In the grand scheme of things, making our Sojos natural pet food mixes is a relatively simple process. We source the ingredients (typically in 50 lb. sacks), carefully blend them together in the correct proportions, bag the mix, and it’s ready to go. After all, the whole point of fresh, raw pet food is to leave the ingredients in tact so that the naturally-occurring nutrients and enzymes are present. On the other hand, manufacturing kibble or extruded pellets is not quite as simple. It is an extremely complicated process, the end result of which is quite different than the original ingredients used.
So how in the heck are those little mystery pellets made? Well it all starts with a bunch of dry ingredients. Because extruded pet food is made in massive quantities, ingredients are purchased by the truck-load and are typically stored in silos. The first step in making extruded pet food is that a machine called a hammer mill grinds the ingredients to a precise size so that they can be used to create a completely homogenous product. If the particles are too small or too large, they won’t absorb the correct proportion of water and the kibble won’t cook correctly. Typically ingredients are ground to the size of coarse flour.
Next the ingredients are blended together using a machine called a ribbon mixer (which is the same machine that Sojourner Farms uses to mix ingredients in our natural pet food). Computers control the scales and assure precise proportions of each ingredient.
Next the mixture must be pre-conditioned before moving onto the extrusion process. Preconditioning is the process by which the dry ingredients are mixed together with wet ingredients including the fats and the meat along with hot water and pressurized steam. This hot water and steam begins the cooking process, and the starch in the ingredients begins to gelatinize. Approximately 1/4 of the cooking takes place at this time. Once preconditioned, the ingredients are ready for extrusion.
The extruder is like a massive metal tube with a giant screw inside of it. Originally these machines were designed for the plastics industry. Dough is fed in one end and on the other end is a die, which determines the shape of the kibble. The walls of the tube are heated to a high-temperature so that the ingredients cook as they touch the wall, moving through the tube as they’re propelled forward by the screw. The tube is also filled to the point where there is a massive amount of pressure inside, which, along with the heated walls of the tube brings the dough to extremely high temperatures. This typically causes the naturally-occurring nutrients to be destroyed. As the dough is squeezed out through the die and cut by a knife, it is released from the pressure and hits open air. This causes the kibble to expand about 50%. These puffed-up kibbles are hot and soft.
Finally a process called enrobing occurs. The food goes into dryers where it is hardened. Because much of the nutrition has been cooked out of the kibble, synthetically-formulated nutrients must be sprayed on, along with flavor enhancers in the form of liquids or powders. Now the kibble dries again, and finally it is ready to be weighed and bagged.
So what are the pros and cons of extruded food? The number one advantage is convenience. Much like fast food for humans, kibble doesn’t require a lot of effort. You simply open the bag and pour it into a bowl. The other advantage is a relatively long shelf life, due to the high heat and preservatives that have been applied during processing. The down-side to kibble is that you don’t get any of the naturally-occurring nutrients which are destroyed during all of the pulverizing, processing, cooking, and preserving that goes on. Synthetic nutrients aren’t as easily absorbed by the body and, despite kibble’s long shelf-life, synthetic nutrients are less shelf-stable and can be destroyed during storage or shipping. Another disadvantage is that the artificial preservatives used in kibble can cause dog health problems. It’s also important to beware of a product trying to extend shelf-life by using natural preservatives like vitamin E, as they aren’t as shelf-stable and can spoil or lose their effectiveness over time.