Alcoholic fermentation parameters

A simple mathematical model is used for quantitative description of the process and consists of a set of equations relating inputs, outputs, and key parameters of the system. The model for an alcoholic fermentation fed-batch process developed by Mayer (10) and adapted with the Ghose and Tyagi (11) linear inhibition term by the product was used as the starting point for the development of a model-based substrate sensor with product (ethanol) and biomass on-line measurements. 

A set of alcoholic fermentations experiments was conducted in order to verify the performance of the model-based substrate sensor. Diluted molasses was used in the experiments as feed substrate and bread yeast, Saccharomyces cerevisiae, as inoculum. The operational conditions and kinetic parameters used are given in Table 1 for two different experiments (tests 1 and 2), and values of ethanol and biomass concentrations were also determined off-line using gas chromatography (CG) and dry cell weight standard (7) methods, respectively. 

Many aspects related to optimization of the ethanol production process have been addressed in previous works. A key to the optimization of a process is a thorough understanding of the system s dynamics, which can be obtained using an accurate model of the process. Atala et al. (1) developed a mathematical model for the alcoholic fermentation based on fundamental mass balances. The kinetic parameters were determined from experimental data and were described as functions of the temperature. The experiments were conducted with high biomass concentration and sugarcane molasses as substrate to simulate the real conditions in industrial units. 

The parameters were adjusted as functions of the temperature from the experimental data and are given in Table 1. The proposed model described the dynamic behavior of the alcoholic fermentation (1). 

As for grape dehydration, the management of alcoholic fermentation is still linked to traditional practices, which provide very poor control of the fermentation parameters, such as microbial population and temperature. 

In Vin Santo, due to the slow sugar metabolism, maturation already starts when the alcoholic fermentation has still not reached completion. Furthermore, depending on the initial sugar content and on the other process parameters, maturation of Vin Santo can generally last 2-i years, and in some case more (Tachis, 2003). 

Analysis of Fermentation Parameters of Wine 1.3.1. Alcoholic Fermentation... 

A Distributed Parameter Diffusion-Reaction Model for the Alcoholic Fermentation Process... 

A DISTRIBUTED PARAMETER DIFFUSION-REACTION MODEL FOR THE ALCOHOLIC FERMENTATION PROCESS... 

The following is an example for the development of a distributed parameter model for the yeast floe in the alcoholic fermentation process. The model takes into consideration the external mass transfer resistances, the mass transfer resistance through the cellular membrane, and the diffusion resistances inside the floe. The two-point boundary-value differential equations for the membrane are manipulated analytically, whereas the nonlinear two-point boundary-value dilferential equations of diffusion and reaction inside... 

Elnashaie, S. S. E. H. and Ibrahim, G. A distributed parameter diffusion reaction model for the alcoholic fermentation process. Appl. Biochemi. Biotechnol. 30(3), 339-358, 1991. 

Following alcoholic fermentation, the bacterial population remains in a latent phase for a varying period, which can last several months when the pH, ethanol and temperature parameters are at their lower limits. Usually, this phase lasts only for a... 

The duration of dry white wine fermentation depends on several parameters juice extraction conditions sugar and assimilable nitrogen concentrations turbidity yeast strain aeration and fermentation temperature. The winemaker can adjust and control all of them. A slow or stuck fermentation is most often the result of carelessness and always affects wine quality. The alcoholic fermentation of a white wine should not exceed 12 days. Longer fermentations should not be songht after except in the case of exceptionally high sngar concentrations. 

Let us carry out a so-called screening experiment in which we attempt to discover if the fermentation temperature (factor x ) has a significant effect on the response (% alcohol content). We will choose two levels of temperature, 23°C and 27°C. This is the minimal number of factor levels required to fit the two-parameter model... 

This volume is divided into eight chapters, by subject. Due to its multidisciplinary nature, analytical techniques are not described, apart from brief introductions to Chapters 7 and 8, to which readers are referred for more specific analytical chemistry books. Again, due to the enormous number of subjects discussed, only a brief summary of methods, including materials and instruments used, is given, and readers are referred to single publications. The main parameters of wine fermentation are treated in the first chapter, but discussion of volatile esters and higher alcohols were deemed to be more suitably located in Chapter 5 on aromatic compounds. 

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