Question

es a choice in terms of fat, sugar, and sodium? 7. Name five methods of food preservation. Which methods destroy harmful bacteria and which merely retard their growth?

Answer 1

Food preservation is the technique used to keep food from spoilage and prevent the growth of pathogens in them.

Five commonly used methods of food preservation are as follows:

• Drying: Drying is the oldest and the most common method of long term food preservation. It involves removal of any moisture from the food, either by heat (air, sun) or freeze drying. Removal of moisture from food can keep them from spoilage for a long time. Complete dehydration restricts the growth of harmful micro organisms in the food and prevents their fermentation. Thus this technique does not destroy harmful bacteria, but merely retards their growth. Mostly fish, meat, fruits and even some vegetables are preserved by drying.
• Pickling: Pickling is a popular way to store food by storing them in brine or acidic fluid such as vinegar water. The idea behind pickling is that at a low acidic pH, most harmful bacteria can not survive and is therefore an effective way to preserve food and avoid spoilage. An acidic pH kills off most bacteria, and hence pickling is the method of food preservation which destroys the harmful bacteria. Vegetables, meat, dairy, eggs etc. can be stored by pickling.
• Canning: Canning is the process of food preservation where first food is first processed and then stored in air tight containers. They have significantly long shelf life of up to 5 years. Before canning, food is rid of bacteria either by freeze drying, boiling or by a process called pressure canning. Boiling is used in highly acidic food such as tomatoes, most citrus foods to kill bacteria. Non acidic food should however be pressure canned to completely destroy Clostridium botulinium spores (which are not present in the acidic foods), which can withstand boiling. Most foods can be canned. Canning is a technique which completely destroys harmful bacteria in the stored food.
• Vacuum packing: Vacuum packing is the method of removing air from the package before sealing it. This causes a lack of aerobic conditions in the package and thereby prevents the growth of aerobic bacteria. It is commonly used technique to store processed food as well as dry foods such as cereals, nuts etc. It is therefore a process which merely inhibits the growth of aerobic bacteria by removing suitable conditions. It is often paired with other processes to inhibit the growth of anaerobic bacteria.
• Pasteurization: Pasteurization is the process of treating food, especially dairy and liquids such as beer with mild heat to destroy any micro organisms or enzymes present in them to induce spoilage. Pasteurization usually kills most of the active disease causing bacteria in the food, but often is not very effective in destroying the heat resistant spores present in them. However these spores are not virulent, and hence we can say that this technique kills harmful bacteria, as opposed to merely inhibiting their growth.