Bacteria need
water
food
time
warmth
oxygen
low acid environment
to survive and grow
- dehydration - bacteria need water, time, food, warmth, oxygen and a low acid environment to survive and multiply. Remove the water and the food keeps for a long time.This is called drying and can be simple air drying, drying in the oven or a microwave. eg beef jerky, peas
- salting - bacteria need water, time, food, warmth, oxygen and a low acid environment to survive and grow. Remove the water from the cells of the food and the food keeps for a long time. eg corned beef
- sugar - bacteria need water, food, time, warmth, oxygen and a low acid environment to survive and grow. Sugar has a dehydrating effect like salt. If you increase the natural sugar levels in the food by adding sugar the bugs cannot grow. eg jam
- adding chemicals - bacteria need water, food, time, warmth, oxygen and a low acid environment to survive and grow. Salt and sugar are the main chemicals used to preserve food but now more chemicals have been developed and can be identified on labels of foods. Preservatives are in the 200s, antioxidants are the 300s
- smoking - bacteria need w........, f.........., t........, w........, o.......... & l.......... a......... e........ to survive and grow. Smoking food dries it and also the chemicals in the wood preserve the food. These chemicals add flavour and character to the food (like chicory) but some can be carcinogenic (cancer causing). eg smoked salmon.
- freezing - bacteria need w......., f....., t....., w.... , o......& l.... a..... e...... to survive and grow. Keeping the temperature of food low (below the temperature danger zone for food - 5-60 degrees C) stops the bacteria from growing. eg............
- bottling/canning - bacteria need.............. Heating then sealing the food kills off the bacteria then stops any oxygen from getting getting to the food. eg.............
- Adding acids - bacteria need ................. Adding an acid such as acetic acid (vinegar) prevents the growth of micro organisms. It also adds flavour. eg.....
- Oxygen elimination - bacteria need.... Oxygen can be remove manually - like squeezing all of the air out of a package. Vacuum packaging or cryovac is a mechanical way of removing oxygen.
