Texture analysis of wet petfood

Published 19/12/2019

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The texture of any given foodstuff is dependent on many different factors, and in turn links to other aspects of the food, including palatability and ease of ingestion. Hervé Rehault offers a brief insight into the science of texture analysis and how it impacts on formulating a diet suitable for small dogs.

Royal Canin technology

The texture of a foodstuff can be critical for diets designed for small dogs. This is true for dry food because of the small jaw size of these breeds, but also very important for canned or wet foods. Indeed, small dogs can be very fussy about what they eat, and texture plays an important role in palatability. This paper gives some background as to how Royal Canin assess the texture of a wet petfood scientifically.

Introduction

The texture of a substance is a complex and subjective notion dependent on many different criteria; in particular, when related to petfoods, several questions are immediately apparent. What is the preferred texture for an animal foodstuff? Does texture affect its palatability? What are the links between a product’s texture and its packaging? Can texture affect how easily an owner finds the food to use? How is the texture of a new product characterized, and how do the textures compare before and after a product is reformulated? What are the key parameters in the manufacturing process that influence the final texture? And how is the texture of a marketed petfood maintained between batches?

Rheology and texture analysis

Figure 1. The texturometer is designed to allow texture analysis using a variety of tests. © Hervé Rehault

Rheology is the branch of science that studies the flow, deformation and rupture of powders, liquids, or solids when subjected to stress. The rheological properties of a foodstuff, as determined by measuring the application of a force to the product and how it is deformed by that force as a function of time, affect its texture 1. Different analytical methods can be employed to assess solids, liquids, gels and powders 2; for petfoods one of the most useful is the texturometer (Figure 1). This versatile device employs probes or modules to analyze a food product in various ways (Figure 2); penetration and compression tests are the most commonly employed methods for both dry and wet petfoods 3.

Figure 2. Various tests can be performed using the texturometer. © Hervé Rehault

Texture profile analysis

The texture profile analysis (TPA) produced by the texturometer is now widely used in the industry and can evaluate different texture parameters for a petfood using a single experiment. It involves subjecting a food sample to a double compression (to mimic the chewing process) under standardized conditions – for example, the compression and return speeds must be the same, the sample must be deformed to a certain percentage of its initial height, and the sample size must be uniform. Using data from these tests allows construction of a force-time graph (Figure 3), making it possible to extract textural properties from a food product and correlate them with sensory analysis results. The parameters obtained with a TPA test, and the definitions for each parameter, are shown in Table 1.

Figure 3. Texture profile analysis calculations for texture expert software. © Hervé Rehault

Texture parameters	Relevant area on graph (Figure 3)	Definition
Fracturability	Point 1	Strength at which the product breaks down (does not apply for all products)
Work of compression 1	Area 4	Work required for the first compression
Hardness 1	Point 2	Hardness of the product during the first compression Force required to deform the product
Work of release 1	Area 5	Work corresponding to the first release
Adhesiveness 1/ Work of cohesion 1	Area 3	Cohesion of the product during the first ascent of the module/work required to remove module from product
Adhesive force 1	Maximum negative force during the withdrawal phase	Maximum force required to separate module from product
Work of compression 2	Area 6	Work required for the second compression
Hardness 2	Point 3	Hardness of the product during the second compression Force required to deform the product
Work of release 2	Area 7	Work corresponding to the second release
Adhesiveness 2/ Work of cohesion 2	Area 8	Cohesion of the product during the second ascent of the module/work required to remove module from product
Springiness	Length 2/Length 1	How the product returns to shape after being deformed during the first compression
Resilience	Area 5/Area 4	How the product "struggles" to return to its initial position
Cohesiveness	Area 2/Area 1	How the product resists a second deformation after being subject to the first compression
Gumminess	For semi-finished products Hardness 1 x Cohesiveness	Energy required to break down a semi-solid food into a ready-to-swallow state
Chewiness	For finished products Gumminess x Springiness	Energy needed to chew a solid product into a ready-to-swallow state

Table 1. The different parameters obtained with a texture profile analysis (TPA) test, and the definitions for each.

This analytical method originally made it possible to obtain both primary parameters (Hardness, Cohesiveness, Springiness and Adhesiveness) and secondary parameters (Fracturability, Chewiness and Gumminess) for a foodstuff. However, recent developments have allowed analysis of other parameters, and so the technical team must identify the most relevant textural parameters for any given product before commencing a study.

The TPA analysis & Royal Canin

The ability to characterize the texture of wet products is an invaluable asset, especially since Royal Canin has such a wide variety and complexity of recipes. At present, the “Hardness” parameter resulting from the first TPA test compression seems to be the most discriminating to characterize a “loaf” type foodstuff. Product texture measurement obviously requires the implementation of several methods to obtain a full profile for a foodstuff. For quality control, and to use texture as a key quality attribute, such methods must be able to be deployed quickly in the manufacturing plant and should not be prohibitive in terms of time and cost. The TPA test thus remains a primary tool for both new product development and for ongoing assessment of existing products.

References

Tabilo-Munizaga G & Barbosa-Canovas GV. Rheology for the food industry. J Food Engin 2005;67:147-156.
Scher J. Rhéologie, texture et texturation des produits alimentaires. Techniques Ingénieur 2006;F3300.
Chen L & Umezuruike LO. Texture measurement approaches in fresh and processed foods — a review. Food Res Int 2013;51;823-835.

Hervé Rehault