Functional Properties of Gelatinisation

Hey guys! welcome back. For this weeks blog post we will be discovering the functional properties of gelatinisation and how the chemical reactions occur when used in cooking.

For this week, I cooked two recipes that involves gelatinisation. The first recipe was the White Sauce, second recipe was the Risotto.

Gelatinisation is the process in which starch granules are heated in a liquid, causing the starch granules to swell.
The heat breaks down the starch molecules allowing it to absorb the liquid. Any type of starch can be used. Gelatinisation is used as a thickening agent of food systems. The ratio of amylopectin and amylose and the method used determines the physical qualities of the gel that is produced.

Starches contain around 25% amylose and 75% amylopectin. Starches that contain more amounts of Amylose are more useful in food preparation. Starches that contain a higher amount of amylopectin creates clearer gels and thick liquid, while starches that contain 25% amylose creates opaque gels that are quite solid. Amylose and Amylopectin have a few differences, such as that amylose are more soluble in water, while amylopectin is less soluble. However, amylose does not form starch gel or paste, while amylopectin does. Although, amylose is soluble in hot water without even swelling, while amylopectin swells up in soluble hot water. Amylose is a part of 20% of the starch, while amylopectin is a part of 80% of the starch.


For the White sauce:
The equipment's we will be needing for this recipe are:
-1/2 cup of milk
- Either: 2 tsp plain flour, corn flour or rice flour
- 10g butter
- 1 tbs cheese
- 1/2 tsp dried parsley
- 2-3 tsp frozen corn
- 1/8 Turkish roll, roasted

For the Method:
1. Melt butter in a small saucepan on a medium heat. Remove from the heat. Stir in flour to absorb butter. Return to heat (this help to break open the starch molecules in the flour) for 1 minute. Remove from heat.
2. Slowly whisk in milk, until all lumps have been removed. Return to heat until sauce thickens.
3. Allow to cool for 2 minutes, and stir through cheese, corn and parsley. Season with salt and pepper.
4. Serve with torn, toasted Turkish bread.

Now for the Risotto,
The equipment's that are needed are:
- 2 3/4 cups hot chicken stock
- 1/2 chicken breast, sliced
- 2 Tbs oil
- 1/2 onion, chopped
- 1 cup (440g) Arborio rice
- 1 tsp lemon rind, finely grated
- 2 rashers of bacon, diced
- 1/4 cup white wine
- 1 garlic clove, finely chopped
- 1/4 cup (40g) finely grated parmesan
- Salt and Pepper to season
- 1/2 cup fresh basil leaves, roughly torn

For the Method:
1. Heat 1tbs oil in a small fry pan over a medium heat. Add chicken and cook until golden. Transfer to a bowl and cover with foil. Add bacon and fry for 1-2 minutes. Add to bowl.
2. Meanwhile, in a separate medium size fry pan, sweat (without browning) onion and garlic in remainder of the oil for 2-3 minutes or until soft (cook on medium heat with lid on.) Add the rice and stir until well coated in oil. Add white wine and allow to reduce.
3. Add 1 cup of the hot stock and cook, stirring often, until the stock is absorbed. Continue adding the hot stock, 1 cup at a time, stirring until the stock is absorbed and the rice is just tender.
4. Stir the lemon rind and grated parmesan through the risotto and then season to taste. Fold 3/4 of the basil through the risotto. Divide among the serving dishes. Top with the remaining basil and shaved parmesan. Serve immediately.

We were able to tell that the gelatinisation in the white sauce and risotto was occurred by the consistency and look. The longer it was in the heat the thicker and more gel like it gets. The risotto rice went from being hard and nutty ,to becoming a thick gel consistency, it was because of the rice absorbing the liquid which caused the rice to break down. In the white sauce, the sauce became thicker and thicker the longer it was in the presence of the heat, it went from a runny, watery like consistency to a thick sauce. The observations showed us that gelatinisation had occurred on both recipes.

My observations of the rice before and after cooking it was;
Rice before: White, Hard, Grainy, Nutty, Thin shape 
Rice After: Almost transparent, Soft, Smooth, Slightly thicker shape

When starch is in the presence of heat, it softens, giving it the chance to absorb the liquid. When the temperature reaches 86 degrees - 90 degrees, the starch granule bursts and the amylose and amylopectin is released which absorbs the liquid, giving us a thick gel like product. Without heat, the molecules wont burst therefore the amylose and amylopectin are not released.

Starch is a polysaccharide, which means it is able to break down. Polysaccharide are found in plants, starchy vegetables and grains such as rise and wheat. When the molecule breaks down, it processes chemical changes like gelatinisation and dextrinization. Corn starch and plain flour are most commonly used to help thicken liquid such as water. For potato starch, it used with things like potato soup and mashed potato, it is also commonly used in fast food restaurants. Also, corn starch and rice starch are commonly used to make edible sweets and lollies (Hegenbart,1996).

Arborio rice is commonly used to make risotto because it contains a high level of starch, while brown rice or long grain rice has lower levels and does not produce a sticky creamy texture like Arborio rice.  Long grain rice cooks up fluffy and doesn't clump together, therefore it will not make the required texture for a risotto (Tamarkin, 2015). Also, long grain rice and brown rice wont absorb as much liquid compared to Arborio rice,  therefore they both don't have that sticky and thick result. They both have more levels of amylose then amylopectin, and like I said before in the previous paragraphs, it is the amylopectin that thickens the liquid, whilst amylose gives the product more of a solid opaque gel end result.

It is important to add acid such as lemon in the risotto after it was cooked because gelatinisation can be affected by additives such as sugar and acid, the pH level can be altered which gives it different results. Acids like lemon juice can affect the thickness of the mixture, while for sugar, it affects the temperature of gelatinisation.

Here are my resources:

Diana Maricruz Perez Santos, n.d., Science Meet Food, viewed 1 March 2016, http://sciencemeetsfood.org/starch-gelatinization/

Major Differences 2015, Major Differences, viewed 1 March 2016, http://www.majordifferences.com/2013/02/difference-between-amylose-and_17.html#.VtaQ249OLIV

Scott Hegenbart 1996, Understanding Starch Functionality, viewed 3 March 2016, http://www.naturalproductsinsider.com/articles/1996/01/understanding-starch-functionality.aspx

David Tamarkin 2015, When to Use Long-Grain, Medium-Grain and Short-Grain Rice, viewed 3 March, http://www.epicurious.com/ingredients/rice-guide-long-grain-short-medium-article

I hope you enjoyed this weeks blog and learned things!

Thanks, Kae