Efficiency in feed production and control of the pelletizing process

In the feed safety and management system, we need to create critical control points very well and identify really critical points. Otherwise, we may encounter pellet quality problems such as dusting, shrinkage in pellet length, capillary cracks, and negative customer feedback very often.

Ertuğrul Yılmaz
Business Manager – Feed Safety and Management System Manager
Korkutelim Feed

The purpose of the feed production process is to produce the compound feeds under controlled conditions. That is why it is necessary to conduct hazard analyzes and identify critical control points, as well as to establish a chain of processes. While determining the critical control points, the most critical and indispensable parts for a feed factory and the critical limits of these sections should be taken into consideration. These must also be recorded at each production time, that is, in each batch.

In a feed factory, mycotoxin control of raw material and mycotoxin control of the final product, the compound feed, should be among the critical control points. Another critical control point to be addressed after mycotoxins should be the pelleting process.

As you know, pellet feed has become increasingly important in recent years due to its many advantages. Features such as reducing feed losses, allowing various feedstuffs to be added to the ration, destroying pathogenic microorganisms under the influence of temperature applied during production are important advantages for the feed manufacturer. In addition, it has important advantages in terms of animal nutrition, such as increasing the use of feed, providing more energy per unit volume, allowing starch and protein to be digested better, and increasing the flavor of the feed.

The core of the enterprise in pellet feed plants is the pellet press process. Among the many factors that affect pelleting in this process is an often overlooked part called the pelletizing cell. In this pelletizing cell section, the powder feed mix is converted into the pellet feed form. This section, called the pelletizing cell, consists of disk and roll sections. Disk or matrix partitions are special molds that determine the shape of pellet feed. On the other hand, the roller is an important pelletizing cell section that plays an active role in the formation of pellet feed together with the disk.

The pelletizing machine operator is one of the employees who are effective in the production and quality of pellet feed. These employees need to adjust the degree of feed flow to the disk and roller area well. Failure to adjust the feed flow well leads to a shortening of the life of the disk and roller. Such reasons as mass density, cellulose content can change the flow of powdered feed to the roller and disk area. Some feed raw materials tend to flow quickly to the back of the disk. For example, corn with a high density of mass flows quickly; or alfalfa flour with a high cellulose content has little ability to flow… An indicator that the degree of feed flow is well adjusted is that the abrasions are even and uniform along the disk surface. Crushing and corrosion in the field of pelletizing cells are one of the problems affecting production. The crush indicates that the rolls are set too tightly to the disk surface. In this case, the input angle of the disk channel is destroyed, and the diameter of the hole input becomes smaller than the diameter of the channel. Extra friction heat is created because the entry angle is eliminated. In this case, a chain of problems occurs, which, respectively, lead to crushing, the formation of wedges, and the clogging of the pellet machine. Therefore, after the production is stopped and the entry angle is corrected, the production should be continued. If the rolls are set too loose, clogging will occur, and if they are set too tightly, there will be distortions in the disk channel entry angle due to pressure. The disk and rolls need to be adjusted to allow a thin layer of powdered feed.

When it comes to factors affecting the quality of pellet feed, the formulation, that is the mixed feed ratio and the raw materials used, is the most important factor that causes dusting, cracks, and shrinkage in pellet feed. For example, the oil contained in the natural structure of raw materials during the pressing process has little effect on friction in the disk channel. But the effect of compound feed from the outside, that is, the liquid oil added directly to the mixer, is great. In particular, in poultry and experimental animal rations, it was observed that the oil added by more than 2% caused crumbling in the pellets and a decrease in pellet durability. This is because the powder feed passing through the matrix holes cannot be compressed sufficiently and the friction in the matrix holes decreases.

Starch gelatinization and protein denaturation occur with the steam applied in the conditioner. This is one of the important parameters of starch gelatinization and denaturation of protein in terms of pellet quality. When powder or steam is applied in the conditioner, the starch granules contained in the structure of the starch sources do not dissolve in water, the water in the steam enters the structure of the starch granules, and the granules swell. As the temperature increases (at a certain temperature value), the regular structure of the granules and the amylose-amylopectin structure deteriorate. This is also the point at which the starch is gelatinized.

The raw materials we use in feed formulation also affect the quality. Some raw materials have a positive effect on the quality of pellets, while others may have a negative effect. For example, raw materials such as wheat grains or wheat by-products (wheat bran, gluten), barley, cottonseed solvent meal, flaxseed meal, soybean meal are easily pelleted; maize and maize by-products are difficult to pellet.

Another factor affecting the quality of pellet feed is the particle size of raw materials to be used in compound feed. Using too much or moderately ground raw materials in the production of pellet feeds increases the area exposed to steam application, which allows it to retain more moisture. Since the water vapor applied to the conductor affects large surfaces, powdered feeds that have been turned into small particles are turned into higher quality pellets. Quality pellets cannot be obtained from the powder feed component that is poorly ground in the hammer mill or that is pressed coarsely as a result of the abrasion of the mill sieve holes or the tearing of the sieves. Coarse and big particles cause natural cracks and crumbles in the pellets. Also, the desired pellet length cannot be achieved.

The importance of steam applied in the conditioner is very great. Therefore, the pellet press operator needs to adjust the steam pressure, temperature, and residence time of the conditioner very well. In the production of the pellet feed, steam should be applied so that there are no dry spots on the powder feed. In general, in feeds with high starch content, a larger amount of steam must be applied so that the desired temperature of 80-88 degrees can be formed during pelletizing. This is due to the starch gelatinization, which occurs on the outer surface of feed particles, negatively affects the formation of intraparticle bonds necessary for durable pellets. That is why the duration of stay of the compound feed in the conditioner, the applied vapor pressure, and temperature are important. The minimum stay time of the powder feed in the conditioner is 30 seconds. This time can last up to 4-5 minutes. This period varies depending on the starch content in the powder feed, the amount of protein, vitamin-mineral additives, and the amount of added fat.

On the other hand, disk selection is one of the factors affecting the pellet feed quality, although not as much as the formulation factor. There are a lot of holes on the disk, and the powder feed is compressed into these holes by the rollers, turning it into pellet feed. For this reason, the holes on the matrix should be checked on a weekly basis within the framework of the machine-maintenance process control. Excessive growth of these holes causes the powder feed not to be sufficiently compressed in the holes and causes dusting in the pellet feed. Increases in pellet durability are observed as the matrix thickness or, as it is also called, the length of the hole increases.

In the abovementioned photo, we see capillary cracks on the pellet feed. Most often we encounter these capillary cracks due to errors made in the cooler section. The duration of the pellet feed’s stay in the coolers and the amount of air it receives also affect the pellet quality. Rapid cooling of pellets in the cooler causes more water and temperature to be lost from the surface of the pellet, and more water to remain in the interior of the pellet and its temperature to be high. Then this process causes capillary cracks on the pellet surface (formed by the water remaining in the pellet).

In the feed safety and management system, we must very well establish critical control points and identify really critical points. Otherwise, we may encounter pellet quality problems such as dusting, shrinkage in pellet length, capillary cracks, and negative feedback very often. The calculation of pelletizing coefficients and pellet quality of raw materials in the ration should be well known. Apart from these factors in the production of the quality pellet feed, pellet press operators and loading employees should be under control, as well.

About Ertugrul Yilmaz
Ertugrul Yilmaz has been working as Business Manager and also Feed Safety and Management System Manager at Korkutelim Feed Company for 7 years. He has taken part in many national and international congresses in the fields of process controls in animal nutrition and feed production with his papers. In addition, many of his articles have been published in national and international journals. Yılmaz, who has been involved in many projects and researches related to experimental animal feed, also works as an expert on animal life insurance at Tarsim A.Ş.