Maltose fermentation

FlC. 1.—Relative Rates of Activity Against Glycosides at Various pH Values. [A. Hydrolysis of sucrose by /3-D-fructofuranosidase of Saccharomyces cerevisiae O, intact cells and A, toluene-treated cells (results of Wilkes and Palmer40). B. Maltose , fermentation by intact baker s yeast A, hydrolysis by a-D-glucosidase (results of Hestrin41 see also Ref. 42).]... 

Palacios, J. and Serrano, R. (1978). Proton permeability induced by polyene antibiotics. Aplausible mechanism for their inhibition of maltose fermentation in yealsEBS Lett, 91,198-201. 

Sutton D. D. and Dampen J. O. (1962) Localization of sucrose and maltose fermenting systems in Saccharomyces cerevi-siae. Biochim. Biophys. Acta 56, 303-312. 

Arrow-root starch (500 g.) in 8 liters of water containing 1 g. of sodium chloride was hydrolyzed at pH 6.5 with 50 ml. of saliva. After twenty-four hours, 50% of maltose had been formed. The reaction mixture was kept under toluene for thirty-two days. The reducing power then corresponded to 89% maltose. Fermentation experiments, however, showed that 63% maltose and 14% D-glucose had been formed, the latter by the secondary action of maltase. As mentioned above, the salivary amylase does not form D-glucose as a primary product but differs in this respect from malt a-amylase. The pancreatic enzyme is... 

The heat evolution on maltose fermentation can be approximated by multiplying the figure for glucose by two and adding the further 15.9 kj/mole required for maltose hydrolysis (Eq. 16.9). Fermentation temperatures of 15-18°C are desirable for beer production. 

The sedimentary yeast forms a solid plug at the base of the vessel and through it the wort permeates. Some of the yeast is carried upwards by the flow of wort and by the dispersing of the yeast floes by maltose. Fermentation proceeds as the wort rises, with the rate of wort injection being so adjusted that at the top of the tower the wort is completely fermented. Yeast tends to fall from suspension in this region aided by an inclined chute provided near the beer... 

Kodama, Y., Fukui, N., Ashikari, T., Shibano, Y, Morioka-Fujimoto, K., Hiraki, Y, et al. (1995). Improvement of maltose fermentation efficiency constitutive expression of MAE genes in brewing yeasts. Journal of the American Society of Brewing Chemists, 53, 24-29. 

Fermentabihty of com symps by yeast is important in certain food appHcations, eg, baking and brewing. The fermentable sugars present in corn symp are dextrose, maltose, and maltotriose. Fermentabihty of maltose or maltotriose depends on the specific fermentation process and organism. In general, greater fermentabihty is obtained at higher DE levels. 

In the canning and preserving industries, com symps are used to prevent crystallization of sucrose, provide body, accentuate tme fmit flavors, and improve color and texture. In the beverage industry, the predominant use is in the beer and malt-Hquor areas. High conversion symps are used to replace dry cereal adjuncts, provide fermentable sugars, enhance flavor, and provide body. These symps contain controlled amounts of dextrose and maltose for proper fermentation. 

Fermentable Sugars. Fermentable sugars like glucose [50-99-7]., maltose [69-79-4]., and maltotriose [1109-28-0] can be fermented by distiUer s... 

Yeast (qv) metabolize maltose and glucose sugars via the Embden-Meyerhof pathway to pymvate, and via acetaldehyde to ethanol. AH distiUers yeast strains can be expected to produce 6% (v/v) ethanol from a mash containing 11% (w/v) starch. Ethanol concentration up to 18% can be tolerated by some yeasts. Secondary products (congeners) arise during fermentation and are retained in the distiUation of whiskey. These include aldehydes, esters, and higher alcohols (fusel oHs). NaturaHy occurring lactic acid bacteria may simultaneously ferment within the mash and contribute to the whiskey flavor profile. 

The converted mash is pumped to a clean sterilised fermentor and the yeast inoculum is added. The set temperature range for whiskey fermentation of 72 hours is usually 17—21°C. At the beginning, the mash converted composition is approximately 80% sugars, mainly maltose and some (<1%) dextrose (primary conversion). The pH is adjusted to reduce initial bacterial growth. Grain neutral spidts are usually set at 27—29°C to expedite fermentation. Temperatures above 35°C inhibit yeast reproduction and promote rapid bacterial growth. Above 40°C actual yeast kill occurs. 

After 30 hours, the maximum and critical fermentation is underway and the pH must remain above 4.0 for optimal fermentation. However, accompanying bacterial contamination from various sources such as yeast contamination, improper cleaning procedures, slow yeast growth, or excessive temperatures can result in a pH below 4.0. The remaining amylase enzymes, referred to as secondary conversion agents, are inactivated and can no longer convert the dextrins to maltose. Under these circumstances, the fermentor pH continues to drop because of acid production of the bacteria, and the pH can drop to as low as 3.0. The obvious result is a low ethanol yield and quaUty deterioration. 

Despite the similarities of their structures, cellobiose and maltose have dramatically different biological properties. Cellobiose can t be digested by humans and can t be fermented by yeast. Maltose, however, is digested without difficulty and is fermented readily. 

The distinctive aroma of ammonia is often apparent in bakeries but not in the final product. Bakers yeast performs its leavening function by fermenting such sugars as glucose, fructose, maltose, and sucrose. The principal products of the fermentation process are carbon dioxide gas and ethanol, an important component of the aroma of freshly baked bread. The fermentation of the sugar, glucose—an example of a decomposition reaction — is given by the equation in Fig. 5.19.1. 

Glucose or maltose by selective fermentation with washed baker s yeast dextrine by difference. b Average degrees of polymerization of dextrine were calculated from their reducing values as follows ... 

Time (minutes) Color with iodine Theoretical maltose from reducing valuea Glucose linkages hydro- lyzed Fermentable sugar Dextrins ... 

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