Transformation of elastic and chalky curd with an acidic flavour to ductile full flavored cheese can be accomplished by proper cheese ripening. During cheese ripening process various changes in physical, chemical and microbial characters takes place. In this process there is breakdown of proteins, carbohydrates, lipids, fats and sugar which are released by micro-organism and enzyme.
The breakdown of this product results in contribution of flavour and texture to the cheese. The development of flavour and texture of cheese also depends upon pH, salts, temperature, humidity and composition of cheese.
Further this curd is cut by using knives, steel frames and the curd is cut into small cubes. In this process of cheddar cheese formation the acidity of the curd is increased up to 4. Cheese is normally packed with a protective coating at a particular stage of ripening. The coating of cheese may vary from vegetable oil to special plastic films. The cheese is cut into rectangular form and coated with a plastic film. Cheddar cheese is pressed in large cylindrical blocks and due to pressing compact cheese blocks are formed,packed and sold in the market.
When we think about cheese, the first step in the fermentation process happens when the milk is inoculated with lactic acid bacteria, our primary microflora, and rennet in a vat. The lactic bacteria converts the sugar or lactose in milk to lactic acid. The lactic acid and rennet cause the milk to curdle, which separates the curds made of milk solids, fats and proteins and whey which is mostly water.
The curds soak until the lactic acid bacteria create a concentration that is just right, then the whey is drained off. The curds are then pressed, salted and mixed with different types of secondary microflora, and is then sent for aging. The cheese ripens for a designated amount of time to improve taste and consistency. During this time, the enzymes and bacteria continue to modify proteins, fats and sugars in the cheese. Starter-culture addition.
The type of commercially available starter preparation to be used will be determined by the cheese recipe. As previously stated, large-scale processing relies on using defined, commercially available starters, while for traditional cheeses, a natural fermentation whey from the previous lot is often used.
Top - Brine salting of cheeses in a large-scale plant processing 20 tons of cheese a day. Common steps to most cheese making processes.
During coagulation, modifications on the milk protein complex occur under defined conditions of temperature and by action of a coagulant agent, which changes the physical aspect of milk from liquid to a jelly-like mass.
Various coagulants are available, e. These enzymes have an acidic nature, meaning they have optimum activity in a slightly acidic environment. Therefore, the action of LAB in this phase is crucial as they are required to rapidly release enough lactic acid, to lower the milk pH from 6.
Cutting the coagulum. The resulting coagulum may be cut with appropriate knives into curd particles of a defined size, e. The cutting or ladling of the coagulum is a very important step in the manufacture of some cheese varieties as it determines the rate of acid development and the body firmness and texture of the cheese. Heating or cooking the curds.
During heating, the curds and whey are often stirred to maintain the curd in the form of separate particles. Whey removal. After heating and stirring, and when the curd particles have firmed and the correct acid development have taken place, the whey is removed allowing the curd particles to mat together. Milling the curd.
In cheeses such as Cheddar, when the curd has reached the desired texture, it is broken up into small pieces to enable it to be salted evenly.
Milling the curd can be done either by hand or mechanically. Salting is usually done to enhance the taste of the curd and to increase its safety and shelf life. Finally, for most cheeses, the resulting mass is molded and put to ripening for periods that may vary from 15 days to one, two or more years.
Ripening is a slow phase, crucial for the development of aroma and flavor, brought about by the action of the many enzymes released by LAB. During ripening the protein in cheese is broken down from casein to low molecular weight peptides and amino acids. Proteolysis is the major — and certainly the most complex of biochemical events that take place during ripening of most cheese varieties and LAB play an important role in it.
This happens while the cheeses are stored in the curing cabinets and in some cases in caves, usually with temperature and humidity controlled Figure 3. During coagulation, the initial step of casein hydrolysis is performed by chymosin milk coagulant and proteinases from starter lactic acid bacteria, starter moulds and other microorganisms. The further degradation of high molecular weight peptides produced at the initial step, is subsequently catalised to low molecular weight peptides by endopeptidases from LAB during ripening see Fig.
Simplified view of the biochemical changes that lead to texture and flavour changes in cheeses. General pathways leading to intracellular meatabolites, and their degradation routes to potential flavour compounds. More specifically, pathways from methionine to flavour compounds methanethiol, thioesters, sulphur compounds are shown Adapted from Kranemburg et al. Primary proteolysis leads to the formation of large water-insoluble peptides and smaller water-soluble peptides Fox, , Mooney et al.
Secondary proteolysis products include those peptides, proteins and amino acids soluble in the aqueous phase of cheese and are extractable as the water-soluble nitrogen WSN fraction.
The WSN fraction is a complex mixture of large, medium, and small peptides and amino acids. These components result from the action of milk clotting enzymes, milk proteases, starter LAB and contaminating microorganisms Rank et al. Lanes 1, 8 and 15, Na- caseinate; lanes cheese A; lanes cheese B Kongo et al.
Typical cheese pH values measured at 3—7 days after manufacture are 4. Typical pH vs time profiles for several cheese varieties time is in minutes unless otherwise noted. During processing, the pH history of the cheese is a good indicator of the actual product safety.
For most ripened varieties the combination of a low pH and ripening time, which leads to moisture decrease in the cheese, will in general cause a gradual decline of all groups of bacteria due to increasing inhospitable conditions inside the cheese. The pH history of a cheese and the hygienic practices applied in its manufacture are thus key factors to guarantee safe products. Thus, the isolation of autochthonous LAB intend to be used for development of specific starter cultures with improved acid production and other antimicrobial activities may be an excellent way towards reaching the goals of simultaneously obtaining safe traditional cheeses, still bearing their unique flavors.
Nowadays, western consumers still enjoy artisan cheeses thanks to their outstanding gastronomic qualities; however, in most industrialized countries the large-scale cheese processing is the most important branch of the food industry.
In such cases, there is a strong need to control the fermentation process towards maximum efficiency in terms of yields and standardization of the end product. Originally, starter cultures for the cheese industry were maintained by daily propagation, and later, they became available as frozen concentrates and dried or lyophilised preparations, produced on an industrial scale, some of them allowing direct vat inoculation Sandine, Because the original starter cultures were mixtures of several undefined microbes, the daily propagation, eventually led to shifts of the ecosystem resulting in the disappearance of certain strains.
Because some important metabolic traits in LAB are plasmid-encoded, there was a risk that they would be lost during propagation Weerkamp et al. Lactococci are generally used as starter cultures in the production of industrial cheeses and cultured milk products. In traditional cheeses the natural starter cultures may harbor many different species and strains.
On the other hand, cheeses manufactured in a standard large-scale processing manner, are considered as safer because of the application of pasteurization and following the standard hygienic practices, including the HACCP. Traditional cheeses have their own specific processing methods, namely the common use of raw milk, however the hygienic procedures and HACCP approaches adapted to their specificities should be applied as well.
Main bacteria associated with cheeses or other fermented products From: Broome et al. As previously stated, LAB are only a part of the complete microflora of raw milk Kongo et al, and this, associated to other technological methods such as pressing, allows the production of a diversity of traditional cheeses Parguel, This raw-milk microflora represents the contamination from the environment air, utensils, the animal skin , and the load and its diversity will thus vary with local, season and livestock type, influenced by temperature.
These microbial mixes have an interdependent activity when together in their ecosystem and therefore their physiological properties may differ when the biodiversity is disrupted. In fact, it has been shown that certain microbial associations reveal a higher protecting effect against pathogens such as listeria, than when their association diversity is disrupted, Montel see Figure 9.
Bacteriocinogenic probiotic bacteria could be beneficial when used as starter cultures in cheese, as they may prolong the shelf-life of the products, while simultaneously providing the consumer with a healthy advantage at a low cost Gomes et al.
The presence of bacteriocins in foods is, in general, seen as safe for consumers because bacteriocins are inactivated by pancreatic or gastric enzymes Liu et al. Level of L. Many LAB produce exopolysaccharides EPS , which may provide viscosifying, stabilizing, and water-binding effects in cheeses. The growing demand for all-natural, healthy food products, foods with low fat or sugar content and low levels of additives, as well as cost factors has increased the interest of food industry to use LAB polysaccharides.
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