TEXTURE ANALYSIS: Replicating Consumer Preferences

Orally, visually, manually—texture is assessed in many ways. While subjective analysis may still play a role in determining product quality, many major food processors routinely use instruments to measure results. This ability to objectively know if dips are too watery or if butter remains spreadable helps food manufacturers to consistently replicate the mouthfeel that consumers enjoy. Sensory factors like hardness, cohesiveness, viscosity, springiness, adhesiveness, fracturability, chewiness and gumminess can all motivate a sampling, or (re)purchasing. So as demands on food manufacturers become more pressing and markets become more competitive, concrete figures can help determine the effects of raw-material quality and ingredient/ processing variables on the end-product.

Industry practice

Here, are some the ways that accurate texture analysis can address common manufacturing issues:

a) fat reduction

Texture analysis has become increasingly important in the fl ourishing low-fat and reduced-calorie food markets, as these products can become watery (in the case of dips); too fi rm (in pâtés, for example); or suffer from a loss of fl avor. In this area, processors often substitute fat with soy proteins, gums, carrageenans and starch; or alternatively, they use technological procedures such as massaging and pre-blending to manipulate mouthfeel. So objective analysis is important to help processors assess the impact of fat reduction, as well as to select the appropriate ingredient or process which best restores product texture.

A typical penetration test carried out on two pâtés highlights important differences in texture. A negative region of a graph, produced on probe return, indicates the adhesive property of the pâté and/or a certain amount of product adhering to the probe. The reduced-fat pâté requires more force to penetrate and therefore indicates a fi rmer consistency than its full-fat counterpart.

b) cookie crunchiness For the consumer, a cookie’s ideal texture is crunchy, but not diffi cult to bite; and, crumbly, but not to the point of disintegration. One of the most common tests carried out on biscuits and cookies is the ‘snap’ test, which measures how hard a product is. During a recipe change, the use of chocolate chips or an increase in sugar content may strengthen the structure of the baked biscuit. So, a texture analyzer can compare the bend properties of both chocolatechip and plain-cookie samples. It can also be used to determine quality control and gauge shelf-life, by determining the consistency and durability of crunch. How does it work? Users employ a ‘three-point bend rig’ which provides a base with variable support length up to 70 millimeters and accommodates samples up to 90 millimeters wide. A fl exure unit is attached to the load cell. The unit is lowered centrally between the two supports on which the cookie rests, measuring the force needed to bend or snap the product. As the test progresses, the force imparted increases steadily as the cookie resists breaking. At a force (for example) of nearly 1200 grams, the cookie snaps and the force rapidly sinks again, as the fl exure unit encounters no more resistance. c) topping spread-ability The most critical performance factors of fats and oils relates to consistency, plasticity, fi rmness and spreadability. But measuring these accurately, to indicate process or fi nished-product performance, is not easy. Fats are prone to ‘worksoftening’ and their spreadability and fi rmness can be altered at different temperatures. Traditionally, the hardness and softness of table spreads were assessed using cylinder and conical probes. Stable Micro Systems’ TTC Spreadability Rig takes a different approach to take a more precise reading. It presses a sample into a female 90° perspex cone to eliminate air pockets, and then the surface is smoothed with a knife. A matching male cone is lowered into the sample, forcing the butter or margarine upwards and outwards at 45°. Therefore, the ease with which the sample fl ows is an indication of its spreadability. Because temperature has a signifi cant impact on the rheological or fl ow properties of refrigerated spreads, closely-controlled conditions should also be used. Stable Micro Systems’ temperature-controlled Peltier Plate and Peltier Cabinet and Total Immersion Temperature Chamber, for example, maintain constant temperature when testing products such as butter, shortenings, caramel and cake toppings. d) cereal crunchiness A simple but reliable way of measuring the crispiness of breakfast cereals is compressing them in bulk with a fl at plunger. Test results show multi-peak jagged curves, with each peak corresponding to the fracture of an individual fl ake (which would be perceived in the mouth as a crispy texture). However, one of the issues consumers face is the rapid degradation of these crispy characteristics when the product is submerged in milk. Using the normal procedure, it would be necessary to prepare the sample, then move it to the texture analyzer after draining the liquid, before the test could be started. The watertight plate for the Ottawa Cell has been designed to minimize the disturbance to the prepared sample, and eliminate the delay between immersion and the beginning of the test. The Cell has a watertight base which allows immersion for a defi ned period of time, after which the base plate is lowered to drain the liquid. Relationship between textural parameters

What are your options for texture analyzers? Today, texture-analysis equipment has evolved from singleparameter to multi-functional testing instruments. As a result, penetrometers have given way to fully-computerized Windowsbased systems, which can carry out a variety of measurements. Multi-functional equipment such as Stable Micro Systems’ TA.XTplus uses different fi xtures according to the individual test. Each fi xture is designed for a specifi c application, and can be attached to the analyzer’s base and/or horizontal arm. Samples are either placed on the base of the analyzer or on the lower fi xture; or held between two fi xtures (e.g. needle probes, cylinder probes, tensile grips, ball probes and conical probes). In a simple test, the arm of the texture analyzer containing a loadcell moves down to penetrate or compress the product, and returns to its initial position as specifi ed the user. During testing, time, distance and force values (at a rate of up to 500 points per second) are collected. Then, these values are typically plotted on a Force/Distance or a Force/Time graph and analyzed. The test results can be viewed in spreadsheet, chart or report format. Coeffi cients of variation (CV) account for variations between individual samples, and low CVs demonstrate reliability and accuracy of results.

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