Dairy products lactic acid bacteria

Cells of microorganisms have constituted a portion of human food siace ancient times. Yeast-leavened baked products contain the residual nutrients from the yeast cells destroyed duriag bakiag (see Bakery processes and leavening agents). Cultured dairy products, such as yogurt, buttermilk, and sour cream, contain up to lO cells of lactic acid bacteria per gram (19) (see Milk and milkproducts). Other examples of fermented foods consumed siace early times iaclude fermented meats, fish, and soybean products. 

Lactose is mainly used as a fermentation substrate for lactic acid bacteria in dairy products, such as yogurt and cheese. These bacteria break down lactose into lactic acid, which solidifies the milk, and creates an acid environment that favors the benign lactic acid bacteria over those that are more harmful. 

Hydroxy-2-butanone (acetoin) is a characteristic constituent of butter flavour used for flavouring margarine and can be obtained as a by-product of molasses-based and lactic acid fermentations [49, 71]. The closely related 2,3-butanedione (diacetyl) has a much lower organoleptic threshold than acetoin and is an important strongly butter-like flavour compound in butter and other dairy products [72] in buttermilk, for instance, the diacetyl concentration is only about 2-4 mg [73]. a-Acetolactate (a-AL) is an intermediate of lactic acid bacteria mainly produced from pyruvate by a-acetolactate synthase. In most lactic acid bacteria, a-AL is decarboxylated to the metabolic end product acetoin by a-AL decarboxylase (ALDB) [71] (Scheme 23.5). 

Fermented milks are cultured dairy products manufactured from whole, partly skimmed, skim, or slightly concentrated milk. Specific lactic acid bacteria or food-grade acids are required to develop the characteristic flavor and texture of these beverages. Fermented milks are either fluid or semifluid in consistency, with various proportions of lactic acid. Fermented products are regulated by federal standards in the United States, as stated in Table 2.2. Other fermented milks without established federal standards are regulated by state standards. Compositional standards for fermented milks have been proposed by the International Dairy Federation (Hargrove and Alford 1974). Typical analyses of various fermented milks, as well as of their condensed and dried counterparts, are given in Table 2.4. 

Fruity flavor in dairy products is the result of ethyl ester formation, usually catalyzed by esterases from psychrotrophic or lactic acid bacteria. Ester formation by P. fragi involves liberation of butyric and ca-proic acids from the one and three positions of milk triglycerides and the subsequent enzymatic esterification of these fatty acids with ethanol (Hosono et al. 1974 Hosono and Elliott 1974). Consequently, among the esters formed, ethyl butyrate and ethyl hexanoate predominate. Pseudomonas-produced fruity flavor can occur in fluid milk, cottage cheese, and butter. 

Dacre, J. C. 1953. Cheddar cheese flavor and its relation to tyramine production by lactic acid bacteria. J. Dairy Res. 20, 217-223. 

Sour milk products are always cultured dairy products with lactic acid bacteria (depending on the food legislation of the respective country). After increasing the dry matter, pasteurisation and incubation of culture, they are processed into yoghurts of set, stirred or drinking consistency, with or without a final heat treatment. 

Alternatives to using ruminant foods to provide CLA in the diet are of great interest to the food-processing industry, perhaps most so in dairy processing. Sieber et al (2004) reviewed the impact of microbial cultures on CLA in dairy products. Several strains of Lactobacillus, Propionibacterium, Bifidobacterium, and Enterococcus are able to form CLA from linoleic acid lactic acid bacteria and propionibacteria appear to show promise to increase CLA during ripening of cheese. Presently, data are not convincing that this... 

Aslim, B., Yuksekdag, Z.N., Sarikaya, E., and Beyatli, Y. 2005. Determination of the bacteriocin-like substances produced by some lactic acid bacteria isolated from Turkish dairy products. Swiss Society of Food Science and Technology 38 691-694. 

Davidson, B.E., Llanos, R.M., Cancilla, M.R., Redman, N.C., and Hillier, A.J. 1995. Current research on the genetics of lactic acid production in lactic acid bacteria. International Dairy Journal 5 763-784. 

Lactic acid bacteria and bifidobacteria are preferred as protective and probiotic cultures, and have been used since the beginning of history as starter cultures. They have a long history of being safely used and consumed. LAB are widely used for fermentation of milk, meat, and vegetable foods. In fermentation of dairy products, lactose is metabolized to lactic acid. Other metabolic products, hydrogen peroxide, diacetyl, and bacteriocins may also play inhibitory roles and contribute to improving the organoleptic attributes of these foods, as well as their preservation (Messens and De Vuyst, 2002). 

One example of fermentative bacteria is a group termed the lactic acid bacteria. These bacteria, which are commercially important in the cheese and dairy industry as well as in pickle and sauerkraut production, produce lactic acid by fermenting sugars. 

Shortly after their development in the 1940s, antibiotics were used in veterinary medicine, first to prevent or treat mastitis in cows and later for the treatment of other diseases. Initial concern about antibiotic residues in milk was not a public health issue but came from dairy processors who noticed inhibition of starter cultures used in the production of cheese and yogurt, thus generating a need for screening tests to examine milk for antibiotic residues. " Since inhibition of starter cultures by penicillin in milk was the main problem, the earliest microbial inhibition assays were based on growth inhibition of lactic acid bacteria. Spores of Bacillus species were also utilized spores are easier to handle and far more stable than the vegetative cells. 

Most polysaccharides used today are of plant origin. However, also bacteria produce polysaccharides. Especially extracellular polysaccharides (eps s) produced by lactic acid bacteria may find application in foods. Lactic acid bacteria are food-grade organisms and the eps s produced offer a wide variety of structures. The presence of eps is considered to contribute greatly to texture and structure of fermented milk products. An exopolysaccharide produced by Lactococcus lactis ssp. cremoris B40 was chosen as a subject of study. The eps was a gift from the Dutch Institute of Dairy Research (NIZO), Ede, the Netherlands. The eps had no gelling properties, could not be precipitated in plates by ethanol or cetylpyridinium chloride and did not show interaction with Congo red. 

G, Hugenholtz, J, et al. 2002. Mannitol production by lactic acid bacteria a review. International Dairy Journal, 12 151-61. 

Many dairy products are made through the process of fermentation. The quality of such products depends strongly on the cultures used with fermentation. The functional micro-organisms involved in these processes may have very different properties, but they are often lactic acid bacteria. Those cultures are referred to as starters . 

Can lactic acid bacteria (LAB) exopolysaccharides (EPSs) play a role in improving gastrointestinal health More specifically, can the EPSs serve another role by interacting with the human immune system or even the human microbiome itself More recent gains in knowledge of the mechanisms by which EPS interacts with the intestinal tract, the microbiome and immune function seem to present an additional nutritional role that is offered by fermented dairy products. 

Fermented dairy product Associated lactic acid bacteria... 

Cerning, J. (1995). Production of exopolysaccharides by lactic acid bacteria and dairy propion-ibacteria. Lait, 75(4-5), 463 72. 

Degeest, B., Vaningelgem, R, De Vuyst, L. (2001). Microbial physiology, fermentation kinetics, and process engineering of heteropolysaccharide production by lactic acid bacteria. International Dairy Journal, 11(9), 747-757. 

Van der Meulen, R., Grosu-Tudor, S., Mozzi, F, Vaningelgem, F., Zamfir, M., Font de Valdez, G., et al. (2007). Screening of lactic acid bacteria isolates from dairy and cereal products for exopolysaccharide production and genes involved. International Journal of Food Microbiology, 118(3), 250-258. 

Weerkamp, A. H., Klijn, N., Neeter, R., Smit, G. (1996). Properties of mesophiUc lactic acid bacteria from raw milk and naturally fermented raw milk products. Netherlands Milk and Dairy Journal, 50, 319-332. 

Wisselink, H. W., Weusthuis, R. A., Eggink, G., Hugenholtz, J., Grobben, G. J. (2002). Mannitol production by lactic acid bacteria a review. International Dairy Journal, 12(2—3), 151-161. 

Urbach, G. (1995). Contribution of lactic acid bacteria to flavour compound formation in dairy products. International Dairy Journal, 5(8), 877-903. 

Spermine (15) and spermidine (16) stimulate growth of Helianthus tuberosus in explant cultures, but are effective spore inhibitors against a number of fungi, including Pewici/-lium digitatum. Spermidine is used for stimulating lactic acid bacteria in the dairy industry. Polyamines are converted into a variety of products that are summarized in Fig. 28.11 (Slocum et al., 1984). 

---