Question

1) Explain how a high salt concentration would affect the cell structure and growth of potential pathogens on a food product.

2) Define the term optimum temperature. What would you expect of the growth rate at this temperature compared to just below the maximum temperature? How do these growth conditions affect the bacterium (what is starting to happen within the cell.)

Answer 1

1.Water in cell moves toward the highest concentration of salt. If there is more salt in a cell than outside it, the water will move through the membrane into the cell, causing it to increase in size, swelling up as the water fills the cell in its imperative to combine with the salt. If a higher concentration of salt is placed outside of the cell membrane, the water will leave the cell to leave the cell to bond with it. The loss of water from this movement causes plant cells to shrink and wilt.

Salt plays an important role in reducing the growth of pathogens and organisms in food that spoil products and reduce their shelf life. Salt is effective as a preservative and inhibit the growth of pathogens because it reduces the water activity of foods. The water acitvity of a food is the amount of unbound water available for microbial growth and chemical reactions. Salt's ability to decrease water activity is thought to be due to the ability of sodium and chloride ions to associate with water molecules. Adding salt to foods can also cause microbial cells to undergo osmotic shock, resulting in the loss of water from the cell and therby causing cell death or retarded growth. For some microorganisms, salt may limit oxygen solubility, interfere with cellular enzymes, or force cells to expend energy to exclude sodium ions from the cell, all of which can reduce the rate of growth.

2. Optimum temperature is the temperature at which a procedure is best carried out, such as the culture of a given organism or the action of an enzyme. Increase in temperature will increase enzyme activity. But if temperatures get too high, enzyme activity will diminish and the protein ( enzyme) will denature. Lowering temperature will decrease enzyme activity. The growth rates are the highest at the optimum temperature for the organism. At optimum temperature the bacterial enzymes functions most effectively. Based on their temeperature preferences bacteria are classified as - Psycrophilic, mesophilic, thermophilic and hyperthermophilic. A mesophile is an organism that grows best in modertae temperature, neither too hot nor too cold, typically between 20 and 45 degree C. Bacterial enzymes functions effectively and bacterial cells multiplication occurs more during the optimal temperature for growth.