Unripened Cheese
Cottage Cheese
Periods: Three
Period 1: Planning
Period 2: Manufacture
Period 3: Product Formulation
Objectives:
(a) To familiarize the students with the principles and methods of manufacture of acid-precipitated unripened soft cheese.
(b) To acquaint the students with specific procedures for composition and quality control.
Background:
Unripened cheese, or cheese which is consumed when fresh, is manufactured in many countries. The names and the manner in which the cheese is ultimately prepared for sale and consumption may vary. But, with few exceptions, unripened cheese is manufactured from skim milk, the curd is obtained by acidification of the milk, and the finished cheese has a relatively high moisture content. The curd may be processed into a smooth homogenous mass or the curd may be recovered as discreet particles. Milk fat is frequently incorporated or blended with the curd to obtain the finished products. Common unripened cheeses include cottage cheese, bakers cheese, cream cheese and Quark. Of these Cottage cheese is manufactured in the largest quantities in the US.
Cottage cheese is a soft, unripened, white, cooked curd made from skim milk, to which cream and salt are added. It is basically an acid coagulation and may have a small amount of rennet to assist in the coagulation process. The rennet reduces the time required for coagulation. There are three general processes used for cottage cheese manufacture: (a) short set – 5 hours for coagulation; (b) medium set – 7-8 hours for coagulation and (c) long set – overnight set, 12-16 hours for coagulation. After cooking it is washed to remove residual lactose. It has an acid taste and a mild diacetyl note. It is generally sold as "creamed" cottage cheese with a final fat content of 4%.
Procedures:
A. Starter Culture - Activation of freeze-dried cultures (optional, see instructor)
1. Two days before cheese manufacturing, heat approximately one quart of skim milk to 180-190° F for 30 min. Cool to 72° F and inoculate the milk with a freeze-dried culture. Incubate at 72° F for 16-18 hours. Place in refrigerator.
2. The day before cheese manufacturing, treat approximately 2 gallons of skim milk as indicated above. Inoculate the cooled milk with approximately 1% of the activated culture and incubate at 72° F as stated. This is the cheese starter.
B. Cheese Manufacturing and Addition of Cream Dressing - The total time of manufacturing and dressing is approximately 7 hrs. Therefore, schedule the project so someone can be in attendance during the entire period. Once the skim milk has been set (Step #2) only periodic attendance is necessary until the curd is ready to be cut.
212 lbs. of pasteurized skim milk will be used. Proceed as follows:
1. Place the skim milk in the cheese vat. Adjust the temperature to 88-92° F. Check the acidity.
2. Add 5% well mixed starter. Stir the mixture and check the acidity again. The acidity should have increased by 0.025-0.03%.
3. For the next 1.5 hours stir the skim milk every half hour.
4. After 1.5 hours check the acidity which should have increased by 0.04-0.06% over the value right after the addition of starter. If not, additional starter should be added (1-2%).
5. At this point add rennet, 0.5-1.0 ml per 1000 lbs of milk. Dilute the rennet with 40 times as much water and mix well with the skim milk. Cover the vat to hold the temperature at approximately 90° F until the correct cutting acidity is reached.
6. About 3.5 hours after adding starter check the skim milk for coagulation. When the curd is sufficiently firm, obtain a sample of coagulum from well below the surface and filter to collect clear whey for an acidity test. From this first acidity estimate how long will it be before the curd is ready to be cut. The proper cutting acidity is between 0.48-0.52%. Recheck the acidity as often as desirable.
7. When the proper whey acidity has been reached, cut the curd - first length-wise with the horizontal knife, next lengthwise with the vertical knife, and finally crosswise with the vertical knife.
8. Leave curd alone for about 15 minutes.
9. Start agitation of the curd and during the next hour heat the curd to 130° F. With continuous agitation, heat the curd 5° F the first 15 min., 5° F the next 15 min., and 15° F each of the last 15 min. periods. To heat, use warm water in the vat jacket. For the first hour have water temperature 20° F above the curd temperature and 30-40° F higher during the last hour. (Temperature differentials vary somewhat with the type of vat.) Curd temperature should be kept in line with acid development and the rate of heating may be increased or decreased accordingly. Check the whey acidity regularly during cooking. The whey acidity increase during the first hour should not be more than 0.04%
10. When the temperature reaches 130° F check the firmness of the curd. Continue agitation at 130° F until the curd reaches the desired firmness.
11. When the curd is cooked, push it back from the gate end. Drain the whey until the curd shows. Add tap water until the curd is cooled to 80-85° F. After thorough stirring drain all of the whey. Add a second wash water, stir again and drain. A third washing with chilled water is often necessary to get curd properly cooled to below 50° F.
12. After the last wash water has been removed, pile the curd along the sides of the vat and allow it to drain for 2 hours.
13. The cottage cheese dressing can contain various combinations of fat, cream and salt, with a trend today to use reduced fat cream dressings. Cultures are sometimes added to the dressing to increase the diacetyl content of the final product Some simple creaming mixture combinations include:
Pounds of cream/10 pounds of curd Composition
3 18% fat with 4.4% salt
4 15% fat with 3.5% salt
5 13% fat with 3.0% salt
6 11% fat with 2.7% salt
C. Analysis and evaluation –
Do a simple sensory evaluation of the finished product for color, flavor and texture.
Determine the pH. Evaluate the microbiological quality of the cottage cheese using Petrifilm plates for SPC and coliform organisms.
Run other evaluations as appropriate.
References:
Emmons D and Tucky S. Cottage Cheese and Other Cultured Products. Chas Pfizer & Co.. Inc. NY. 1967.
Kosikowski, F. V. 1982 Cheese and Fermented Milk Foods. F V Kosikowski and AssociatesBrooktondale NY 2nd Ed.