process under control.
STORAGE AND DOSING.
Segregation of each load delivered should be the goal, as only then can any deviations that have been detected during or after processing be traced. Tebodin CCE’s Harm Klein acknowledges that in many existing feed mills this is very difficult to achieve.
In practice, deliveries are generally combined and inevitably mixed in large silos. This way, it is impossible to follow a specific load as it is received from a supplier. This process becomes even more difficult if, as is often the case, the silos do not operate on a first-in, first-out system.
Mass flow instead of funnel flow will facilitate tracing a specific product through the process. Separation of loads can be realized more easily through the use of smaller silos, for instance 3x30 tons instead of 1x90 tons (figure 5). If these 30-ton silos are installed on top of each other, a simple flow process will be achieved. If the remainder of a delivery is left in a large silo and a new load is received at the intake, silo-cycling will take place — the remains of the old load will be transported to a smaller available silo.
As mentioned when discussing intake procedures, some smaller amounts and critical raw materials can be stored in containers; premixes and other smaller components will be stored in small silos.
Additional scales can be installed under the silos — for example, a separate weigher for each "family" of products (figure 6). In this way, a weigher has fewer dead areas, and a weigher for critical raw materials is only used when needed.
Recycling product returns from the farmer involves a level of risk because it is not possible to be certain what has happened to the product while outside the mill. There is no way of knowing for sure how it has been treated or if it has been infected in any way. It is best to treat this product as a special case, in a separate part of the plant, before dosing it again.
It is not acceptable to re-use returns without giving them special attention. The same applies to fines; these must be stored in several separate silos in order to be sure that material is dosed with the right batches. Fines, return products or recalls containing medication should never be accepted.
GRINDING AND MIXING.
This process line should be designed to have a minimum of stations because each bin contributes and introduces extra contamination. The grinding section with the aspiration system must be built in such a way that the premixes in the mixer are not sucked up into the filters. This can be achieved by airtight valves and efficient automation.
Mixing of dry products and liquids with one mixer is a critical process. The dry mixing takes time to reach the required homogeneity, and the addition of liquids introduces the risk of cross-contamination in the mixer.
Several new mixers try to cope with these problems. With the high quantity of liquids in modern feed formulation, installing two serial mixers could be a solution worth considering — the first for dry components, the second for adding the liquids (figure 7).
This is not an inexpensive solution. However, an upper bin for the liquid mixer is not required, and there is no need for a continuous molasses mixer. Amounts of up to about 3% molasses could be added in the second mixer. The rest, depending on the formula, is added in the conditioner in the pelleting line.
The need for two parallel mixers will be dictated by, among other things, whether animal proteins will be permitted for inclusion in the future. They would be added directly in only one of the mixers. For other groups of products that must not be cross-contaminated, a second mixing line provides a dedicated option and is the solution of choice. Check weighing can take place when the mixers are installed on load cells.
Smaller press meal bins that hold only a few batches provide a better means of tracing (figure 8). For different groups of products, which must not be cross-contaminated, more lines are desirable.
If medicines can be added on a small mixer in the press line, contamination in the mixing line upstream can be avoided (figure 9).
The new round-booted elevators now available are suitable for contamination-free transport of the pellets to the sifter. Some plants use pneumatic transport for this despite the high energy and maintenance costs.
Be sure that the fines from the sifter are only combined with products of the same formula. This is also important to watch when switching formulas.
FINISHED PRODUCT SILOS.
Are large finished product silos still needed? Isn’t it better to produce to order and store in smaller bins instead of producing to stock, where tracking and tracing is almost impossible?
According to Tebodin CCE, an option for smaller amounts or special demand is direct production into small contra-sets with bins of the same size as the truck compartments. For these highly sensitive products, Tebodin CCE says it is even better to discharge finished products directly into transfer containers. The trucks leave behind the containers with finished product at the customer’s farm and collect them after emptying. After cleaning, the containers may be reused (figure 10).
Further bulk blending contributes to a cleaner finished product and a more flexible response to the individual client’s needs (figure 11).
CONVEYORS AND ELEVATORS.
In recent years, the quality of internal transport elements has improved considerably. They are made of more appropriate materials: chain conveyors have rounded bottoms, elevators have close-to-clean bottom designs, etc. These improved products are regularly seen in modern plants.
"Pneumatic transport and free-flowing systems improve the possibility of contamination-free transport, so these have to be applied where possible and feasible," Klein recommends.
Another important alternative is the horizontally and vertically moving bin (figure 12). If this bin is designed in the right way, made from suitable material and completed with necessary accessories, a high level of functionality can be reached. The moving bin may be used for conveying and as a buffer bin after positioning. For each process step where this equipment is used, the type, number and speed will have to be determined.
It is clear that for the optimal "food-safe" feed plant, the concepts that were applied in the past need rethinking. However, during the past few years, other fundamental principles have been introduced that allow more effective tracing and tracking.
New concepts must be introduced, together with sophisticated automation, to improve security and safety of the end product. Some of these concepts are here already; some are theoretical.
In most situations, it won’t be feasible to implement all recommendations in one step. Limitations will be found in the existing layout of the plant and its operations.
Economic considerations also may limit how much can be done and how quickly. In all probability, a step-by-step approach will be most realistic in order to solve existing problems and to arrive at the required level to be a food-safe animal feed plant.