Treatment of Milk for Cheese making

Like most dairy products, cheese milk must first be clarified, separated and standardized. The milk may then be subjected to a sub-pasteurization treatment of 63…65 °C for 15 to 16 sec. This treatment results in a reduction of high initial bacteria counts before storage. It must be followed by proper psteurization. While pasteurization (72 °C for 16 sec) is often used, an alternative heat treatment of 60 °C for 16 sec may also be used. This less severe heat treatment is thought to result in a better final flavor cheese by preserving some of the natural flora. If used, the cheese must be stored for 60 days prior to sale, which is similar to the regulations for raw milk cheese.

Homogenization is not usually done for most cheese milk. It disrupts the fat glob and increases the fat surface area where casein particles adsorb. This results in a soft, weak curd at reuniting and increased hydrolytic rancidity.

Additives

The following may all be added to the cheese milk: Calcium chloride, nitrates, color, hydrogen peroxide, lipases

Because milk color varies from season to season, color may add to standardize the color of the cheese throughout the year. Annatto, Beta-carotene, and paprika are used. The addition of hydrogen peroxide is sometimes used as an alternative treatment for full pasteurization. Lipases, normally present in raw milk, are inactivated during pasteurization. The additions of kid goat lipases are common to ensure proper flavor development through fat hydrolysis.

Task 3 Read the article below and choose the best word to fill each gap.

Inoculation and Milk Ripening

The basis of cheese (building / boiling / making) relies on the fermentation of lactose by lactic acid bacteria (LAB). LAB produce lactic acid which lowers the pH and in turn (assists / gives / produces) coagulation, promotes sunrises, helps prevent spoilage and pathogenic bacteri from growing, contributes to cheese texture, flavor and keeping quality. LAB also produces growth (facts / factors / things) which encourages the growth of non-starter organisms, and provides lipases and proteases necessary for flavor (development / emergence / advance) during curing.

After inoculations with the (starter / initial / first) culture, the milk is held for 45 to 60 min at 25 to 30 °C to ensure the bacteria are active, growing and have developed acidity. This stage is called ripening the milk and (has / is / was) done prior to reuniting.

Task 4 Read the article below and choose the best phrase from the given below:

can be recovered; the formation of a gel; With the addition of acid; with the starter

culture; denaturation of the whey proteins; accomplished with; in the newly formed

matrix.

Milk Coagulation

Coagulation is essentially 1. _____ by destabilizing the casein micelles causing them to aggregate and form a network which partially immobilizes the water and traps the fat globules 2. _____ This may be 3. _____: enzymes, acid treatment, heat-acid treatment.

Enzymes

Chamois, or rennet, is most often used for enzyme coagulation.

Acid Treatment

Lowering the pH of the milk results in casein micelle destabilization or aggregation. Acid curd is more fragile than rennet curd due to the loss of calcium. Acid coagulation can be achieved naturally 4. _____, or artificially with the addition of gluconodeltalactone. Acid coagulated fresh cheeses may include Cottage cheese, Quark, and Cream cheese.

Heat-Acid Treatment

Heat causes 5. _____ The denatured proteins then interact with the caseins. 6. _____, the caseins precipitate with the whey proteins. In rennet coagulation, only 76…78 % of the protein is recovered, while in heat-acid coagulation, 90 % of protein

7. _____ Examples of cheeses made by this method include Paneer, Ricotta and Queso Blanco.

Task 5 Read the article below and answer the following questions:

1. How is the milk gel cut?

2. Why is it done?

3. What happens to the curd pieces?

4. What is meant by the cooking stage?

5. What contributes to the shrinkage of the curd particles?

6. What is the moisture content dependent on?

7. When are the curds separated from the whey?

8. How can the whey be removed?

9. Why is curd mixture placed in moulds?

10. What do some cheese varieties include?

Curd Treatment

After the milk gel has been allowed to reach the desired firmness, it is carefully cut into small pieces with knife blades or wires.

This shortens the distance and increases the available area for whey to be released. The curd pieces immediately begin to shrink and expel the greenish liquid called whey. This process is further driven by a cooking stage. The increase in temperature causes the protein matrix to shrink due to increased hydrophobic interactions, and also increases the rate of fermentation of lactose to lactic acid.

The increased acidity also contributes to shrinkage of the curd particles. The final moisture content is dependant on the time and temperature of the cook stage. This is important to monitor carefully because the final moisture content of the curd determines the residual amount of fermentable lactose and thus the final pH of the cheese after curing.

When the curds have reached the desired moisture and acidity they are separated from the whey. The whey may be removed from the top or drained by gravity. The curd-whey mixture may also be placed in moulds for draining. Some cheese varieties, such as Colby, Gouda, and Brine Brick include a curd washing which increases the moisture content, reduces the lactose content and final acidity, decreases firmness, and increases openness of texture.

Curd handling from this point on is very specific for each cheese variety. Salting may be achieved through brine as with Gouda, surface salt as with Feta, or vat salt as with Cheddar To achieve the characteristics of Cheddar, a shuddering stage (curd manipulation), milling (cut into shreds), and pressing at high pressure are crucial.

Task 6 Read the article below, there is an extra word in every sentence, find the mistakes.

Cheese Ripening

1. Except for fresh cheese, the curd is ripened, or matured, at about various temperatures and times until the characteristic flavor, body and texture profile is achieved.

2. During ripening, degradation of lactose, proteins and fat are carried on out by ripening agents.

3. The ripening of agents in cheese is: bacteria and enzymes of the milk lactic culture, rennet, lipases, added moulds or yeasts, environmental contaminants.

4. Thus the microbiological content of the curd, the biochemical composition of the curd, as well as temperature and humidity affect on the final product.

5. This final stage varies from weeks to years according with to the cheese variety.

Task 7 Read, translate and discuss the process of yogurt production. Make up questions disclosing its method.

Yogurt Manufacturing Method

The milk is clarified and separated into cream and skim milk, then standardized to achieve the desired fat content. The various ingredients are then blended together in a mix tank equipped with a powder funnel and an agitation system. The mixture is then pasteurized using a continuous plate heat exchanger for 30 min at 85 °C or 10 min at 95 °C. These heat treatments, which are much more severe than fluid milk pasteurization, are necessary to achieve the following: produce a relatively sterile and conducive environment for the starter culture denature and coagulate whey proteins to enhance the viscosity and texture.

The mix is then homogenized using high pressures of 2000 – 2500 psi. Besides thoroughly mixing the stabilizers and other ingredients, homogenization also prevents creaming and wheying off during incubation and storage. Stability, consistency and body are enhanced by homogenization. Once the homogenized mix has cooled to an optimum growth temperature, the yogurt starter culture is added.

A ratio of 1:1, ST to LB, inoculation is added to the jacketed fermentation tank. A temperature of 43 °C is maintained for 4 – 6 h under quiescent (no agitation) conditions. This temperature is a compromise between the optimums for the two microorganisms (ST 39 °C; LB 45 °C). The turntable acidity is carefully monitored until the TA is 0.85 to 0.90 %. At this time the jacket is replaced with cool water and agitation begins, both of which stop the fermentation. The coagulated product is cooled to 5…22 °C, depending on the

product. Fruit and flavor may be incorporated at this time, then packaged. The product is now cooled and stored at refrigeration temperatures (5 °C) to slow down the physical, chemical and microbiological degradation.

UNIT 41

ICE CREAM PRODUCTION

Task 1 Read, translate and discuss the following article on ice cream history.

Task 2 Choose the best phrase from the given below to fill each of the gaps.

A. This story is just one;

B. Unfortunately;

C. Once upon a time;

D. Most of the following material;

E. Most books are full.