Alcoholic fermentation impact

A new method for the preparation of soy sauce has been developed. The new scaled-up method divides the moromi process into two processes autolysis and fermentation. Because of the utilization of high temperatures, the new process permits the production of a NaCl free autolyzate from koji. Division of the fermentation process into two separated processes permit better control of lactic acid fermentation and alcohol fermentation processed which used to require great skill. The new scale-up procedure for soy sauce production yields a product in half the time required by the traditional (conventional) method and still produces a soy sauce with high levels of the desirable Bavor component, glutamic acid. Utilization of this protocol by the soy sauce producing industry should have significant economic impact to bo producers and consumers. 

The unique chemical composition of botrytized must greatly impacts the products and by-products of alcoholic fermentation, as well as subsequent reactions. The changes have been extensively studied by German and French authors and have been reviewed by Dittrich (1977, 1989), Jackson (2008), Ribereau-Gayon et al. (2000), and Dittrich and Grossmann (2011). The chemical composition of some traditional (German and Hungarian) botrytized wine styles are illustrated in Table 6.5. 

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. 

The yeast strain used for fermentation had no impact on the enantiomer distribution of these volatile thiols. 3SHA is generally considered to be formed by esterification of 3SH by yeast during alcoholic fermentation. The esterase or lipase involved probably acetylates 3SH with a certain enantioselectivity. In contrast, the enantiomer distribution of 3SH in wine made from botrytized grapes (Botrytis cinerea) is 25 75 in favor of the S form, which has also been found in botrytized must (Thibon et al. 2007,2008a). 

Bataillon, M., Rico, A., Sablayrolles, J.-M., Salmon, J.-M., Barre, R (1996) Early thiamin assimilation by yeasts under enological conditions impact of alcoholic fermentation kinetics. Journal of Fermentation and Bioengineering, 82, 145-150. 

Methanol is always present in wine in very small quantities, between 30 and 35 mg/1. It has no organoleptic impact. Methanol is not formed by alcoholic fermentation, but results exclusively from enzymic hydrolysis of the methoxyl groups of the pectins during fermentation ... 

Although 2,3-butanediol is a C4 molecule (Table 2.3) it is really a diol. It is a by-product of alcoholic fermentation and is probably also formed by malolactic fermentation. This compound has little odor and its flavor is slightly sweet and bitter at the same time, but it does not have much organoleptic impact in wine. It is stable, and, above all, unaffected by bacteria. 

Figure 9.14 Potential targets for wine yeast strain development. The primary role of wine yeast is to conduct the alcoholic fermentation during which grape sugars (mainly glucose and fructose) are converted into ethanol, carbon dioxide and other minor, but important, metabolites. The main emphasis in strain development programmes is on the development of Saccharomyces cerevisiae strains with improved fermentation, processing and biopreservation abilities, and the capacity to enhance the wholesomeness and sensory quality of wine. It is hoped that such genetically improved yeast strains could enhance cost-effective production of wine with minimised resource inputs, improved quality and low environmental impact. Adapted from Pretorius (2000).

Lysozyme s application is directed primarily toward white wines for the control of LAB. Unlike compounds previously discussed, lysozyme exhibits activity toward all species and strains of LAB studied. At its suggested use level of 250-500 mg/L, the enzyme preparation may be added before alcoholic fermentation to prevent MLF, at some time during MLF, or upon completion to prevent subsequent activity of unwanted LAB. Its activity is not affected by ethanol, although upon reaction with tannin and pigment complexes, activity decreases (Villa, 1996). Similarly, bentonite dramatically decreases activity. In white juice, this ranged from 37% reduction after bentonite additions of 0.25 g/L to complete inactivation with additions of 1 g/L. In white wines, the impact of bentonite was less, ranging from 10% reduction with 0.25 g/L to 75% reduction at 1.0 g/L. The effect of sulfur dioxide additions in white wine was also investigated. In this case. Villa reports that SO2 at 80 mg/L had an indirect effect on lysozyme activity... 

Adding sulfur dioxide when the must is put into vat also has an impact on malolactic fermentation. The fermentation may be delayed to a variable extent, depending on the concentration of sulfur dioxide used and the way it is mixed into the must (Section 8.8.1) and may, in extreme cases, even be permanently inhibited. The concentration chosen must be sufficient to retard malolactic fermentation, to avoid its interference with alcoholic fermentation and the associated risks, but not so excessive that the malolactic fermentation cannot be completed within a reasonable time period. 

Foam Control. Fermentations tend to froth because metabolites have surfactant properties. Prevention commonly is by addition of antifoam agents such as oils, heavy alcohols, fatty acids, or silicones. High-speed rotating impellers destroy bubbles by direct impact and by throwing them against the wall of the vessel. 

The third and fourth influential factors on wine aroma chemistry arise from the problems caused by the matrix on both the isolation and preconcentration of molecules and on the sensory assessment of the role played by the impact odorants. The presence of major volatiles, such as ethanol and fusel alcohols, complicates the isolation of the other wine odorants, particularly of those present at low levels. This has a marked influence on the way in which the extracts for screening and for further qualitative or quantitative studies should be prepared. On the other hand, ethanol and the major fermentation volatiles have also a deep influence on the way in which the odor chemicals are released and perceived. 

Another potentially adverse impact on fermentation ethanol markets is presented by the options available for the manufacture of mixed alcohols from synthesis gas. Sufficient experimental data have been accumulated to show how the alcohol yields and distributions can be manipulated and what catalysts and conditions are effective. Some of these data have established the utility of mixed alcohols as motor fuels and motor fuel components. 

Sugars are used as fermentation substrates to yield products such as lactic acid, citric acid, and ethanol. Ethanol can be used as a food product, as a food solvent, or as a source for energy. In very recent times, with rapidly escalating demand for power alcohol, concern over the economic impact of this latter usage has raised serious challenges to the availability of sufficient quantities of some cereal grains for food use [82]. 

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