Joseph P Kearns

Joseph P Kearns

Editor, International Petfood Magazine

Baked petfoods and or treats, temperature confirmation for bacteria kill step, treats and snacks, dies and zoo feeds are all interesting topics and the ones we close out International petfood magazine’s first year. It has been exciting and challenging at the same time. Hoping our readers have enjoyed the first year and we are looking forward to 2023. With this in mind it would be quite interesting if the readership offered up some topics for review and if you are interested in passing some questions on send to joek@perendale.com for review in 2023 issues.

Baking of petfoods is a method to achieve the cook and temperature to achieve a good product and one that is bacteria free. In fact, commercial petfoods before extrusion were in many cases by-products from human food factories. Scrap breakfast cereals, fines and or broken crackers and bits from any baking industry were bagged and sold as a base product for pets. Pet owners learned that the food needed to be cooked if it contained starch as the pets’ digestive tracts could not handle raw starch. Many pet owners used table scraps to cook up a concoction of ingredients to feed dogs and cats. The scraps from baking factories allowed food to be prepared and not have to be cooked due to the starch being gelatinized already with combinations of other products added by the pet owners.

In more recent times the baking of petfoods has mainly centred on baked treats. Years ago, in New Zealand a product called TUX was shown to me and it was a baked dogfood. Having been in a position to sell petfood extrusion production machinery a discussion continued and it was a hard one to overcome. This was a famous New Zealand brand designed for their needs. I was told sheep farmers would feed the sheep dogs by tossing them a few biscuits a day out on the range. They were considered very convenience, balanced nutrition and included trusted ingredients. No bags no bowls, a few biscuits could be carried easily in a vehicle or on horseback. Today we see a number of outfits making baked petfoods and treats. The main claim is lower temperature and longer time yielding fewer nutrient losses. There is a difference in texture and flavours no doubt. We could analyse all the data but basically the bacteria needed to be eliminated and the moisture level or water activity was controlled. Both processes achieve these goals. In fact, recently the 2 processes are blending together, extrusion processes allowing high meat as well as a variety of ingredients, not all centred on cereal grains but include vegetables are being extruded with higher moisture levels out of the extruder and the balance of the process happens in the dryer much like the baking process. The textures from these processes are similar.

The baking industry is a time and temperature process and this would allow for predictable temperatures being hit with a selected formula over a set amount of time. Extrusion is a bit different as the process adds water, steam etc. to make the mix higher in water and the cooking by friction all happens in about 2 to 3 minutes, 2 minutes preconditioning and 30 seconds in the extruder barrel. Baking petfoods is a higher moisture dough prepared, formed and placed on a continuous baking sheet. Some current extrusion processes are extruded at such a high moisture the product is dough like off the die resulting in special handling or pre drying so the kibble holds it shape and can be conveyed to the final dryer or oven. The evolution of petfood production continues.

The extrusion process having so many actions going at once such as adding the dry and wet ingredients, controlling the cook profile, getting the die correct and expansion of the kibble as desired and the ability of an operator to insure all of this and control bacteria has pushed this process to computer controls and advanced sensing devices such as flow meters and temperature indicators in precise areas. Slide gates after the preconditioner and a flow restriction by pass device at the end of the extruder barrel allow for very accurate temperature control of the product. Typically, about 77 to 80OC minimum out of the preconditioner and right at 125 OC out of the extruder die are the approximate goals in the extrusion process. Since this is a guaranteed type of desired effect, the entire mass flow needs to hit the minimum temperature level. Temperature probe location is critical and needs to be located in the lowest temperature product flow area. The most important time for all of this is when the system is not in steady state operation, during start up and shutdown procedures. Basically, the slide gate on the preconditioner stays closed until the desired temperature is reached, it then opens and flow progresses. If the temperature goes down the slide gate shuts until conditions are met for it to open again. At the end of the extruder the same happens, temperature is reached the product exits the die and continues downstream, if temperature is too low which happened in every product start up the material is bypassed until the correct temperature is reached. Done correctly and you have achieved your kill step for bacteria. Keeping it clean downstream from the kill step is another topic.

Pet treats and snacks articles produced via the baking process will add details to this topic in coming issues. Many zoo feeds are extruded and are very specialized will all also be covered in future issues. We look forward to reviewing these and many others in more detail in next year’s additions. Happy Holiday Season to all.