Lactic acid bacteria characteristics

The inability to obtain complete protein sequence analysis of purified bacteriocins has been reason to suspect the presence of N-blocked peptide sequences (34) or lantibiotic residues (14). Recently, Piard et al. (14) have shown from partial sequencing and composition analysis that lacticin 481, a broad spectrum bacteriocin produced by L. lactis 481, also contains lanthionine residues. The early widespread interest in nisin and nisin-producing strains had given the impression that lantibiotics may be characteristic of bacteriocins of lactic acid bacteria. However, recent studies with other LAB bacteriocins suggest that simple peptide bacteriocins may prevail among the LAB. 

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. 

Cultured buttermilk is manufactured by fermenting whole milk, reconstituted nonfat dry milk, partly skimmed milk, or skim milk with lactic acid bacteria. Most commercial cultured buttermilk is made from skim milk. Mixed strains of lactic streptococci are used to produce lactic acid and leuconostocs for development of the characteristic diacetyl flavor and aroma. Buttermilk is similar to skim milk in composition, except that it contains about 0.9% total acid expressed as lactic acid. The percentage of lactose normally found in skim milk is reduced in proportion to the percentage of lactic acid in the buttermilk. According to White (1978), the fat content of buttermilk usually varies from 1 to 1.8%, sometimes in the form of small flakes or granules to simulate churned buttermilk, the by-product of butter churning. Usually 0.1% salt is added. 

Dyachenko, P. F., Shchedushnov, E. V. and Nassib, T. G. 1970. Characteristics of proteolytic activity of thermophilic lactic acid bacteria used for cheesemaking. XVIII Int. Dairy Congr. IE, 274. 

This is the main reaction of MLR Chemically it consists of a simple decarboxylation of the L-malic acid in wine into L-lactic acid. Biochemically, it is the result of activity of the malolactic enzyme, characteristic of lactic acid bacteria. This transformation has a dual effect. On the one hand, it deacidifies the wine, in other words, it raises the pH, an effect that is greater at higher initial quantities of malic acid. It also gives the wine a smoother taste, replacing the acidic and astringent flavour of the malic acid, by the smoother flavour of the lactic acid. 

As well as fruity and buttery aromas, MLF has also been associated with other characteristic aromas such as floral, roasted, vanilla, sweet, woody, smoked, bitter, honey, etc. (Flenick-Kling 1993 Sauvageot and Vivier 1997). However, further studies are required to be able to relate the wine characteristics that are modified during malolactic fermentation with the production and/or degradation of a specific chemical compound by wine lactic acid bacteria. With this information, the winemaker can choose the best strain of lactic acid bacteria to obtain wine with a specific aroma or flavour. 

Nettles, C.G. and Barefoot, S.F. 1993. Biochemical and genetic characteristics of bacteriocins of food-associated lactic acid bacteria. J. Food Prot. 56, 338-356. 

Lactic acid is a major end product from fermentation of a carbohydrate by lactic acid bacteria (Tormo and Izco, 2004). However, lactic acid can be produced commercially by either chemical synthesis or fermentation. The chemical synthesis results in a racemic mixture of the two isomers whereas during fermentation an optically pure form of lactic acid is produced. However, this may depend on the microorganisms, fermentation substrates, and fermentation conditions. Lactic acid can be produced from renewable materials by various species of the fungus Rhizopus. This has many advantages as opposed to bacterial production because of amylolytic characteristics, low nutrient requirements, and the fungal biomass, which is a valuable fermentation by-product (Zhan, Jin, and Kelly, 2007). 

Cai, Y., Benno, Y., Ogawa, M., and Kumai, S. 1999. Effect of applying lactic acid bacteria isolated from forage crops on fermentation characteristics and aerobic deterioration of silage. Journal of Dairy Science 82 520-526. 

Volatile phenols originate from hydroxycinnamic acids (ferulic, p-coumaric, or caffeic acid) by the action of hydroxycinnamate decarboxylase enzyme, which turn the hydroxycinnamics acid into vinylphe-nols (Albagnac, 1975 Grando et al., 1993). Then, these compounds are reduced to ethyl derivatives by vinylphenol reductase enzymes characteristic of species, such as Dekkera bruxellensis, Dekkera anomala, Pichia guillermondii, Candida versatilis, Candida halophila, and Candida mannitofaciens (Edlin et al., 1995 1998 Dias et al., 2003 Chatonnet et al., 1992 1995 1997 Dias et al., 2003), apart from very small quantities produced by some yeasts and lactic acid bacteria under peculiar growth conditions (Chatonnet et al., 1995 Barata et al., 2006 ... 

The growth of microorganisms may have an important effect on the flavour of food. An example is the lactic acid bacteria Lactococcus lactis, which produce mainly lactate providing a characteristic acidic flavour and contributing to the preservation of fermented food. In an innovative approach, in situ 13C NMR was used to investigate glycolysis by an L. lactis strain deficient in lactate dehydrogenase.272... 

Reis, J., Paula, A., Casarotti, S., and Penna, A. (2012) Lactic acid bacteria antimicrobial compounds characteristics and apphcations. Food Eng. Rev., 4, 124-140. 

Nguyen, T.T.T., Loiseau, G., Icard-Verni re, C., Rochette, I. et al. (2007) Effect of fermentation by amy-lolytic lactic acid bacteria, in process combinations, on characteristics of rice/soybean slurries a new method for preparing high energy density complementary foods for young children. Food Chem., 100, 623-631. 

Eresh fruits are strongly recommended in the human diet since they are rich in vitamins, dietary fibres, minerals and antioxidants. In particular, sweet cherries contain remarkable contents of polyphenols, such as anthocyanins, which give them the characteristic colour and antioxidant properties. Fermentation can further enhance the antioxidant properties of sweet cherries. Sweet cherry Prunusavium L.) puree fermented by selected autochthonous lactic acid bacteria (L. plantarum, Pediococ-cus acidilactici, Pediococcus pentosaceus and Leuconostoc mesenteroides subsp. mesenteroides) at 25 C for 36h has been reported to exhibit significantly higher DPPH radical-scavenging capacity compared to unfermented sweet cherry puree (Cagno etal., 2011). 

Table 13.1 Lactic acid bacteria metabolic groups and tbeir characteristics (Hammes Vogel, 1995)...

Weckx, S., Van derMenlen, R., Maes, D. S. I., Huys, G., Vandamme, P. D. V.L. (2010). Lactic acid bacteria commnnity dynamics and metabolite production of rye sourdough fermentations share characteristics of wheat and spelt sourdough fermentations. Food Microbiology, 27, 1000-1008. 

Chang, J. H., Shim, Y. Y, Cha, S. K., Chee, K. M. (2010). Probiotic characteristics of lactic acid bacteria isolated from kimchi. Journal of Applied Microbiology, 109, 220-230. DaescheL M. A., Andersson, R. E., Fleming, H. P. (1987). Microbial ecology of fermenting plant materials. FEMS Microbiology Reviews, 46, 357-367. 

Nakagawa, A. (1978). Beer-spoilage lactic acid bacteria - principal characteristics and simple methods of their selective detection. Bulletin of Brewing Science, 24, 1-10. 

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