Cheese Ripening

Key Points in Cheese Making Converting a liquid into a solid

pH 4.6 comprised mostly of casein and water

Addition of chymosin (or rennet) Casein micelles, contain casein, with subunits s1, s2, , κ Chymosin hydrolyzes the peptide bond between 105 (Met) and 106

(Phe) in κ casein, releases glycomacropeptide fraction of κ casein, remaining part sensitive to calcium-precipitation

Coagulated casein network trap also milk fat Recombinant chymosin now also produced by E. coli

Moderate acid addition (pH 6.0) plus high heat (>85°C) Contain also whey proteins Ricotta cheese, and Hispanic-style cheeses and a Gjetost (Norway)

Key Points in Cheese Making Cultures

Mesophilic versus thermophilic Gas production Homolactic versus heterolactic fermentation Starters versus adjuncts Bacteriophage attack Stability Inhibitory compounds

Key Points in Cheese Making Heat treatment

With and without pasteurization Microbial quality issues

In US, cheese aged for more than 60 days at temp no less than 1.7C is OK

Chemical issues Whey proteins Enzyme inactivation (flavor and texture)

Temperature in cheese making Hard versus soft

Key Points in Cheese Making Ripening

Enzymes from milk, or added, such as rennet, lipase extracts

Microbial enzymes Endogenous Starters Ripening conditions affect activities

Ripening

Surface ripened by bacteria Most aromatic and flavorful Limburger, Muenster, Brick, etc. Sulfury volatile compounds by Brevibacterium linens Applied to cheese after its manufacture, produce orange-red

pigment Mold-ripened cheese

Blue-mold cheeses have Penicillium roqueforti grown at the surface and within the curd Spores of which added to curds or milk along with LAB, prior to

setting Grow and produce proteases, peptidases and lipases

White-mold ripened cheese Camembert and Brie Spores of P. camembertis or P. caseicolum added to milk or later

on the surface Proteolysis and lipolysis

Key Points in Cheese Making Accelerated cheese ripening

Proteolysis Cell lysis Accelerate cell lysis Starters, non-starters, endogenous

Key Points in Cheese Making Pickled cheese

High-salt, high-acid Feta

Processed cheese Made by adding emulfifying salts to natural cheese, along

with water and other dairy and non-dairy ingredients Mixed and heated to ~70°C Sodium or potassium polyphosphate and citrate

emulsifying salts raise pH, displace calcium ions forming more soluble sodium casein, which has both lipophilic and hydrophilic regions

Blend aged and young cheese