(strong electrostatic forces), and between hydrophobic groups (slightly weaker hydrophobic
Some forces are also involved in stabilising intramolecular loops.
The hydrophilic groups on the outside of these proteins, because they are charged, help individual
protein bundles to stay separate from each other. Raw protein sources are thus often transparent
because the gaps between individual protein bundles allows light to pass through. This gives raw egg
whites and meat and fish flesh their transparency.
-------- inner protein bonds
Hydrophilic group Hydrophobic group
In their highly folded form, proteins trap a considerable amount of water molecules within their highly
folded structures. As these proteins start to denature, some water is actually freed from between the
proteins and this causes an initial increase in “free water”, which in food tends to be perceived as
The weak bonds that hold the protein 3-dimensional structure together can be fairly easily broken – by
the addition of heat, acid, salt or mechanical force (e.g. mixing). As these bonds holding the proteins
structure together break, the protein unfolds into its long chain, exposing all its previously protected
amino acids. This process is called denaturation. Our stomachs more easily digest denatured proteins,
so proteins are often expressly denatured (either by cooking with heat, curing with salt, or pickling with
acid) before they are consumed. Heat is quicker to denature proteins than acid, salt or mechanical
force, which is why cooking meat is a much quicker process than curing or marinating meat.
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Uses of denaturation:
Denatured proteins have many useful functions in cooking. Not only are denatured proteins much
more digestible than raw proteins (the groups are more accessible to digestion by enzymes), they are
also useful in food preparations. Their use in such food preparations tends to be based on the
principle that in denatured proteins, unlike in raw proteins, both the hydrophobic and the hydrophilic
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