The function of emulsifiers and stabilisers

UNDERSTANDING YOUR FOOD<br /> the ultimate educational resource<br /> TEACHER NOTES<br /> <br /> teachers’ notes E2.1<br /> E2. The function of emulsifiers and stabilisers<br /> Pupils are asked why the food industry usesemulsifiersandstabilisers.<br /> Pupils may suggest the following reasons for the food industry using<br /> stabilisers:<br /> • the quantities produced are very much larger than for foods produced<br /> at home<br /> • there needs to be greater consistency between batches<br /> produced for consumers<br /> • foods are likely to be transported over large distances and stored<br /> for long periods of time before use<br /> • some additives allow the production of food which it is not<br /> possible to produce at home<br /> • there is a trend for more of this sort of product to be purchased<br /> ready made because:<br /> - there may be a lack of time due to work<br /> - these products are more convenient to use<br /> - there may be a lack of the necessary skills<br /> - ready made products may be cheaper.<br /> Pupil activity sheet E2 accompanies<br /> this activity.<br /> Requirements (per group)<br /> • test tubes<br /> • test tube rack<br /> • 5 cm<br /> 3<br /> tap water<br /> • 5 cm<br /> 3<br /> cooking oil<br /> • 1 cm<br /> 3<br /> whisked egg yolk.<br /> Investigating the action of an emulsifier<br /> Pupils carry out a simple practical activity to investigate the stabilising<br /> effect of egg yolks.<br /> Following the introduction the pupils conduct a simple investigation which<br /> looks at emulsions and emulsifiers.<br /> Pupils should find that before shaking, the liquids form separate layers in<br /> the tube with oil floating on top. The egg yolk may sink to the bottom.<br /> Immediately after shaking, the contents of the tubes appear to have<br /> mixed. However, on leaving to stand, the tube without the egg yolk will<br /> quickly revert back to two layers. The tube with the egg yolk should<br /> remain mixed.<br /> Egg yolk contains thephospholipid,lecithin. Lecithins are used as food<br /> additives and have the E-number, E322. Lecithin acts an emulsifier<br /> because it enables the vinegar and oil to mix. Eventually, most emulsions<br /> will separate out into their components. The use of stabilisers prevents this<br /> for a considerable period of time.<br /> KS4<br /> project in food technology<br /> Timing - various<br /> <br /> teachers’ notes E2.2<br /> Pupil activity sheet E2, accompanies<br /> this activity.<br /> Requirements<br /> • kitchen blender with horizontal<br /> blade attachment<br /> • balance or scales<br /> • granulated sugar<br /> • table salt<br /> • white vinegar<br /> • water<br /> • vegetable oil<br /> • fresh egg yolk<br /> • chopped white cabbage<br /> • grated carrot<br /> • various bowls, spoons, etc<br /> • ’HAMULSION’ - a commercial<br /> stabiliser* supplied with this<br /> resource; store this in a dry<br /> place<br /> * Further samples of the stabiliser<br /> are available from the Chemical<br /> Industry Education Centre,<br /> University of York, Heslington,<br /> York, YO10 5DD<br /> per 100g<br /> vegetable oil<br /> egg yolk<br /> sugar<br /> energy<br /> (kcal/kJ)<br /> 900/3780<br /> 350/1470<br /> 400/1680<br /> fat<br /> (g)<br /> 100<br /> 30<br /> 0<br /> carbohydrate<br /> (g)<br /> 0<br /> 0<br /> 100<br /> protein<br /> (g)<br /> 0<br /> 16<br /> 0<br /> Investigating using a stabiliser in a mayonnaise for coleslaw<br /> More able groups/older pupils will be able to make the mayonnaise for this<br /> investigation, otherwise you may like to carry out the investigation as a class<br /> exercise.<br /> Stabilisers have been developed which are added to mayonnaise to give<br /> good viscosity and ‘cling’ properties in cold conditions. A mayonnaise<br /> suitable for the commercial market has to be able to thoroughly coat the<br /> pieces of vegetable and not ‘run off’. The mayonnaise lubricates the<br /> vegetables and helps to prevent decay over the shelf life of the product<br /> (typically 16 days under refrigeration). During the shelf life the vegetables<br /> release water, which is mopped up by the mayonnaise while still<br /> maintaining its clinging properties.<br /> In this investigation, a mayonnaise is produced with the use of an industrial<br /> stabiliser. It is compared to the same mayonnaise made without the<br /> stabiliser. The mayonnaise without the stabiliser has the consistency of<br /> water, separates into an oil layer and a lower aqueous layer and is not<br /> suitable as a coating mayonnaise.<br /> The instructions for making the mayonnaise and carrying out the<br /> investigation are on the pupil activity sheets E2. You may have to<br /> increase the quantities of the ingredients in the mayonnaise to make sure<br /> that the horizontal blades are covered during mixing, otherwise a froth will<br /> be formed.<br /> More able pupils may be able to calculate the cost of the two dressings (the<br /> cost of the stabiliser is negligible). They may also be able to compare the<br /> nutritional value of the dressings with respect to any, or all, of the following:<br /> <br /> pupil activity E2THE FUNCTION OF EMULSIFIERS AND STABILISERS<br /> Stabilisers and emulsifiers arefood additives. They, and other similar additives, are<br /> numbered fromE331(c)toE495. They are widely used in the food industry in products<br /> such as salad dressings, processed cheese, preserves, margarine, yoghurt, instant<br /> desserts, ice cream, low fat products and others.<br /> Emulsifiers and stabilisers are used to help to retain the physicalqualities of products.<br /> Emulsifiers make water and oilmix together evenly. Stabilisers give products good<br /> textureandmouthfeel.<br /> When you make food at home, such as some of the items mentioned above, there is<br /> often no need to add extra emulsifiers or stabilisers to the recipe. So why does the<br /> food industry use emulsifiers and stabilisers so often? To answer this question you<br /> should think about the differences between producing food for the home and food<br /> for sale in shops and supermarkets.<br /> Home-made foods such as salad dressings, yoghurt and ice cream are excellent and<br /> nutritious products. However, nowadays more of these products are bought from<br /> shops rather than made at home. Think of as many reasons as you can to explain this<br /> trend.<br /> Investigating the action of an emulsifier<br /> What are emulsifiers and emulsions? Carry out the following investigation to helpyou<br /> to answer this question.<br /> Method<br /> 1.Pour about 2 cm depth of tap water into a test tube. Carefully add an equal<br /> depth of cooking oil to the same tube. Note down what the contents of thetube<br /> look like.<br /> 2.Pour about 2 cm depth of water into another test tube. Carefully add an equal<br /> depth of cooking oil to the same tube. Add 1 cm depth of egg yolk. Notedown<br /> what the tube looks like.<br /> 3.Put a bung in each tube and then shake both of the tubes for 30 seconds.<br /> 4.Leave the tubes to stand in a test tube rack.<br /> 5.Look carefully at the tubes over the next few minutes and describe what is<br /> happening in each tube.<br /> Discuss with your group and with your teacher the explanation for your<br /> observations.<br /> <br /> THE FUNCTION OF EMULSIFIERS AND STABILISERS pupil activity E2<br /> Investigating using a stabiliser in a mayonnaise for coleslaw<br /> SAFETY NOTE<br /> YOU MUST NOT EAT ANY OF THE MAYONNAISE<br /> MADE IN THIS INVESTIGATION<br /> HORIZONTAL BLADES ARE EXTREMELY SHARP;<br /> BE VERY CAREFUL WHEN HANDLING AND<br /> WASHING THEM.<br /> Ingredients for mayonnaise:<br /> 50 cm<br /> 3<br /> vegetable oil<br /> 10 cm<br /> 3<br /> egg yolk<br /> 20 g sugar<br /> 9 g salt<br /> 40 cm<br /> 3<br /> white vinegar<br /> 70 cm<br /> 3<br /> water<br /> 2 g of a commercial stabiliser<br /> Method<br /> 1.Secure thehorizontal bladesin a blender. Put the water, vinegar, sugar and salt<br /> into the blender. Mix on slow speed for 30 seconds.<br /> 2. Mix the stabiliser in about 5 cm<br /> 3<br /> of the oil.<br /> 3.Add this to the mixture in the blender and blend on slow speedfor 3 minutes.<br /> 4.Add the egg yolk and blend to mix this in.<br /> 5.Veryslowlyandcarefullyadd the remaining oil.<br /> 6.When all the oil has been added continue to blend for at least 3 minutes until the<br /> final mayonnaise is white and homogeneous (evenly mixed).<br /> 7.Transfer the mixture to a bowl and wash the blender and blades thoroughly.<br /> 8.To show what the stabiliser does in the mayonnaise, make up exactly the same<br /> recipe butdo not add any stabiliser.<br /> What differences are there between the mayonnaisewith the stabiliser and the<br /> mayonnaisewithoutthe stabiliser? Compare the two by looking at:<br /> •the colour<br /> •the consistency or thickness<br /> •the homogeneity or how evenly mixed it is.