On food and cooking the science and lore of the kitchen ( PDFDrive ) 370
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wayofmaintainingtheirbodyfluidsatthe
rightconcentrationofdissolvedsubstances.
Waterintheopenoceanisabout3%saltby
weight,whiletheoptimumlevelofdissolved
mineralsinsideanimalcells,sodiumchloride
included,islessthan1%.Mostocean
creaturesbalancethesaltinessofseawaterby
fillingtheircellswithaminoacidsandtheir
relativestheamines.Theaminoacidglycine
issweet;glutamicacidintheformof
monosodiumglutamateissavoryand
mouthfilling.Shellfishareespeciallyrichin
theseandothertastyaminoacids.Finfish
containsome,butalsorelyonalargely
tastelessaminecalledTMAO(trimethylamine
oxide).Andsharks,skates,andraysusea
differentsubstance:slightlysaltyandbitter
urea,whichiswhatanimalsgenerallyturn
proteinwasteintoinordertoexcreteit.The
problemwithTMAOandureaisthatoncethe
fisharekilled,bacteriaandfishenzymes
converttheformerintostinkyTMA
(trimethylamine)andthelatterintokitchencleanserammonia.They’rethusresponsible
forthepowerfullybadsmellofoldfish.
Fish muscle tissues, shown in cross-section.
Below left:Most fish swim intermittently, so
their muscle mass consists mainly of fast
whitefibers,withisolatedregionsofslowred
fibers. Center:Tuna swim more continuously
and contain larger masses of dark fibers,
while even their white fibers contain some
myoglobin. Right:Soles, halibuts, and other
bottom-huggingflatfishswimontheirside.
Freshwaterfishareadifferentstory.Their
environmentisactuallylesssaltythantheir
cells,sotheyhavenoneedtoaccumulate
aminoacids,amines,orurea.Theirfleshis
thereforerelativelymild,bothwhenit’sfresh
