The Texture of Dairy Foods is as important as flavour and colour

Texture can make or break a product’s perception. How to talk about it, how to target it and how to tap into the ingredient toolkit is a definite requirement for dairy developers. 

With everything from Greek-style yoghurt to efforts at fat reduction underscoring texture’s importance, there’s no time like the present to turn texture to your advantage.   

“In the past, consumers didn’t really notice texture until it was ‘wrong,’ such as a powdery texture in a smoothie or a slimy, cohesive texture in a sauce,” said Shana Brewer, a marketing manager at Ingredion Inc., Westchester, IL. 

“But food manufacturers are now using texture as a key differentiating quality to improve a product’s overall consumer appeal.” 

She cites as proof the uptick in front-of-package texture claims, noting that research from Innova Market Insights found the use of texture claims more than doubled globally over the last five years.

Testing the Behaviour of a Keyboard using a Texture Analyser

When performing an objective test on a keyboard, the main components under investigation are the switches, actuated by pressing keys.

From keyboard to keyboard, there is little a given manufacturer can do to affect a switch's performance. The switches come in batches from switch makers, and keyboard manufacturers mount them onto printed circuit boards and do not have the ability to alter them. Seth Colaner at Tom’s Hardware has developed a procedure for testing mechanical keyboard switches using a TA.XTplus Texture Analyser.

Previous attempts at testing switch performance has involved the use of small weights, but this is not an accurate technique. Maintaining the balance of multiple weights placed on top of keys with varying geometry affects the measurement as it is easy for weights to move off-centre. Additionally, the forces required to actuate a switch can be very small (on the order of 50g), so the way even small weights are placed can fluctuate the actual load and throw off the measurement.

Viscoelasticity in the Materials Industry

Many industrial materials have viscoelastic properties depending on their constituents, processing conditions and the conditions during use.

They can be very obviously viscoelastic when held in the hands, or this behaviour may not be apparent until heated up to 1000°C and put under a large stress. The relaxation time also varies a large amount. Whether this viscoelasticity is beneficial or not depends on the material’s type and intended use.

Memory foam mattresses are becoming very popular due to their ability to mould to the shape of the sleeper’s body, relieving pressure on painful joints. They have a layer of temperature-dependent viscoelastic material - when a load is applied (a person), the material relaxes away to take on the load’s shape. They then show slow springback when the load is removed.

Viscoelasticity in the Pharmaceutical and Cosmetics Industries

Many pharmaceutical and cosmetic products have viscoelastic properties that can be measured using a Texture Analyser.

Pharmaceutical tablets show viscoelastic stress-strain behaviour when the powder compact is being loaded and unloaded, and this behaviour continues once the load has been fully removed. This can cause problems for tablet manufacturers such as capping, when either the upper or lower part of the tablet separates from the main body when ejected from the press or during the handling process. 

Viscoelastic properties are functions of the compression conditions as well as the formulation. It is important to investigate every instance of capping to ensure the problem is not repeated (which is very costly) and to measure the viscoelastic properties of new formulations before they reach the mass manufacturing stage. 

Viscoelasticity in the Food Industry

The vast majority of food materials show a combination of viscous and elastic behaviour although many show much more of one than the other.

There are some exceptions – hard crackers are generally completely elastic, whereas oil and runny honey usually show no elastic behaviour. Viscoelastic testing is best used as a comparative measure as many food products have an unusual geometry, so conventional viscoelastic equations cannot be used to find fundamental parameters.

If a cracker is not completely elastic when bitten, it may have become stale. The degree of viscous behaviour can be measured to study this effect. A sample so brittle is not easily clamped without fracturing, so tensile testing is not an option, but equally it is not a suitable shape for compression. 

Measuring Viscoelasticity using a Texture Analyser

What is viscoelasticity?
 
When a force is applied to a material, it causes the material to deform. This deformation can take one of two extremes – pure elastic deformation (e.g. a spring) or pure viscous flow (e.g. oil). 

The force causes the elastic material to instantly deform by a set amount, and the viscous material to flow for the whole time the force is applied. When the force is removed, the elastic material instantly returns to its original state, whereas the viscous material does not recover at all.

Elastic behaviour is usually caused by the bonds stretching between atoms (which is instant). Viscosity is caused by atoms or molecules moving past each other, which takes time but is also not easily reversed, unlike elasticity.

Texture Analysis in Action 2: Powder Vertical Shear Rig

Anyone who has handled powders has almost certainly come across a clogged hopper, and will know that this is caused by caking, arching or rat-holing. 

To measure the tendency of a powder to show these properties, the main property to consider is the powder’s bulk resistance to the initiation of flow. 

This helps to imitate the consolidation that occurs under the powder’s own weight when the outlet is shut and the feeder is switched off. It is when the outlet is opened and the feeder started again that the blockages can build up.

Texture Analysis in Action 2: Indexable Powder Compaction Rigs

Indexable Powder Compaction Rig (A/IPC0.5)

Many years ago we introduced two variants of Powder Compaction Rig (high tolerance and low tolerance) suited to high force applications. 

However, there is a need for powder compaction testing of similar sample volumes at lower compaction forces than the existing methods that require a TA.HDplus Texture Analyser. 

As such, we have developed two low force powder compaction fixtures – offering a choice of volumes for 10 samples – to provide indexable testing up to 50kg.f and to increase  useability and efficiency.