Yeasts starter cultures

The calculated amount of S02 is added and mixed thoroughly with the grapes, and the opening of the vessel is covered with a cloth to prevent the entry of insects. After 2-4 hrs the pure-yeast starter culture is added—again with stirring so that there is thorough mixing. The cloth cover is replaced. Active fermentation will be apparent within a day or so. 

Henick-Kling, T., Edinger, W., Daniel, P., and Monk, P. (1998). Selective effects of sulfur dioxide and yeast starter culture addition on indigenous yeast populations and sensory characteristics of wine. J. Appl. Microbiol. 84, 865-876. 

In many countries, alcoholic fermentation is induced by inoculation with a yeast starter culture of Saccharomyces selected for its desirable winemaking qualities (Kunkee, 1984 Kunkee and Bisson, 1993 Rainieri and Pretorius, 2000 Reed and Chen, 1978 Reed and Nagodawithana, 1988). Starter cultures of S. cerevisiae strains are generally used because of to their increased ethanol and sulfur dioxide resistance and production of desirable aromas and flavors (Boulton et al., 1996 Ebeler, 2001 Nykanen, 1986 Reed and Chen, 1978 Reed and Nagodawithana, 1988). 

Mateo, J. J. Jimenez, M. Pastor, A. Huerta, T. (2001). Yeast starter cultures affecting wine fermentation and volatiles. Food Research International, Vol.34, No.4, (April 2001), pp.307-314, ISSN 0963-9969... 

Ammonium sulphate Bacteria (MLF starter culture) Diammonium phosphate Diatomaceous earth Yeast (starter culture and ghosts)... 

Successful cultivation of microorganisms for growth and identification requires use of various types of media, either liquid (referred to as hroths) or solid by inclusion of agar. For winemakers, a growth medium may he as simple as diluted sterile grape juice for the activation and expansion of yeast starter cultures or as complicated as that necessary to grow lactic acid bacteria. 

Commercially available yeast extracts are made from brewers yeast, from bakers yeast, from alcohol-grown yeast (C. utilis) and from whey grown yeast (K fragilis). Extracts are used ia fermentation media for productioa of antibiotics, ia cheese starter cultures, and ia the productioa of viaegar. They are also exteasively used ia the food iadustry as condiments to provide savory flavors for soups, gravies and bouillon cubes, and as flavor intensifiers ia cheese products. 

Yeast and culture starter Lactobacillus bulgaricus Lactic acid bacteria Cheese and yoghurt production... 

If the culture is to provide both the yeast and the flavour of sour dough then either it must acquire a wild yeast or a starter culture that includes yeast must be added. In some cases the sour dough culture is only used to give the sour dough taste while conventional yeast is added. 

To limit this possibility, Torulaspora delbrueckii, in mixed or sequential culture with S. cerevisiae, has been proposed for fermentation (Bely et al., 2008 Ciani et ah, 2006 Lafon-Lafourcade et ah, 1981 Renault et ah, 2009). Although this yeast generates little alcohol, its application in mixed starter cultures is promising. It may also reduce the accumulation of other undesirable by-products, such as acetaldehyde, ethyl acetate, and acetoin. 

Henick-Kling, T, Park, Y.H. (1994). Considerations fort he use of yeast and bacterial starter cultures SO2 and timing of inoculation. Am. J. Enol. Vitic., 45, 464 69. 

Ugliano, M. Moio, L. (2005). Changes in the concentration of yeast-derived volatile compounds of red wine during malolactic fermentation with four commercial starter cultures of Oenococ-cus oeni.J. Agric. Food Chem., 53, 10134-10139. 

Table 8D.4 Types of yeasts and starter cultures used in winemaking...

Starter culture Yeast species Wine characteristics... 

Fermentation can be spontaneous or be induced by specifically added microorganisms. An everyday example of such an induced fermentation is the addition of baking yeast to flour to make bread or cakes. As with bread, fermentation can be done in a normal environment where many different microorganisms are present. A more sophisticated way is to exclude unwanted microorganisms by sterilization of the materials before adding a starter culture. 

Cell mass Yeast, lactic acid bacteria, single cell protein Used as starter cultures, animal feed... 

To a limited extent a starter culture once established can be propagated on site (sour dough, yoghurt cultures, yeast in the brewery). 

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. 

Swiss cheeses are distinguished from other varieties by different starter cultures used and the subsequent growth of propionibacteria with gruyere cheeses, yeasts and coryneforms. Fermentation of lactic acid and residual sugars by propionic bacteria to propionic acid is vital in flavor development, and follows initial lactic acid fermentation by the starters. The propionibacteria also apparently contain peptidases which release the sweet-tasting amino acid proline, according to some investigators(13), an important Swiss cheese tastant. 

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