On food and cooking the science and lore of the kitchen ( PDFDrive ) 1347

thenormalfunctionofourbraincells.

Yeast.Cellsofbrewer’syeast, Saccharomyces
cerevisiae,as seen through an electron
microscope. Each is about 0.005 mm in
diameter.Thecellattheupperrightcenteris
in the process of reproducing, and bears the
scarsofpreviousbuddings.
YeastsandAlcoholicFermentation

Yeastsareagroupofabout160speciesof
single-celledmicroscopicmolds.Notallare
useful:somecausethespoilageoffruitsand
vegetables,somecausehumandisease(for
example,theyeastinfectionofCandida


albicans).Mostoftheyeastsusedinmaking
breadandalcoholicdrinksaremembersofthe
genusSaccharomyces,whosenamemeans
“sugarfungus.”Wecultivatethemforthe
samereasonthatweuseparticularbacteriato
sourmilk:theymakefoodsresistantto
infectionbyothermicrobes,andproduce
substancesthataremainlypleasanttous.
Essentialtotheyeasts’productionofalcohol
istheirabilitytosurviveonverylittle
oxygen,whichmostlivingcellsusetoburn
fuelmoleculesforenergy,leavingbehind
onlycarbondioxideandwater.Intheabsence
ofoxygen,thefuelcanbebrokendownonly

partly.Theoverallequationfortheproduction
ofenergyfromglucosewithoutoxygengoes
likethis:
C6H12O6 2CH3CH2OH+2CO2+energy
Glucose alcohol+carbondioxide+energy
Yeastsintroduceavarietyofother
compoundsintothegrapejuiceorgrainmash
thatcontributescharacteristicflavors.For