Baking scones

UNDERSTANDING YOUR FOOD<br /> the ultimate educational resource<br /> TEACHER NOTES<br /> <br /> teachers’ notes A4.1<br /> A4. Baking scones<br /> Pupils investigate raising agents used in baking scones.<br /> Flour - acid or alkali?<br /> Pupils test small quantities of plain ?our, and self raising ?our in suitable<br /> dishes, with the Universal indicator.<br /> Results<br /> KS3/4<br /> food technology<br /> Timing - 50 - 60 minutes.<br /> Two pupil activity sheets A4<br /> accompany this activity.<br /> Requirements for baking scones<br /> activity plain ?our<br /> self-raising ?our<br /> Universal indicator & chart<br /> Apparatus (per batch)<br /> • 300 g plain ?our<br /> • 62.5 g margarine<br /> • 62.5 g sugar; (it is possible to<br /> make the scones without sugar<br /> in order to save money)<br /> • 120 cm<br /> 3milk<br /> • balance accurate to 0.1 g<br /> • <10 g commercial<br /> bicarbonate of soda<br /> • <10 g monocalcium phosphate*<br /> (acid calcium phosphate) -<br /> supplied with this resource<br /> • various mixing bowls, knives, etc.<br /> • pastry cutters<br /> • greased baking trays<br /> • oven at 230oC<br /> • Universal indicator & chart<br /> • ink and sponge (optional)<br /> What makes scones rise?<br /> Hints for the teacher<br /> • To save time it might be more convenient to have the ?our plus the<br /> raising agent mixtures already weighed out and prepared.<br /> • It is important to roll the scones out to the same thickness. The use<br /> of roller guides would help this process.<br /> • If the cut surfaces of the cooked scones are brushed over with an ink-<br /> soaked piece of sponge, a texture print can then be made.<br /> Alternatively, the cut surface of the scones can be photocopied.<br /> Results for scones<br /> <br /> The taste of sodium<br /> hydrogencarbonate used as the sole<br /> raising agent is soapy and thus its<br /> use is limited to bakedproducts which<br /> have strong flavours, such as<br /> gingerbread and parkin so that the<br /> unpleasant taste is masked.<br /> The pupils’ sheet does not specifically ask pupils to smell or taste the<br /> scones but this is permissable. The scones with just the sodium<br /> hydrogencarbonate may smell and taste ‘soapy’. Obviously, the fourth<br /> batch of scones should be the most acceptable.<br /> Discussion of results:<br /> pH<br /> • The pH of the final scones shows that flour alone is acidic.<br /> • Sodium hydrogencarbonate alone makes the scones alkaline (and<br /> would give them a soapy taste).<br /> • The monocalcium phosphate alone makes the scones acidic.<br /> • A combination of the two results in a typical acid-alkali (carbonate)<br /> reaction and results in the scones being approximately neutral.<br /> raising properties<br /> • A combination of an acid and alkali is needed to produce an<br /> acceptably risen product as this reaction produces carbon dioxide<br /> which is responsible for making the scones rise.<br /> • The sodium hydrogencarbonate alone will make the scones rise a<br /> little as the compound decomposes thermally to produce carbon<br /> dioxide.<br /> colour<br /> • The use of sodium hydrogencarbonate alone produces a yellow colour.<br /> This<br /> is desirable in some industrially produced cakes such as some<br /> chocolate cakes.<br /> Pupils may wonder why the acid and alkali are not present in equal<br /> amounts. They could make scones where this is the case (use 3.61g of<br /> each). This will produce a slightly alkaline, pale yellow scone which has a<br /> softer texture. In commercial situations the proportions of acid (and acid<br /> type) to alkali vary according to the product taking into account factors such<br /> as added flavours, waiting time between mixing and baking and others.<br /> Most usually the proportion of monocalcium phosphate to sodium<br /> hydrogencarbonate is 1.2 : 1.0.<br /> Tests on the unbaked flours<br /> mixture<br /> plainflour<br /> plain flour + sodium<br /> hydrogen carbonate<br /> plain flour +<br /> monocalcium<br /> phosphate<br /> plain flour, sodium<br /> hydrogen carbonate<br /> + monocalcium<br /> phosphate<br /> colour<br /> even orange<br /> even yellow/greenthe<br /> colour becomes<br /> darker with timeeven<br /> orange/red<br /> even orange with<br /> red specks; goes<br /> greener with time<br /> pH<br /> ~ 5<br /> 6 - 7.5<br /> 4 - 5<br /> 4 - 5<br /> comment<br /> plain flour is an acidic<br /> substance on its own<br /> sodium hydrogen<br /> carbonate is an alkali<br /> monocalcium<br /> phosphate is anacidic<br /> substance<br /> similar to self raising<br /> flour<br /> teachers’ notes A4.2<br /> <br /> BAKING SCONES pupil activity A4<br /> Before being eaten, any product which contains flour must be cooked. This alters the<br /> starch in the flour so that it becomes digestible. Flour is used in many savoury and<br /> sweet dishes, particularly in foods that consist of adough.<br /> Cakes, bread and other similar dishes often contain araising agent. A raising agent<br /> consists of an acid and an alkali. The acid present can vary but the alkali used is<br /> usually sodium hydrogencarbonate. Raising agents are classed as food additives; the<br /> two most important ones being E341 - the acid calcium phosphates and E500 -<br /> sodium carbonate.<br /> You are going to investigate what makes scones rise.<br /> Flour - acid or alkali?<br /> 1.Place a small sample of ordinaryself raising flour into a suitable dish.<br /> 2.Add some Universal indicator solution. Leave for two minutes. Describe and<br /> explain what happens.<br /> 3.Repeat this using ordinaryplain flour. Describe and explain what happens.<br /> What makes scones rise?<br /> You are going to produce and comparefourdifferent batches of scones. It maybe<br /> better to work in 4 groups and share results.<br /> Recipe A<br /> 1.Sift 250 g ofplain flourinto a mixing bowl.<br /> 2.Rub 62.5 g ofmargarineinto the flour.<br /> 3.Add 62.5 g ofsugar into the mixture.<br /> 4.Gradually add approximately 120 cm<br /> 3<br /> of milk and mix to give a good<br /> dough. The amount of milk you will need to add may vary.<br /> 5.Roll out the dough on a lightly floured surface or board. It must be 1cm thick.<br /> 6.Cut the dough into scones using a pastry cutter.<br /> 7.Place the scones onto a lightly greased baking tray and bake for 12 to 15<br /> o<br /> minutes in an oven at 230C.<br /> Recipe B<br /> 1.Weigh out 300 g ofplain flour.<br /> 2.Add to this 3.61 g ofsodium hydrogencarbonate.<br /> 3.Mix these dry ingredients very thoroughly.<br /> 4.Take 250 g of this mixture and sift it into a mixing bowl. Keep the rest ofthe<br /> mixture for a later test.<br /> Carry out steps 2-7 of recipe A.<br /> Recipe C<br /> 1.Weigh out 300 g ofplain flour.<br /> 2.Add to this 4.33 g ofmonocalcium phosphate(acid calcium phosphate).<br /> 3.Mix these dry ingredients very thoroughly.<br /> 4.Take 250 g of this mixture and sift it into a mixing bowl. Keep the rest ofthe<br /> mixture for a later test.<br /> Carry out steps 2-7of recipe A.<br /> <br /> pupil activity A4 BAKING SCONES<br /> Recipe D<br /> 1.Weigh out 300 g ofplain flour.<br /> 2.Add to this 3.61 g ofsodium hydrogencarbonateand 4.33 g ofmonocalcium<br /> phosphate(acid calcium phosphate).<br /> 3.Mix these dry ingredients very thoroughly.<br /> 4.Take 250 g of this mixture and sift it into a mixing bowl. Keep the rest of the<br /> mixture for a later test.<br /> Carry out steps 2 - 7 of recipe A.<br /> When the scones are ready and cool, cut each of the scones in half so that you can<br /> see inside. Compare them in the following ways:<br />
”Describe the colour; white, off-white, pale yellow or yellow.<br />
”Which scone has risen the most? Give 4 to the highest scone, 3 to the next, 2<br /> to the next and 1 to the smallest.<br />
”Describe the texture/structure; closed, medium or open.<br />
”Add three drops of Universal indicator to each cut surface. Wait for one<br /> minute. Describe what happens in terms of colour and pH number.<br /> You should have samples of unused mixtures from recipes B, C and D and some plain<br /> flour as used in recipe A. Add 3 drops of Universal indicator to each of these mixtures<br /> and comment on what you observe.<br /> Present your results in tables similar to those below. Try to explain the differences in the<br /> results.<br /> Comparison of scones from the four recipes<br /> scone mixture plus volume colour texture/ Universal<br /> structure indicator<br /> nothing(Recipe A)<br /> sodium hydrogen<br /> carbonate(Recipe B)<br /> monocalcium<br /> phosphate(Recipe C)<br /> sodium hydrogen<br /> carbonate and<br /> monocalcium<br /> phosphate(Recipe D)<br /> Comparison of flour mixtures prior to baking<br /> flour mixture sample colour/pH comments<br /> from recipe A from<br /> recipe Bfrom recipe C<br /> from recipe D