Control starter bacteria

Figure 10.20 Formation of water-soluble nitrogen (WSN) in (A) Cheddar cheese with a controlled microflora (free of non-starter bacteria) (B) controlled microflora chemically-acidified (starter-free) cheese (C) controlled microflora, rennet-free cheese (D) controlled microflora, rennet-free, starter-free cheese.

MLF most commonly occurs after alcoholic fermentation but may occur simultaneously with the primary fermentation. Because relying on natural microflora can be unpredictable and difficult to control, starter cultures of pure strains of bacteria have been developed (Henick-Kling, 1993 Krieger et al., 1993 Kunkee et al., 1964 Nielsen et al., 1996 Pilone, 1995). Although selected strains of Lactobacillus can be inoculated, O. oeni is the primary species to conduct MLF because of acid tolerance and the flavor profile produced (Guzzo et al., 1994 Krieger et al., 1993 Kunkee et al., 1964 Liu, 2002 Nielsen et al., 1996 Wibowo et al., 1985). 

Bactericide A pesticide used to control or destroy bacteria Basal diet Ration for adults and starter ration for the young, appropriate to the species it should meet the standard nutritional requirement Base pair mutagens Chemicals or agents that produce a base change in the DNA BEA 2-Bromoethalamine BEI Biological exposure index BLL Blood lead level BEN Balkan endemic nephropathy... 

The traditional koji process may be considered the archetype of SSF. Koji is a generic Japanese name for starters used in a variety of fermentations its functional importance lies in its high content of various amylolytic and proteolytic enzymes which can catalyze the degradation of starches and proteins to soluble products capable of subsequent fermentation by yeasts or bacteria. A variety of raw materials are used in the production of kojis but, typically, steamed rice is inoculated with spores of an Aspergillus oryzae strain and incubated under carefully controlled conditions of temperature and humidity [7]. 

The PCR technique succeeds by the use of the DNA-dependent DNA polymerase from bacteria living in hot sources (taq-polymerase). This enzyme is able to elongate primers (oligonucleotide starter molecules) in a complementary pattern to a template DNA single strand at a temperature of about 70 °C. This high temperature is necessary in order to create a temperature-controlled three-step process. The whole process includes the following steps ... 

The regular use of well-defined starter cultures ensures a balanced yeast to lactic acid bacteria ratio. This contributes not only to the sensory properties, but at the same time the batch-to-batch variation in proofing time is reduced. As a consequence, the proofing time is easily controlled. 

The role of pH has diverse practical consequences in the control of the malolactic fermentation. First of all, the malolactic fennentation is initiated more easily and rapidly in press wines than in the corresponding free run wine. A partial chemical deacidification of wine may be advisable in the most difficult cases. It is especially recommended in the preparation of a malolactic fermentation starter—used for the inoculation of recalcitrant wine tanks. Finally, particular attention must be paid to musts and wines with elevated pHs. They sustain a more or less anarchic bacterial growth of a large variety of bacteria and are thus subject to spoilage. A sensible sulfiting is the only tool for controlling these microorganisms. 

The reactivation procedure previously described could be assumed to confer an indispensable characteristic to bacteria. It would therefore be very difficult (if not impossible) to obtain commercial preparations ready for use in wine. However, since 1993, Chr Hansen s Laboratory Danmark A/S has marketed a starter, under the name Viniflora Oenos, that can be inoculated directly into wine immediately after alcoholic fermentation. Experimental results obtained with this preparation in the laboratory and in the winery have shown that bacterial growth and malolactic fermentation can be obtained 15 days in advance, with respect to a control (Figure 12.14). No organoleptic flaws are observed. 

Wouters, D., Bernaert, N., Anno, N., et al. (2013) Application and validation of autochthonous lactic acid bacteria starter cultures for controlled leek fermentations and their influence on the antioxidant properties of leek. Int J Food Microbiol 165, 121-133. 

Lefeber, T., Janssens, M., Moens, E, et al. (201 lb) Interesting starter culture strains for controlled cocoa bean fermentation revealed by simulated cocoa pulp fermentations of cocoa-specific lactic acid bacteria. Appl Environ Microbiol 77, 6694-6698. 

LAB are the most important bacteria used in food fermentations and many LAB species are involved. Their presence results from either a natural, spontaneous contamination derived from the raw materials themselves or the environment, the inoculation by foods from a previous batch (a practice referred to as back slopping), a dehberate addition of cultures (starters), or a combination of these different sources (Table 19.2). Most fermented foods consumed in developing countries are manufactured from spontaneous fermentation, without addition of any starters (Tamang and Delwen 2010). However, food fermentations have evolved towards a systematic use of starters to control fermentation, and nowadays starter cultures are widely used in the manufacture of many fermented products, such as dairy products, sourdough, and fermented dry sausages (Leroy et al. 2006). 

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