DO WE NEED PREMIXING?
The use of premixers for premixing micro-ingredients is technics widely used in the feed industry. The benefits for such process have been promoted by many experts for many years. The main rationale behind the premixing is the optimization of the dispersion of micro-ingredients. But recently, I discussed with one Feed technology expert in Thailand who mention that we can get similar dispersion by incorporating the micro-ingredient directly in the mixer.
This statement is going against all the beliefs regarding the need for premixing.
Actually, I found several publications confirming this statement. A study made by Mc Elhiney and Tangprasertchai demonstrated indeed no major difference of CV depending on the premixing dilution.
Some other publications mentioned that actually the premixing will impact positively the dispersion for cohesive powder and will enable to reduce the time of mixing. Pfost claimed that a premixing for a ingredient incorporated at 30% in the mixer would get dispersed faster than the same quantity ingredient incorporated only at 11% of the mixer. Friedrich and Jansen compared the CV% of a micro-tracer of different dilutions of premixes. They obtained lower CV% when using premixing for short mixing time (60 seconds). But they noticed as well that the differences of dispersion disappeared when the mixing time get extended.
The last testimony that I found came from Tecaliman (http://www.tecaliman.com). Tecaliman is a French laboratory specialized in process optimization in Animal Nutrition. The table below illustrates the impact of premixes dilution for 2 different feeds at 2 different mixing times. Both cases demonstrated acceptable recovery rate. For the Feed 1, there are no significant differences between the incorporation of premixes at 100%, 50% and 12.5%. For the Feed 2, they worked with short mixing time and with a more cohesive feed due to higher fat content which could limit the dispersion of additives. The CV% is improving with the dilution of the premixes but the differences stay limited. The fact that they used shorter mixing time and higher fat content could explain the relatively lower dispersion for the pure premix.
In summary, it seems that the use of premixes does not impact that much the dispersion of micro-ingredient in the final product. Nevertheless, there are other reasons that would support the use of premixes
1.Precision of the weighting of the micro-ingredients
Micro-ingredients would require a much higher precision of weighting than the macro-ingredients. That would ask for adapted equipment that should be dedicated and set up specifically for micro-ingredients
2.Savings of mixing time
As mentioned above, the preparation of premixes can help to reduce the processing time. Indeed, the weighting of the micro-ingredients can be very time-consuming and it would be more productive to organize this process in parallel to the preparation of the macro-ingredients.
3. Reduction of crossed contamination
The incorporation of diluted micro-ingredients into the system will leave lower traces than if the same micro-ingredients was incorporated pure. Moreover, it would be easier to clean up the premixing equipment because of its smaller size and easier access.
4. Supply optimization
Despite the elements above, there is still a lot of value to get premixes from specialized suppliers. They may have access at lower purchasing prices and may help to simplify the management of wide range of micro-ingredients. I encourage you to organize your own tests and close collaboration with your premixes partners or additives suppliers. Each ingredient would behave differently according to your equipment, time of mixing and nature of the carrier. Selecting the right ingredient with proper carrier and flow ability could enable you to adjust your mixing practices.