University of Guelph scientists have been collecting fats from a range of different foods. With the study any type of fat was considered, provided it was edible. To explore the nature of fats, the researchers have taken things down to the nanoscale. Here they were not only interested in the content of the fat, but what happens to the biological material as it is heated or mixed.
The long-term aim is to find out what fats contain and why they appeal to people. Having identified this, the next step is to try to mimic the sensory experience (taste, texture and smell) and to replicate this into healthier alternatives.
To achieve this, a detailed analysis of fats was required and this required the latest in food science technology. Samples of various fats have been taken to the Advanced Photon Source at Argonne National Laboratory. Here fat samples have been subjected to bright X-rays to reveal the structure of fats contained in foods like oils, milk fat, and cheese.
It has been long-established that the basic molecules that compose edible fats are triglycerides (TAGs). These are three hydrocarbon chains that form fatty acids. Beyond this, the structures of fats are very complex. For example, common plant oil contains less than 10 TAGs, whereas milk fat is made up of over 200.
To add this, the forms of the fats vary. Most fats consumed are semi-solid, which means that some TAGs are solid and some are liquid. The ratio between these physical states varies between different types of food. For example, cocoa butter is 60 percent solid when used to make chocolate; whereas olive oil is only 14 percent solid when used for cooking. Moreover, when food is processed, as other ingredients and flavors are added, different crystal structures form.
The methods that reveal the nature of fasts are X-ray diffraction and cryogenic-transmission electron microscopy (TEM).
X-ray diffraction is a powerful method for revealing molecular structures because crystals, as in food, are regular arrays of atoms. When subjected to the electromagnetic radiation of an X-ray, atoms scatter X-ray waves, and this produces secondary spherical waves. This elastic scattering reveals the molecular configuration. By way of an added innovation, the use of a small ultra-small angle-scattering camera allows three dimensional structures to be revealed at different temperatures, without altering the samples.
With the TEM method, samples are studied at cryogenic temperatures in order to suspend all chemical processes. With the process, a beam of electrons is transmitted through an ultra-thin specimen. The beam interacts with the specimen as it passes through it. An image is formed as a result of the interaction of the electrons.
Of particular interest to the researchers are the crystalline nanoplatelets that develop during cooling of food, as TAGs aggregate together. The researchers think this provides the blueprint to the sensory experience of eating fats. For instance, this process has revealed milk fats to be three times as long (600-900 nanometers) as they are wide; a previously unknown property.
Such data feeds into a computer model, designed to predict edible fat structures during cooling, heating, shearing (mixing) and other production processes. It is hoped, in the long-term, this model becomes the basis for developing ‘healthier’ foods with the same taste and structure as more fatty foods.
The research findings are published in the journal Food Chemistry. The research is titled “Characterization of the nanoscale structure of milk fat.”
