On food and cooking the science and lore of the kitchen ( PDFDrive ) 561
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usedtocrushthetissue.Mashingbyhand
leaveslargecellaggregatesintact;thescreens
infoodmillsandstrainersproducesmaller
pieces;machine-poweredfoodprocessor
bladeschopveryfinely,andblenderblades,
workinginamoreconfinedspace,chopand
shearmorefinelystill.Persistentcelluloserichfiberscanberemovedonlybypassingthe
pureethroughastrainer.
Juices Juices are refined versions of the
puree: they are mainly the fluid contents of
fruit and vegetable cells, made by crushing
the raw food and separating off most of the
solid cell-wall materials. Some of these
materialsinevitablyendupinthejuice—for
example, the pulp in orange juice — and can
causebothdesirableandundesirablehaziness
andbody.Becausejuicingmixestogetherthe
contents of living cells, including active
enzymes and various reactive and oxygensensitivesubstances,freshjuicesareunstable
andchangerapidly.Appleandpearjuicesturn
brown, for example, thanks to the action of
browningenzymesandoxygen(p.269).Ifnot
usedimmediately,they’rebestkeptchilledor
frozen, perhaps after a heat treatment just
shortoftheboiltoinactivateenzymesandkill
microbes.Modernjuicingmachinescanapply
very strong forces, and make it possible to
extract juice from any fruit or vegetable, not
justthetraditionalones.
Foams and Emulsions The cell-wall
carbohydratesinpureesandjuicescanbeused
to stabilize two otherwise fleeting physical
structures, a foam of air bubbles and an
emulsionofoildroplets(pp.638,625),which
are especially easy to prepare with modern
electrical blenders and mixers. If a puree or
juiceiswhippedtofillitwithairbubbles,the
cell-wallcarbohydratesslowtheflowofwater
out of the bubble walls, so the bubbles take
longer to collapse. This allows the cook to
