Fats, Oils, and the Uneasy Truces of Emulsions and Foams

Of all food constituents, perhaps that which receives the worst press is fat. The merest mention of fat in food tends to be regarded as a negative thing, and for years the advice of nutritionists has tended to uniformly focus on its avoidance or reduction in our diet. While recent years have perhaps seen a reevaluation of the relative importance of fat, and its reputation may be undergoing a gradual thawing, my focus in this chapter is not on the controversies of its merits or otherwise from a nutritional perspective. As should be clear by now to anyone reading this book, neither my expertise nor my focus is in such realms, and so, for now, without fear or favor, I consider the properties of fats from an impartial perch, in their own regard as key constituents or ingredients of many food products, whether we like it or not. The picture of fat I want to paint here is one of a material that, before it enters our bodies to exert whatever physiological effects it may, hugely affects the properties of many food products, and in some cases can have effects on food texture even more significant than those of proteins and polysaccharides described in earlier chapters, where the level of fat present is sufficient to allow it to dominate the properties of the food. Why is this? Imagine for a moment a hypothetical magic material that determined texture and consistency of food in a way that was dependent on temperature such that it changed its properties dramatically when exposed to different temperatures regularly encountered by food. Maybe such a material would be solid, or almost so, at refrigeration temperatures, but melt at almost exactly the temperature of our mouths when we consumed the food, to soften and make our food easier to chew, while, at higher temperatures yet, as it might encounter during processing or cooking, it became a liquid, which could flow and move and be molded and reshaped, or even divided up, as we saw fit.