As the fat is heated, the temperature will rise above the melting temperatures of more and more triglycerides and these will melt. Thus, there will be fewer solid particles. This means the fat gets runnier and eventually liquefies completely.

Lard is fairly solid whereas cooking oil is a liquid. Thus, most of the triglycerides in lard have a melting temperature higher than room temperature. However, in cooking oil most of the triglycerides have a melting temperature below room temperature.

Chocolate
Chocolate is made from cocoa, cocoa butter and sugar. Cocoa butter is made up of only a few different types of triglyceride molecule so can have a fairly sharp melting temperature. In fact it can solidify in six different forms. This means the molecules can pack together in different ways leading to different types of crystal. One of these forms melts at 33.81°C. Thus it melts in your mouth (36.91°C) not in your hand. This form is also smooth and glossy. To persuade it to solidify in this form the chocolate is cooled and maintained at just below 33.81°C. It is also stirred so the fat crystallizes into very small crystals, which gives chocolate its velvety texture.

If chocolate is subjected to fluctuations in temperature, as in a shop window, a bloom develops on the chocolate. This is not mould but is the fat crystallizing out in different crystalline forms. Since cocoa butter is such a difficult fat to crystallize in the desired form, chocolate substitutes have to be used in cooking.

Proteins
Most people will know what fats or sugar physically look like. Proteins, however, are more difficult to identify because they occur in so many different forms. Most people would identify protein with eggs, cheese or beef, but even in lean beef there is only 20% by mass of protein, the rest being water and fat. In eggs the figure is 12%. Low fat soya flour has one of the highest levels of protein at 45%. Some proteins turn up in nature as the structural part of tissue, as in muscle, tendons and hair. Others play an important part in cells as the molecules that carry out and control many of the body’s functions.

Proteins are long-chain molecules, and are known as biopolymers. Proteins are made by joining together smaller compounds called amino acids. Alanine is a typical amino acid.

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