Question

Why can the food be kept longer in a cold house than in normal conditions?
A. Insect cannot enter
B. Bacterial multiplication stops
C. Bacterial multiplication is reduced
D. There is plasmolysis at low temperatures

Answer 1

Temperature is one of the major factors that affect bacterial activities. Temperature below or above a particular temperature affects the growth of an organism in a specific manner.

Complete solution:
The temperature has an important role to play in bacterial growth. At lower temperatures, molecules move at a slower rate due to a lesser amount of kinetic energy. Lower temperatures affect the growth of bacteria directly or indirectly. The decrease in growth rate, decrease in enzyme activities, differential nutritional requirements, alteration in cell composition are some of the direct effects. Indirect effects include a change in solubility and diffusion rate. When food items are kept in colder conditions, there is an exponential reduction in the activity of bacteria present in them. Because of this reduction, there is a delay in the chemical reactions occurring in the food. This results in causing bacteria to become dormant. This means that the bacteria are still present there and are alive but they have stopped growing or producing toxins that are responsible for spoilage of food items. Molecules tend to move slower at lower temperatures. In this scenario, enzymes are unable to mediate in chemical reactions, as a result of which, the viscosity of the interior cell brings a halt to all the activities. When the temperature is increased, molecules tend to move faster, and thus enzymes speed up the process of metabolism. This results in a rapid increase in the size of cells.
It has been found out that at a temperature between ${5^ \circ }C$ and ${60^ \circ }C$, there is an enhancement in bacterial growth. When the temperature is further increased above ${60^ \circ }C$, bacteria die because they are unable to resist the high temperature. And when the temperature is lowered below ${5^ \circ }C$, there is a slowdown in its growth.

So, the correct answer is option C.

Note: Most of the bacteria dies at ${165^ \circ }F$, but somehow certain spore-forming bacteria survive this high temperature.