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Chapter 5 Cheese, Yogurt & Sour

Curdled and A durable form of processed ! - 5 -10 times milk concentrate milk – using • Likely first prepared acids and from soured milk and Porons of Annotated PPT as milk was stored in enzymes to stomach pouches make milk • Lactose (sugar) products allows this to happen as it serves as a source of food for microbes

Types of Cheese The Process of Cheese Making

• Curdling – separation of milkfat and protein from Acid Coagulated Fresh Cheese (lactic acid from bacteria) o Acid, heat, enzyme • no enzyme is used to finish the () or combinations all cause curdling • Cottage and • Curd setting – finishing Heat-Acid Precipitated Cheese (acid and heat o pH, salt content, bacteria precipitate/coagulate the protein and cause milk fat to culture, cooking times curdle) • Ripening - aging – o (react with oxygen) and • Add low amounts of acid to 75-100 C temp milk allow molds and or other • High moisture and protein bacteria to alter fresh • Ricotta (Italy) Channa and (India) curd to hard aged cheese

Casein – key for cheese Milk

Proteins and Sub micelles are Fat Globules held together by phosphorylated casein – calcium ion interactions - k-casein caps the growing micelle, binds water and repels interactions with other casein micelles

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Metabolism – Curd Formation lactic acid production

Acidifying milk, increasing temperature and action of rennet lead to curd formation. i.e. disruption of casein micelles… Fermentation is a - acid formation (adding acid – acetic or citric) or production of way for bacteria to lactic acid from metabolizing bacteria limit protein interaction replace limited amounts of NAD+ Loss of charged glutamates and • Lactate is side asparc acids product diminishes ability of casein to bind to • Typically used calcium and for aged neutral charged k- casein stop repulsion and form weak aggregated precipitates (curd)

Rennet attacks kappa-casein Next step – Removing Moisture

The negative tail of Fresh cheeses k-casein is cleaved retain moisture and by specific sugars recognition by rennet Aged pressed - Forms stronger cheeses are than acid only pressed to dry and precipitation have less lactose

Drying the Brining the Cheese

Gravity – through mold and drained – used for soft cheeses Osmosis – removal of water (camembert…) from the cheese - net movement of dissolved Cutting curd – smaller the dryer, particles from a region of high creates a more firm cheese due to concentration to a lower increased surface area/mass ratio concentration

Heating and stirring curds Water and salt move in continues denaturation of proteins opposite directions in a high to release water from curd salt brine - exposed hydrophobic protein amino Temps impact final dryness of cheese acid side groups will not interact with - Cheddar 100oF - water is removed from water reducing “holding” capacity - Gruyere 120oF cheese by salt brine and salt - Activates bacteria and enzymes for - Parmesan 130oF is driven into cheese more acid and creation of new flavor Higher salt inhibits pathogenic bacteria compounds growth and alters enzyme funcon to create flavor compounds

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Chemistry of ripening Cheese Flavoring Enzymes breakdown fat, protein and carbohydrates to new flavor compounds Protein, fat and metabolites (know this word!) • Proteins – mostly degredation products of casein • Amines – the amino portion of amino acids • Fish smell – trimethylamine • Putrescine – polymer of amines The more finished • Sulfur – from cysteine- amino acid side group the more flavors – • Ammonia – nitrogen from amino acids why? • Amino acids themselves have tastes • Fats – different sized and modified fatty acids add different flavors and textures – molds typically alter fats • Short chain fatty acids – buttery or peppery taste • Smaller break down products – ketones – highly fragrant

Finishing Microbes

Smear Bacteria – smelly cheeses like munster and Mold actively modifies fats limburger cheese producing short modified fatty acids • Live in high salt (most bacteria won’t do well)

• Grow on surface of cheese – need oxygen and can’t grow in acidic conditions from starter culture • The cultures are swiped or smeared P. Camemberti - Lactic acid is further degraded by surface on surface of pressed cheeses smear – higher pH results in • Responsible for protein breakdown precipitation of calcium into… stinky molecules phosphates of casein forming Sulfur containing compounds – methanethiol a hard shell and produces lactones, ketones and sulfur And methylthioacetate from fats and proteins

Cooking with cheese

Melting cheese – process of changing state of & Cheez Whiz – made from mixtures of young and old scraps of cheese matter from solid to liquid • Phosphate salts – highly charged molecules bind well to – Melting requires adding energy to defeat chemical water and casein keeping proteins in a loose protein form bonds holding molecules in place (solid) – soft cheese • The more and stronger the bonds the higher the heat/ • The reduction in protein interaction and low stringy energy it takes to break the bonds cheese makes this great for melting – Cheese is a complex of many types of solids with different interactions MILK, WATER, MILKFAT, WHEY, WHEY PROTEIN CONCENTRATE, SODIUM PHOSPHATE, MILK PROTEIN CONCENTRATE, ALGINATE (algae cell wall – Water, fat and protein content and type all alter polysaccharide- emulsifier), SODIUM CITRATE, APOCAROTENAL (COLOR), ability of cheese to melt or cook well ANNATTO (COLOR), ENZYMES, CHEESE CULTURE.

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