In this issue discussions on packaging, process control and moisture sensing are all tied together in getting a good quality product in the pet owner’s hand. What is involved? Follow the water. Ingredients received usually at 12 percent moisture. In the process preparing the ingredients including grinding which can slightly lower moisture. Yes, tracking where the water goes. In the extruder where almost all ingredients come together the evenness in the moisture out of the preconditioner and extruder are directly related to the moisture of the pellets into the dryer. With computer control and dry and liquid flow metering the accuracy of the liquids injected, water, steam and others with the measured dry flow is very accurate. Pumps, flow meters, NIR’s all have an impact on this moisture through the extruder. If you want equally sized pieces, small range in density variation and other moisture related specifications then you will want to closely control water along the process.
Even moistures to the dryer over time allow for even moistures out of the dryer assuming the dryer is designed for a low moisture variation. If the moisture to the dryer, with a normal 20-minute retention time, varies it will most likely vary upon exiting the dryer. In fact, special attention to dryers was needed to take a very even moisture product into the dryer and make it exit evenly. Time, temperature and air flow adjustments is where attention was addressed so that each and every pellet is equally treated and yields the desired results in moisture variation. The tighter the variance at this point the higher moisture setting you can have and not exceed the maximum you allow. Work over the years on both horizontal and vertical dryer have improved their ability to dry evenly. Efficiencies are greatly improving with designs and air temperature and flow control in and out of the dryer.
So, we now wish to place this dried product in our bags, first what is the product temperature? It needs to be within five degrees Celsius or lower of ambient temperature or you don’t run the risk of moisture condensation forming on the inside of the bag. This will at some point moisten a few kibbles in that area and possibility of mould and bacteria growth greatly increase. What this means is the cooling devise needs to be sized correctly for maximum capacity as well as have enough air flow taking into account your local climatic conditions, so the product is cooled as noted above. Possible cooler locations to avoid condensation from unusual hot or cool areas in the plant might need to be considered.
In some cases, the product needs to be cooled multiple times. Cooled after dryer to lower the temperature some so the fats added will absorb in the pellet due to elevated coating level. Complete cooling to a low temperature allows the fat coating to remain on the surface for palatability. Elevated coating temperatures of coated kibbles might require a post coating cooler again the goal of within five degrees Celsius is needed right before the packing.
Concluding the process controls all along the line, backed up by sensors to verify the specification at that point all have a big effect on what is placed in the bag. There are minimum and maximum guarantees, and your goal is to be as close to these as possible for maximum profitability. Doing it at maximum or elevated tonnes per hour requires all devices on deck and working.
