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

Tuesday, 13 January 2015

It’s time to perform Textural Magic! Part Three

Gastronomy on a plate 2
Performing textural magic with the use of new food preparation techniques

The Croquanter Technique – creating crunchy fruit and vegetables

Dehydrating foods is a process which has been carried out forever but, more recently, molecular gastronomy chefs have been using the dehydration technique in very creative ways.

Crunchy Sheets is a technique developed by molecular gastronomy Chef Ferran Adria to create a variety of shapes of crispy sheets of ingredients such as fruit, vegetable and yogurt with the addition of caster sugar, isomalt and/or glucose. The crunchy sheets are made at relatively low temperatures (under 80°C) to preserve the delicate aromas of the main ingredient and a dehydrator is used to obtain the crunchy texture.

Measuring Crispness/ Crunchiness - Capturing sound during a test
In today’s ever-changing market climate, burdened with stringent retailer and consumer demands, new areas of texture analysis are being explored to further improve product quality, gain competitor advantage and increase market share.

Two recent developments in this field are the analysis of acoustic emissions from food products during deformation, and the video recording of the test during texture measurements to supplement traditional force-distance-time information.

Analysing the sounds emitted from food can provide vital information on actual and perceived product quality. When crispy or crunchy foods, such as snacks, confectionery, hard fruit and vegetables, are crushed through mastication or mechanical testing, unique sounds are emitted by the brittle fracture of the product’s cell walls.

These sounds play a major role in determining the consumer’s perception of a product. A sharp, crisp sound emitted on biting into an apple, for example, implies freshness; without it, the apple could be less appealing to the consumer.

Every product has its own particular acoustic characteristics and the level or type of noise produced can determine the consumer’s acceptance or rejection of it. Acoustic analysis can therefore help manufacturers identify and analyse the sounds emitted from products and the results used to improve texture. For manufactured foods, for example, the ingredients, process or machinery employed could be altered, whereas for fresh produce, it may be necessary to make changes to the handling or packaging processes.

Until recently, there have been few developments in instrumentation designed specifically to analyse acoustic emissions. Manufacturers have traditionally used mainly force-distance-time data, or relied on makeshift methods and tools that are inaccurate or incompatible with existing texture analysis equipment. Today, however, significant advances have been made to enable the measurement of acoustic emissions alongside traditional force-distance-time data, so providing accurate and realistic results. This acoustic analysis technology, provided by the Acoustic Envelope Detector [5], can be used in conjunction with existing texture analysis equipment and offers many advantages:

5 - Acoustic envelope detector
•    Unwanted background noise can be omitted. Sophisticated equipment will discriminate between the sounds emitted from the product and mechanically-generated noise, so only the relevant acoustic emissions are recorded.

•    Force and sound profiles from individual tests can be synchronised, so the resulting curves are analysed simultaneously. The relationship between acoustic and force events can then be easily identified.

•    The tests themselves and the sound acquisition can be handled automatically by software incorporated into sophisticated texture analysis instruments. This saves time, facilitates use and increases accuracy.

•    Data can be saved in smaller files to aid the interpretation of test results. Previous means of acoustic data collection that have not used fully integrated or compatible equipment have often produced large, unmanageable files, sometimes in the region of several megabytes.

The result is a more synergistic and detailed analysis of a product’s texture.

Manufacturers can now also look at force-distance-time graphs synchronised with frame-by-frame video with the Video Capture and Synchronisation System [6].

Exponent software supplied with the TA.XTplus texture analyser processes the data.

As the instrument begins collecting data, a signal is relayed to the Video Capture Interface that activates its commencement of recording.

6 - Video capture and synchonisation system
When replayed later, each frame is automatically synchronised with the data points on the force-time graph, allowing slow replay of those frames that record a significant event which may not have been seen by the naked eye in real time. You are then able to relate graph events to visual events on the product.

Texture analysis has long helped food manufacturers improve product quality and keep customers satisfied. Acoustic analysis, together with synchronised video playback, is emerging as a new tool to help manufacturers keep pace with the market.

With it, you can investigate new dimensions in food texture, and you can do it more accurately and objectively than before.

Sous Vide Cooking – cooking under vacuum

Sous vide is French for “under vacuum” and describes the cooking of raw ingredients in heat-stable, vacuumised pouches at precise temperatures. Tough meat, fish and poultry in particular can benefit by holding at a specific temperature until they have reached the desired tenderness. Cooking in this way helps food to retain its moisture and flavour as well as tenderising tough cuts of meat.

Precise temperature control has several important benefits: it allows almost-perfect reproducibility; it gives greater control over doneness than traditional cooking methods; the food can be pasteurised and made safe at lower temperatures, meaning that it doesn’t have to be cooked well-done to be safe; and tough cuts of meat can be made tender and still be of a medium or a medium-rare doneness. Vacuum-sealing allows for efficient heat transfer from the water (or steam) to the food; it increases shelf-life by eliminating the risk of recontamination during storage, it helps inhibit off-flavours from oxidation, and it prevents evaporative losses of flavour volatiles and moisture during cooking.

Measuring Toughness

Recent Shearing Variations to Meat Testing Methods & Analysis Techniques

The University of Arkansas has developed a new test method for quantifying poultry firmness. The method was presented recently in the Journal of Food Science and presents a new shearing method for the determination of poultry meat tenderness and uses a Razor Shear Blade [7a] or Craft Knife [7b] type attachment to perform a cutting/shearing test. It is claimed to exhibit a higher correlation to sensory attributes than the Kramer Shear method.

7a - Razor shear blade and 7b - Craft knife blade
This new method not only has a higher sensory predictive value, but also requires shorter sample preparation time than the Kramer Shear test or traditional Warner-Bratzler method, because it is conducted on intact fillets. Measured forces are substantially lower than those produced with a Kramer Shear test, thereby allowing testing on a TA.XTplus Texture Analyser.

When performing cutting/shearing tests, the consistent sharpness of the blade is always a consideration or cause for concern. The benefit of performing tests using a readily available craft knife blade is that the blade can be removed and replaced after each test or an agreed number of tests, assuring edge sharpness and therefore increasing the repeatability of the results.

Razor blade shear energy and shear force are determined on intact fillets at predetermined locations on the fillet. Using the Texture Analyser, the razor is set to penetrate to a depth of 20mm at a test speed of 10mm/s. The razor blade shear force is calculated as the maximum force recorded during the test, whereas the razor blade shear energy is calculated as the area under the force deformation curve from the beginning to the end of the test.

Disappearing Transparent Ravioli – creating edible packaging

Disappearing transparent raviolis (an edible film creation) are made with round ultra-thin and transparent edible film discs made of potato starch and soy lecithin that instantly dissolve as they come into contact with water. However, the discs do not dissolve when in contact with oil or liquid ingredients with low water content. Their neutral flavour makes them ideal for any type of savoury or sweet preparation.

Disappearing transparent ravioli
They can be filled with a wide variety of ingredients such as crèmes, flavoured oils, honey, Nutella, fresh fruit and vegetables, fried fish, meat and many other ingredients with low water content. The discs can be cut with regular scissors to obtain any desired shape and can be sealed by applying heat with a sealer.

Measuring Tensile Strength

The Film Support Rig [8] allows the measurement of burst strength of thin film-like foods that must be strong enough to resist breakage when handled by the consumer. Using this rig manufacturers can identify weaknesses and adjust formulations accordingly. During a test the maximum force to rupture the product is recorded and is referred to as burst strength. The additional measurement of resilience and relaxation parameters broadens the application of this rig.

8 - Film support rig
It’s uncertain as to whether ‘Air Bread’, ‘Mozzarella Balloons’ or ‘Honey Handkerchiefs’ will ever be designed for the mainstream market, but there are certainly plenty of innovative ingredients and techniques to keep food technologists busy in the laboratory in the race to enter this new age of food entertainment.

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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