Fats

UNDERSTANDING YOUR FOOD<br /> the ultimate educational resource<br /> TEACHER NOTES<br /> <br /> teachers’ notes AO2.1 <br /> <br /> <br /> AO2. Fats <br /> This exercise revises information on the structure of fats and encourages <br /> pupils to improve their diet with respect to fats. Some pupils may be over <br /> concerned with their weight. Pupil sheets A02M and A02F show ranges of <br /> heights and weights for young people between the ages of 5-18. These <br /> could provide data for group or class discussions. <br /> Answers to questions on Pupil sheets AO2: <br /> <br /> 1. A bar chart is the most suitable method of displaying the information. <br /> <br /> 2. To calculate the angles required to produce a pie chart, e.g. for beef fat: <br /> <br /> saturated fatty acids 55/100 x 360 = 198o <br /> <br /> monounsaturated fatty acids 40/100 x 360 = 144o <br /> <br /> polyunsaturated fatty acids 5/100 x 360 = 18o <br /> 3. Lard is pig fat. <br /> <br /> 4. Herring oil (from fish) has a relatively low % of saturated fatty acids. <br /> Coconut oil has a relatively high % of saturated fatty acids. (Pupils <br /> could give answers that referred to correspondingly low % of <br /> unsaturated fatty acids.) <br /> 5. Olive oil, maize (corn) oil and herring oil have the greatest % of <br /> total unsaturated fatty acids and would be expected to go rancid <br /> most quickly. <br /> 6. Answers will vary according to chosen foods. Antioxidants are used in <br /> these foods to prevent the fat in the food reacting with oxygen (prevent <br /> oxidation) to produce rancidity. <br /> <br /> KS4 <br /> science and food technology <br /> Timing - 30 minutes <br /> possible homework exercises <br /> Two pupil activity sheets AO2 <br /> accompany this activity, plus optional <br /> sheets A02M and A02F. <br /> Requirements <br /> • graph paper <br /> • compass for drawing circles <br /> • protractor (angle measurer)<br /> <br /> H <br /> <br /> <br /> A great variety of fats are present in our foods, such as butter, lard, olive oil and suet. <br /> All fats have very similar structures. Each molecule of a fat is made from one <br /> molecule of a simple substance called glycerol joined to three molecules of <br /> substances called fatty acids. Fats may be described as triglycerides. Fats are <br /> also sometimes called lipids. <br /> The fatty acid part of the fat molecule contains a long chain of carbon atoms to <br /> which hydrogen atoms are attached. <br /> <br /> H H H <br /> H H H H <br /> C C C <br /> C C C C <br /> H H H <br /> H H H H <br /> <br /> a saturated molecule <br /> <br /> If each carbon atom is attached to its full amount of hydrogen atoms, the resulting <br /> molecule is said to be saturated. Molecules of saturated fat contain only carbon to <br /> carbon single bonds. <br /> When one or more pairs of hydrogen atoms are missing from neighbouring carbon <br /> atoms, the resulting molecule is said to be unsaturated. Unsaturated molecules will <br /> have some double bonds between the carbon atoms. When one pair of hydrogen <br /> atoms is missing the fatty acid is said to be monounsaturated. When two or more <br /> pairs of hydrogen atoms are missing the fatty acid is said to be polyunsaturated. <br /> <br /> H <br /> H <br /> C H H<br /> <br /> C <br /> C C <br /> H<br /> <br /> C <br /> H <br /> H <br /> C <br /> <br /> <br /> H H <br /> H C C <br /> C C C C <br /> H <br /> Monounsaturated <br /> H H H H <br /> Polyunsaturated <br /> <br /> Whether or not fats contain saturated or unsaturated fatty acids is of considerable <br /> importance. The more saturated a fat is, the harder the fat tends to be. Fats which <br /> are from animal sources tend to be saturated and harder, though there are <br /> exceptions. The more unsaturated a fat is, the softer it is and oils may be formed. <br /> Fats from plant sources tend to be unsaturated and softer, though there are <br /> exceptions here as well. <br /> Medical evidence suggests that the saturated fats are also associated with a higher <br /> risk of circulatory and heart problems. We are advised in general to cut down on the <br /> amount of fat we consume. When we do eat fats we are advised to use the <br /> monounsaturated or polyunsaturated fats. <br /> Unfortunately, for the food industry and the home, the unsaturated fats are more <br /> susceptible to attack by oxygen. In other words they are more prone to oxidation. <br /> When fats undergo oxidation they produce unpleasant and sometimes harmful <br /> substances that make the fat rancid. There are many substances which are used as <br /> antioxidants in food processing to delay the process of oxidation. <br /> Oxidation reactions in the body, except those associated with the release of energy in <br /> respiration, can lead to heart and circulatory problems. The consumption of <br /> antioxidants in foods may help to reduce this. <br /> pupil activity A02<br /> <br /> FATS pupil activity A02 <br /> <br /> The table shows the composition of some fats and oils with respect to saturated, <br /> monounsaturated and polyunsaturated fatty acids. These figures are typical, average <br /> figures. It must be remembered that the composition of fats, even from the same <br /> source, will vary considerably. <br /> <br /> <br /> <br /> % saturated fatty <br /> acids <br /> % monounsaturated <br /> fatty acids <br /> % polyunsaturated <br /> fatty acids <br /> beef fat 55 40 5 <br /> lard 43 48 9 <br /> cow’s milk fat 70 27 3 <br /> human milk fat 44 43 12 <br /> herring oil 21 65 14 <br /> maize (corn) oil 17 34 49 <br /> cocoa butter 65 32 3 <br /> coconut oil 94 5 1 <br /> palm oil 55 34 11 <br /> olive oil 14 79 6 <br /> <br /> 1. Present the figures in the table as a suitable graph. <br /> 2. Choose two of the fats from the table. Show the % of saturated, <br /> monounsaturated and polyunsaturated fatty acids present in each of these fats as <br /> two separate pie charts. <br /> 3. Where does lard come from? <br /> 4. Read the information from the third paragraph again. From the table, which <br /> animal fat seems to be an exception to the rule? Which plant fat seems to be an <br /> exception? <br /> 5. Name a fat from the table which you think would go rancid quickly. Explain why <br /> you have chosen this fat. <br /> 6. Using food labels, find the names of three foods which contain an antioxidant. <br /> Write down the names of the foods, the names of the antioxidants and their <br /> E-numbers. <br /> <br /> Explain why antioxidants are used in foods.<br /> <br /> HEIGHT AND WEIGHT CHART (MALE) <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> Source: Adapted from Child Growth Foundation charts <br /> pupil activity A02M<br /> <br /> HEIGHT AND WEIGHT CHART (FEMALE) pupil activity A02F <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> Source: Adapted from Child Growth Foundation charts