Oxidation reduction potential (O – R)
Organisms can be classified into aerobic and anaerobic based on their oxygen requirements. There fore, the reducing and oxidizing power of the food influences the type of organism that growth on it.
Foods with high oxidation potential favours the
growth of aerobes organisms.
Foods with low oxidation potential favours the growth of anaerobic and faculitative anaerobic organism.
Growth inhibitors: - These are chemicals such as sodium chloride (NaCl), Nitrate, Nitrite, Sulphur dioxide and hypochlorites that are added to foods to the growth of certain organisms.
It was found that E.coli, for example, requires the following periods for a cell to divide at different temperatures.
60minutes at 200C
40 minutes at 250C
29 minutes at 290C
17 Minutes at 370C
19 minutes at 400C
32 minutes at 450C
No growth at 500C
It is clear that rate of growth is optimal at 370C, but decreases when the temperature is lowered below, or raised above 370C. 6. Water acitivity (aW)