Texture analysis is the mechanical testing of food, cosmetics, pharmaceuticals, adhesives and other consumer products in order to measure their physical properties.
It is an important attribute in that it affects processing and handling, influences habits, and affects shelf-life and consumer acceptance of products.
Because of its adaptability, texture analysis has become commonplace in many industries to measure a specific or range of characteristics or properties relating to the way a material behaves, breaks, flows, sticks, bends, etc. Typical texture and physical properties than can be measured include: crispiness, stickiness, brittleness, spreadability, chewiness, firmness and consistency.
Texture refers to those qualities of a food that can be felt with the fingers, tongue, palate, or teeth.
Foods have different textures, such as crisp crackers or potato chips, crunchy celery, hard candy, tender steaks, chewy chocolate chip cookies and sticky toffee, to name but a few.
Texture is also an index of quality. The texture of a food can change as it is stored, for various reasons. If fruits or vegetables lose water during storage, they wilt or lose their turgor pressure, and a crisp apple becomes unacceptable and leathery on the outside.
Products with a crust, skin or multilayers bring textural variety to a product. The breaking
of the skin of an apple when bitten into or the biting through the
layers of the perfect pastry product brings a textural sensation that is
highly desirable and anticipated. Failure to notice a difference in the
layers of such products brings disappointment.
The
collection of detail of a thin, brittle, laminated or multi-phased
structure is best performed with a small diameter probe or thin, sharp
fixture. A larger probe such as a platen, cylinder or sphere will give
bulk compressive properties but will not resolve the properties of each
layer. It is beneficial to penetrate the sample slowly in most cases to
give a larger time gap between fracture or puncture events so they can
be more easily identified.
Thin samples are notoriously difficult to test. This is a short guide with some tips to make your thin sample testing more accurate and repeatable.
Compression or penetration
When
testing the hardness of thin products by compression or penetration,
the measured force may show a sudden exponential increase as shown in
the graph below. This occurs as a result of the probe moving nearer to
the base.
Either the test will abort because the load cell has
overloaded, or the test will finish, collecting irrelevant data that
does not reflect the true properties of the product. Comparison could
then incorrectly be made between maximum forces that are not sample
derived.
The spreadability of margarine and butter is of paramount importance for consumer acceptability.
It is a physical property and results from the fact that these products
consist of a dispersion of solid fat crystals in liquid oil.
The
ratio of solid to liquid fat in a product is probably the most
important factor determining hardness and spreadability. However,
hardness and softness are not the only factors influencing
spreadability; smoothness and brittleness are also important.
Fats and oils perform a key role in defining the sensory characteristics of our favourite
prepared foods. They affect the structure, stability, flavour,
shelf-life, palatability, mouthfeel and visual appearance of food
products.
For manufacturers to obtain the desired
performance, it is important to recognise that different applications
require a fat or oil product with different physical and organoleptic
properties.
Customers are wary of manufacturers using taglines to tempt them into buying their product
– a conditioner that states “hair three times suppler after first use”
will not sell well if customers start using it and find no difference to
their tresses.
News travels fast these days with thousands of
cosmetics review sites and online shops, and products that fail to live
up to their claims will be given poor marks. The manufacturers could
have performed a simple bend test on hair specimens treated with their
conditioner and would have found their mistake before it was too late.
The development of methods to measure the effect of cosmetics is driven
by increasing pressure on cosmetic companies to provide solid evidence
to support product claims.
The 2017 exhibition for the Institute of Food Technologists was held in Las Vegas, Nevada, from June 25th to 28th, showcasing thousands of developments in the food technology industry.
The show gives a good reflection of the current wants and desires of consumers, and they seem to be asking quite a lot from manufacturers this year. One major area to consider while keeping up with these trends is food texture. The majority of attendees were heavily aware of the importance of texture measurement in R&D as well as its maintenance in quality control; texture is such an important quality of food and beverage products that many manufacturers mention a textural attribute specifically by name on a product’s packaging or even in the name itself.
