Cheese-mak­ing bac­te­ria

Popular Science - - CONTENTS -

EV­ERY BITE OF CHEESE OWES ITS FEEL, FUNK, AND FLA­VOR to mi­crobes. The tangs and tex­tures that de­fine each type hinge largely on how those mini mobs break milk down into the smaller bits—amino, lac­tic, and fatty acids—that we taste and sniff. Cheese­mak­ers add care­fully se­lected mi­crobes to the start­ing mix (usu­ally milk, salt, and a di­ges­tive en­zyme called ren­net) or just wait for nat­u­rally present bac­te­ria to do their thing; mon­gers also tweak mois­ture, salt con­tent, and pH to ma­nip­u­late the speed and ex­tent of bac­te­rial growth. Each choice in­flu­ences how the fi­nal wheel turns out. Want a stinky, red­dish rind? Wash the out­side with oxy­gen-lov­ing Bre­vibac­terium linens to break pro­teins into amines (a de­riv­a­tive of am­mo­nia, aka eau du cat pee) and sul­furs, cre­at­ing a BO bou­quet. Hop­ing for holes? Pro­pi­oni­bac­te­ria turn lac­tic acid into CO2 bub­bles. The net­work here shows how com­bi­na­tions of these and other teensy crit­ters cre­ate some of the world’s most beloved cheeses.

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