Kibble

Kibble is one of the most cost-effective, easiest, and safest pet food options out there. However, there are many questions and myths surrounding kibble manufacturing. Additionally, pet parents have recently begun shying away from “processed” pet foods and opting for more “natural” options. It is important for pet owners to understand what goes into kibble manufacturing, the safety and regulatory measures that are in place, and why certain processes are used in pet food manufacturing.

How is kibble made?

Most raw ingredients arrive by train or truck. Dry ingredients like grains are stored in silos, while ingredients like meats may be stored in commercial freezers or refrigerators. On arrival, the ingredients are inspected for quality, temperature control, proper storage, and obvious problems. Some pet food companies test all raw ingredients on arrival.

Dry ingredients are ground in a hammer mill to ensure they are the optimal size for processing. Tiny particles are best for kibble manufacturing because smaller size ensures the best water absorption, cooking, and ability to be incorporated with other ingredients and fit into the extruder.

Dry ingredients are weighed out based on formulation and then mixed in a hopper.

Dry and wet ingredients are weighed based on formulation and then combined in the extruder. An extruder is a machine that mixes and cooks the ingredients. The mixture is cooked to between 100-200°C (210-390°F). The final stage of extrusion is when the dough-like mixture is forced out of tiny holes at the end, called a die, and cut with a rotating knife. When the kibble leaves the extruder, it expands, cools, and loses about 3-5% of its moisture. At this point they are soft, spongy, and moist.

This entire process is almost exactly the same as the process for making cereals and pastas.

Next, the kibbles are transferred to a dryer which will remove 10-15% more moisture. Dryers have different temperature zones in order to optimize drying. The kibbles are warmed to around 120-150°C (250-300°F), and then cooled to between 80-100°C (175-210°F).

Coatings can be wet or dry ingredients that are sprayed onto the dried kibbles. They usually include fats and/or flavor enhancers. Fats prevent the kibbles from expanding during storage, while both fat and flavor enhancers increase palatability (taste).

Filling machines are set to deliver a specific weight of product into each bag. The bag protects the kibble, prevents fats from leaching out of the food, and ensures product integrity and safety. Many manufacturers also inject nitrogen gas into the bag before sealing in order to force oxygen out, thereby preventing oxidation (destruction) of fats and ultimately increasing shelf life.

Why is kibble cooked? Is it burnt?

Most extruders cook at high-temperature, short residence time (HTST), meaning the mixture is cooked at a high temperature for a short period of time. This method ensures complete cooking, destruction of all microorganisms like disease-causing bacteria, and denaturation of antinutritional factors. Overcooking may happen with decreased quality control, and will affect the look, taste, and nutrition of the end product. However, ensuring the product is cooked at the right temperature for the right amount of time ensures it does not burn.

Does cooking destroy nutrients?

How nutrients are affected by cooking is well-documented in the scientific literature. Most vitamins are weakened or partially destroyed during cooking, as they are very unstable compounds. However, the addition of vitamins after cooking ensures the end product is complete and balanced. Pet food companies should employ a qualified formulator, such as a board-certified veterinary nutritionist or a PhD animal nutritionist, who understands how these nutrients change during processing, and who can alter the original formula or overall process to ensure the final product is not compromised.

Does cooking decrease digestibility?

Cooking does affect the digestibility of several nutrients. While protein digestibility is decreased slightly, carbohydrate digestibility is significantly increased. Total digestibility may be somewhat lower in kibble than in lightly cooked (“fresh”) or raw diets, but this can be due to a number of factors, including ingredients used, nutrient profile, and processing methods. In reality, no studies have been done comparing identical kibble, “fresh” diets, and raw diets, so it is not known how total digestibility differs between these three types of pet foods.

Why is kibble dried?

Kibble undergoes a drying process to increase stability and shelf life. Less moisture in the final product means it is less likely to grow mold, bacteria, or other microbes. The low moisture content of kibble also improves its ability to be packaged in large quantities, shipped, stored, and sold.

Why is there salt in kibble?

Salt is present in all pet foods, not only kibble. It may not be listed in the ingredient deck because it is inherently part of other ingredients. Salt is present in pet foods because it provides two important nutrients: sodium and chloride. These two minerals are needed in the body for water balance, blood pressure, heart and kidney function, and nerve function. Salt also increases the palatability (taste) of pet foods. In therapeutic urinary diets, salt also encourages water intake.

Does kibble contain chemical additives?

In short: yes. However, everything is made of chemicals! When you look at the ingredient deck and see chemical-sounding names or ingredients you can’t pronounce, these are typically vitamins, preservatives, or additives. Synthetic additives are nothing to fear, as all pet food additives must be approved by the FDA to appear in pet foods.

What are Maillard reaction products? Are they toxic?

Maillard reactions are also known as non-enzymatic browning reactions. These reactions happen to all pet foods, not just kibble, and they occur during cooking, processing, and storage. During the reaction, proteins (amino acids) and sugars combine to form compounds that the animal cannot utilize and therefore the compound is wasted. Maillard reaction products only present a problem if the amino acid involved is limiting or present in a very small amount in the diet to begin with. Typically, though, pet foods contain a lot more protein and amino acids than the animal requires, so they can afford to lose some to Maillard reactions. This is another reason qualified nutritionists should be involved in the formulation of pet foods, because they can predict how Maillard reactions might be a problem, and then work to correct it so it does not affect the final product.

Not all Maillard reactions are negative; controlled Maillard reactions are used in pet food manufacturing to produce desired colors, smells, and flavors in the final product.

What are antinutritional factors? Are they toxic?

Antinutritional factors are substances found in certain ingredients that impact the nutrition of a product. For example, something that inhibits a nutrient’s availability, absorption, or metabolism within the animal. Antinutritional factors include things like trypsin inhibitor (affects protein breakdown) and enzymes that cause rancidity. These factors are non-toxic but do affect the quality of foods. Antinutritional factors are denatured (destroyed) during HTST cooking, the form of extrusion most commonly used in kibble manufacturing. This is another reason it is important for qualified animal nutritionists to be involved in pet food formulation, because they are able to address antinutritional factors so they are not an issue in the end product.

Is processed food bad?

The stigma around processed food comes from the assumption that processed human foods like candy and doughnuts are bad for us. In reality, these foods are not bad for us because they are processed; they’re bad because they are non-nutritious, high-calorie, full of simple sugars, are highly fatty, and because people don’t control or limit their intake. In truth, these foods can be just fine when eaten in moderation (like the 10% rule when it comes to treats).

Kibbled pet foods are processed, yes, but they are also formulated to be complete and balanced, unlike candy and doughnuts.

Processing is any action that alters an ingredient from its original state. For example: skinning and deboning a chicken is processing; grinding wheat is processing; and mixing and cooking ingredients is processing. The term “processed” has a negative connotation, but in reality, all food is processed unless it is eaten in its 100% raw and unchanged state.

What safety measures are in place?

Good pet food manufacturers have strict safety measures and stringent quality control checkpoints at each stage of the kibble-making process.

They will do background checks on their ingredient suppliers to ensure their raw products come from a safe and reliable source. They will inspect and test their ingredients on arrival to ensure quality, checking for proper storage, handling, and temperature. They work with qualified nutritionists (board-certified veterinary nutritionists, PhD animal nutritionists) who are familiar with pet food formulation and manufacturing. The final product will be tested to ensure it meets AAFCO guidelines and is complete and balanced.

 Good pet food companies ensure the safety of their product by ensuring their machines are operational and functioning at the right temperature and speed, and will perform multiple daily checks. They will also perform continuous monitoring during manufacturing, meaning that someone is always watching the machines and the product moving throughout the facility. Their employees will wear proper PPE (hair nets, coveralls, boots, gloves) and maintain good personal hygiene (hand washing, foot baths) at all times. The machines and lines will be cleaned before and after each use. The airflow in the facility will be controlled so that unclean air does not contaminate the product during processing.

What regulatory measures are in place?

The Association of American Feed Control Officials (AAFCO), the US Food and Drug Administration Center for Veterinary Medicine (FDA-CVM), and your state government all work together to regulate pet food. AAFCO sets guidelines and standards for labeling, defines ingredients, and facilitates cooperation between pet food manufacturers and regulatory bodies. The FDA-CVM regulates pet food on a national level, enforces the guidelines set by AAFCO, ensures compliance by pet food companies, and has the authority to fine manufacturers and recall diets if they are substandard. Your state and local governments help the FDA-CVM with pet food regulation, and may pass other laws in addition to those set by the FDA.

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