How to measure and analyse the texture of food, cosmetics, pharmaceuticals and adhesives.

Tuesday, 20 January 2015

It’s time to perform Textural Magic! Part Four

Crunching a crisp
Textural magic – designing texture into your new products

Marketplace developments suggest that consumers — and product developers — are very focused on texture.

The texture movement began around 2010, when the number of best-selling new products with a texture claim doubled over the previous 10-year period; growth has been strong and steady ever since.

The time to flaunt texture is now. Texture has enormous appeal to foodies, who are looking to find more adventure in foods. Texture is increasingly being used to confirm if a product is “real”, “fresh”, or “less processed”. Pieces of real nuts or dried fruit signal quality in cookies and bars. Moreover, texture claims are also helping to manage shoppers’ taste expectations for new products. For example, will that cookie be soft and chewy or crisp and hard?

Look to restaurants as a barometer for the most popular texture claims. According to the Food Research Institute’s MenuMine database, ‘crisp’, ‘tender’, ‘creamy’, ‘stuffed’, and ‘melted’ were the top texture descriptors for savoury menu items. Technomic reports that ‘whipped’, ‘creamy’, ‘crisp/crispy’, ‘brulée’, ‘crunch/crunchy’, ‘moist’, and ‘smooth’ were the top texture dessert descriptors; for restaurant menu items overall, the leading descriptors were ‘crisp’, ‘tender’, ‘creamy’, ‘whipped’, and ‘smooth’.

Younger adults have the greatest interest in texture, which suggests that a focus on texture is a long-term trend worthy of investment by food manufacturers. Snacks, bars, cereals, and dairy (especially cheese) are the most active new product categories globally when it comes to texture claims, according to Innova Market Insights.

By design, extrathin items (e.g., cookies, crackers, and bread thins) are adding crispness and crunch while addressing a fast-emerging low-carb/less bread trend.

Salty snack marketers are making chips in all sizes, shapes, and thickness for added crunch.
Walkers Deep Ridged Crisps’ ridges are “twice as deep” as other chips for maximum crunch. Yogurt is being sold whipped, moussed, twisted, and squished around, while gummy confectionery is fast approaching $2 billion in sales.

Texture and technology are allowing manufacturers to create entirely new product forms such as Kellogg’s Popcorn Chips. However, to sell honestly, the textural claims need to be substantiated. Here’s where a Texture Analyser can be employed as your objective and accurate means of quantifying the texture of your new products.

Measuring Crispness/Crunchiness    

The measurement of crispness of foods by instrumental and sensory methods is of substantial interest. Texture in these cellular open-structured products arises from an incremental and progressive fracturing of cell wall components in response to deformation. During mastication, such fracturing gives rise to specific sensory perceptions – for example, crispness.

Breakfast cereals, such as cornflakes, represent a remarkably non-uniform configuration from piece to piece (flake to flake) and therefore the testing of one flake at a time is often meaningless. Fracture itself represents a very difficult characteristic to measure due to the fact that a fracture event never occurs the same a second time. A convenient physical test is to compress a population of cereal flakes constrained within a container such as the Ottawa Cell [9] which attaches to a TA.XTplus/TA.HDplus Texture Analyser.

9 - Ottawa cell
In such a test, the multi-peak jagged curves obtained will result from the fracture of a number of flakes/pieces, each peak corresponding to the rupture of a single flake/piece. This offers an averaging effect over a more representative portion of the sample, which is much more repeatable. The multi-peak curves obtained may then be analysed using special calculations.

Special Calculation Features in Exponent
Exponent software is unique in its offering of many special calculations, which are of interest in the analysis of multi-peak jagged curves such as those produced from snack food and breakfast cereal testing. Special calculations include the ability to measure parameters such as:

•    Drop Off: This function calculates the average drop in force between consecutive peaks and troughs over the selected region.

•    Linear Distance: This function calculates the length of an imaginary line joining all points in the selected region. A highly jagged line, i.e. lots of fluctuations (peaks) in force due to many fracture events, is often produced from those products that are perceived as crispy or crunchy. The length of this line is measured to be much longer if compared to perhaps a smooth line resulting from the testing of a similar soft product.

•    Curve Best Fit: In addition, this function calculates the length of the line (linear distance) which joins the mid points between consecutive peaks and troughs [10].

10 - Curve best fit graph
•    Dispersion: This function is determined by simply working out the sum of the absolute change in force between each consecutive data point in the selected region.

•    Average Gradient: This function calculates the average gradient of all positive slopes (trough to peak) using all peak and trough pairs in the selected region.

•    Smooth Line: This function creates a smoothed version of the currently selected graph. It requires the user to specify a smoothing factor based on a rolling average calculation.

The Crisp Fracture Rig: Crispness of Individual Potato Crisps
The measurement of potato crisps texture can be performed in a similar way as the testing of breakfast cereal. However for more uniform samples the Crisp Fracture Rig [11] can be employed.

11 - Crisp fracture rig
Testing Multi-Textured Products
It’s a routine part of every cuisine across the globe to introduce variety into the human diet through textures and flavours. The challenge for commercially manufacturing multi-textured foods is to keep the freshly created textures over a long period of time. Moisture and oil migration present challenges and can result in a decrease of desirability, as the expected sensory properties are altered. Some well-known multi-textured food examples include pizza crust with sauce, ice cream in a crispy cone, baked pastry with fruit/meat filling, hard chocolates with liquid centres, chocolate-covered nuts and breakfast bars containing soft fruit.    

The confectionery market is the most popular industry in which to find multi-textured products; food coatings and coextrusion methods result in a wide variety of dual- or multi-phase products in this sector. Chewing gum tablets, wafers, and layered biscuits are typical examples of food products which may be comprised of a crispy/crunchy exterior shell enclosing a soft viscous filler material of a different texture. Inherent differences in the physical state and compositions of the phases offer interesting textural variation to the consumer.

To overcome the challenge of developing multi-texture properties in foods, most commercial products in the market are formulated with high fat levels to reduce water activity and soften the texture at high solids level, high levels of sugar and salt, polyols, film barriers, humectants etc. Measuring the success of these ingredients into the product formulation requires an objectively quantified method of analysis. This type of product is an exciting concept for both manufacturers and consumers but, when developing multi-textured products, the assessment of texture for each of these layers presents a more complex issue.

In order to monitor the textural quality, simple and rapid measurements are needed on the whole food. Differences in the mechanical properties of, for example, the shell and filler of dual-phase pockets, can be highlighted by the use of a 2mm cylinder probe (or needle probe) attached to the Texture Analyser.

The multi-textured product is often positioned on a holed base plate to provide the ability to penetrate through the entire structure of the sample. The diagram shown [12a] depicts the working of the penetration probe and the corresponding force deformation curves for such products.

12a - graphs from multi-textured product testing

The probe is effectively able to differentiate between the mechanical resistances offered by different phases. The force deformation curves show an increasing force which is proportional to the length of the probe penetrating the firm material. Then, a sudden drop is observed consistent with the resistance offered by the softer material.

The increase in the force during the penetration of the softer material is much less pronounced, consistent with the properties of the softer material. The final part of the curve shows again a sudden increase in the force during deformation as expected from the firm material. The parameters derived from the force deformation curve of a penetration test in commercial pockets are also shown [12b].

12b - detailed results from a typical test

A Craft Knife [13] (or Extended Craft Knife) has also proven suitable for the assessment of multi-layer products due to its sharp, small contact area blade which allows the cutting of samples without the compressive action that a standard thickness blade would provide.

13 - Craft knife test on chewing gum

Impress your customers with texture

Coatings play an important role in texture enhancement. Breaded baking/grilling cheeses for the centre-of-the plate are growing in popularity. In Eastern Europe, soft cheese/curd cheese bars enrobed in chocolate are a popular snack; dough-enrobed whole nuts are offered in Western Europe. Meanwhile, if it’s good enough for Heston Blumenthal, adding popping candy to the base of cheesecakes and tarts, or as a sweet topping, gives consumers a pleasant eruptive snap, crackle and pop surprise when they start chewing.

There are a number of ways to achieve texture worth talking about. Certain ingredients naturally have an unusual mouthfeel. Many cooking and preparation techniques work wonders to enhance the textural qualities of an item; even the way a chef slices a vegetable can create an impact. And often, the whole is greater than the sum of the parts — in other words, it’s the play between different textures that is far more interesting than any one texture alone. 

Some typical multi-textured food products are shown undergoing penetration testing [14] along with a typical graph output [15] clearly showing the layers discovered by such a test.

14 - Multi-textured product tests

15 - Typical graph output form a multi-textured product test

A well thought out play on textures makes a dish more successful and memorable; whether a chef chooses to work with an ingredient that already has texture, or use a technique that imparts texture, when done with finesse, textures are what make that food stand out from the crowd. 

We can design and manufacture probes or fixtures for the TA.XTplus texture analyser that are bespoke to your sample and its specific measurement.

Once your measurement is performed, our expertise in its graphical interpretation is unparalleled. Not only can we develop the most suitable and accurate method for the testing of your sample, but we can also prepare analysis procedures that obtain the desired parameters from your curve and drop them into a spreadsheet or report designed around your requirements.

For more information on how to measure texture, please visit the Texture Analysis Properties section on our website.

TA.XTplus texture analyser with bloom jar The
TA.XTplus texture analyser is part of a family of texture analysis instruments and equipment from Stable Micro Systems. An extensive portfolio of specialist attachments is available to measure and analyse the textural properties of a huge range of food products. Our technical experts can also custom design instrument fixtures according to individual specifications.

No-one understands texture analysis like we do!

To discuss your specific test requirements click here...

Watch our video about texture analysis Replicating Consumer Preferences
 Texture Analysis applications

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