Ten ways to measure cheese texture
14 minute read
Cheese accounts for the largest proportion of overall volumes of production in the dairy sector. Here we present ten different ways in which the texture of cheese, in all of its variants, can be measured.
Watch our video covering all of these methods.
1. Measuring firmness/hardness of hard cheese using a Wire Cutter
A simple wire cutting test will demonstrate the firmness and consistency of a cheese, and can also be used for butter and block ice creams.
Attached to the TA.XTplusC Texture Analyser, the Stable Micro Systems Wire Cutter incorporates a standard 0.3mm diameter wire, and assesses the force required to cut through the cheese.
2. Measuring firmness of hard cheese using a penetration test
Testing with cylinder or cone probes on samples larger than the probe itself is believed to give a good indication of cheese maturity. This is a method currently used in a major Camembert producer in France as an online quality control procedure.
A small distance penetration test of uniform products using a Spherical Probe can measure the surface hardness, as well as the ripeness, of a cheese. In addition, by measuring the force required to puncture the surface of a cheese by penetrating to a greater distance, comparisons can be made between its inner and outer firmness.
But, unfortunately, things are not always this easy – an increasing number of cheeses, and ice-creams, contain particulates, including fruit and chocolate chunks. Testing diverse elements within one product, is not only tricky but often results in low reproduceability and misleading data. It may show wide variances between maximum and minimum force resistance, depending on whether the probe reaches a piece of fruit or cheese first.
3. Measuring firmness of hard cheese using a Multiple Puncture Probe
The Multiple Puncture Probe allows food manufacturers to test non-uniform products containing particulates of different size, shape, structure and levels of hardness, to provide repeatable results.
Such products have non-homogeneous textures due to the presence of, for example, dried fruits, vegetables or nuts or consist of different layers to provide more interest to the consumer. By penetrating the product in several areas at the same time, the Multiple Puncture Probe produces an averaging effect and is therefore more representative.
4. Measuring bite force of hard cheese using Fracture Wedges
Measuring the firmness, hardness and brittleness of a cheese is also essential in order to assess its crumbliness, springiness and elasticity, and to make sure that a product maintains a consistent texture and structure from batch to batch.
Fracture Wedges will provide these measurements by quantifying ‘force to fracture’ measurements. One upper and one lower wedge, each with a cutting angle of 30°, is connected to the load cell and the base of a Texture Analyser respectively.
The wedges cut together and the force to fracture gives a measurable indication of the cheese’s composition and strength. For manufacturers, this is a tangible means of quality assurance and can highlight any variations in the finished product.
5. Measuring consistency of cheese sauce using a Back Extrusion Rig
The Back Extrusion Rig offers an invaluable measure of product consistency. A sample container of the test matter is compressed by a disc plunger attached to the Texture Analyser, which extrudes the product up and around the edge of the disc. The effort taken to do this is measured using Exponent Connect software and results give an indication of viscosity.
Such a measure relates to the body or flowing nature of the product, its mouth coating potential and spoonability. Achieving the desired texture of semi-solid product is therefore possible, and can be monitored from batch to batch, and throughout the product’s lifespan.
6. Measuring spreadability of cheese spread using the Spreadability Rig
The spreadability of margarine and butter is an important aspect of the consumer acceptability of these products. Spreadability, in pragmatic terms, is the ease with which a spread can be applied in a thin, even layer to, for instance, bread. Firmness or hardness may be measured by the force required to obtain a given deformation or by the amount of deformation under a given force.
Although spreadability is also a deformation under an external load, it is a more dynamic property. Measurements of firmness and spreadability are usually highly correlated, however the relationship is rarely perfect, and this is partly a function of work softening. Margarine, for instance, work softens (when spread on bread) more easily than butter, which allows it to be more spreadable even when hardness values are initially equal.
Factors affecting spreadability
The ratio of solid to liquid fat in a product is probably the most important factor determining hardness and spreadability. However, hardness and the lack of it, or softness, are not the only factors influencing spreadability.
Smoothness and brittleness are another component of the property of spreadability. This has more to do with the size and shape of fat crystals than with their amount. A product is smooth when the crystals are relatively small and this is possible with hard as well as soft butter or margarine. Brittleness is associated with high solid fat content and/or excessive size of fat crystals.
Under these conditions large crystals interlock to result in a brittle product. Such conditions rarely occur in soft butter or margarine.
Butter has traditionally been poorly spreadable, especially winter butter, and the widespread use of domestic refrigerators has aggravated the problem. Margarine producers have been able to manufacture soft margarines with better spreadability and these soft margarines are now popular in many countries.
Another approach to improvement of the spreadability of butter is admixture of vegetable oil. In the last ten years or so we have seen the advent of very low fat spreads (25% fat and below) in the European market. Being under strong public pressure to produce healthier fat mimetics, manufacturers have attempted to develop new spreads with the emulsion phase inverted (the fat phase is dispersed within the aqueous matrix) whilst attempting to achieve the required ‘plasticity’. Obviously, unsophisticated mixing of ingredients is likely to result in brittle or elastic preparations, i.e. unsuitable for spreading.
Measurement of spreadability and stickiness
Many people are interested in measuring the spreadability of food products such as butter, spreads, peanut butter, margarines, cheese, and cream cheese These products are often very shear sensitive and are difficult to consistently prepare for testing. Penetration and compression style tests are simple methods that give results of sample hardness. Hardness measurements however, even with cone probes, are not always good discriminators of spreadability.
The Spreadability Rig is an attachment which measures the ease with which a product, such as margarine or table spread, can be applied in a thin, even layer. It comprises of a male 90° cone probe and five precisely matched female perspex cone shaped product holders. The material is either deposited and allowed to set up in the lower cone holders in advance of testing or is filled with a spatula and the surface then levelled. Excessive work is not introduced into the product and different styles of filling the material only affect the early part of the test.
The fixture comes with five replaceable female cone sample holders which can be filled in advance of testing and then easily locked into the base holder precisely centred under the matching upper cone probe. The sample holders can be stored in refrigerated or frozen environments, or they can be left ambient before testing.
The important action that the test is designed to measure, spreadability, occurs in the later stage of the test. The cone-shaped holders offer no locations into which the product can be packed or compressed, so the product is forced to flow outward at 45° between the male and female cone surfaces, the ease of which indicates the degree of spreadability. The probe withdrawal may also offer some insights into a product’s adhesive characteristics.
Explanation of test and results
During the test the force is seen to increase up until the point of maximum penetration depth of the cone probe. This peak force value (maximum force to shear) can be taken as the “Firmness” at the specified depth. A firmer sample also shows a correspondingly larger area which represents the total amount of force (or otherwise referred to as ‘work of shear’) required to perform the shearing process. Both of these values have been shown to rank samples in the same order of spreadability (and firmness), but for some samples one many prove to be more suitable than the other. The probe then proceeds to withdraw from the sample and any adhesive characteristics are indicated by a negative force region on the curve.
Knowledge of the rheological properties of a semisolid food, such as margarine, is important in process design, quality control, and development of new products. Soft or tub margarine is mainly used as a spread for toast and sandwiches. Soft margarines have to be stored under refrigeration and should be spreadable when taken from the refrigerator. The spreadability out of the refrigerator and at room temperature should be even and smooth with no syneresis and separation.
7. Measuring stretchability of molten cheese using the Cheese Extensibility Rig
Molten dairy products are not to be forgotten. The extensibility of cheese is an important textural characteristic in a wide range of food applications – in particular, pizza. Freezing, shredding, thawing and even cooking cheese can have a significant impact on its textural characteristics.
Reduced-fat products also display very different characteristics compared to full-fat versions. All of this may result in a texture with undesirable mouthfeel. Previously, one of the most common ways to test the stretchability of cheese was to lift it manually with a fork and estimate the force required to stretch it, as well as the length to which it stretches. This method is inherently subjective and unreliable.
Measurement of extensibility/stringiness
Responding to the need for an objective, repeatable test method for cheese, Stable Micro Systems developed its Cheese Extensibility Rig. Used in conjunction with a Texture Analyser, the rig comprises a microwavable vessel, sample retainer and double-sided fork probe. The cheese is cut into small cubes and microwaved in the vessel until molten. The sample retainer is slotted into the vessel, which is securely fastened to the base of the texture analyser. After the fork probe is attached, the arm of the texture analyser pulls the fork upwards through the molten cheese and Exponent Connect software measures the force required to stretch the cheese and the distance to breakpoint. Typical results show that the longer the distance, the stretchier the cheese. For repeatability and replication of consumer experience, a PT100 Temperature Probe may be used to monitor the temperature of a sample. The test can then be programmed to start when a chosen target temperature is attained.
8. Measuring extrudability of processed cheese in a Forward Extrusion Rig
Extrudability is the work required to push or force out (or expel) a product. For dairy products in tubes, such as processed cheeses and novelty yoghurts, removal of the contents relies upon the consumer squeezing the packaging to extrude the product.
The ability to squeeze the product out effectively is essential and the consistency of the contents of a tube or sachet is therefore fundamental to its ease of removal from the packaging when required. If the substance is too dense, consumers will experience difficulty extracting it; if it is too fluid, the product could leak. Assuming the orifice size remains constant, the force to squeeze the packaging depends largely on the consistency of the e.g. paste/cream.
To attempt to mimic this situation a forward extrusion test can be employed. A Forward Extrusion Rig measures the compression force required for a piston disc to extrude a product through a standard size outlet in the base of the sample container. The base of the container accommodates a disc containing a central hole (termed the orifice) of varying diameter (3, 5, 7 or 10mm), depending upon the consistency of the sample. The tightly fitting plunger which acts almost like a piston compresses the sample and causes forward flow through the orifice of the disc.
Products suitable for this type of test include baking fats, pastes and viscous liquids without the presence of particulates.
9. Measuring consistency/extrudability from processed cheese packaging
A large proportion of dairy products and condiments are now being produced in sachet or tube portions for quick and easy use, as well as to facilitate long-term storage. For products in tubes, such as processed cheeses and novelty yoghurts, the ability to squeeze the product out effectively is essential and is fundamental to its ease of removal from the packaging when required. If the substance is too dense, consumers will experience difficulty extracting it; if it is too fluid, the product could leak.
A new device, the Sachet/Tube Extrusion Rig, has been developed which quantifies the force required to extrude the contents of tube and sachet style packaging. The rig allows the positioning of the end of a sachet or tube vertically between two rollers, clamping the closed end with a grip at the top. The grip then pulls the sachet/tube upwards through the rollers, forcing the contents out. The higher the force recorded during this test, the more difficulty a consumer would experience in squeezing out the required amount.
By testing the force required to extrude the contents of a sachet or tube at regular intervals over a long period of time, product developers can analyse changes in a product's consistency throughout its shelf-life and adapt formulations accordingly. This specially designed extrusion rig, comparing force against time, can alert manufacturers to a product’s suitability for packaging in this format. Such a test at this stage of production could spell the difference between a successful and appealing product and one which will cause waste and inconvenience. For manufacturers, failure at the last hurdle would bring disappointment and huge material losses.
10. Measuring grating force of hard cheese using the Cheese Grating Rig
A Cheese Grating Rig that accurately measures the force needed to grate cheese into shreds has recently been launched. For the first time, dairies can scientifically, objectively and repeatedly measure shreddability, enabling them to perfect their cheese recipes and production and packaging processes.
Retail-ready grated cheese is a fast-growing market throughout Europe as the need for convenience and variety continues to dominate. As a result, cheese which might historically have been offered only in block form must now be able to withstand intense shredding, product transfer and packaging without clogging up machinery. Texture analysis helps dairies evaluate the mechanical properties that will influence not only their product’s mouthfeel, but also processability.
The new grating rig is used in conjunction with the Texture Analyser and comprises a grating platform consisting of interchangeable grating faces and a sample block holder which acts as a sample template and, during the test, holds the sample in place. The Texture Analyser is used in a horizontal position to ensure a constant application of force onto the sample. This configuration also means that samples can be tested repeatedly over several cycles without the need for reloading.
Similarly, the location of a weight above the sample allows the cheese to maintain constant contact with the grating platform face for a consistent measurement. The rig is adaptable, with the provision of two types of grating face and a mandoline blade for the measurement of sliceability. This ensures realistic testing conditions and provides valuable information about the quality and performance of the cheese as well as how it is best processed.
Whether it’s a core ingredient in a sauce or a topping on a pizza, cheese is a versatile performer, able to take on a variety of functional roles. Cheese can, however, be affected by varying environmental conditions which can have an adverse effect on shreddability which is also influenced by factors such as fat, moisture and salt content, pH and maturity. Similarly, the way cheese is handled and processed influences how well it shreds and therefore the quality of a finished shredded product. Our new grating rig allows manufacturers to test many types of cheese, the results of which can help guide research and development plans, optimise processing parameters and inform and facilitate quality control.
As well as evaluating cheese as an end-product in dairies, the grating rig can also be used in food processing environments to ensure it can withstand high speed processing in applications such as pizzas, ready meals, sauces and snack foods.
