The saturated fats are known as the “dangerous” fats due to their link with obesity and coronary heart disease. These fats are mainly found in the animal sources of fat, such as lard, suet and butter. However, polyunsaturated fats tend to be made from vegetable sources such as in the case of sunflower oil. The working characteristics of saturated and unsaturated fats include, shortening, emulsions, aeration, flavourings, plasticity, moisture retention and sealing. For example, during short crust pastry making, butter is used to coat the gluten and create a short crumb texture. When flavouring, butter may be used in cakes and icing. In relation to plasticity, fats such as soft margarine are useful in all -in -one cake mixtures and for spreading straight from the fridge.
Explain the terms hydrolytic and oxidative rancidity. (6)
There are several differences between oxidative and hydrolytic rancidity. Oxidative rancidity occurs as a reaction between unsaturated triglycerides and oxygen from the air.
However, during hydrolytic rancidity enzymes known as lipases hydrolyse fats, thus breaking them down into glycerol and fatty acids.
In oxidative rancidity, oxygen molecules join across the double bond of the triglyceride molecule and form a variety of compounds, which give an unpleasant and rancid taste. This reaction is accelerated by heat, light and traces of metal, such as copper and iron.
Although lipases in hydrolytic rancidity may occur naturally in fats and oils, they can be inactivated by heat treatment. Like in oxidative rancidity, hydrolytic rancidity gives rise to an unpleasant taste as well as smell. However, during hydrolytic rancidity, fats may go rancid due to microorganisms present in fatty foods. This occurs especially in short chain free fatty acids, such as when butter goes rancid; it is mainly due to the fatty acid butyric.
Rancidity is reduced by storing fats and oils in cool, dark places, where the fats are well wrapped and in non-metal containers.
Explain why knowledge of the right choice of fat is important in today’s society. (6)
It is important in today’s society to have the knowledge to choose the right fat due to the rising problems of obesity. This is particularly dangerous because not only does it lessen the quality of life, but also obesity can lead to class two diabetes and coronary heart disease. Although all fats and oils have the same calorific value (that 1g = 9Kcals) they vary in quantity of saturated, monounsaturated and polyunsaturated fat. Even though only about 2% of the total energy supplied, as fat is needed to meet the essential fatty acids, normal fat intake is much greater than this. This has caused growing concern, as society gets more obese. In addition to this, although people are starting to realise that saturated fats such as butter are “dangerous” to their health, they are still lacking in general knowledge about other “danger” fats such as fats which have undergone hydrolysis.
