Acid-coagulated cheeses

On acidification to pH 4.6, the caseins coagulate, which is the principle used to manufacture of a family of cheeses which represent about 25% of total cheese consumption and are the principal cheeses in some countries (Appendix lOB). Acidification is traditionally and usually achieved by in situ fermentation of lactose by a Lactococcus starter but direct acidification by acid or acidogen (gluconic acid-5-lactone) is also practised. The principal 

Quarg-type -Skim milk Quarg -Full I at Quarg -Tvorog 

Cream chcese-iype -double/single Cream cheese -Pelit Suisse -Neul chaiel 

Collage cheese-lype -Low/fat Collage cheese -Bakers cheese 

Acid-heal coaguiaied Queso Blanco Ricolla Mascarpone 

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Figure 10.27 Protocol for the manufacture of fresh acid-coagulated cheese (from Fox et al ...

Acid-coagulated cheeses are usually produced from skim milk and are consumed fresh. Major varieties include quarg, (American) cottage cheese, cream cheese and petit suisse. These cheeses may be consumed in salads, as... 

Acid coagulation Cheese whey protein concentrates, whey protein isolates, individual whey proteins, whey protein hydrolysates, neutraceuticals Lactose and lactose derivatives Fresh cheeses and cheese-based products... 

Acid-coagulated cheeses are consumed fresh but the production of rennet-coagulated cheese can be subdivided into two phases, manufacture and ripening ... 

Cheese is an important dietary source of several minerals, in particular calcium, phosphorus, and magnesium (Table XV). A 100-g serving of hard cheese provides ca. 800 mg Ca, which represents the Recommended Daily Allowance for most adults (Food and Nutrition Board, 1980). However, acid-coagulated cheeses, e.g.. Cottage, contain considerably lower levels of calcium than rennet-coagulated varieties (Renner, 1987). 

There are at least 1000 named cheese varieties, most of which have very limited production. The principal families are Cheddar, Dutch, Swiss and Pasta filata (e.g. Mozzarella), which together account for about 80% of total cheese production. All varieties can be classified into three superfamilies based on the method used to coagulate the milk, i.e. rennet coagulation (representing about 75% of total production), isoelectric (acid) coagulation and a combination of heat and acid (which represents a very minor group). 

Figure 10.26 Examples of acid-coagulated or heat-acid coagulated or whey-based cheese varieties (from Fox et al, 1996a).

Minerals found in milk which are insoluble remain in water in the curd and are more concentrated in the cheese than in milk. About two-thirds of the calcium and one-half of the phosphorus of milk remains in cheese. A major portion of the milk calcium is retained in the curd of cheese made with coagulating enzymes. Acid coagulation alone results in the loss of portions of both calcium and phosphorus salts in the acid whey, since these minerals are more soluble in the acidic medium. Most milk fat and fat-soluble vitamins are retained in the curd, but a considerable amount of water-soluble vitamins is lost during cheese manufacture. Retention of part of some B-complex vitamins in curd is due to their extended association with casein in the original milk. 

The physical and chemical characteristics of cheese curd depend on the method used to form the curd matrix. The curd is formed in basically one of two ways acid or enzymatic coagulation. In acid curd cheeses (cottage, baker s, cream), the curd is formed by direct addition of acid to the milk or by lactic acid produced by the fermentation of lactose. As the pH of the milk approaches the isoelectric point of casein (pH... 

Farkye, N.Y. 2004. Acid- and acid/rennet-curd cheeses. Part C Acid-heat coagulated cheeses. In Cheese Chemistry, Physics and Microbiology, Vol. 2, Major Cheese Groups, 3rd edn (P.F. Fox, P.L.H. McSweeney, T.M. Cogan, T.P. Guinee, eds.), pp. 343-348, Elsevier Academic Press, Amsterdam. 

Analogous to this processing, Korolczuk and Mahaut [80] report the necessity to use ceramic membranes for the filtration of acid-coagulated milk in order to produce UF-fresh cheeses with good taste. Typical fluxes, using Carbosep Ml (cut-off 50,000 D) increase from 10 to 20 1/m h at 40°C, with decreasing concentration factor. 

When an acid-coagulated milk gel is broken, the pieces synerese, expressing whey. Acid-coagulated casein is the starting material for a family of cheeses that are usually consumed fresh, i.e., are not matured (ripened) major examples are Cottage and cream cheeses, Quarg, and fromage frais. 

The conversion of milk to cheese curd essentially involves coagulating the casein, either isoelectrically or enzymatically if present, the milk fat is occluded in the curd. The mechanisms of rennet and acid coagulation of casein and the subsequent manipulation of the coagula to produce cheese curd are described in the following sections. 

The taste of acid-coagulated and young rennet-coagulated cheeses is strongly affected by the concentration of acid in the cheese. 

The fate of aflatoxin Mi in cheese milk is affected by the principal manufacturing steps. Early studies on the distribution of aflatoxin Mi between the curd and whey gave contradictory results. Allcroft and Carnaghan (1962,1963) reported that toxic activity was associated only with the rennet-coagulated curd. In contrast. Purchase et al (1972) reported that Cottage cheese made by acid coagulation of naturally contaminated milk contained... 

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