On food and cooking the science and lore of the kitchen ( PDFDrive ) 1156

gel into a useless soup. And agar gels
remain solid at the ideal temperatures for
bacterialgrowth,oftenaround100ºF/38ºC,
a temperature at which gelatin begins to
melt.
How did microbiologists come to use
agar?Inthelate19thcentury,LinaHesse,
the American wife of a German scientist,
recalled the advice of family friends who
had lived in Asia, and made agar jellies
and puddings that stayed solid in the
summer heat of Dresden. Her husband
relayed his wife’s suggestion to his boss,
the pioneering microbiologist Robert
Koch, who then used agar to isolate the
bacteriumthatcausestuberculosis.
TheNatureofStarch

Starchmoleculesarelongchainsofthousands
ofglucosesugarmoleculeslinkeduptogether.
Therearetwokindsofstarchmolecules:long


straightchainscalledamylose,andshort,
branched,bushychainscalledamylopectin.
Plantsdepositstarchmoleculesin
microscopicsolidgranules.Thesize,shape,
amyloseandamylopectincontents,and
cookingqualitiesofthestarchgranulesvary
fromspeciestospecies.
Linear Amylose and Bushy Amylopectin

The shapes of amylose and amylopectin
moleculeshaveadirecteffectontheirability
to thicken a sauce. The straight amylose
chains coil up into long helical structures
whendissolvedinwater,buttheyretaintheir
basicallylinearshape.Theirelongationmakes
it very likely that one chain will knock into
anotherorintoagranule:eachsweepsthrough
a relatively large volume of liquid. By
contrast, the branched shape of amylopectin
makes for a compact target and therefore a
molecule less likely to collide with others;
and even if it does collide, it’s less likely to