Lecture_21___cheese_making__2_ - Cheese Making Principles...

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1 Cheese Making Principles – contd. Carmen I. Moraru Cornell University Main steps and transformations during cheese making
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2 Coagulation - The essential step in cheese making. It represents the formation of a three-dimensional casein network that entraps other milk components. - In normal milk, aggregation of casein micelles is prevented by two stabilizing factors: - The 'hairy' layer of surface active protein on the surface of the micelle (k-CN), which prevents the micelles from getting close to each other. - The negative charge on the micelles, which determines the micelles to repel each other. - There are two ways destabilize casein and thus coagulate milk: - By removing the ‘hairy’ layer from the micelles = enzymatic coagulation . - By neutralizing the negative charges on the casein micelles, which can be accomplished by acidification or a combination of high temperature and acidification Stages of enzymatic coagulation - review 1. Primary stage: the coagulating enzyme cleaves k-CN. At the natural pH of milk, about 80% of k-CN must be cleaved to allow aggregation of CN micelles. ± ± Chimosin Para - κ -casein Casein glycomacropeptide
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3 Aggregation Aggregation Stages of enzymatic coagulation 2. Secondary stage: aggregation of casein micelles. After losing the water soluble tail of k-CN (CN glycomacropeptide), casein micelles begin to form chains and clusters. Casein micelles Aggregating casein micelles Stages of enzymatic coagulation 3. Tertiary stage: development of the gel network. The CN chains and clusters grow until a continuous gel network is formed. Casein strands
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4 Acid coagulation - Acid milk gels can be formed by using lactic bacteria or acidifying agents such as glucono-delta-lactone (GDL is slowly hydrolyzed to gluconic acid in the presence of water). - Acid coagulation is used in the production of cottage cheese, bakers cheese and quark. - In case of cottage cheese and quark, a small amount of chymosin may be used to make the curd more elastic and less subject to breakage (dusting). Heat-acid coagulation - Allows the recovery of caseins and whey proteins in a single step. - Used in the manufacture of ricotta cheese and other cheeses, and also in the manufacture of "co-precipitated" milk protein concentrates. -
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Lecture_21___cheese_making__2_ - Cheese Making Principles...

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