forming of bonds between the original molecules.
How can one predict that a chemical reaction has occured?
1. Change in state eg liquid ---)) Solid
2. Change in colour
3. Change in Compostion
4.Change of Odour
5. Change in Temperature or energy i.e. exothermic or endothermic
6. Changes in Nutritional properties
7. Changes in consistency
Generally, Plain flour contains lesser glutenin and gliadin while wholemeal flour contains
more.
As for cooking a Pancake (before heating):
Before heat is applied, the batter is in a liquid form and continous phase
While tiny gas bubbles are dispersed into a discontinous phase.
The colour of batter: dull creamy yellow
While cooking:
Maillard Reaction
The proteins and sugar found in batter undergoes Maillard Reaction. This is a
non-enzymatic reaction. There are three stages in this reaction. Firstly, the sugar
and protein(amino acid) undergoes condensation to form glycosylamines. Followed by that,rearrangement occurs. Glycosylamines rearranges to N-substituted-1-amino-l-
deoxy-2-ketose , known as Amadori compounds. Lastly, Amadori compounds polymerises
to melanoidins(brown-coloured polymers). This pigments are responsible for the browning colour in the pancake. This compounds contains nitrogen.
In Plain flour pancake,
as shown in the picture
Plain flour Wholemeal flour
Wholemeal flour has more browned sides than plain flour pancake. This mainly because
of the protein content in wholemeal flour. There are more melanoidins found in it.
Gelatinization
Gelatinization is the process in which the interemolecular bonds between amylose and amylopectin in starch granules breaks down when there is water and heat present.New bonds are formed when the gluten starts developing.
The starch molecules absorbs water and starts gelatinizing.
In Wholemeal flour there are more fibre since 100% of wholegrain is used while plain flour has only 70-75% wholegrain used.
Therefore wholemeal flour absorbs more water which results in weak gel formation and structure.
As for plain flour its vice versa. Plain flour forms a strong structure and firmness.
This explains why the structure of both pancakes varies as shown in above images.
Hydrolysis
-Enzyme hydrolysis
Flour contains amylase enzyme.
Wholemeal flour has more amylase content then plain flour.
Amylase breaks down the complex starch compounds to small dextrins,maltose
and glucose.
This end product provides sweetness to the pancakes. Esp to wholemeal flour pancake.
In addition, this products darkens the browning. This explains why wholemeal flour
pancake is much darker and dull when compared to plain flour.
Caramelization
This is also a non-enzymatic reaction. When sugar is heated or in other words
oxidised, they are broken down into variety of compounds. Volatile chemical are
released which produces caramel flavour. Caramel flavour is a brown and nutty colour. Caramelisation changes the taste of sugar to a new distinctive taste. When the sugar is
heated, the sucrose in sugar undergoes inversion to form invert sugar(glucose and
fructose). The invert sugar later dehydrates to form organic acids, aldehydes and ketones.
Links:
http://en.wikipedia.org/wiki/Chemical_change
http://en.wikipedia.org/wiki/Cooking
