Plasticity
is a property shown by many materials, such as polymers, metals and the
majority of foods. It is the ability of a material to undergo permanent
deformation.
If
you press your finger on a spring, it returns to its original shape. If
you made that spring out of cheese, it would not spring back as far –
it would remain squashed. When stretching a sample, plasticity is seen
on the force-distance graph as a change in gradient after the initial
linear section (straight line). The point where the gradient changes is
known as the ‘yield force’. If this point is reached and more force is
applied, the sample will be permanently changed. Before this point, the
behaviour is elastic and spring-like.
Explaining texture preference
Understanding texture preference and the trends that may result in consumer behaviour change is an area of great opportunity. However, remaining agile before a consumer shift occurs can be a challenge.
A new webinar will address this challenge and will offer:
• A view on techniques to forecast upcoming influences on food trends
• A perspective on the linkage of newly monitored issues to texture and the process used to deliver higher value commercial insights
• Expertise on driving rapid product development through localising relevant texture trends from around the world
Speakers: Janet Carver, Culinology Group; Mary Lynne Shafer, Ingredion; Susan Badarroco, Culinary Tides.
Watch this webinar to learn more...
Fish is loved by consumers – it is unique, nutritious and well-balanced. The four quality elements of food are texture, appearance, flavour and nutrition.
Compared with the meat of livestock, tissue of fish is more soft and delicate in its chemical composition.
With the development of people's living standards and of the food processing industry, texture has attracted more and more attention.
A recently published paper describes several texture parameters, analyses various factors affecting fish tissue texture especially the protein composition of fish muscle tissue from 3 aspects – physical factors, chemical factors and post-mortem changes – and mainly reviews the effects of different processing methods such as heating, freezing, salting and smoking on texture of fish meat.
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.
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.
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.
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.
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.
Plasticity
is a property shown by many materials, such as polymers, metals and the
majority of foods. It is the ability of a material to undergo permanent
deformation. 
