FEED PROCESSING ▶▶▶


Post-thermal application of feed additives


Introducing an alternative design of feed processing line to protect heat-sensitive materials


BY MOHAMMADREZA KOUHKANNEJAD, UNIVERSITY OF TEHRAN, ALIREZA BAYAT, NATURAL RESOURCES INSTITUTE FINLAND, FINLAND, ALI BAZGIR, ASIAB MACHINE IRANIAN COMPANY


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ompound feed is a mixture of main ingredients, in- cluding grains, protein supplements and by-prod- ucts, and feed additives (micro-ingredients) such as minerals, vitamins, commercial enzymes, probi-


otics and prebiotics. In conventional feed mills, these two categories of ingredients are placed in a mixer to produce a uniform mixed feed. Then this feed is transported to the conditioner where the feed is subjected to thermal process- ing and continues on, passing through a hot die to produce hot pellets. In the next step, the temperature and moisture


of pellets are reduced by a cooler. For a typical design of such a feed processing line see Figure 1. In this kind of feed processing line both main ingredients and feed additives are cooked.


Avoid detrimental effects However, thermal processing is a double-edged sword; the applied heat has both positive and negative effects on the main ingredients, but its effects on feed additives usually are negative. Many feed additives, especially commercial en- zymes, probiotics and vitamins are expensive and sensitive to heat, thus it is suggested to protect them from the detrimen- tal effects of thermal processing. the feed industry uses three solutions to maintain heat-susceptible materials: • Excess or over-use of materials to compensate for potential losses during the heating process. This means there is lav- ish use of expensive materials.


• Using a heat-resistant or coated form for some materials to protect them from heat. In many cases, the protection is not complete and this is not possible for all materials.


• Vacuum coating is a technological solution that can be ap- plied to materials after thermal processing. This technolo- gy is usually applied to oils and liquids, and requires addi- tional investment and energy. Nevertheless, it is viable for high-margin products such as extruded aqua feed and pet food.


Figure 1. Conventional design for feed processing line. 16 ▶ ALL ABOUT FEED | Volume 28, No. 5, 2020


Alternative design feed processing line Figure 2 introduces a novel design of the feed processing line. In this design, the main ingredients are grinded, weighed and then subjected to conditioning by a super con- ditioner. Since the feed additives are not yet added to the main ingredients, it is possible to use higher temperatures (e.g. >90 ˚C) and longer retention times in the super condi- tioner, for instance for hygienizing purposes. In the dryer and cooler, the conditioned main ingredients will lose the heat and moisture absorbed in the conditioner. After this stage, feed additives are mixed in a micro-mixer to produce a pre- mixture which is added to the main ingredients in a mixer.


PHOTO: SHUTTERSTOCK


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