Fermentation rates

In baked products, salt controls fermentation (qv) by retarding yeast activity, preventing wild fermentation, important in making a uniform product. During pickle-making, salt brine is gradually increased in concentration, reducing the fermentation rate as the process proceeds to completion. Salt is also... 

Significant differences are also apparent for the effect of pH on the fermentation rate. The narrow pH optimum characteristic of a free cell system is replaced by an extremely broad range upon immobilisation. This effect stems from the gradient pH that exists within the bead. 

DEBRANCHING ENZYME AMYLOSUCRASE Anaerobic fermentation rate,... 

Pure Yeast Culture. Recheck population periodically for purity. If a wild yeast population builds up significantly, discard the culture and begin again from a slant. Some wineries are using mass pitching techniques with dry or frozen yeast very successfully. This eliminates the need for any monitoring of culture population. Wild yeasts often cause unreliable and erratic fermentation rates, and this is often accompanied by off odors and off flavors in the wine. Erratic fermentations also often invite bacterial contamination. 

Ethyl acetate, added prior to fermentation in amounts up to 3%, caused delays in the onset of fermentation proportional to the amount added, but once begun, the fermentation rate was unaffected. When the same levels of ethyl acetate were added to an active fermentation, the fermentation period was sluggish. 

Besides volatile solvents, fermentation with Clostridium acetobutyli-cum yields an appreciable amount of riboflavin. The medium should contain 1.5 and 2.0 ppm iron (Meade et al. 1945) and certain salts of organic acids or calcium carbonate (Yamasaki 1939, 1941 Yamasaki and Yositome 1938) for maximal synthesis of riboflavin and greatest fermentation rates. 

C. acetobutylicum is not too exacting in its growth requirements. Asparagine is needed to effect normal production of solvents in what otherwise would be an acid fermentation. Both biotin and p-aminoben-zoic acid are required in trace quantities, 0.001 and 0.05 /xg/ml, respectively. Iron is essential in small but variable quantities for attainment of maximal fermentation rates (Leviton 1946,1949 Meade et al. 1945). The requirement for iron varies with the composition of the medium potassium is also required (Davies 1942A.B, 1943 Davies and Ste-... 

Monitoring of fermentation rates Process control in food, beverage, and drug industries... 

Romani et al. (2011) also evaluated the yeast population dynamics and fermentation kinetics, and their influences on the analytical profiles of Vin Santo obtained at industrial scale utilizing in separate trials two non-Saccharomyces yeasts, T. delbrueckii and Z. bailii. These results were compared with those obtained both with spontaneous fermentation and with an inoculum of a S. cerevisiae yeast strain. The standard kinetics of fermentations were observed in all of the trials, also if a higher fermentation rate was observed in the trials inoculated with S. cerevisiae compared to those inoculated with the two non-Saccharomyces yeasts, and in the spontaneous one. A rapid decrease in non-Saccharomyces yeast was observed in the trials inoculated with S. cerevisiae. In these last ones, after 6 months, 18.4% ethanol was reached versus 16% of the trials inoculated with the non-Saccharomyces strains. No substantial differences were seen for the higher alcohols or other byproducts assayed. 

Mead is a traditional alcoholic beverage obtained by fermenting mead wort that contains 8-18% (v/v) ethanol. Its production has been known since ancient times. However, mead fermentation and maturation requires an extended period, often lasting several months to years. Mead still remains a relatively empirical and manual exercise, requiring large capacity vessels and the investment of considerable capital in terms of the raw material. In addition, the fermentation rate depends on several factors, such as honey variety, yeast strain, yeast nutrition, and pH. Due to the lack of scientific investigation, mead production has suffered in comparison with other alcoholic beverages and so more research is needed to optimize the production process. 

However, for mead production to become profitable, it is necessary to decrease production time. A major concern in mead fermentation is the notoriously long period required to reach completion. Although fermentation rate depends on the honey variety and its characteristics, through proper selection of yeast strain and fermentation conditions, such as, mixing during fermentation, yeast nutrition, and pH s control, it may be possible to dramatically increase fermentation rate. 

S. uvarum is characterized by several authors as a cryotolerant yeast, showing good growth and fermentation rate at low temperatures (7-13 °C e.g., Castellari et al., 1994 Kishimoto and Goto, 1995). 

The high sugar content of the juice dramatically reduces the growth, fermentation rate, and survival of yeasts (Dittrich, 1977 Lafon-Lafourcade, 1983) and also affects secondary metabolism. Acetic acid... 

The fermentors used in most regions are stainless steel tanks, although wooden barrels are still widely used in Sauternes and Tokaj. The addition of thiamin (0.6 mg/1), diammonium phosphate (300 mg/1), and active dry yeast (10-15 g/hl) is recommended to achieve an optimal fermentation rate, more rapid yeast propagation and reduce SO2 requirements (Dubourdieu, 1999 Hoersch and Schlotter, 1990). 

The rates of chemical processes usually increase in the range 1.5-3.0, and biological processes by a factor of 2.0, for a 10°C increase, respectively (Brezonik, 1994). The most common way, not necessarily the best, of dealing with the temperature dependence of biological processes began with a study of fermentation rates (Berthelot, 1862), where it was suggested that since rate increases with temperature, k at T + 1 is greater than k at T — 1 by a fixed proportion. It has become common to use a ratio over a 10° difference, or what is called the gio, defined as follows ... 

Variables in alcoholic fermentation, the yeast-enzyme conversion of grape sugar to ethanol and carbon dioxide, have a major impact on the character, composition, and quality of North Coast white table wines. Type of yeast, juice solids content, juice S02 content, juice protein content, fermentation temperature, and fermentation rate are factors the enologist may consider and control. 

Fermentation Rate, Wine Composition and Wine Quality, Am.J. Enol. Vitic. 1978, 29, 112-119. 

Currently, research Is In progress to Increase the fermentation rate so that the starch solution will be ready for use within 3 days Instead of 14 days. 

Ough, C.S., (1964). Fermentation rates of juice.l. Effects of temperature and composition on white juice fermentation rates. Am. J. Enol. Vitic., 15, 167-177. 

Fermentation rates have been observed to increase when fermentation is carried out in the presence of wood chips, presumably because the oak chips act as carriers for the yeasts, resulting in the formation of higher quantities of acetates and fatty acid esters, which may help impart a more fruity aroma to wood chip-treated wines (P6rez-Coello et al. 2000b). 

Delfini, C., Costa, A. (1993) Effects of the grape must lees and insoluble materials on the alcoholic fermentation rate and the production of acetic acid, pyruvic acid, and acetaldehyde. American Journal ofEnology and Viticulture, 44, 86-92. 

Houtman, A. C., Du Plessis, C. S. (1981) The effect of juice clarity and several conditions promoting yeast growth on fermentation rate, the production of aroma components and wine quality. South African Journal of Enology and Viticulture, 2, 71-81. 

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