In this article we will discuss about the methods and procedures to make cottage cheese. Learn about:- 1. Cottage Cheese Meaning 2. Manufacturing Methods of Cottage Cheese 3. Methods for Determining Proper Cutting Time 4. Cottage Cheese Dressing 5. Yield of Cottage Cheese 6. Defects in Cottage Cheese.
- Cottage Cheese Meaning
- Manufacturing Methods of Cottage Cheese
- Methods for Determining Proper Cutting Time of Cheese
- Cottage Cheese Dressing
- Yield of Cottage Cheese
- Defects in Cottage Cheese
1. Cottage Cheese Meaning:
Cottage cheese belongs to the class of natural, un-ripened, soft cheeses. It differs from cream cheese in that it has a considerably lower fat content, which gives it a popular place in low-calorie diets.
Cottage cheese is made from pasteurized, skim milk, or reconstituted skim milk powder. Coagulation is accomplished by lactic streptococci, and a very small amount of rennet or coagulator may or may not be added. After curdling, the curd is cut into cubes using 1.3, 1.6, or 1.9 cm wire cheese knives. It is marketed as small curd and large curd cottage cheese. The curd is cooked, washed, and mixed with salt and cream dressing.
Federal standards define creamed cottage cheese as the product containing moisture not exceeding 80% and milk fat not less than 4%.The low-fat product may contain 0.5-2.0% milk fat. Cottage cheese dry curd contains less than 0.5% fat. In addition, silicone antifoams and sorbate preservatives may be used. It may be marketed in flavored form by incorporating little bits of pimientos, chives, or pineapple.
The product is commonly used as a major ingredient of salads. In an ideal creamed cottage cheese, the basic flavor should be similar to fresh, clean, cultured milk or cream. Cottage cheese should have a mild acid, light salty taste, with the flavor and aroma of a good lactic butter culture.
The body and texture should be uniform, smooth and meaty, not too firm and not too soft and pasty. It should be of uniformly sized particles (regardless of style or cut of curd) and have a natural color. Creamed cottage cheese should have a uniform layer of cream around the curd particles with a minimum of free cream. Any excess cream should be of a thick consistency and not whey-like or watery.
2. Manufacturing Methods of Cottage Cheese:
The methods for making cottage cheese can be classified into 3 groups, based upon the length of time allowed for coagulation.
1. Short Set Method:
This method requires 4.5-5.5 hr for coagulation and proper acid development; 5 to 7% lactic culture is used along with a setting temperature of 31°-32°C. This method is designed to be completed, except for packaging, in an 8 hr day. Labor is utilized in the afternoon for cooking, washing, and cleanup.
Raw skim milk is pasteurized at 73°C for 16.5 sec. It is desirable to avoid using any previously pasteurized skim milk as a minimum heat treatment is required to avoid curd weakness. After pasteurization, the skim milk is cooled promptly and pumped to the vat where the proper setting temperature of 32°C is obtained.
The titratable acidity of the pasteurized skim milk is determined in order to judge the rate of subsequent acid development. The bulk culture is added to the vat at the rate of 5 to 7%. The skim milk is then stirred thoroughly every 30 min for 1.5 hr. The temperature should be kept at 32°C.
The acidity test is run after the culture is mixed with the skim milk and again after 1.5 hr. During this time, if the culture is producing acid normally, the acidity should increase by 0.05 to 0.07%. If the acidity has not increased by 0.05%, 1% more culture is added for each 0.01% increment below 0.05%.
The next step is to add rennet or coagulator diluted with 40 volumes of cold water before it is added to the vat. Rennet may be used at the rate of 1 ml per 454 kg of skim milk for large curd and medium curd, and 0.3-0.5 ml per 454 kg for small curd. A commercial coagulator, if used, should be used according to the manufacturer’s instructions for the type of cheese being made. The coagulator or rennet is mixed thoroughly with the skim milk and the vat is covered for 2 hr for consummation of coagulation.
Two hours after the coagulator is added, curd formation is checked. When the curd is ready, the first cut, along the length of the vat, is made with the horizontal knife. It is followed by the second cut lengthwise with the vertical knife and the third cut crosswise of the vat with the same vertical knife. Care should be taken to avoid overlapping of cuts.
After cutting, the curd is held without agitation for 10 min to allow the cut surfaces of the cubes to firm slightly. The water in the jacket of the vat is raised 12°C above the vat temperature. The curd is pushed very gently from the sides of the vat toward the center with a stainless steel stirrer. The vat is stirred every 5 to 10 min.
Jacket temperature is maintained 12°- 18°C above the vat temperature in order to raise the temperature of the vat content to 49°-54°C in 1 to 1.5 hr. A mechanical agitator on slow speed may be used after the temperature reaches 38°-41°C, followed by a gradual increase in agitation speed to prevent matting. Small curd cheese requires more agitation and cooks out faster than large curd cheese.
If the curd is not sufficiently firm when the temperature reaches 49°- 54°C, the curd is held at that temperature with agitation until firm. The firmness of large, intermediate, and small size curd can best be judged by chilling a small amount of curd in cold water (5°C).
The curd is adequately cooked when a handful of water-chilled curd springs apart after being squeezed together with moderate pressure. Alternatively, the curd is ready 1 for washing when you get a reading of 4-5 on a Lundstedt meter which is designed to measure the firmness of the curd.
After the curd is cooked, the jacket of the vat is drained and whey removed until the curd begins to surface. Wash water, acidified and chlorinated, is then added, equal to the volume of whey removed, to reduce the temperature in the vat to 27°-30°C. After 10 min agitation, the wash water is drained. Washing is repeated 2 more times to reduce temperature in the vat to 13°-16°C and then to 5°C or lower.
After the last wash, the curd is trenched and permitted to drain for 30-60 min before creaming or removal to storage. Alternatively, the water-curd slurry is pumped into a special blender for drainage. A new development in curd washing uses a vertical curd washing system designed to effect conservation of wash water. Consequently, a lower BOD in the plant effluent is achieved.
The drained curd is creamed in the vat or in a special blender or by weighing the curd into cans containing a previously weighed amount of dressing described subsequently. The most desirable method is to mix the dressing with the curd in the vat or in a blender and then transfer by gravity or by special pumps directly to the packaging machines.
2. Medium Set Method:
This method works well with a 24 hr operation in which milk is received one day and cottage cheese from that milk is marketed the following day.
This method is essentially the same as the Short Set Method except that 2-4% lactic culture is used at a setting temperature of 27° – 28°C and 8 -10 hr are required for proper acid development and coagulation.
3. Long Set Method:
This method requires the following modifications of the Short Set Method previously described. The setting temperature should be 21°-22°C and 0.1 -1.5% lactic culture is required for a 12 -16 hr setting time. Less culture is required and the work load can be readily distributed over a normal work day. Rennet or coagulator should be added just after the addition of the culture. The cooking should be slower at the start and faster at the finish. Total cooking time is usually 30-60 min longer than for the Short Set Method.
Water used in making cottage cheese is in direct contact with the product and hence is just as important in determining flavor and keeping quality as any other ingredient. The water should be from an approved drinking water supply and should be free of sediment and off-flavors, and practically free of sulfur, sodium carbonate, sodium bicarbonate, and sodium chloride. Water used for the reconstitution of nonfat dry milk and for cottage cheese curd should be adjusted to pH 4.0-4.75 with food-grade phosphoric, lactic, or citric acid.
All water which comes in contact with the product should be chlorinated with 10-20 ppm chlorine with a contact time of at least 10 min. Water containing phenols or phenol-like compounds may develop chlorophenol (medicinal) flavor when chlorinated and should be treated or filtered before chlorination. For example- activated carbon may be used to remove the phenolic materials.
The culture (Streptococcus lactis or Streptococcus cremoris and low levels of Leuconostoc cremoris or Streptococcus lactis subsp. diacetylactis) should possess a clean, smooth, and fine flavor as well as good activity.
3. Methods for Determining Proper Cutting Time of Cheese:
Three methods can be used for determining the proper time to cut cottage cheese curd:
1. Titratable Acidity of Whey:
When the curd is firm, a sample of the whey is drawn from at least 10 cm (4 in.) below the surface using a plastic pipette. The sample is filtered to get clear whey. The titratable acidity of the clear whey should be checked periodically until it is 0.34 to 0.36% higher than the initial titratable acidity of the skim milk.
For skim milk fortified with nonfat dry milk to 10, 11, or 12% solids, the acidity of the whey at cutting should be 0.55, 0.60, or 0.65%, respectively. Cutting at low acidity yields a sweeter cheese which cooks out faster but may tend to mat during cooking. Cutting at high acidity yields a more acidic cheese which is brittle and more difficult to cook out but tends to mat less during cooking.
2. pH Determination:
Cottage cheese may also be cut when the pH of the curd is in the range of 4.6-4.7.
3. Acid Coagulation Test:
The acid coagulation or A-C test can also be used to determine the proper time for cutting. This test can be used alone or with one of the other tests to determine the correct titratable acidity or pH at which to cut curd from any particular milk supply.
The steps in the A-C test are as follows:
(1) Proceed through the regular manufacturing steps and then, just before adding rennet, remove 200 ml of the seeded skim milk into a stainless steel beaker.
(2) Add rennet to the vat but not to the beaker of skim milk.
(3) Suspend the beaker of skim milk in the vat to ensure the same temperature and rate of acid development.
(4) When the skim milk in the vat has coagulated, check the sample in the beaker for evidence of coagulation.
(5) When a gel can be detected, cut with 1 or 2 strokes of a small knife or spatula.
(6) Repeat cutting at intervals of 5 min until fine lines of whey appear within 1 min after cutting. This is the A-C endpoint and the curd is ready for cutting.
4. Cottage Cheese Dressing:
A properly prepared cottage cheese dressing adds a significant shelf life to the finished product and enhances flavor and appearance of the cheese. A certain level of viscosity, obtained by the use of a suitable stabilizer, is necessary to properly bind the free flowing cream and whey in the cheese.
For the preparation of the dressing, a standardized blend is prepared to contain 12.5% fat, 8.5% milk solids-not-fat, 2.7% salt, and 0.25% cottage cheese stabilizer. For low-fat cottage cheese, the composition is 3.0% fat, 15.0% milk solids-not-fat, 2.7% salt, and 0.25% stabilizer. Before heat is applied (or at a temperature below 32°C), the stabilizer is added.
The amount of stabilizer added will largely govern the viscosity of the finished product. It is advisable to start at a low point and, if a more viscous product is desirable, slightly increase the amount of stabilizer. It is preferable to mix stabilizer, salt, and milk solids before addition to the dressing mix in a pasteurizing vat.
A practical way of introducing the dry ingredients is through a funnel attached to a centrifugal pump. If this is not feasible, the vat agitator is started at high speed and the dry ingredients are slowly sprinkled into a partially filled vat. The agitator is kept at high speed and the product is heated to a temperature of 75°- 77°C and held for 30 min.
The dressing is homogenized at 13.8 kPa, single stage, at 57°C and cooled to below 4°C. Fresh dressing is made every 2 days. Approximately 1 part of cream dressing mixed with 2 parts of dry cheese curd will yield a finished creamed cottage cheese of 4% milk fat. Similarly, this ratio will yield a low-fat product of 1% milk fat.
The production of desirable aroma and flavor in cottage cheese may be augmented by the use of certain cultures in culturing skim milk or cream dressing. Mather and Babel (1959A) reported 2.3 ppm diacetyl and 55.7 ppm of acetoin in skim milk coagulum.
After cutting, whey removal, and washing, the curd retained only 1 ppm diacetyl and 29 ppm of acetoin. Work of Babel and Mather (1961) and Lundstedt and Fogg (1962) have resulted in development of processes for flavor enhancement utilizing the flavor producing characteristics of Leuconostoc cremoris and Streptococcus lactis subsp. diacetylactis, respectively.
These organisms are added to cottage cheese via cream dressing. The growth of Leuconostoc cremoris produces certain metabolites inhibitory to Pseudomonas fragi, Pseudomonas putrefaciens, and coliform organisms.
The spoilage of cottage cheese is considerably controlled by reducing the pH of creamed cottage cheese below 5.0. This effect is ascribed to the retardation of the growth rate of bacteria from several genera, including Pseudomonas, Achromobacter, and Alcaligenes, which are involved in proteolytic and lipolytic degradation of cottage cheese.
5. Yield of Cottage Cheese:
Cottage cheese yield from a vat of skim milk is commonly expressed as the kg of curd per 100 kg of skim milk. Alternatively, the yield may be expressed as the kg of curd per kg of solids in the skim milk. Occasionally, it is expressed as the kg of curd per kg of casein in the milk.
A satisfactory yield of large cottage cheese curd (prior to creaming) made-with the conventional method from skim milk of 9% solids, is 15.5 kg per 100 kg of skim milk or 1.72 kg of curd per kg of solids in the skim milk. The curd can be increased by about 1.80 kg for every kg of dry milk solids fortified into skim milk. A fortified skim milk containing 12% solids should yield 21.6 kg of curd per 100 kg of the starting material.
The yield of cottage cheese changes as the solids or casein content of the skim milk varies with the breed of cows, season of year, and stage of lactation. Also, the moisture content of a curd, normally 80%, may vary due to the cooking and draining methods used prior to creaming. Furthermore, over pasteurization may result in a weak and fragile curd subject to shattering and loss during cooking and draining.
Excessive acidity at the cutting step may result in curd losses due to shattering. Proper care in cutting, cooking, and washing can reduce mechanical losses considerably. Some lactic cultures have been found to coagulate milk more firmly than others and give better cottage cheese yields.
6. Defects in Cottage Cheese:
Common defects and possible causes in cottage cheese have been discussed by Angevine (1972) and Lundstedt (1972, 1974).
They are enumerated here as follows with a description of probable causes:
1. Acid Flavor—Too high and acidity before cutting; failure to expel whey; insufficient or improper washing; poor quality skim milk and/or starters.
2. Bitter and Unclean Flavor—Contamination by unclean wash water, equipment, utensils, undesirable bacteria during or after manufacture; use of poor quality skim milk, starter, and/or cream for creaming.
3. Weak, Soft Curd—Excessive heat treatment of skim milk before setting, or of nonfat dry milk during manufacture; too high and acidity at the time of cutting; insufficient heating during cooking; too much coagulator along with too high and acidity.
4. Shattered Curd—Excessive heat treatment of skim milk before setting; excessive preheat treatment of skim milk during dry milk manufacture; too much acid at cutting; improper cutting and stirring; undesirable bacteria producing gas; chilling curd too fast.
5. Tough, Rubbery Curd—Insufficient acid development at cutting; cooking too rapidly or too much heat during cooking; excessive loss of moisture after manufacture.
6. Floating or Gassy Curd— Water supply high in carbonate content; contaminated or poor starter cultures; insanitary equipment; gas-producing cultures.