On food and cooking the science and lore of the kitchen ( PDFDrive ) 1518

Amino acids and proteins, denaturation and
coagulation. Top:Three of the 20-odd amino
acidsimportantinfood.Eachaminoacidhas
a common end including an amino (NH2)
group, by which amino acids bond to each
other into long chains called proteins, and a
variable end or “side group” that can form
different kinds of bonds with other amino
acids. Center:A chain of amino acids shown
schematically, with some of the side groups
projecting from the chain. The amino acid
chaincanfoldbackonitself,andsomeofthe
side groups form bonds with each other to
hold the chain in a folded shape. Bottom:


Heating and other cooking processes can
breakthefold-stabilizingbondsandcausethe
long chains to unfold, or denature (left,
center). Eventually the exposed side groups
form new bonds between different protein
chains,andtheproteins coagulate,orforma
permanentlybondedsolidmass(right).
ProteinsinWater

Inlivingsystemsandinmostfoods,protein
moleculesaresurroundedbywater.Because
allproteinsarecapabletosomeextentof
hydrogenbonding,theyabsorbandholdat
leastsomewater,althoughtheamountsvary
greatlyaccordingtothekindsofsidegroups

presentandtheoverallstructureofthe
molecule.Watermoleculescanbeheld
“inside”theprotein,alongthebackbone,and
“outside,”onpolarsidegroups.
Whetherornotaproteinissolublein
waterdependsonthestrengthofthebonds