Physical Property Measurement: Fracture Testing by Compression

Compression tests can be carried out on a wide variety of products that experience such a force in natural conditions. 

These may include fruit and vegetables, puffed cereals, cakes and biscuits, confectionery and pharmaceuticals. 

Normally, as these products may be oddly shaped, a compressive test is the most reliable way of assessing their fracture behaviour.

Physical Property Measurement: Fracture Testing in Tension

Many foods and pharmaceuticals are not normally subject to tensile forces in their manufacture and consumption. There are, however, exceptions, e.g. dough, gels, spaghetti and adhesives. 

These tests can also be performed on materials from which elongated test specimens can be cut and gripped within the clamps of the Texture Analyser to be stretched. This could include fruit, vegetables and meat. In any case this type of test yields reliable results for tensile modulus, yield stress and strain, strength and strain to fracture, and, if the crack area can be measured, the fracture toughness of the material.

Physical Property Measurement: Types of Fracture

Fracture is simply crack propagation. Force has to be exerted to initiate a crack, then energy has to be supplied to propagate it. This is the energy that goes into breaking the bonds within the material in order to generate new surfaces. 

There are three ways a crack can propagate within a material. All structural failures are the result of material failure in one of these three modes.

Physical Property Measurement: Introduction to Fracture

What is Fracture? This is the first of a set of blog posts on the subject of fracture testing. Traditional information on fracture testing focusses on techniques for assessing engineering materials using standard methods and strict geometries. However, these may not be so useful for the typical user of a Texture Analyser.

The loosest definition of fracture is “a form of failure in which the material separates into two or more pieces due to an applied load”. Fracture strength is the stress at which a specimen fails or fractures. Fracture can be brittle, ductile or semi-ductile. This refers to the nature of deformation and will be covered in the next post.

Measuring Food Quality with a Texture Analyser

More than ever before, the food industry is finding itself forced, through outside pressures, to improve constantly its product quality and to maintain that quality at a consistently high level. Food quality is an important concept, because the foods people choose depend largely on quality.

Consumer preference is important to the food manufacturer, who wants to gain as wide a share of the market for the product as possible. Quality is difficult to define precisely, but it refers to the degree of excellence of a food and includes all the characteristics of a food that are significant, and that make the food acceptable.

Texture: The Final Frontier of Food Science?

Back in February, Kendra Pierre-Louis of Popular Science wrote this interesting article.  

She indicated that ‘Tweaking texture could give us healthy versions of our favourite junk foods—and that's just the beginning.’

She talks about how she has embraced culinary novelties such as glass potato chips, grilled whale and poisonous shark but cannot stomach the sensation of hollandaise sauce.

Food Texture – Likes and Dislikes

Apart from crispy foods like crackling, British consumers embrace softer-feeling food.  Industrialised, processed food is often marketed as soft and creamy in the UK, with adverts for such foods playing on the sensual and comfort associations that have set in from a young age.

Our childhood association with pureed food is one of the reasons we turn to soups when we are ill.

The Vocabulary of Food Texture

The chef Mario Batali says that the single word “crispy” will sell a restaurant dish quicker than any number of clever adjectives. 

Picture “aubergines” on a menu. You might hesitate to order them, fearing they would be flaccid or oily, as they so often are. Now think how much more appealing “crispy aubergines” sound. “Crispy” makes everything appear as safe and crunchy as chips.

The word’s universal appeal is a sign of how much we are governed by texture in what we eat. Yet we hardly seem to mention it (unlike in China, where many foods, from fungus to tripe, are prized for texture alone).