Yeast generation

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. 

Conduct of Fermentation. The ameliorating material normally is added to the sulfited juice prior to the onset of fermentation and thoroughly mixed in. An actively fermenting yeast starter is added. The large wineries maintain a yeast generator for the propagation of a continuous supply origi-... 

The anaerobic fermentation of sugars by Saccharomyces wine yeasts generates a variety of volatile metabolites that contribute to the sensory profile of wine. The important compounds include esters, higher alcohols, volatile fatty acids, carbonyls, and volatile sulfur compounds. The accumulation of these compounds in wine depends on the strain of yeast, must composition (chemical, physical and nutrient composition) and fermentation conditions. In addition, a variety of... 

Two examples of Py-MS spectra dominated by the ions generated from the sugar moiety are the spectrum for a DNA sample from calf thymus obtained by Curie point Py-MS and El at 14 eV [8] (shown in Figure 13.2.1) and the Py-MS spectrum for a RNA sample from baker s yeast generated in the same experimental conditions [8] (shown in Figure 13.2.2). 

The reason why mnltiple yeast generations can have a negative effect on a culture s fermentation performance is nnclear. However, multiple generations will result in reduced levels of intracellular glycogen and an increase in trehalose, indicating additional stress conditions as the cycles progress (Table 2.3) (Boulton Qnain, 2001). 

In this thiamine pyrophosphate-mediated process, ben2aldehyde (29), added to fermenting yeast, reacts with acetaldehyde (qv) (30), generated from glucose by the biocatalyst, to yield (R)-l-phen5l-l-hydroxy-2-propanone (31). The en2ymatically induced chiral center of (31) helps in the asymmetric reductive (chemical) condensation with methylamine to yield (lR,23)-ephedrine [299-42-3] (32). Substituted ben2aldehyde derivatives react in the same manner (80). 

At 70—140°C, peroxide is vaporised. Peroxide vapor has been reported to rapidly inactivate pathogenic bacteria, yeast, and bacterial spores in very low concentrations (133). Experiments using peroxide vapor for space decontamination of rooms and biologic safety cabinets hold promise (134). The use of peroxide vapor and a plasma generated by radio frequency energy releasing free radicals, ions, excited atoms, and excited molecules in a sterilising chamber has been patented (135). 

FIGURE 12.37 Tertiary interactions in yeast phenylalanine tRNA. The molecnle is presented in the conventional cloverleaf secondary strnctnre generated by intrastrand hydrogen bonding. Solid lines connect bases that are hydrogen-bonded when this cloverleaf pattern is folded into the characteristic tRNA tertiary strnctnre (see also Figure 12.36). 

The term fermentation was obtained from the Latin verb fervere which describes the action of yeast or malt on sugar or fruit extracts and grain. The boiling is due to the production of carbon dioxide bubbles from the aqueous phase under the anaerobic catabolism of carbohydrates in the fermentation media. The art of fermentation is defined as the chemical transformation of organic compounds with the aid of enzymes. The ability of yeast to make alcohol was known to the Babylonians and Sumerians before 6000 bc. The Egyptians discovered the generation of carbon dioxide by brewer s yeast in the preparation... 

Action of yeast on extracts of fruit juice or, malted grain. The biochemical reactions are related to generation of energy by catabolism of organic compounds. 

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