| Curdling | | | | The curd is also mixed (or milled) for a |
| The only strictly required step in | | | | long period of time, taking the sharp |
| making any sort of cheese is separating | | | | edges off the cut curd pieces and |
| the milk into solid curds and liquid | | | | influencing the final product's texture. |
| whey. Usually this is done by acidifying | | | | Washing: (Edam, Gouda, Colby) The curd |
| the milk and adding rennet. The | | | | is washed in warm water, lowering its |
| acidification is accomplished directly | | | | acidity and making for a milder-tasting |
| by the addition of an acid like vinegar | | | | cheese. |
| in a few cases (paneer, queso fresco), | | | | Most cheeses achieve their final shape |
| but usually starter bacteria are | | | | when the curds are pressed into a mold |
| employed instead. These starter bacteria | | | | or form. The harder the cheese, the more |
| convert milk sugars into lactic acid. | | | | pressure is applied. The pressure drives |
| The same bacteria (and the enzymes they | | | | out moisture — the molds are designed |
| produce) also play a large role in the | | | | to allow water to escape — and unifies |
| eventual flavor of aged cheeses. Most | | | | the curds into a single solid body. |
| cheeses are made with starter bacteria | | | | Aging |
| from the Lactococci, Lactobacilli, or | | | | A newborn cheese is usually salty yet |
| Streptococci families. Swiss starter | | | | bland in flavor and, for harder |
| cultures also include Propionibacter | | | | varieties, rubbery in texture. These |
| shermani, which produces carbon dioxide | | | | qualities are sometimes enjoyed—cheese |
| gas bubbles during aging, giving Swiss | | | | curds are eaten on their own—but |
| cheese or Emmental its holes. | | | | usually cheeses are left to rest under |
| Some fresh cheeses are curdled only by | | | | carefully controlled conditions. This |
| acidity, but most cheeses also use | | | | aging period (also called ripening, or, |
| rennet. Rennet sets the cheese into a | | | | from the French, affinage) can last from |
| strong and rubbery gel compared to the | | | | a few days to several years. As a cheese |
| fragile curds produced by acidic | | | | ages, microbes and enzymes transform its |
| coagulation alone. It also allows | | | | texture and intensify its flavor. This |
| curdling at a lower acidity—important | | | | transformation is largely a result of |
| because flavor-making bacteria are | | | | the breakdown of casein proteins and |
| inhibited in high-acidity environments. | | | | milkfat into a complex mix of amino |
| In general, softer, smaller, fresher | | | | acids, amines, and fatty acids. |
| cheeses are curdled with a greater | | | | Some cheeses have additional bacteria or |
| proportion of acid to rennet than | | | | molds intentionally introduced to them |
| harder, larger, longer-aged varieties. | | | | before or during aging. In traditional |
| Curd processing | | | | cheesemaking, these microbes might be |
| At this point, the cheese has set into a | | | | already present in the air of the aging |
| very moist gel. Some soft cheeses are | | | | room; they are simply allowed to settle |
| now essentially complete: they are | | | | and grow on the stored cheeses. More |
| drained, salted, and packaged. For most | | | | often today, prepared cultures are used, |
| of the rest, the curd is cut into small | | | | giving more consistent results and |
| cubes. This allows water to drain from | | | | putting fewer constraints on the |
| the individual pieces of curd. | | | | environment where the cheese ages. |
| Some hard cheeses are then heated to | | | | For the blue cheeses (Roquefort, |
| temperatures in the range of | | | | Stilton, Gorgonzola), Penicillium mold |
| 35°C–55°C (100°F–130°F). This | | | | is introduced to the curd before |
| forces more whey from the cut curd. It | | | | molding. During aging, the blue molds |
| also changes the taste of the finished | | | | (P. roqueforti or P. glaucum ) grow in |
| cheese, affecting both the bacterial | | | | the small fissures in the cheese, |
| culture and the milk chemistry. Cheeses | | | | imparting a sharp flavor and aroma. The |
| that are heated to the higher | | | | same molds are also grown on the surface |
| temperatures are usually made with | | | | of some aged goat cheeses. The soft |
| thermophilic starter bacteria which | | | | cheeses Brie and Camembert, among |
| survive this step—either lactobacilli | | | | others, get a surface growth of other |
| or streptococci. | | | | Penicillium species, white-colored P. |
| Salt has a number of roles in cheese | | | | candidum or P. camemberti. The surface |
| besides adding a salty flavor. It | | | | mold contributes to the interior texture |
| preserves cheese from spoiling, draws | | | | and flavor of these small cheeses. |
| moisture from the curd, and firms up a | | | | Some cheeses are periodically washed in |
| cheese’s texture in an interaction | | | | a saltwater brine during their ripening. |
| with its proteins. Some cheeses are | | | | Not only does the brine carry flavors |
| salted from the outside with dry salt or | | | | into the cheese (it might be seasoned |
| brine washes. Most cheeses have the salt | | | | with spices or wine), but the salty |
| mixed directly into the curds. | | | | environment may nurture the growth of |
| A number of other techniques can be | | | | the Brevibacterium linens bacteria, |
| employed to influence the cheese's final | | | | which can impart a very pronounced odor |
| texture and flavor. Some examples: | | | | (Limburger) and interesting flavor. The |
| Stretching: (Mozzarella, Provolone) The | | | | same bacteria can also have some impact |
| curd is stretched and kneaded in hot | | | | on cheeses that are simply ripened in |
| water, developing a stringy, fibrous | | | | humid conditions, like Camembert. Large |
| body. | | | | populations of these "smear bacteria" |
| Cheddaring: (Cheddar, other English | | | | show up as a sticky orange-red layer on |
| cheeses) The cut curd is repeatedly | | | | some brine-washed cheeses. |
| piled up, pushing more moisture away. | | | | |