Cheese as Vegetarian Food
Vegetarian Cheese, which uses non-animal rennet, is freely available in the UK and used in restaurants such as Pizza Hut.
If you want to eat cheese, please discern and only eat those cheeses that are vegetarian – ignorance is not bliss.
The first step in cheese making is to separate milk into curds and whey.
Curds are milk solids that consist of casein (a protein), fat, water and some carbohydrate (milk sugar, or lactose). Whey is a liquid of yellowish color that contains water, milk sugar (lactose), and whey proteins.
Separation, or coagulation, of the milk requires two stages. First, bacterial cultures and enzymes are added to reduce the PH and prepare the milk for the addition of rennet.
Rennet is added after cultures and enzymes are used. Rennet is the dried commercial extract of rennin, the enzyme that is responsible for most of the milk coagulation that takes place.
Traditionally, rennet is derived from animals. However, some vegetable juices and extracts are used as rennin, and modern advances in science have enabled micro-organisms to produce enzymes that mimic animal rennet. Hence, "rennet" can come from animals, vegetables, or micro-organisms.
Animal : Obtained from the stomach region of a suckling mammal, usually a calf or lamb. As mentioned, this is the traditional way to make cheese; nearly all European cheeses use animal rennet.
Vegetable : Derived from plants, these enzymes are extracted and modified into a form similar to that of animal rennet. This is a less common form of rennet, due to its expense, but some cheeses are traditionally made from this type of rennet. This type of rennet is acceptable to loacto-vegetarians.
Microbial : This is a common and less expensive rennet, made from micro-organisms through a process of fermentation. Common micro-organisms include fungi and bacteria. This type of rennet is also acceptable to lacto-vegetarians.
Cheese is made by coagulating milk to give curds which are then separated from the liquid, whey, after which they can be processed and matured to produce a wide variety of cheeses. Milk is coagulated by the addition of rennet. The active ingredient of rennet is the enzyme, chymosin (also known as rennin). The usual source of rennet is the stomach of slaughtered newly born calves. Vegetarian cheeses are manufactured using rennet from either fungal or bacterial sources. Advances in genetic engineering processes means they may now also be made using chymosin produced by genetically altered micro-organisms.
Manufacture : The exact processes in the making of cheese varies between different varieties. However, all cheeses are made by essentially the same method. Initially, the milk is usually pasteurized by heating at 72°C for 15 seconds to destroy potentially harmful bacteria. The milk is then cooled to around 30°C and a starter culture of lactic acid bacteria is added to help souring. These convert lactose into lactic acid and help in the coagulation process. In addition, they also have a beneficial effect on the eventual quality, taste and consistency of the cheese. Some cheeses are coagulated entirely by lactic acid bacteria and are known as lactic-curd or acid-curd cheeses. However, some cheeses sold as lactic-curd cheese may have had rennet added.
The next stage is the addition of rennet, containing the enzyme chymosin. Rennet is usually sourced from the abomasum (fourth stomach) of newly born calves. Here, chymosin aids the digestion and absorption of milk. Adult cows do not have this enzyme. Chymosin is extracted by washing and drying the stomach lining, which is then cut into small pieces and macerated in a solution of boric acid or brine at 30°C for 4-5 days. Pepsin may sometimes be used instead of chymosin. This is usually derived from the abomasum of grown calves or heifers, or less commonly pigs. Pepsin may be mixed with calf rennin. Rennet coagulates the milk, separating it into curds and whey. This is called curdling.
Chymosin breaks down the milk protein casein to paracasein which combines with calcium to form calcium paracaseinate, which separates out. Milk fat and some water also becomes incorporated into this mass, forming curds. The remaining liquid is the whey. The strength of different rennet's can vary, though usual strength varies between 1:10,000 and 1:15,000 i.e. one part rennin can coagulate 10-15,000 parts milk.
Other substances may also be added during the cheese making process. Calcium chloride is added to improve the curdling process, and potassium nitrate is added to inhibit contaminating bacteria. Dyes (e.g. annatto, beta-carotene), Penicillium roquefortii mould spores to promote blue veining, or propionic acid bacteria to encourage hole formation may be added.
Following curdling, the curds are cut and drained. The size of the cut and the methods used vary for different cheese varieties. For soft cheeses, the curds are sparingly cut and allowed to drain naturally. For hard cheeses, the curds are heated and more whey is drained off. The curds are then cut into small pieces, placed in vats and pressed.
After pressing, the curds may be treated in a number of ways. They may be molded into different shapes, soaked in a saltwater solution, be sprayed with mould forming spores or bacteria, washed in alcohol, or covered in herbs.
The final stage is ripening, or maturation. This can vary in length from 4 weeks to 2-3 years, depending on the type of cheese. During ripening flavors develop, the cheese becomes firmer and drier, and special characteristics such as holes, blue veining and crust formation occurs.
Vegetarian Cheeses : Vegetarian cheeses are made with rennet of non-animal origin. In the past, fig leaves, melon, wild thistle and safflower have all supplied plant rennet for cheese making. However, most widely available vegetarian cheeses are made using rennet produced by fermentation of the fungus Mucor Miehei. Vegetarian cheese may also be made using rennet from the bacteria Bacillus subtilis or Bacillus prodigiosum.
Advances in genetic engineering techniques mean that some vegetarian cheeses may now be made using chymosin produced by genetically engineered micro-organisms. The genetic material (DNA) which encodes for chymosin is introduced into a micro-organism which can then be cultured to produce commercial quantities of chymosin. This is done by extracting genetic material from calf stomach cells which acts as a template for producing the chymosin encoding DNA. This can then be introduced into the micro-organism. Once the genetic material is introduced there is no further need for calf cells. Alternatively, the chymosin encoding DNA can be bio-synthesised in the laboratory without the use of calf cells.
The chymosin produced is identical to that produced by calf stomach cells. The development of genetically engineered chymosin has been encouraged by shortages and fluctuations in cost of rennet from calves. It's manufacturers claim that genetically engineered chymosin will end the cheese making industry's reliance on the slaughter of calves.
Chymosin encoding DNA has been introduced into three different micro-organisms. These are the yeast Kluyveromyces lactis, the fungus Aspergillus niger var awamori, and a strain of the bacteria Escherichia coli. All of these have now been approved and cleared for use by the Ministry of Agriculture, Fisheries & Food. There is no legal requirement for manufacturers to state whether a genetically engineered rennet has been used in the cheese making process.
Vegetarian cheeses are widely available in supermarkets and health food stores. A wide variety of cheeses are now made with non-animal rennet and labeled as suitable for vegetarians. No particular type of cheese is exclusively vegetarian. Soft cheeses are as likely to be non-vegetarian as hard cheese.
Types Of Cheese : The type of cheese produced depends on the milk used and the cheese making process. The milk used may be full fat, semi-skimmed or fully skimmed, this affecting the fat content of the cheese. It may be pasteurized or un pasteurized. Milk from different animals and different breeds is important in determining the final flavor. As well as cow's milk, cheese may be made from sheep or goat's milk.
Soft cheeses may be fresh or ripened. Fresh cheeses include quark, cottage cheese and cream cheese. Ripened soft cheeses include Brie and Camembert. Semi-soft cheeses include Stilton, Wensleydale and Gorgonzola. Hard cheeses include Cheddar, Cheshire, and Gruyere. Parmesan is a strongly pressed, very hard, dry cheese ripened for 2-3 years and then grated. Whey cheeses such as Ricotta are made as a by-product of other cheeses from the whey removed during pressing. Processed cheeses are either made with trimmings that are left over from the manufacture of other cheeses, or from dried milk powder. Flavorings, colorings and other additives are used.
Nutritional Aspects : Cheese is a good source of protein, calcium, zinc, and vitamin B12. However, full fat cheese is a major source of saturated fat which can lead to raised serum cholesterol levels. Also, it contains no carbohydrate or fiber, and is a very poor source of iron. Vegetarians, particularly new vegetarians, should be wary of too high a consumption of cheese.