Denaturation and Coagulation

Hey guys! welcome back to my blog. This week in class we made two delicious recipes, mini quiches and chocolate meringue kisses. In class we learned about the functional properties of proteins, which are Denaturation and Coagulation.

For the mini quiche, here is the recipe:

For the bacon and tomato filling:

- 20g butter


-  ½  brown onion, finely chopped


-  1 garlic clove, finely chopped

-  ½ tomato, sliced

-1 rasher bacon, diced

- 50g cheese, grated

- 2 eggs

- 90ml cream

-Salt and pepper to season

For the shortcut pastry:

-1 cup flour

- 75g butter, chilled, chopped

-1  egg yolk


-Pinch of salt

-1-3 tbs ice water


Method:
For Pastry:

1. Preheat oven to 220C. Grease a mini quiche baking tray with butter.

2. Sift together the flour and salt

3. Rub butter into flour using fingertips until the mixture resembles fine breadcrumbs. Add water gradually to make stiff dough.


4. Wrap in plastic film and refrigerate for at least 15 minutes

5. Roll out dough 2mm thick between 2 sheets of baking paper. Use a large cookie cutter to cut pastry cases. Place into well-greased quiche baking tray. Cover each case with baking paper and blind bake (bake with cooking weights) for 10 minutes. Remove weights and cook for a further 5 minutes.


For Filling:


1. Melt butter in a small frying pan over medium heat. Add onion and garlic (and bacon). Cook, stirring, for 5 minutes until onion has softened (and bacon is crispy) (add spinach and cook for 1 minute).  Transfer mixture to a bowl. Set aside for 10 minutes to cool (once cool mix through crumbled feta or tomato).

2. Beat together egg and cream.  Season with salt and pepper. Transfer to a pouring jug. Evenly spoon either bacon or spinach mixture into your pastry cases and then pour egg mixture into each case. Sprinkle with grated cheese and bake for 15-20 minutes or until set. Stand for 5 minutes. Serve with salad.

For the chocolate meringue kisses:

 - 1 eggwhite

-  1/4 cup caster sugar

- 45g dark chocolate

- 30g sour cream

- Cocoa powder to dust

Method:

1. Preheat oven to 150°C/130°C fan-forced. Line 2 baking trays with baking paper.

2. Using an electric mixer, beat eggwhites until stiff peaks form. Add caster sugar. Beat for 8 minutes or until sugar has dissolved.

3. Place mixture into a piping bag fitted with a 5mm fluted or plain nozzle. Pipe 2cm wide swirls of mixture onto prepared trays, allowing 2cm between each for spreading. Bake for 20 minutes or until meringues are firm. Turn off oven. Allow to cool in oven with door slightly ajar.

4. When meringues are cool, place the chocolate and sour cream in a heatproof bowl. Place bowl over a saucepan of simmering water; stir until chocolate melts.

5. Dip the base of a meringue in the chocolate and sandwich with another meringue. Repeat with remaining meringues and chocolate. Dust with cocoa powder.

The physical changes that occurred throughout the making of the quiche is the mixing ingredients for both the filling and the pastry. The physical change that occurred in the filling were the dicing of the bacon, onion, garlic and tomato. For the pastry, the rolling out of the dough to make it thin and smooth was a physical change.

In the making of the mini quiche and the chocolate meringue kisses, the process of denaturation and coagulation occurred. Egg was the protein that was mainly responsible of the chemical changes that occurred for both the quiche and meringue. When denaturation occur the strands of the helix separate and unravel and the bonds that holds the helix shape breaks. In coagulation, it occurs when protein strands that were unravelled begins to re-join with other strands which forms a solid mass.

There are several chemical changes that occurred in both recipes. There are 4 factors that allow these chemical changes to occur. They include temperature, agitation, acidity and enzyme action. For The higher the temperature is the quicker proteins will coagulate. Heat also causes proteins to unravel. But, different temperatures will affect the process properties of different food. Denaturation occurs when the bonds between strands of amino acids begins to break. Acid is also used to help thicken dairy products.The function of the food can be affected if there is too much mixing and if its mixed too much the strands will be stretched too much to the point where the protein is denatured, that factor is called Agitation. And lastly, enzyme action can also affect denaturation and coagulation.

For eggs to coagulate it requires temperature. Egg whites begin to thicken when it reaches 63 degrees Celsius, at 65 degrees Celsius egg whites become tender solid and the yolk protein starts to thicken, this is when coagulation occurs. The egg yolk sets at 70 degrees Celsius. When it hits 73 degrees Celsius the whole egg sets. If eggs are left in the heat for too long it will continue to coagulate and water is pushed out from between protein molecule, the egg will get rubbery.

There are two types of denaturation of proteins, reversible and irreversible. In many proteins (unlike egg whites), denaturation is reversible when the proteins regain their native state when the denaturing influenced is removed, this process can be called renaturation. In under certain conditions, the process coagulation may be reversible. The characteristics of a protein change when coagulated, among which is loss of solubility in water and dilute salt solutions.

There are many different types of protein. Proteins enable foods to set. These properties are useful to commercial food processing. The two processes are denaturation and coagulation. To denature means to change properties; once a protein has denatured, it cannot return to its original form. An example of this is when heat is applied to an egg. Coagulation helps thicken and changes into a semisolid mass. Examples of denaturation and coagulation are scrambled egg, baked custard and beaten egg white. The process of denaturation and coagulation is affected by the application of acid, alkalis, sugar and salt.

That is the end of my blog. I hope you that helped you understood more about denaturation and coagulation!

Thanks, Kae :)

Bibliography:

EndInformatics 1999, Science project ideas using eggs, viewed 17 March 2016, http://www.edinformatics.com/science_projects/egg_proteins.htm


Florina 2014, Kkkjjm, viewed 18 March 2016, http://www.slideshare.net/priyankaflorina/denaturation-of-proteins


StasoSphere 2007, Coagulation of proteins, viewed 18 March 2016, http://chestofbooks.com/food/science/Experimental-Cookery/Coagulation-Of-Proteins.html