Pre-fermentation processes

Pre-fermentation processing enzymes have been used for a long time by the wine and juice industries (van Rensburg and Pretorius, 2000). The first commercial enzyme preparations used were pectinases, enzymes responsible for the breakdown of pectin. Conventional application of pectinases pre-fermentation can enhance juice yield by degrading polysaccharides (e.g., pectin) that interfere with juice extraction. These preparations also improve the extraction of color (red wines) and flavor molecules trapped in grape skins as well as reduce the potential for post-fermentation instabilities. Newer commercial preparations may also contain secondary activities such as the ability to degrade cellulose to further enhance cell wall breakdown. 

Measured quantities of the pre-ferment are mixed with flour. The dough is then subjected to the combination of intense mixing and the action of the oxidising agent. It is then extruded and cut into loaf sized portions, proved and baked. Bread made by the Do-Maker process has a very even crumb texture, which is characteristic of the process. 

The AMFLOW process is similar to the Do-Maker process but the mixing chamber is horizontal rather than vertical. The pre-ferment stage is more complicated as it is multi-stage. 

We can illustrate fermentation processes using the process developed by Iogen to convert lignocellulosic materials such as wheat straw into ethanol (Fig. 2.10) [66]. The straw is chopped and milled prior to a steam-explosion pre-treatment to... 

A biotransformation, as defined by Straathof et al., ° is a process that describes a reaction or a set of simultaneous reactions in which a pre-formed precursor molecule is converted using enzymes and/or whole cells, or combinations thereof, either free or immobilised . Fermentation processes, with de novo product formation from a carbon and energy source, such as glucose via primary metabolism, are outside the scope of this chapter and book unless employed in conjunction with a biotransformation. 

Microbial production of secondary metabolites is also an important source of novel therapeutic agents. However, the physiological and biochemical factors that determine the onset of production of a specific secondary metabolite in a particular species are incompletely understood. Generally, a range of analytical techniques, often elaborate, time-consuming and involving extensive sample pre-treatment, have to be developed in order to monitor the details of the metabolic changes and substrate consumption that accompany secondary metabolite production. In order to provide rapid multi-parametric information about the microbial fermentation process, H HPLC-NMR has been applied to characterise microbial metabolites directly in the broth supernatants from a... 

The production of (-R)-PAC by fermenting yeast was one of the first industrially applied biotransformations, which is used to nowadays to obtain (R)-PAC as a chiral pre-step for L-ephedrine 2 [6-9] (Scheme 1), and the optimization of the fermentation process is still a matter of research [10 23],... 

The purpose of sample preparation is to create a processed sample that leads to better analytical results compared with the initial sample. The prepared sample should be an aliquot relatively free of interferences that is compatible with the HPLC method and that will not damage the column. The whole advanced analytical process can be wasted if an unsuitable preparation method has been employed before the sample reaches the chromatograph. Specifically, analytical work with samples from fermentation processes require a sample pre-treatment that eliminates the fermentation broth before the analytes can be injected into the chromatographic columns. This is primarily to remove macromolecular sample constituents, which easily clog the columns. Complex matrices often require a more selective sample preparation than for instance pharmaceutical solutions. In practice the choice of sample-preparation procedure is dependent on both the nature and size of the sample and on the selectivity of the separation and detection systems employed. Sample pre-treatment may includes a large number of methodologies. Ideally, sample preparation techniques should be fast, easy to use and inexpensive. In papers I and II careful sample pre-treatment was performed before all injections. 

Figure 13 (a). Chromatogram obtained from injection of pre-treated process liquid from the beginning of the fermentation process, detected at wavelength 245 nm. (b) The three dimensional spectra-chromatogram obtained with the DAD from the same injection as (a). 

The first of the separation techniques to be used in process measurement was gas chromatography (GC) in 1954. The GC has always been a robust instrument and this aided its transfer to the process environment. The differences between laboratory GC and process GC instruments are important. With process GC, the sample is transferred directly from the process stream to the instrument. Instead of an inlet septum, process GC has a valve, which is critical for repetitively and reproducibly transferring a precise volume of sample into the volatiliser and thence into the carrier gas. This valve is also used to intermittently introduce a reference sample for calibration purposes. Instead of one column and a temperature ramp, the set up involves many columns under isothermal conditions. The more usual column types are open tubular, as these are efficient and analysis is more rapid than with packed columns. A pre-column is often used to trap unwanted contaminants, e.g. water, and it is backflushed while the rest of the sample is sent on to the analysis column. The universal detector - thermal conductivity detector (TCD)-is most often used in process GC but also popular are the FID, PID, ECD, FPD and of course MS. Process GC is used extensively in the petroleum industry, in environmental analysis of air and water samples" and in the chemical industry with the incorporation of sample extraction or preparation on-line. It is also applied for on-line monitoring of volatile products during fermentation processes" ... 

Addition to the food processing of a pre-fermented food containing bacteriocinogenic... 

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