Lactic starter cultures, production

As shown in Table I, antibiotics may be added to foods directly for technological reasons, indirectly through treated animals and feeds or naturally through lactic starter culture biosynthesis. Recent increases in antibiotic use for food production as well as for disease control poses certain risks. 

The production of natural antibiotics by lactic starter cultures has been well documented (40) Some of these compounds have been isolated and identified as noted in Table IX. 

Batish, V. K., Grover, S., Lai, R. (1989). Screening lactic starter cultures for antifungal activity. Cultured Dairy Products Journal, 24, 21-25. 

Staphylococcus aureus > Salmonella spp. and Clostridium botullnum (22) In the case of the latter, the combination of lactic starter with either sucrose or dextrose has proven effective in preventing toxin production even without nitrite (23, 24). Table IV illustrates the Inhibitory effect of lactic cultures on the growth and production of enterotoxin by staphylococci in dry sausage (25) ... 

The primary function of cheese starter cultures is to produce lactic acid at a predictable and dependable rate. The metabolism of lactose is summarized in Figure 10.12. Most cheese starters are homofermentative, i.e. produce only lactic acid, usually the L-isomer Leuconostoc species are heterofermentative. The products of lactic acid bacteria are summarized in Table 10.4. 

Milk can be converted easily by lactic acid starter cultures into various cultured and culture-containing milk products. Within the last ten years, consumption of these products (e.g., yogurt, sour cream, and acidophilus milk) has increased appreciably in the United States. (Rasic and Kurmann 1978 Shahani and Chandan 1979 Helferich and... 

The most important fermentative reaction used in dairy processing is the homofermentative conversion of lactose to lactic acid. The efficient manufacture of high-quality cultured products, including most cheese varieties, yogurt, and cultured buttermilk, requires a rapid and consistent rate of lactic acid production. Lactic acid helps to preserve, contributes to the flavor, and modifies the texture of these products. Nearly all starter cultures used to produce acidified dairy products contain one or more strains of lactic streptococci, because these organisms can produce the desired acidity without causing detrimental changes in flavor or texture. Strains of lactic streptococci can be classified as... 

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. 

Microorganisms are, however, also used to produce and finish foodstuffs and to preserve them by fermentation (c.f. chapter 2.2 and 3.2.1.1.2). The production of high quality beer or wine would be inconceivable without yeasts. Cured sausages with their typical lactic acid starter cultures and sometimes with mould cultures on their surface also depend on microorganisms. 

Foods that include the incorporation of microbial metabolites as part of their production are an intricate component of the world s food supply and for ethical and sensory-nutritional reasons it is essential for all the world s population to have access to this form of food. It is a process that has been in use since the early history of mankind. An Egyptian pot dating from 2300 BC (McGee, 1984) was found to contain residues of cheese and in passages in the Bible the use of some kind of fermentative starter culture is indicated. It is, therefore, possible that the use of bacteria such as the lactic acid bacteria (LAB) dates back at least four to five thousand years, although the exact principle behind the process may not have been known to the civilizations of those times (Davidson et al., 1995). Production of fermented foods, where organisms such as the LAB are involved, is a technological process that has been used for centuries at least (Herreros et al., 2005). 

Gelman, A., Drabkin, V., and Glatman, L. 2000. Evaluation of lactic acid bacteria, isolated from lightly preserved fish products, as starter cultures for new fish-based food products. Innovative Food Science and Emerging Technologies 1 219-226. 

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). 

Low Molecular Weight Carbonyl Compounds. In the dairy field, a major product made this way is starter distillate. The main component is diaceyl which is a very important aroma compound responsible for the characteristic buttery flavor of fermented dairy products such as sour cream or buttermilk. The dairy industry relies upon fermentation by lactic streptococci for the production of diacetyl in cultured products. Starter distillate is a natural product rich in diacetyl which is produced by distilling such lactic cultures. The key intermediate in the biosynthesis of diacetyl is aL-acetolactic acid which is decarboxylated to form diacetyl (Figure 3). The starting material of the biosynthetic pathway is citrate which is a natural component of milk. 

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