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Microbial stress and food processing

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2003). In the due course, these unfavorable conditions as well as the stress might lead to population that includes health, unhealthy and dead cells. In these regard, the experiment aimed at exposing the E-coli strain to different unfavorable conditions that reflect stresses experienced in real food production. Therefore, we wanted to know how these conditions affect the organism. This was established through microbial count with the use of Miles and Misra technique. Also flow cytometry technique was used and has the capacity of measuring the live dead and injured bacterial cells.
In the experiment, two techniques were used to determine the effect of these unfavorable conditions that reflect the stresses experienced in the real food production. These techniques include Flow cytometry technique and Miles and Misra technique. For the flow cytometry, its principle of operation is based on the viable cells and dead cells, whereby for the viable cells, the dye has the capacity of penetrating the cell membrane. In case of cell surface proteins, the dye will react with it and dim staining will be observed. For the dead cells, the dye has the capacity to permeate through the destroyed membrane and then stain both the inside and outside (reacts with the amines to form a more intense staining. There is a 50-fold difference in the fluorescence intensity between the dead and live cells. In relation to this, after the exposure of the bacteria to these unfavorable conditions, we were able to determine the dead and the viable bacteria then made a conclusion in regards to the effect of these conditions (Goodson and Rowbury 1989). The dye used for the flow cytometry was Propidium iodide(PI) and oxonol DiBAC4 (BOX).These two dyes are normally used together whereby they are excited by the same laser but the emission spectra is different ,hence being detected distinctly. PI normally