Implications of spreadability for dairy and bakery products

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. 

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, though such conditions rarely occur in soft butter or margarine.

Butter is always hard to spread when it comes straight from the fridge. Margarine producers manufacture soft margarines by using a mixture of vegetable oils instead of dairy fat. The graph below illustrates this point in the comparison of three fat types using the Spreadability Rig.

Test and results
 
During the test the force is seen to increase until the point of maximum penetration depth of the cone probe. This peak force value (or force at another chosen penetration depth) 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 (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.

The rheological properties of a semisolid food, such as margarine are 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. When taken from the refrigerator, a margarine should spread evenly and smoothly with no syneresis and separation. The graph (right) shows the difference in spreadability properties of a table spread tested at 5°C and 20°C.

Low-fat spreads

Since the early 1990s 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'. Unsophisticated mixing of ingredients is likely to result in brittle or elastic preparations, making them unsuitable for spreading.

Cake products

Fats and oils perform many functions in cake products - they trap in air during the creaming process, lubricate the gluten and starch particles (breaking the continuity of the gluten/starch structure of the cell walls for a tender crumb), and emulsify and affect water holding capabilities for moisture retention and shelf-life properties.

Margarines or fats that are too hard impair the beating activity and result in poor mixing. Conversely, margarines can be too soft to provide sufficient resistance to the mixing blades to produce a lump free, well-emulsified mix or batter. Butter and other milk-fat derivatives are widely used in bakery products, especially in cakes, because of their desirable flavour. Although bakers continue to favour the use of butter, variations in butter quality and functionality have encouraged a search for fat alternatives to be used in cake recipes.

Margarines and baking fats can be suitable for producing cake products if the melting range, consistency and whipping properties are good.

Puff pastry

In general, a margarine for puff pastry applications must be plastic, dry, tough and have a constant consistency. During lamination the margarine or fat must spread easily without forming lumps.

The characteristic features of a puff pastry shortening are plasticity and firmness. Plasticity is necessary to form smooth, unbroken layers of fat between dough layers during repeated folding and rolling operations to achieve over 1200 layers. Firmness is equally important, because soft and oily fat products can be absorbed by the dough, destroying its role as a barrier between the dough layers. A five-to six-fold increase in the height of a test pastry shell after baking can be achieved provided that the fat contributes a satisfactory performance.

Conclusion

Testing the wide choice of fat alternatives for their suitability as a replacement for traditional fats is now possible both precisely and objectively. The range of ingredients has broadened to provide manufacturers with new opportunities for gaining a marketing, textural or economic selling edge. Parallel with this, artisan skills must give way to objective measurement of ingredient performance parameters in order to create products which are of reproducible quality and consistency over large batches.

Fats and oils are fundamentally important ingredients affecting a wide range of properties. Texture analysis systems provide computer-controlled precision with a wide range of probes, fixtures and temperature control equipment which enable manufacturers to select ingredients for performance, quality and economy.

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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.

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.

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