Physical Properties of Dry Pet Food

Dry pet food makes up a large share of the ever expanding pet care market, and manufacturers are keeping up with this trend by sinking more of their R&D budget into quality control and physical testing.

For a manufacturer to turn a profit, safe products that pet owners want to buy must be made and sold at a price they are willing to pay. Pet food production must be cost-effective, sustainable, meet food safety requirements and produce appetising, nutritious products for owners to feed their pets. 

High levels of physical quality are important down through the whole supply chain – manufacturer, retailer, pet owner and pet all benefit from careful texture analysis. Texture analysis is important for process control, quality control and product development as well as process efficiency (reducing extruder power consumption).

Texture is influenced by several parameters including ingredients, processing methods, packaging and storage conditions. After extrusion, kibbles are dried, coated and cooled before being packed. The conveying process can be long and the kibbles are subject to constant stress that weakens them, resulting in dust and breakage. Consequently, the durability and hardness of pellets are considered to the most important factors that are measured during quality control before distribution. Durability is the ability to handle the final product without unacceptable breakage, which produces dust particles that are not eaten by the animal.

The composition of raw materials and their quality and processing all affect physical pellet quality, as does the manufacturing technique. It is important to understand all of the factors that influence the physical quality of pet food in order to consistently achieve the best final product quality possible. Instrumental texture analysis is a fast, accurate and repeatable method for assessing (and perfecting) kibble quality, and many of the necessary measurements can be performed using the TA.XTplus or TA.HDplus Texture Analyser by Stable Micro Systems.

Individual Pellets

Kibble hardness, elasticity, chewability and crunchiness, and the stickiness of moist kibble all affect palatability when given to the pet. If the food is rejected, the owner will automatically be pushed to go out and find a new brand. Preconditioning and extrusion affect key parameters including strength, density and cooking method. Density control, kibble texture and the cooking process are important as these can affect digestibility and cause diarrhoea in pets (a factor that will certainly cause owners to look towards other brands).

The durability of pellets is influenced by the percentage of nutrients in the materials and their interaction within the structure of the pellet. If a change is made to the nutrients (for example, to become gluten free), the manufacturing technology and the compaction forces that create the network between nutrients will need to be adjusted to keep the physical properties consistent, and texture analysis must be performed at every stage.

The hardness of the pellets also affects their appearance and storage properties. Analysing pellet hardness allows the understanding of the forces necessary to break the pellet after manufacturing and helps to decide the ingredients and processes that should be used during manufacturing. Hardness analysis can be performed on individual pellet samples by compressing them using a flat probe, recording the forces needed to break the pellets. 

More useful results for oddly-shaped kibble can be achieved by performing a test of four or five samples with a Compression Platen, which creates an averaging effect. 
 
Stable Micro Systems provide a range of cylindrical test platens. When these are used along with Exponent software, an easy, automated testing procedure can be developed that saves product data in batches, with all date, time, sample weight and dimension, and instrumental data at hand.

Although compression tests give a clear graphical indication of kibble hardness, many manufacturers are supplementing this data with audio and video recordings of the test using the Stable Micro Systems Acoustic Envelope Detector and Video Capture and Synchronisation System. This information can be synchronised with the force data and played back frame by frame to observe and hear the fracturing of the pellets, which happens too quickly to be understood by the human eye.

Bulk Pellets
 
Waste is a very important parameter to reduce. It is expensive and generates customer complaints, and is caused by broken kibble and dust. Bulk compression of a large number of pellets in a Kramer Shear Cell attached to a TA.HDplus will show how pellets interact when pressed against each other under high stress, such as during storage or transport. The HD can exert forces up to 750kg, which will stand up to even the hardest pellets in bulk and show the force peaks and drops as pellets fracture. Some pellet shapes will withstand higher forces in bulk; spherical pellets are likely to be the strongest as there are no asperities to be broken off.

Additionally, many pet owners pre-soak kibble before feeding their animals. It is easy to get the volume of liquid wrong or to leave it soaking for too long. This results in an unattractive mush. 

The Ottawa Shear Cell with watertight base allows pellets and fluid to be tested in the same secure container, and its use helps manufacturers to define the idea volume and soaking time to give guidance to their customers.


Powder

Particle size distribution in the powder and granules used for extrusion is another key quality parameter, as finely ground materials positively influence kibble appearance and texture. Mixing efficiency and homogeneity is also important, with wide particle size variability causing segregation and separation during pre-extrusion mixing. This also has a negative impact on the nutritional value of the product, as each kibble should have the same nutritional content. Stable Micro Systems offer a wide range of powder and granule testing solutions. The Powder Flow Analyser is perhaps the most valuable in this application, enabling careful automatic analysis of flow, caking, cohesive and bridging properties.

Don’t let yourself get lost in the expansive global pet food market. Update your physical testing procedures with a Texture Analyser and ensure you are the brand that customers turn to time and again because they know they are feeding their pet a product of the highest quality.

Contact Stable Micro Systems today to discover the full range of Texture Analysis solutions.

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For more information on how to measure texture, please visit the Texture Analysis Properties section on our website.

The TA.XTplus texture analyser is part of a family of texture analysis instruments and equipment from Stable Micro Systems. An extensive portfolio of specialist attachments is available to measure and analyse the textural properties of a huge range of food products. Our technical experts can also custom design instrument fixtures according to individual specifications.

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