Role in cheese ripening

Salt plays several important roles in cheese ripening ... 

Lb.helveticus is used as a bacterial starter in Emmental cheese. Lb.casei occurs normally in cheese milk and cheesemaking equipment and is a part of the natural flora. It seems, however, to have a benefical role in cheese ripening. We compared how these two bacteria differ when growing in milk, investigating two different strains of each bacterium. Lb.casei strains were isolated from cheese and Lb.helveticus strains from pure cultures intended for Emmental cheesemaking. 

Quantification of FFAs in dairy products, especially in cheese, is particularly important due to the impact of some FFAs on flavor. However, FFAs act as precursors of a wide range of flavor compounds (e.g., methyl ketones, lactones, esters and aldehydes), (Singh et al, 2003). The extent of lipolysis in cheese varies widely between varieties (Table 19.2). Typically, those cheeses with more than 3000 mg/kg have a characteristic lipolytic aroma/flavor and lipolysis plays an important role in their ripening. A major difficulty in quantifying FFAs in cheese is the distribution of FFAs of different chain length within the cheese matrix. SCFFA (C4 o—C8 0) partition mainly into the aqueous phase, whereas medium (Cio q—C14 0) and longer... 

Baankreis, R. (1992). The role of lactococcal peptidases in cheese ripening. Ph.D. Thesis, University of Amsterdam, The Netherlands. 

Bhowmik, T., and Marth, E. H. (1990b). Role of Micrococcus and Pediococcus species in cheese ripening A review. J. Dairy Scl 73, 859-866. 

However, propionic acid bacteria play only a minor role in the ripening of cheeses processed at lower temperatures (second heating at 40-42 C), such as Cheddar or Gouda. 

The main role of propionic acid bacteria in cheese ripening consists in the utilization of lactate produced by lactic acid bacteria as an end product of lactose fermentation. Lactate is then transformed into propionic and acetic acids and CO2. The volatile acids provide a specific sharp taste and help preserve a milk protein, casein. Hydrolysis of lipids with the formation of fatty acids is essential for the taste qualities of cheese. The release of proline and other amino acids and such volatile compounds as acetoin, diacetyl, dimethylsulfide, acetaldehyde is important for the formation of cheese aroma. Carbon dioxide released in the processes of propionic acid fermentation and decarboxylation of amino acids (mainly) forms eyes, or holes. Propionic acid bacteria also produce vitamins, first of all, vitamin At the same time, an important condition is to keep propionibacteria from growing and producing CO2 at low temperatures, since this would cause cracks and fissures in cheese. 

The production of sulphur compounds is believed to be very important in the development of Cheddar cheese flavour. Residual sulphydryl oxidase activity may play a role in initially reoxidizing sulphydryl groups exposed upon heating cheesemilk the sulphydryl groups thus protected may be reformed during the ripening process. 

Rennets. The use of rennets in cheesemaking is the principal application of proteinases in food processing and is second only to amylases among industrial applications of enzymes. The sources of rennets and their role in milk coagulation and cheese ripening are discussed in Chapter 10 and will not be considered here. 

The primary starter performs several functions in addition to acid production, especially reduction of the redox potential ( h, from about + 250 mV in milk to —150 mV in cheese), and, most importantly, plays a major, probably essential, role in the biochemistry of cheese ripening. Many strains produce bacteriocins which control the growth of contaminating micro-organisms. 

Yiadom-Farkye, N. 1986. Role of chymosin and porcine pepsin in Cheddar cheese ripening. Ph.D. Thesis. Utah State University, Logan. 

The activity of rennet in some maturing cheese is essential for normal cheese ripening. The practice of using less rennet in making cheese with concentrated milk has shown that the cheese does not develop characteristic sharp flavors (Chapman et al. 1974). The role of rennet in flavor development of cheese is to produce peptides that are degraded subsequently by the bacterial flora of the cheese. 

During cheese ripening, proteases associated with starter culture organisms are released into cheese after cell lysis (Law et al. 1974). The proteolytic activity associated with lysed lactic streptococci is necessary for proper flavor development in Cheddar and other cheese varieties. The role of streptococcal proteases and peptidases appears to be production of flavor compound precursors such as methionine and other amino acids, rather than direct production of flavor compounds (Law et al. 1976A). Additional discussion of cheese ripening is presented in Chapter 12. 

Cheese is a complex matrix of several components. Isolation of compounds of interest and the analysis of target compounds without interference from the matrix has been a challenge with analytical techniques. With the development of extraction procedures and new sampling techniques for analysis, not only has this challenge been overcome to a certain extent but also the speed, quality, accuracy, and reliability of analysis have improved tremendously. With the mechanisms behind the formation of several flavor compounds in cheese still not clearly understood, these techniques have an increasing role in the efforts to understanding cheese ripening. Often times most of the techniques provide... 

The role of milk-fat in the development of flavor in cheese during ripening will be discussed below although it should not be forgotten that lipolysis and the metabolism of fatty acids do not occur in isolation from other important biochemical events during ripening. 

Lipolysis plays an important role in providing the characteristic flavor of many milk products. In particular, the ripening of most cheese varieties is accompanied by lipolysis due to microorganisms or to added enzyme preparations, and, in raw milk cheese, to the milk LPL. Lipolysis is not extensive, but is more pronounced in some cheeses (e.g., blue-veined and hard Italian varieties), than in others. Excessive lipolysis renders the cheese unacceptable (Fox and Law, 1991 Gripon et al., 1991). 

Cheese Ripening. Rennet plays a major role in the texture and flavor development of cheese during the ripening process. Besides the rapid cleavage of the key phenylalanine-methionine bond to coagulate milk, chymosin has been shown to hydrolyze at least 22 other bonds in the casein molecules. The favored amino acids at the point of cleavage are leucine, isoleucine and phenylalanine. 

Proteases for Accelerating Cheese Ripening. Proteolysis plays such a major role in developing the flavor and texture of hard cheese that the addition of exogenous microbial proteases has been attempted using every commercially available protease preparation. 

Milk lipases may give undesirable rancidity when fresh milk is used for cheese making. The heat sensitivity of these lipases restricts them playing a major role in ripening of cheese made from pasteurized milk. Lipases play a very important role in flavour formation especially in mould cheeses such as Roquefort and Gorgonzola. 

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