Food production sequence

Metais, A. and Mariette, F. 2003. Determination of water self-diffusion coefficient in complex food products by low field h-1 PFG-NMR Comparison between the standard spin-echo sequence and the T-l-weighted spin-echo sequence. J. Magn. Reson. 165, 265-275. 

The example presented in section 6.4 of this chapter showed that process synthesis can be applied to structured food products. Moreover this application is of true value since significant cost savings could be achieved. However, a complete methodology is not yet available. One of the main outstanding questions is how to perform the identified (necessary) tasks in an optimal sequence to obtain the desired product Besides this the success of application depends critically on the availability of domain knowledge about all relevant aspects of the process. Several factors relevant for food processing were not considered in this example ... 

The following factors appear to control the emulsification properties of milk proteins in food product applications 1) the physico-chemical state of the proteins as influenced by pH, Ca and other polyvalent ions, denaturation, aggregation, enzyme modification, and conditions used to produce the emulsion 2) composition and processing conditions with respect to lipid-protein ratio, chemical emulsifiers, physical state of the fat phase, ionic activities, pH, and viscosity of the dispersion phase surrounding the fat globules and 3) the sequence and process for incorporating the respective components of the emulsion and for forming the emulsion. 

In the second group of mixer agglomeration techniques, powders are moistened to a much lesser extent than the wet capillary state. Relatively weak powder clusters are formed. An example is the moistening, equilibration, drying and cooling sequence used to produce instantized food products. 

Application of data obtained from simple clean reaction systems in biological or chemical studies of heme catalysis also has its problems. Chemical model systems use chelators, model hemes, and substrate structures that are quite different from those existing in foods. Reaction sequences change with heme, substrate, solvent, and reaction conditions. Intermediates are often difficult to detect (141), and derivations of mechanisms by measuring products and product distributions downstream can lead to erroneous or incomplete conclusions. It is no surprise, then, that there remains considerable controversy over heme catalysis mechanisms. Furthermore, mechanisms determined in these defined model systems with reaction times of seconds to minutes may or may not be relevant to lipid oxidation being measured in the complex matrices of foods stored for days or weeks under conditions where phospholipids, fatty acid composition, heme state, and postmortem chemistry complicate the oxidation once it is started (142). Hence, the mechanisms outlined below should be viewed as guides rather than absolutes. More research should be focused on determining, by kinetic and product analyses, which reactions actually occur and are of practical importance in specific food systems. 

The initiation and promotion of neoplastic transformation is followed by the final stage of the carcinogenic process, known as progression, which comprises the growth of the tumor and its spread to other body parts. There are several lines of evidence that at least some carcinogens present in food products are able to give rise to the described above sequence of events in higher and lower vertebrates (Anon., 1993). 

There are many articles and textbooks available for further information about fermentation processes and bioreactor engineering. " The technology continues to be an area of study to improve production of pharmaceuticals, specialty chemicals, antibodies, and food products. Choosing the correct cell type and reactor strategy is of utmost importance. This choice also effects the downstream processing or separation sequence used to purify the product thus, a systems approach to fermentation is extremely valuable. 

Somer, L., and Kashi, Y. (2003) A PCR method based on 16S rRNA sequence for simultaneous detection of the genus Listeria and the species Listeria monocytogenes in food products. J Food Prot. 66, 1658-1665... 

Animal species determination in processed material or food products can be performed by PCR amplification of mitochondrial DNA followed by sequencing analysis of the product (see Chapter 6) or by RFLP. RFLP analysis can be successful only if the DNA detected is from a species with a known RFLP pattern. In addition, if DNA from only one animal is detected by sequencing analysis or RFLP, there is actually no guarantee that DNA from other species is also present at very low amounts. Low contaminations can also be detected by real-time PCR. For sequencing analysis or RFLP, PCR primers are used that amplify DNA from almost aU mammals. In contrast, for real-time PCR, primers specific for each species have to be used. 

Animal species determination in meat, processed material, or food products can be carried out by PCR amplification of mitochondrial DNA (mtDNA) followed by sequencing of the product by RFLP or real-time PCR (see Chapters 3 and 4). The structure of mitochondrial DNA is shown in Figure 6.6. The size of mtDNA can vary from 15,700 to about 20,000 bp in higher animals such as mammals, frogs, and insects. In the same species, differences of up to 900 bp can be observed [4]. 

A further apphcation is the detection and sequencing of resistance genes such as the plasmid RE25, which transfers resistance to tetracycline, lincomycin, chloramphenicol, erythromycin, and similar antibiotics. This plasmid can be found in Enterococcus strains isolated from food products. By sequencing, differences or similarities to related plasmids with other resistances can be detected and, for example, influence the antibiotic therapy [16]. 

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