Page 7 - Daviscope - Spring 2015
P. 7
Working Smart
It’s All About the Cheese
Learning the Science Behind the Cheese
In Kartik Shah’s cheese training class, the pace is fast, the Powerpoint graphics are interesting, and the audience learns the “how and why” of cheese-making from the start to the end of the process.
The first part is a history lesson about how cheese was in- vented, how the first cheese factory was built by Jesse Wil- liams in Oneida County, New York in 1851, for example, and how mozzarella originated. From there, Shah covers the composition of milk and the steps of the cheese-making process including what happens to the milk as it comes into the plant, with details of each step to the point to where curds and whey separate during cooking.
Rennet coagulation, ultrafiltration, and the importance of standardizing milk for cheese are covered in detail in the class. The science behind each step is well documented in the eye-catching graphics and by the careful and complete explanations given by Shah throughout the class.
As an example, here’s how Shah breaks down milk protein and explains milk coagulation in one part of the course:
“Milk consists of water, protein, lactose, lipid, minerals and some minor components such as enzymes, free amino acids, and peptides. Milk proteins are comprised of caseins and whey proteins. The casein in milk is the main struc- tural protein of rennet-induced gels. The casein micelle is heterogeneous and is comprised of four caseins such as αs1, αs2, β and κ, which represent about 38, 10, 35 and 15 g 100 g−1 of the total casein, respectively.
“Casein in milk exists in the form of colloid particles, which are called casein micelles. Although various models of the casein micelle have been proposed, one of the widely accepted casein micelle models is the sub-micelle model (Schimdt, 1982). According to this model, the sub-micelles are connected together by colloidal calcium phosphate (CCP). The κ casein is mainly located at the outside sur- face of the casein micelle. This κ casein orientation on the casein micelle is responsible for the steric repulsion of the casein micelle and therefore provides stability to the ca- sein micelle in the system, as shown in diagram 1.
A Closer Look of Casein Micelle (Schmidt, 1982):
“When rennet (enzyme), is added to the cheese milk, the “hairy layer” or κ casein on the casein micelle surface is hydrolyzed, and therefore cleaves it at a specific location. This results in reduction of repulsive forces between the para-casein micelles and increases tendency to stick to- gether. The ‘gel’ formed as a result is also called as para casein complex, as shown in diagram 2.
Rennet Gel
“Coagulation of milk is an enzymatic process. Some of the factors that affect this phenomenon are pH of the cheese milk, Casein-to-Fat (C: F) ratio of the milk, buffering ca- pacity of the milk, concentration of enzymes, temperature of the cheese milk, etc.
“Standardization of milk for cheese manufacture is a very important aspect of the cheese manufacturing process. Methods such as separation of milk or adding milk solids can be adopted to standardize the milk for cheese manu- facture. If the milk composition is not consistent, the cheese manufacture may not have similar analyticals and therefore the cheese ripening process will vary. This will in turn affect the functional property, as well the flavor pro- file, of the cheese within the same day of production.” n
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