Food Preservation

Question 1

Reasons for preserving food

Answer 1

• extension of shelf life
• prevention of waste from surplus
• increased range of food choices all year around
• transportation of food over long distances
• trading of food between countries
• maintenance of the nutritive value of food
• easier and more convenient meal preparation

Question 2

What are food preservation principals

Answer 2

1- exclusion of air
2- Removal of moisture
3- control pH
4- control temperature

Question 3

What are different preservation techniques

Answer 3

Dehydration, bottling, canning, salting, pickling, jam making, freezing, freeze drying, chilling, pasteurisation, ultra-high temperature treatment, fermentation.

Question 4

What are causes of food spoilage

Answer 4

• physical damage
• enzymic activity
• microbial activity
• rodent activity
• environmental factors

Question 5

Dehydration

Answer 5

Removal or moisture. Food needs to be dehydrated to the moisture content of foods needs to be reduced to 5-6%

Question 6

Bottling

Answer 6

Bottling is a method of preserving food by heating it in a container. The heat kills microorganisms that causes food spoilage and creates a partial vacuum that seals the bottle so that the food is stored in a controlled environment

Question 7

Canning

Answer 7

Control of temperature and exclusion of air. Cana killed with the food product and a liquid is added to force air out of the package.

Question 8

Salting

Answer 8

Reducing moisture levels

Question 9

Salting

Answer 9

Reducing moisture levels. Salt preserves by drawing moisture from food cells. The salt dissolves in this moisture, raising the salinity level and making it unsuitable for micro-growth

Question 10

Pickling

Answer 10

A method of preserving food in which salt is used to draw the water out of vegetables.

Question 11

Jam making

Answer 11

Control pH. Adding sugar creates an environment that is not suitable for microorganisms to grow because the moisture levels are restricted.

Question 12

Freezing

Answer 12

Control of temperature. The storage of food at temperature below -18C. Enzyme activity occurs more slowly at low temperatures. Microorganisms numbers are reduced by the freezing process

Question 13

Freeze drying

Answer 13

Control of temperature and removal of moisture. Freeze drying works by freezing the food and then reducing the surrounding pressure to allow the frozen water in the food to change from a solid to a gas and so dehydrate the food

Question 14

Chilling

Answer 14

Control of temperature. Chilling slows the growth and activity of enzymes and the growth of microorganisms. Chilling cooling has no effect on the number of bacteria present

Question 15

Pasteurisation

Answer 15

Control of temperature. The process either kills all specific heat sensitive micro-organisms or reduces their numbers.

Question 16

What are the 2 types of pasteurisation

Answer 16

1- holder process method- milk is heated to 65C held at this temp for 30mins and cooled
2- high temperature short time pasteurisation, milk is heated to 72C very quickly and held there for 15 second using a heat exchanger

Question 17

Ultra-high temperature treatment

Answer 17

Control of temperature, milk is heated to about 140C for a few seconds to kill all heat resistant bacteria. Once opened it must be refrigerated

Question 18

Fermentation

Answer 18

Changing pH. Fermentation occurs when carbohydrates are converted to acids of alcohol through the action of micro-organisms. The bacteria feeds on the carbohydrates multiples and creates lactic acids