What is Quantitative Techniques?
Microbial quality of substances like food, milk, air, water, soil etc. can be assessed both qualitatively and quantitatively. Quantitative enumeration of microorganisms in a given sample can be accomplished in a laboratory by employing various methods, either by direct or indirect counts, each having its own advantages and disadvantages. No single method is always best. The most appropriate approach will depend on the experimental situation. These methods can also be used to measure microbial growth, determining growth rate and generation time. These methods devised for microbial quantitation either measure the cell numbers or determine the cell mass or cell constituents like DNA, protein, O2 uptake, carbon dioxide production, turbidometric measurement for increase in cell number, membrane filter count and the serial dilution agar plate method etc. Microbial populations are very large, therefore, most of the methods of counting are based on direct or indirect counting of a very small sample, achieved indirectly by a series of dilutions. Calculations then determine the size of total population.