Bacteria Ripening

Parmesan or Grana, as it is known in Italy, is a group of very hard bacteria-ripened, granular-textured cheeses made from partially skimmed cow s milk. They originated in Parma, near Emilia, Italy, hence the name. Special lipolytic enzymes derived from animals are used, in addition to rennet, to produce the characteristic rancid flavor. 

Dufosse, L. and de Echanove, C., The last step in the biosynthesis of aryl carotenoids in the cheese ripening bacteria Brevibacterium linens ATCC 9175 (Brevibacterium aurantiacum sp. nov.) involves a cytochrome P450-dependent monooxygenase. Food Res. Int, 38, 967, 2005. 

The objective of irradiation of food with y-rays is elimination of parasitizing insects, fungi, and bacteria to prevent premature spoiling of the food and the outbreak of diseases. In addition, retardation of aging and ripening of fruits and vegetables can be achieved. In the Federal Republic of Germany, irradiation of food with the exception of spices is not permissible. 

It is the principal factor affecting the water activity of young cheeses and has a major effect on the growth and survival of bacteria and the activity of enzymes in cheese, and hence affects and controls the biochemistry of cheese ripening. 

The contribution of these agents, individually or in various combinations, has been assessed in model cheese systems from which one or more of the agents was excluded or eliminated, e.g. by using an acidogen rather than starter for acidification or manufacturing cheese in a sterile environment to eliminate non-starter lactic acid bacteria (NSLAB). Such model systems have given very useful information on the biochemistry of ripening. 

In surface smear-ripened cheeses, e.g. Munster, Limburger, Tilsit, Trapist, the surface of the cheese is colonized first by yeasts which catabolize lactic acid, causing the pH to increase, and then by Brevibacterium linens, the characteristic micro-organism of the surface smear but which does not grow below pH 5.8, and various other micro-organisms, including Micrococcus, Arthrobacter and coryneform bacteria. 

Blue cheeses undergo very extensive lipolysis during ripening up to 25% of all fatty acids may be released. The principal lipase in Blue cheese is that produced by Penicillium roqueforti, with minor contributions from indigenous milk lipase and the lipases of starter and non-starter lactic acid bacteria. The free fatty acids contribute directly to the flavour of Blue cheeses but, more importantly, they undergo partial /J-oxidation to alkan-2-ones (methyl O... 

With that problem solved, we can now take up the case of the exploding Swiss cheese. Characteristic of this type of cheese are the large holes produced by the carbon dioxide gas that forms during the aging process. Cheese makers add a variety of bacteria to their creations as a way of ripening them. To Swiss cheese they also add a strain of Propionibacter shermanii. This bacterium uses the lactic acid secreted by other microbes as... 

The classification presented here is based upon consistency brought about by differences in moisture content (soft, semisoft, hard, very hard), the manner of ripening (bacteria, mold, yeast, surface or interior microorganisms, combinations or unripened), the method by which the curd is produced (acid or coagulating enzymes, or by acid and high heat, or combinations), and the type of milk employed (National Dairy Council 1979). 

The lactic streptococci used in cheese manufacture produce only the l( + ) isomer of lactic acid (Lawrence et al. 1976). However, ripened cheeses contain both d(-) and l( + ) lactate isomers (T irner and Thomas 1980). Nonstarter bacteria (pediococci and lactobacilli) form d( —) lactate from residual lactose or by conversion of l( + ) lactate (Thomas and Crow 1983). 

Micrococci comprise approximately 78% of the nonlactic bacteria in raw milk Cheddar cheese (Alford and Frazier 1950). The proteolytic system of Micrococcus freudenreichii functions optimally at 30 °C and at a pH near neutrality (Baribo and Foster 1952). An analysis of pro-teinases present in 1-year-old Cheddar cheese indicates that micrococci may contribute to proteolytic activity (Marth 1963). Proteolytic micrococci also contribute to the ripening of surface-ripened cheeses such as brick and Camembert (Lenoir 1963 Langhus et al. 1945). Micrococcal proteases probably contribute to development of ripened cheese flavor when ripening temperatures are above 10°C (Moreno and Kosikowski 1973). This effect results from degradation of /3-casein. 

Penicillium caseicolum produces an extracellular aspartyl proteinase and a metalloproteinase with properties very similar to those of the extracellular enzymes produced by P roqueforti (Trieu-Cout and Gripon 1981 Trieu-Cout et al. 1982). Breakdown of casein in mold-ripened cheese results from the synergistic action of rennet and the proteases of lactic streptococci and penicillia (Desmazeaud and Gripon 1977). Peptidases of both lactic acid bacteria and penicillia contribute to formation of free amino acid and nonprotein nitrogen (Gripon et al. 1977). 

Laboratory-scale experiments which used L. casei symbiotically with Propionibacterium freudenreichii in the fermentation of whey gave an average yield of 2.2 mg of vitamin per liter the maximum was 4.3 mg/liter. Production of vitamin Bi2 is not species-specific. All species of Propionibacterium, when cultivated under the same conditions, produce active substances, but in different quantities. P freudenreichii and P zeae synthesized sufficient quantities to warrant their consideration for commercial exploitation. Because propionic acid bacteria are active during Swiss cheese ripening, it was anticipated, and actually demonstrated, that production of vitamin Bi2 in Swiss cheese is influenced by the same factors that influence its production in pure culture, particularly by the cobalt content of milk (Hargrove and Leviton 1955). 

Shakeel-Ur-Rehman, F., Bank, J. M., McSweeney, P. L. H., and Fox, P. F. (2000). Effect of ripening temperature on the growth and significance of non-starter lactic acid bacteria in Cheddar cheese made from raw or pasteurized milk. Int. Dairy J. 10,45-53. 

During cheese ripening, the population of starter bacteria generally decreases while the number of non-starter lactic acid bacteria (NSLAB) generally increases these changes are well documented for many full-fat rennet-curd cheese varieties, (e.g., Cheddar) (Cromie et al., 1987 Jordan and Cogan, 1993 McSweeney et al., 1993 Lane et al., 1997 Haque et al., 1997 Beresford and Williams, 2004). 

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