Food Tech - functions of food

Nota:

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

1. Formed when

   Nota:

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

1. Formed when

   Nota:

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

   Nota:

   • 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)

Nota:

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

1. Gelatinisation

   Nota:

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

   Nota:

   • EG: flour, cornflour, pectin, gelatine

Nota:

• AKA modified starches Starches altered to change their working properties

1. Pre-gelatinised

   Nota:

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

   Nota:

   • 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

   Nota:

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

1. Immiscible

   Nota:

   • 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

   Nota:

   • 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

Nota:

• 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

Nota:

• Very stretchy

1. Gluten

   Nota:

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

      Nota:

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

Nota:

• 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

Nota:

• 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

   Nota:

   • 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

   Nota:

   • 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

   Nota:

   • 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

   Nota:

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

   Nota:

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

1. Work by

   Nota:

   • 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

   Nota:

   • 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

   Nota:

   • 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

   Nota:

   • 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

   Nota:

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

   Nota:

   • 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

   Nota:

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

      Nota:

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

      Nota:

      • sweetens adds colour through caramelisation softens structure
   3. eggs

      Nota:

      • 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

      Nota:

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

   Nota:

   • 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

   Nota:

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

1. functions
   1. flour

      Nota:

      • bulk ingredient forms structure colour through dextrinisation
   2. fat

      Nota:

      • shortens gives colour
   3. water

      Nota:

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

      Nota:

      • adds flavour
2. Modifications

   Nota:

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

   Nota:

   • 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

   Nota:

   • 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

   Nota:

   • 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

   Nota:

   • 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

   Nota:

   • 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

Nota:

• 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

   Nota:

   • add flavour, moisture and nutritional value
2. Synerisis

   Nota:

   • 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

   Nota:

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

   Nota:

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

Nota:

• 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