In this article we will discuss about the steps involved in manufacturing cottage and processed cheese.
How to Manufacture Cottage Cheese?
(i) Receiving Skim Milk:
The skim milk should be fresh, sweet, and low in fat and bacterial content and clean in flavour. It should be pasteurized immediately after separation, preferably by the holder method (since higher heating temperatures result in a softer curd, which is easily broken while cutting and handling).
(ii) Adding Calcium Chloride:
Calcium chloride is generally added to the skim milk at the rate of 1 ml. saturated solution per 100 litres of milk. The object is to restore the concentration of calcium ions (which is lowered due to pasteurization) to the original level, for formation of the firm curd desired. It is added after the pasteurized milk has been cooled to the setting temperature.
(iii) Adding Starter:
A high-quality lactic starter prepared from skim milk is added as indicated in Table 7.7 and thoroughly mixed into it.
(iv) Adding Rennet:
Rennet is added at 2-2.5 ml. per 1000 litres of milk. Before adding, it is diluted with 40 times its volume of (potable) water for uniform distribution.
Note:
Cheese colour may be added, if desired, at 2-4 ml. per 1000 litres of milk before adding rennet.
(v) Setting:
The temperature and time of setting have already been indicated in Table 7.7.
(vi) Cutting:
The most desirable acidity of whey at cutting is approximately 0.5 per cent (pH 4.6-4.7). The whey should come from the interior of the curd and should be clear and free from curd particles. The method of cutting and the size of curd cubes are the same as for cheddar cheese.
Note:
Too low an acidity at cutting causes an undesirable rubbery consistency in the curd. On the other hand, too high an acidity induces a brittle consistency in the curd; and this causes it to shatter during handling, thus decreasing the yield.
(vii) Cooking:
This begins soon after cutting and continues for an hour or two until the temperature reaches 46°C (115°F), or until the curd becomes firm enough to remove the whey. The temperature is increased slowly at first; and the final temperature is reached in one-and-a-half to two hours. Stirring during cooking is kept at a minimum and is very gently done in the early stages.
(viii) Drainage of Whey:
Whey is removed when the curd cubes no longer have a ‘soft centre’ and when a handful of them squeezed gently show slight elasticity. The whey is removed from the curd approximately two hours after cutting. By this time the size of the curd cubes is approximately two-thirds of their original volume. The whey is drained in the same way as in cheddar cheese.
(ix) Washing and Draining:
The curd is washed after all the whey has been removed. This treatment makes the curd firmer and hard to the touch; it also removes acid-whey from around it and helps produce the desired mildness in flavour. The wash water is applied in at least two treatments.
In the first, the temperature is about 21°C (70°F) and the quantity not less than twice the volume of curd in the vat; after soaking the cubes for 15 minutes, the wash water is removed. The second (or third, if necessary) lot of wash water is at 16°C (60°F) or below, in the same quantity as above.
After it has been washed, the curd is drained. Draining should be thorough. It is best done by placing the curd cubes in a draining rack with perforations at the bottom, which can be wheeled into refrigerated rooms.
(x) Salting:
This is done when free moisture has been drained from the curd. Salt can be added to the curd in the vat, or it can be dissolved in the cream for creamed cottage cheese. Coarse salt is preferable. Salt is added @. 1 per cent of curd (or 15 per cent of milk).
(xi) Creaming:
This is done immediately after draining, if the product is to be packaged at once. Holding the curd overnight in a cold room before it is creamed makes it more firm when creaming. The amount of 20 per cent cream required to give 4 per cent fat in the finished product is then homogenized before mixing so as to form thick glossy coats over the curd particles.
(xii) Packaging and Storage:
Cottage cheese, creamed or un- creamed, may be packed in waxed/polythene-coated paper cups or in polythene bags. It should be stored at 5-10°C.
How to Manufacture Processed Cheese?
1. Receiving Raw (Natural) Cheese:
Processed cheese manufacturers usually prefer to control the curing of their cheeses (meant for processing), so that the quality and quantity of the same meet their needs.
2. Analysing:
On receipt, each block of cheese is sampled and then analysed for acidity, fat, moisture, salt, etc. The record of analysis stays with the cheese till it is all used up.
3. Selection for Blending:
Blending is the operation of bringing together for processing cheeses of different age-groups. It produces the desired physical characteristics and uniformity of chemical composition in the finished product. Blending is an important operation which requires judgement, experience and technical skill.
The guidelines for selecting cheeses for blending in a particular batch are as follows:
(a) It is desirable that 75 per cent of the cheese used be 0-3 months old and about 25 per cent of the cheese be 6-12 months old.
(b) If the cheese is highly acid/sour, it should make up not more than 5 per cent of the total; if gassy, not more than 2 per cent.
Note:
Selection of raw cheese is determined chiefly by age, acidity and pH, flavour, body and texture, and composition of the blocks available. Relatively young cheese produces a mild flavour, smooth texture, firm body, and has good slicing properties; while older well-cured cheese produces a strong flavour, grainy texture, weak body, and has poor slicing properties. Highly acid cheese tends to produce a grainy texture.
4. Tempering and Cleaning:
Tempering of cheese refers to bringing it to the proper consistency or hardness. Cleaning refers to the removal of inedible portions of cheese before processing.
Cheese is brought from the curing/storage room to the blending room till it attains a temperature of 16-21°C (60-70°F) in about 48 hours. This is called tempering of cheese and has the effect of softening it, facilitating cleaning, cutting and grinding operations. The tempered cheese is cleaned shortly before it is actually required for processing. First the paraffin is removed and then all inedible portions of the cheese are scraped off or cut away.
5. Quartering and Grinding:
The cheese blocks are first cut into four pieces each (which is called quartering), in order to facilitate grinding. Then each quarter is conveyed to the grinder, which is similar to a meat grinder for small batches. For large batches, each quarter is first shredded and then forced through a heavy metal perforated screen.
6. Processing:
This involves the following operations: addition of water, colour, salt and emulsifiers; and heating, stirring and emptying the kettle/cooker.
(a) Addition of Water, Colour, Salt and Emulsifier:
At first a portion of the ground cheese is dropped into the cheese processing kettle/cooker; and to this are added the calculated amount of water, colour, salt and emulsifier. Then the remaining ground cheese is added.
The emulsifier has very important roles to play in processed cheese.
These are:
(i) To prevent separation of fat from cheese during the heating operations;
(ii) To cause specific soft and smooth characteristics in the body and texture of the finished product;
(iii) To produce desirable melting and slicing properties in the finished cheese.
The two most commonly used emulsifiers are di-sodium phosphate and tri-sodium citrate, and mixtures of these salts. Used to a lesser extent are rochelle salt, sodium pyrophosphate and sodium metaphosphate. The amount of emulsifier varies from 0.5 to 3.0 per cent by weight of cheese. The calculated amount of emulsifier is mixed with water and added to the kettle/cooker.
(b) Heating, Stirring and Emptying of the Kettle/Cooker:
The kettle is used for small batches, while the cooker for large ones. The kettle initially used was open, upright, and steam-jacketed with double- acting agitators. The modified kettle used today is closed and equipped to permit the use of vacuum or pressure to aid heating and emptying. It is heated by direct steam and the excess moisture has to be removed; and it is emptied through an opening at the bottom.
The cooker now generally used is horizontal and cylindrical or trough-like in shape, and closed at both ends; the cheese is stirred with one or sometimes two screws or spiral-shaped horizontally-acting conveyors. The cheese enters through a hopper at the top-rear of the cooker, and is forced towards the gate-end of the machine by conveyors; at the same time live steam is injected into it.
As the charge approaches its capacity, the partially melted cheese flows back over the agitators so that complete mixing and thorough heating of the batch is accomplished in minimum time. The rapid emptying of these cookers is accomplished by the positive delivery action of the above conveyors, which force the melted cheese through the wide-mouthed gate at the end of the cooker opposite the entry side.
The optimum temperature-time relationship of processing is 65°C (150°F) for 2-5 minutes, although a higher heating temperature and a longer time span ensures more efficient microbial destruction.
(c) Changes during Heating:
When heat is first applied, the cheese becomes sticky and tends to cluster in lumps or balls. This condition is minimized by efficient agitation. Fat may separate at this stage, although a proper blend may show no visible fat separation.
At about 54°C (130°F), the free fat, if any, begins to be absorbed. As the heating temperature approaches 65°C (150°F), the mass becomes more plastic, ductile, smooth, homogeneous and glossy; although it is highly viscous at this stage, it flows readily.
7. Packaging:
In large-scale operations, the cheese, after being processed, is conveyed or piped to the package filler; in small-scale operations, it is drawn directly from the processing kettle into the final package. The cheese should be kept hot and well-stirred as long as a semi-fluid condition is needed for satisfactory packaging. The packaging machinery is an essential part of large-scale operations.
8. Cooling and Storage:
The packaged processed cheese is at first slowly cooled to 18-21°C (65-70°F) and then only afterwards kept under refrigeration at 2-4°C (35-40°F).
9. Modern Trend:
A modern trend has been the manufacture of cheese especially for processing. After draining out the whey, the curd is immersed in a lactic acid solution and heated with agitation to 39-43°C (102-110°F) for 6-40 minutes. The dilution is then drained off and the curd washed with cool water, salted, hooped, pressed and stored for 2 days at 5-6°C, when it is ready for processing.