BITING/CUTTING FORCE gives an indication of the firmness/hardness of a product.
Bearing in mind that if a row of top front teeth were pulled from a
curve into a straight line they would represent a 'knife edge', using a
knife blade gives a close representation of the biting or cutting
action.
TOUGHNESS – whilst Hardness/Firmness is usually the textural property possessed by most products, the word 'toughness' or ‘chewiness’ may be substituted for a textural property more associated with the product.
TENSILE STRENGTH is the measure of the force or stress required (resistance to lengthwise
stress) to pull a sample to the point where it breaks or before
permanent deformation results.
Usually it is the maximum amount of tensile stress that it can be subjected to before failure, although the definition of failure can vary according to material type and design methodology.
In the fields of material science, mechanical engineering and structural engineering there are three typical definitions of tensile strength:
- Yield strength: the stress at which material strain changes from elastic deformation to plastic deformation, causing it to deform permanently.
- Ultimate strength: the maximum stress a material can withstand.
- Breaking strength: the stress coordinate on the stress-strain curve at the point of rupture.
SPRINGINESS is the rate at which a deformed material goes back to its undeformed condition after deforming force is removed.
It is a measurement of elastic recovery – the textural property possessed not only by baked goods such as cakes or breads but also by novel confectionery products and pharmaceutical materials (e.g. cosmetic sponges).
RUPTURE FORCE – the force that is required to produce a major break/rupture in a
sample – can be related to the firmness and brittleness of a product. It
is related to burst force – the force causing a sample to break
suddenly and violently into pieces. Rupture force measurement can be
crucial for such products as medical implants, which may be required to
resemble soft tissue but must remain intact for the duration of their
intended residence.
Several other products, such as gel capsules
containing vitamins, possess bursting as a desirable property, but must
withstand transport and handling before ultimately bursting in the
mouth.
SEAL STRENGTH is the ability to resist forces that can separate materials that have been sealed together.
It may be a flexible surface from a rigid surface or another flexible surface.
Seal strength tests are useful for a variety of products and can be performed on containers such as trays and packaging pouches as well as assessment of adhesive, cosmetic and medical products such as surgical pouches and sterile packaging.
SYRINGEABILITY can be described as the ability of a product to be successfully administered by a syringe and appropriate needle.
Syringes are used in hospitals, surgeries and homes around the world on a daily basis, and for a multitude of purposes. Successful administration, as well as comfortable receipt of the material under the skin, rely on the effective tracking of the syringe piston within its outer tube.
FIRMNESS/HARDNESS/SOFTNESS are textural properties that are on the same general property spectrum.
A soft product is one that displays a slight resistance to deformation, a firm product is moderately resistant to deformation, while hardness describes a product which shows substantial resistance to deformation.
However, it is also likely that, depending upon the particular industry, one of these words may be more favourable or pertinent to a specific product.
GEL STRENGTH is a measure of the ability of a colloidal dispersion to develop and retain a gel form.
In the gelatine world, gel strength is traditionally referred to as Bloom. It is the force, expressed in grams, necessary to depress by 4 mm the surface of a gelatine gel with a standard 0.5" diameter cylinder probe.
Whilst gels are commonly accepted in the food industry the measurement of gel strength is also of widespread interest in the manufacture of pharmaceutical, medical and cosmetic products.
Gel properties such as elasticity and rupture force of, for example, pectin, gelatine, agar etc. are important in the development of such products as coronary stents where hydrogel polymers are selected due to their soft, rubbery nature which gives them a strong, superficial resemblance to living, soft tissue.
