b) What are the factors affecting the growth of microorganism?
ANS- Food is a chemically complex matrix, and predicting whether, or how fast, microorganisms will grow in any given food is difficult. Most foods contain sufficient nutrients to support microbial growth. Several factors encourage, prevent, or limit the growth of microorganisms in foods, the most important are aw, pH, and temperature.
aw: (Water Activity or Water Availability). Water molecules are loosely oriented in pure liquid water and can easily rearrange. When other substances (solutes) are added to water, water molecules orient themselves on the surface of the solute and the properties of the solution change dramatically. The microbial cell must compete with solute molecules for free water molecules. Except for Staphylococcus aureus, bacteria are rather poor competitors, whereas molds are excellent competitors.
aw varies very little with temperature over the range of temperatures that support microbial growth. A solution of pure water has an aw of 1.00. The addition of solute decreases the aw to less than 1.00.
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