Microorganisms and Food

Bread - the yeast turns to carbon dioxide and ethanol. The CO2 makes the bread rise.

Wine - yeast turns the sugar in the grape to ethanol (alcohol) and C02.

Cheese - bacteria turns the sugar in the milk to lactic acid which causes the milk to curdle.

Microorganisms:

• grow rapidly under the right conditions - quick food production
• grow on a range of inexpensive materials
• environment can be artificially controlled - can be grown anywhere
• conditions for growth are easy to create
• can last longer in storage than the raw product they're made from.

but..

• there's a high risk of food contamination as conditions are favourable to harmful microorganisms
• small changes in temperature or pH coulf kill the microorganisms

Salting

• Salt inhibits the growth
• interferes with the ability to absorb water
• water moves down concentration gradient into the salt

Adding Sugar

• same as salting

Freezing

• slows down the reactions taking place in microorganisms
• freezes the water in the food so microorganisms can't use it

Pickling

• vinegar has a low pH which reduces enzyme activity
• this inhibits their growth

.

Heat Treatment

• kills any microorganisms present

.

Irradiation

• involves exposing foods to radiation
• X-rays or Gamma Rays
• kills any microorganisms present.