Why Does Our Food Rot?
Food will eventually rot. We need food to survive. Microbes (bacteria, fungi) also need food to survive. They grow on and in the food causing it to decay or rot.
Unfortunately, microbes will increase in numbers as they destroy the food and when people eat rotten food they are more likely to get sick because of the large number of microbes present in the rotten food.
Most vegetables and fruits are available only during certain seasons of the year. It is very difficult and extremely wasteful to kill an animal every day to get meat and then throw away the rotting remains. To make the food last it must be preserved in some fashion. Since the beginning of recorded time people have been developing ways to preserve food.
Basically, all the methods of food preservation slow down or eliminate decay by either slowing down the growth of the microbes or eliminating the microbes. Chemical and biological processes do have effects on food; however, they usually only cause the appearance of the food to change. For example, the browning of an apple due to exposure to the oxygen in the air after peeling may not be appealing to look at but it won't cause someone to become ill if they eat it.
There are many methods of preserving food. Below is a list of preservation techniques commonly used. All of these techniques in some way either eliminate the microbes or slow their grow.
- Refrigeration/Freezing
- Pasteurization
- Canning
- Pickling
- Salting/sugaring
- Fermentation
- Chemical preservation
- Dehydration
- Freeze drying
- Irradiation
These preservation techniques can be placed into the following larger groupings.
- Temperature changes: refrigeration/freezing, pasteurizing, canning
- Chemical treatments: pickling, salting/sugaring, fermentation, chemical preservation
- Drying: dehydration, freeze-drying
- Radiation: irradiation
Over the next four weeks I will discuss how and why these various means of food preservation prolong the shelf life of our food. This week, let's consider how changing the temperature can prolong the life of the food.
Changing the temperature at which food is stored can prolong the life of food because microbial growth is slower or stopped at high and low temperatures. Microbes grow best within a certain temperature range. Proteins in the microbes called enzymes help the microbes by encouraging the breakdown of food, the growth of new cells and production of energy (ATP). These enzymes work best at certain temperatures. If the temperature is too low this will slow the ability of these enzymes to encourage the completion of the tasks listed above. If the enzymes are slowed down energy generation is also slowed. Less energy means slower growth. The organisms are not killed by the cooling; however, they grow much more slowly. If the temperature of the food
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