4.4 b The performance Characteristics of eggs (p 115) Coagulation (Denaturation) Peptide bonds between amino acids broken Permanent change 3D network – water trapped Heat, acid or mechanical Egg white coagulates 60-65°C Egg yolk 65-70°C Over cooking = syneresis Bain Marie protects overheating Acid firmer set, sugar looser 1 egg sets 250ml milk More yolk – firmer set
Foam Gas in a liquid – air through egg white Ovalbumin stretches & holds air Proteins denatured – uncurl 3D air / liquid structure = stable Salt - lower pH resists foaming Sugar – interferes with bonds more whisking Fat – (inc egg yolk) won’t foam Alkalis – increases pH less time to foam Acids – softens foam Egg yolk foam – Swiss roll – over steam – mechanical & heat
Emulsification Emulsion = one liquid dispersed in small droplets into another liquid (doesn’t naturally mix) e.g. milk, salad dressing, mayonnaise Emulsifying agent needed Egg yolk – holds fat in emulsion Lecithin in yolk – hydrophobic & hydrophilic components = suspension Creamed cake mixture = fat in sugar emulsion
Eggs also . . . Colours & enriches – nutrition & colour through carotene (vit A) Flavours –Baked products due to fat content
4.4 c Behaviour Changes (bread, cakes, sauces & pastry) (p123) Beating = incorporating air into a mixture Creaming method = Sugar & fat creamed = air in fat foam. Abrasive action of sugar separates fat & traps air
4.4 c Behaviour Changes (bread, cakes, sauces & pastry) (p123) Whisking - Adding air – denatured = mechanical & some coagulation as heat produced Shortening – fat = crumbly texture. Particles coated with fat = waterproof barrier. Reduces gluten formation. Also traps air
4.4 c Behaviour Changes (bread, cakes, sauces & pastry) (p123) Kneading = adds strength to dough. Gliadin & Glutenin = proteins = gluten when kneaded. Structure of bread – holds pockets of Co2. Produces springy, elastic dough
4.4 c Behaviour Changes (bread, cakes, sauces & pastry) (p123) Heating = cooking food = chemical & physical changes Melting method = sugar & fat melted other ingredients added. Bicarbonate of soda released Co2 = soapy taste masked by spices
4.4 c Behaviour Changes (bread, cakes, sauces & pastry) (p123) Moist heat on Carbohydrates = starch grains soften & absorb liquid = gelatinisation 75-87°C. Sauce making Roux sauce All in one Blended method
4.4 c Behaviour Changes (bread, cakes, sauces & pastry) (p123) Dry heat on Carbohydrates = non enzymic browning Maillard reaction – proteins (amino acids) & starch (maltose) = brown colour. Starch – dextrin = dextrinisation = brown crust Caramelisation = oxidation of sugars - sucrose
4.4 c Behaviour Changes (bread, cakes, sauces & pastry) (p123) Heat on proteins = denatured. Permanent change = coagulation Heat on fat = solid fat melts – assists with gelatinisation Over heating = break down to glycerol & fatty acids
4.4 c Behaviour Changes (bread, cakes, sauces & pastry) (p123) What happens in the oven? Creamed cake – Self raising flour, margarine/butter, caster sugar, eggs Whisked sponge – plain flour, egg, caster sugar Pastry – plain flour, lard, margarine & water Bread – Strong flour, fat, yeast, salt, water