Food Tech - functions of food

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• sols EG: fruit juice, brine, sugar and water syrups do not separate when left to stand

1. Formed when

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   • liquid dissolved in another liquid (fruit squash in water) solid dissolved in a liquid (sugar in tea)

1. Formed when

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   • solid particles are added to a liquid but don't dissolve (EG: starch particles don't dissolve)
2. Mix

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   • If the suspension isn't agitated (mixed) the solid particles fall to the bottom (EG: if a sauce isn't stirred when heated then lumps form)

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• Gel is a solid, jelly like substance. most are actually liquids but act as solids due to gelling agents

1. Gelatinisation

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   • Gels are formed when starch is heated in a liquid and then cooled this is gelatinisation
2. Gelling agents

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   • EG: flour, cornflour, pectin, gelatine

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• AKA modified starches Starches altered to change their working properties

1. Pre-gelatinised

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   • Allows them to thicken instantly EG: dried custard powder/ pot noodles
2. No synerisis

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   • Synerisis is the water produced when starch is reheated This allows the sauce to be reheated without synerisis EG: ready meals
3. Tolerance to acid

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   • Altered so tha they aren't affected by acidity, can be used to thicken acid foods EG: low calorie salad dressing

1. Immiscible

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   • Liquids that cannot be mixed together EG: oil and water when shaken together they form an unstable emulsion and separate when left to stand
2. Emulsifier

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   • if an emulsifier is used then the mixture remains stable EG: lecithin in egg yolk is an emulsifier - used in mayonnaise to hold oil and vinegar together -helps fat in cakes mix with egg whites

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• gas mixed into a liquid giving it a light texture EG: meringues - when you bake them the air expands and the egg whites coagulate to give them a solid structure

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• Very stretchy

1. Gluten

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   • gluten has elasticity allows food made from wheat flour to rise (EG: cake/ bread) no other cereal has this property
   1. How its made

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      • Wheat contains two proteins - glutenin and gliadin. when water is added they form gluten

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• describes how fat changes under pressureEG: rubbing/ spreading You can easily rub in: margarine, butter, lard - which allows for shortening to take place Oil can not be rbbed in easily

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• Fat coats the starch and protein molecules in the flour - this stops liquid coming in contact with flour, so stopes gluten forming. any gluten that does form is in short lengths rather that long stands that are needed for elasticity. shortening gives cakes, biscuits and pastry a crumbly melt-in-the-mouth texture

1. Bacteria in milk

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   • naturally produce acid by changing lactose into lactic acid this coagulates the protein casein and makes the milk go lumpy and sour   lumps = curds liquid = whey. drained curds are made into cheese this can happen in recipes using acid, to prevent, thicken milk with cornflour before adding the acid
2. Citric acid

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   • lemon/ lime juice adding to cream or condensed milk coagulates the protein and gives it a thicker consistency which is used in key lime pie etc. adding citric acid can prevent oxidation, EG: add to fruit salad
3. Acetic acid

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   • vinegar prevents crystallisation in meringues by changing some of the sucrose to glucose and fructose (invert sugar) preserves vegetables by preventing bacterial growth (EG: pickling) gives a sharp flavour (EG: salad dressing)
4. Ascorbic acid

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   • vitamin c speeds up fermentation in bread making
5. In sauces

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   • when making sauces acid breaks down the starch granules, making it thicker allow sauce to thicken fully before adding acid

1. Work by

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   • incorporating gas into the mixture when you heat gases they expand and rise, then escape from the mixture leaving a light and open texture. they can be adding mechanically (EG: sifting/ beating) or in the ingredients (EG: yeast/ bi carbonate of soda)
2. Natural

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   • Gases - air, steam, carbon dioxide add air mechanically - whisking, sieving, creaming of fat and sugar, beating of batter, rubbing fat into flour or rolling and folding of pastry steam is used in mistures with a high proportion of liquid (EG: yourkshire pudding or choux pastry) it usually has an open and uneven texture co2 can be added biologically in yeast or chemically through bicarbonate of soda
3. Chemical

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   • produce co2 when heated with a liquid EG: self raising flour (convenient as it already contains RA) bicarbonate of soda - produces co2 and washing soda when heated, washing soda is dark yellow with a soapy taste so is used with stong flavours to disguise soap (gingerbread) bicarb + acid - to prevent the soapy taste ( vinegar or cream of tartar) baking powder - bicarb + acid + starchy filler to keep it fresh
4. biological

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   • Yeast is a micro organism that gives off co2 in needs warmth (25 - 28`c), liquid, food (sugar, or obtained through flour), and time (mixture is covered and left to rise)

1. why

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   • prevent food poisoning improves palatability preservation easier to digest improves the absorption of nutrients less bulky (EG: spinach)
2. Heat transfer

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   • changes food physically and chemically conduction - molecules are heated and vibrate faster convection - as molecules become hotter they rise, and fall when cool (EG: boiling water in pan) Radiation - transfer of energy from a heat source to food, radiation waves travel to food and the centre is then heated by conduction, hot spots can occur so be sure to stir

1. Methods

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   • whisking = fatless sponges (swiss roll) rubbing in = scones/ fruit cakes melting = gingerbread/ brownies creaming/ all-in-one = sponges (Victoria sandwich)
2. Functions
   1. Fat

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      • adds flavour extends shelf life traps air when creamed - acts as a raising agent
   2. sugar

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      • sweetens adds colour through caramelisation softens structure
   3. eggs

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      • trap air acts as an emulsifier in creamed cakes adds colour forms structure through coagulation provides moisture - whichcontverts to steam on heating and acts as a raising agent
   4. flour

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      • structure of cake gives colour through dextrinisation of starch bulk ingredient
3. Aeration

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   • incorporating air into the mixture creaming of fat and sugar - all-in-one methods aren't creamed so require extra baking powder sieving of flour whisking eggs and sugar together
4. modifications

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   • flour flavourings decoration enrobing - icing/ marzipan/ chocolate shape/ size

1. functions
   1. flour

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      • bulk ingredient forms structure colour through dextrinisation
   2. fat

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      • shortens gives colour
   3. water

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      • binds ingredients helps form structure creates steam - helps with rising
   4. salt

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      • adds flavour
2. Modifications

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   • additional flavours shape/ size type of pastry
3. Uses

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   • ratio of ingredients and how they are combined gives different results of texture, taste and appearance. shortcrust = quiche/ jam tarts choux = profiteroles flaky/rough puff = sausage rolls/ vanilla slices suet = pies/ jam roly poly filo = baklava/ samosas hot water crust = pork pie
4. Finish

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   • brush with egg or milk to give brown appearance sprinkle with sugar - attractive finish and shows its a sweet product lid = lattice, pinched or forked around edge, decorations can be cut out of lid or made with extra pastry and put on top
5. ready made

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   • shortcrust/ flaky/ filo can be frozen or chilled shortcrust can be found in a packet mix advantages = quick, reliable outcome, guaranteed quality disadvantages = more expensive to buy, may contain additives, has to be stored until needed

1. Ingredients

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   • strong plain flour = bulk ingredient, forms structure gluten allows dough to stretch, dextrinisation gives colour yeast = makes bread rise salt = flavour and helps development of gluten, water = binds dry ingredients, helps gluten develop and helps yeast ferment
2. Modifications

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   • flour add flavourings use wholemeal - increases NSP, taste texture and appearance are altered add cheese - taste, texture and appearance, adds protein and fat content add dried fruit - sweetens bread, increases NSP affects appearance and taste add toppings

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• Liquids that are thickened they can form part of a dish (cheese sauce in lasagne) can be served with a meal (gravy) used in food products (lemon meringue pie)

1. Function

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   • add flavour, moisture and nutritional value
2. Synerisis

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   • happens when proteins are over cooked, they continue coagulating and squeeze out fat and water. it is a thin liquid that separates from a sauce to stop this, manufacturers use modified starches
3. thickening sauces

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   • gelatinisation of starch (roux) coagulation egg protein (custard) emulsification (mayonnaise) gelatine (glaze on flans) pureeing (fruit coulis)
4. modifications

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   • swap whole milk for semi skimmed to tailor for the ever growing market for low fat food add ingredients - parsley, cheese, sugar

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• Layering food - trifle change toppings - cake/ crumble change finish - add decorations,alter glazings or enrobing change cooking method change preparation methods change basic ingredients add ingredients