Structuring oils without highly saturated fats – how far are we?

Abstract

Eckhard Flöter The interest to structure oil-based products with materials different from highly saturated fats has increased significantly during the time when ‘fat technologists’ were busy to find solutions to reduce and widely eliminate trans fatty acids from our food products. Next to the trans fatty acid elimination the reduction of saturated fatty acids has become a generally acknowledged target. This is expressed in the FAO/WHO goal to limit the energy intake from saturated fatty acids to 10%. The motivation to develop alternative structuring technologies for soft-solid lipid phases could increase beyond current ‘low SaFA’-claims through ongoing discussions on the taxation of saturated fats in products as currently present in Denmark and additionally the risk that the application of natural saturated fatty acids, with palm oil as primary source, becomes more complicated. The latter could be either due to availability issues driven by competing usages or developments of the public opinion with regard to the consumption of tropical oils. As an alternative to replace saturated fats organogelators are now of considerable interest. In simple terms the desired organogelators are to vegetable oils the analogue of what gelatine and other biopolymers are with respect to the structuring of water. These structurants, preferentially applied at low concentration levels, deliver semi-solid lipid phases that have practically the same lipid nutritional profile as liquid oils. Oil structuring or organogelation is not new and the field of organogels outside food is highly active. Non-food applications cover optical materials, drug delivery systems, oil spill recovery techniques, and home and personal care products. Even though the limitation to edible applications reduces the number of candidate structuring materials the size of the haystack for searching some magic needles is still sizable. The scientific efforts of the past decade have not yet delivered a true breakthrough and hence the door for broad food applications of organogels is still closed. The structuring systems that have been studied can arbitrarily be categorized in three classes. First, there are the obvious one component systems familiar to the products considered such as waxes, fatty acids, fatty alcohols and mono- and diacylglycerols. These seem to deliver only limited, if at all, benefits over triacylglycerols. However, in this category of single structurants, materials such as ceramides and 12-hydroxystearic acid offer a clear SaFA benefit compared to structuring vegetable oils by fat crystals. Second, there is a class of composed structuring systems. These usually binary systems such as β-sitosterol and oryzanol, or fatty acids and fatty alcohol, the combination lecithin and sorbitolesters are unfortunately very prone to losing their structuring potential in product applications. This is for example due to either the presence of an oil-water interface or the formation of hydrates that tend to deplete the self-assembled structure in at least one of its components. Third, there is oil structuring through components that are alien to the products considered and mostly deliberately synthesized. Here, ethylcellulose and protein fibrils have to be mentioned. The field of edible oil structuring and the current status of different approaches has been reviewed and discussed repeatedly 1-3. Undoubtedly substantial progress has been made with respect to the number of different structuring systems and the comprehension of their mechanism of action. However, the step from gelling oil on the laboratory bench to deliver a robust structured lipid phase in a food product appears to be quite big. At first some structuring systems are just too costly or the availability of the necessary material is limited. Secondly, food products and their manufacturing processes appear to be quite hostile for oil structuring systems because oil–water interfaces, water activity levels or shear during manufacturing can be critical for the organogels. Additionally, the perceivable properties of gelled oils are different from conventional semi-solid lipid phases. Typically there will be no cooling sensation and also other product disintegration characteristics will change. This is understandably a major obstacle in any product development effort. However, the time might be ripe to selectively move oil structuring from the laboratory bench towards product development. Recently a good example of a successful product application was reported by Zetzl et al. 4. Here the domains of animal fat in Frankfurter sausages were substituted by pieces of ethylcellulose structured vegetable oil. Since it is unlikely that a single oil structuring system will be a general substitute for fat crystals one can expect different application specific structuring solutions varying from hybrid systems, combinations of saturated TAG and organogelators, to full replacement of the structuring fat. Finally, the future market success of organogel-based products will not only depend on the technical ability to formulate acceptable products, which is certainly easier for completely new ones without any reference perception, but also on the ‘consumer digestible’ communication concerning the structuring materials. Eckhard Flöter Editor