Texture Analysis of Pet Food and Animal Feed

Quick rejection of undesirable petfood provides enough motivation for pet owners and pet food manufacturers alike to provide animals with the correct food. In the pet industry, some aspects of the food must also appeal to the owner feeding the animal – the smell, appearance and texture must all be pleasant and not off-putting. After determining the parameters necessary for a high quality product, it is usual to use instrumental texture analysis techniques to determine the measurable properties. Instrumental texture analysis is a fast, accurate and repeatable method for assessing (and perfecting) petfood and animal feed quality, and many of the necessary measurements can be performed using the TA.XT Plus Texture Analyser by Stable Micro Systems.

Dry pet food makes up a large share of the 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. 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).

Typical Texture Analysis Tests for Petfood and Animal Feed

How to Measure Kibble Hardness/Durability

Texture is influenced by several parameters including ingredients, processing methods, packaging and storage conditions. 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. 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 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.

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 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.

Comparison of compressibility of three kibble types using a cylinder probe

Comparison of compressibility of three kibble types using a cylinder probe

How to Measure Kibble Crunchiness

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 usually happens too quickly to be understood by the human eye.

Acoustic Envelope Detector and Video Capture and Synchronisation System

Acoustic Envelope Detector and Video Capture and Synchronisation System

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 cell (below) allows pellets and fluid to be tested in the same secure container, and its use helps manufacturers to define the ideal volume and soaking time to give guidance to their customers.

How to Measure Snack Stick Brittleness

Petfood snack sticks can be tested by the use of a Three point bending test. The stick is positioned on two base supports and load applied from above in the centre of the stick. The force to break indicates the brittleness or flexibility of the stick – such characteristics being of great importance to the acceptability of the product.

Three Point Bend test of a dog biscuit

Three Point Bend test of a dog biscuit

How to Measure Wet Petfood Texture

Wet foods make up the majority of products sold in pet shops, consisting of meat and liver with a range of other ingredients. The textures are solid, pureed, shredded, cuts, cubes and blends of human food ingredients. These are much more palatable than dry foods to most cats and dogs - neither dogs nor cats are drawn to sticky foods but both show a preference for wet food rather than dry. Cats are even fussier than dogs about the texture of their food. The downside is that stools in the litter box are generally softer and smellier if the foods are not formulated correctly, providing more motivation to work on the texture of the food (as well as the nutritional content).

The majority of wet foods contain several different textures held within a jelly or gravy matrix. This presents a textural challenge as a single point penetration test in different areas of the food will give different results. However, Stable Micro Systems offer a Multiple Puncture Probe that provides an average of many areas, providing more repeatable results. Probes can be removed for cleaning and can be replaced easily if damage has occurred.

Penetration test on canned dog food using a Multiple Puncture Probe

Penetration test on canned dog food using a Multiple Puncture Probe

For a full summary of typical texture analysis tests that can be performed on hair and haircare products:

This information has been sourced, reviewed and adapted from materials provided by Stable Micro Systems Ltd.

For more information on this source, please visit Stable Micro Systems Ltd.

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