Evaluation of the firmness of full fat and low fat margarine by penetration using a 5 mm cylinder probe.
Butter is made from dairy cream with a butterfat content of at least 80%. Margarine has a similar fat content but, unlike butter, its fats are derived from vegetable oil. Vegetable oils are liquid at room temperature and by the process of hydrogenation the oils can be solidified. Products containing 80% or more fats generally consist of fat crystals and liquid oils.
The texture of margarine can vary depending on temperature, origin, and fat content. Temperature varies the texture by determining the consistency of the margarine. It alters the state of the fat content, thereby varying the distribution of solid and liquid glycerides and size of fat crystals. In general, larger fat crystals (>5Ám) and a high solids content make a harder, grainy and more brittle product. The origin of margarine also affects texture by determining the type of fats and predominating fats (saturated or unsaturated) present. Fat content, like temperature and fat origin, plays an integral part in margarine texture. A high fat content generally gives a product higher hardness values and low spreadability values. Such products also tend to be more adhesive and less cohesive.
Textural properties of margarine such as hardness (firmness), spreadability, graininess, brittleness, oiliness and stickiness can be determined using the CT3 Texture Analyser. This study utilises the instrumental textural property of firmness to compare full-fat and low-fat margarines. Using a cylinder probe, the CT3 Texture Analyser measures the sample consistency and firmness.
The following graphs show the firmness of full-fat and low-fat margarine:
Figure 1 shows the force required to penetrate full-fat and low-fat margarine tested at room temperature.
Figure 2 shows the force vs. distance of full-fat and low-fat margarine tested at room temperature.
When a trigger force of 5 g has been attained at the sample surface, the probe proceeds to penetrate the sample at a test speed of 2 mm/s to a specified distance of 12 mm before returning to its original position. The maximum force on the graph is a measure of sample firmness, and the area under the positive peak is a measure of the work done. The higher the force value, the firmer the sample. The negative part of the graph is produced as the probe returns to the sample surface. The maximum negative peak is a measure of adhesive force (the force necessary to overcome the attractive forces between the sample and the probe). The area under the negative part of the graph is a measure of adhesiveness (the energy required for the probe to pull away from the sample). Full fat margarine is firmer and more adhesive than low-fat margarine due to a higher fat content.
Mean values for the firmness, work done, adhesive force and adhesiveness of full-fat and low-fat margarine are shown below: