The How & Why



Energy!!!!!! We need it, we want it!

the easiest form of energy in nature is from STARCH…

a carbohydrate found in roots, seeds, fruits and stems of plants – root vegetables (like potatoes) are usually referred to as starches (starting to make sense now?)

but…to get the energy out, our body use enzymes called amylases…

these amazing little enzymes breakdown the starch into glucose which can be absorbed by the body and used for ENERGY.

The main sources of starch are cereal grains:
corn, wheat, rice, grain sorghum, oats, legumes, potatoes, tapioca and sago – this is were we get starch from to use in industry.

In the food industry we use starches as stabilizers, texturizes, thickeners and binders…Because they just LOVE to absorb WATER, making the little molecules (circles) fat with water! To me they are like little Piglets :)

There are two different types of starch molecules…

Amylose – which gives our puddings and sauces a gel consistency when cold, and thick consistency when hot
and Amylopectin – which keeps the sauce together and gives sauces its thickness through gelatinization when hot

Nerd alert:


is a polysaccharide (carbohydrate) made up of thousands of molecules (called glucose) joined together


Starch molecule:

there are two types, the one is a single long chain called amylose, the other is a chain with branches (bushy like a tree) called amylopectin, both of these molecules form starch granules


Starch granules:

tiny organized starch molecules placed in seeds and roots of plants


Gel consistency:

something that will hold its shape when turned out of a container, but can still wobble – like jelly



this is when starch granules are heated (5 – 85°C) in water making them swell, which thickens your puddings and sauces

There are TWO ways to heat a starch….


1. Dry heat

(think toast)

which causes COLOUR changes – it turns from golden to brown or black (burnt)

and FLAVOUR changes – it becomes slightly sweet like caramel or peanutty

Nerd alert:

Dry heat:

starch molecules break down into dextrins (molecules smaller than starch molecules) known as dextrinization causing changes in colour and flavour


2. Moist heat

(think cheese sauce)

which causes THICKENING – starch molecules don’t normally dissolve in water, but if it is heated, it swells and thickens

and PASTING – if heated for too long or at temperatures higher than 95°C the starch structures start to break down again and lose their thickness and translucency (clearness) known as pasting

Nerd alert:

Moist heat:

starch molecules absorb the water when heated and swell, making the mixture thick (known as gelitinization), it also becomes more translucent (see-through/ clear)


Gelatinization of Starch:

when these granules are heated (5 – 85°C) in water they swell, this is called gelatinization, which thickens your puddings and sauces when heated



at 95-100°C starch granules reach their maximum volume and begin to implode (explode from the inside out)! Decreasing thickness and translucency (clearness)

So….that was easy, but what else effects starch cooking? Just a few more points to keep in mind:

STIRRING….this is important because it gives us a smooth even sauce, but always stir slowly and continuously so that the granules don’t implode (explode from the inside out!)

SUGAR…if less than 40% sugar is added it increases the thickness of the sauce or soup and makes it clearer, but if more than 50% sugar is added, it makes the sauce or soup thinner.

ACIDS…at a pH of 4 there will be less thickening and the starch molecules will break down into smaller molecules, making the mixture clearer

FATS….coat the starch granules, preventing them from swelling, giving the mixture a lower gelatinisation temperature

EGGS…these are normally added to puddings for flavour – break down the starch making the mixture thinner (more runny)

Nerd alert:


this is when starch granules are heated (5 – 85°C) in water making them swell, which thickens your puddings and sauces

More questions?….me too!


1. HOW do I prevent lumps forming in my sauce?

STIR during heating – this prevents lumps because the starch sits at the bottom of the pot cooking and thickening

add SUGAR – in puddings sugar separates the starch granules

make a ROUX – this is when equal parts of fat (melted butter) and starch (flour) are cooked together

finally…make a SLURRY – this is when the starch is mixed with cold water before added it to a hot liquid, ideally you would add a small amount of the hot liquid to the slurry before mixing it all together


2. WHY does a skin form at the top of my white sauce when I leave it to cool?

When starch cools, water evaporates and dries out forming a skin…to prevent this just cover the hot surface with cling film by laying the cling film directly on top of the sauce, leaving no air bubbles before cooling


now there’s NO WAY you can’t make the best cheese sauce – good luck and have fun!

Megan Potgieter

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