Lab 3: Food Preseveration: Canning, Freezing, Drying

Question 1

which people need to watch out for canned foods?

Answer 1

People who are on a sodium or carbohydrate restricted diet (hypertension or diabetes)

Question 2

What are the main causes of deterioration in foods?

Answer 2

Microbial growth, enzyme action, and insect damage

Question 3

During canning, what is ‘processing’?

Answer 3

Heating jars of food to temperatures high enough to destroy microorganisms and enzymes.

Processing drives air out of jars, and as the jar cools, an airtight vaccuum seal forms.

Question 4

T or F: Canned foods are shelf stable in a cool, dark room for an indefinite period of time

Answer 4

F: Can keep at room temperature

Question 5

What is one spoilage organism that home canners should worry about? Why?

Answer 5

Colstridium botulinum.

They are destroyed at high temperatures, but they form hardy spores, that produce a deadly toxin.

Question 6

How can these hardy spores be destroyed?

Answer 6

Processing in a pressure canner at a temperature of 116C.

Question 7

What kind of foods need to be processed in a pressure canner

Answer 7

Low acid foods: Meat, vegetables and foods in oil (pesto, garlic in oil or flavoured oils)
They must be processed at a minimum of 116C to kill of the spores

Question 8

Where should pesto, garlic in oil or flavoured oils be kept? For how long?

Answer 8

In a refrigerator, for 3 weeks

Question 9

What are some high acid canned foods?

Answer 9

Jams, jellies, marmalades, fruits, fruit preserves, pickles, etc.

Question 10

What is carrageenan?

Answer 10

A seaweed from the North Atlantic ocean, it has a powerful gelling agent.

Question 11

What is carrageenan used for?

Answer 11

jams, ice cream, sherbets, condensed milk, instant soup, cakes, cookies and candies. (Acts as a stabilizer, thickens or gels)

Question 12

T or F: freezer jams don’t require processing. Why?

Answer 12

T.

Freezing (-18C) halts bacteria growth

Question 13

How do freezer jams differ from regular jams?

Answer 13

Artificial sweeteners can be used, (b/c they are not exposed to high temperatures)

Question 14

Who would benefit from eating freezer jams?

Answer 14

People who wish to restrict their calorie or sugar intake, people who are diabetic or on weight loss diets

Question 15

How do low sugar preserves differ from regular jams?

Answer 15

Concentrated fruit juices and artificial sweeteners can be used to reduce/modify CHO content. Spices, herbs or flavourings can increase the flavour.

Question 16

What kind of fruit is prone to color loss in canning? What can be done?

Answer 16

Lightly colored fruit.
Place in a colour protection solution prior to canning and 5-7 ml lemon juice/ 250 ml canning liquid can be added to prevent discolouration

Question 17

How does freezing preserve foods?

Answer 17

Halts the growth of surface microorganisms and slow enzyme activity

Question 18

What occurs when food is frozen slowly? What happens when you thaw the food?

Answer 18

The water in the food form ice crystals which puncture the cell walls. Upon thawing there is drip (loss of liquid)

Question 19

What occurs when food is frozen rapidly? What happens when you thaw the food?

Answer 19

Allows for formation of small ice crystals. This reduces the drip

Question 20

How can rapid freezing be achieved?

Answer 20

cool food before freezing in small portions

Question 21

How does freezer burn occur? How can you prevent freezer burned food?

Answer 21

Occurs doe to the cool, dry air

Packaging should be air tight

Question 22

Where is thawing the safest? __h /kg of food

Answer 22

Fridge. 10h/kg of food

Question 23

What are some steps for successful freezing?

Answer 23

SELECT foods of high quality
PREPARE foods quickly and w/ great care
BLANCHING helps preserve color, inactivates surface enzymes, easier to remove skins
PACKAGE in odourless, tasteless, vapour and moisture proof freezer bags
FREEZE at -18C
THAW foods carefully and use immediately

Question 24

How does drying food preserve?

Answer 24

Uses heat to evaporate water from food. Lack of moisture limits microbial growth.

Question 25

Why is it important to blanch foods before drying? What are some ways to prevent discolouration?

Answer 25

blanching: breaks skin to allow moisture to escape

Treatment Solutions and Methods:

• Sodium bisulphate solution, salt solution, citric acid or ascorbic acid solution.
• Lemon, lime, orange, pineapple juice
• Jello powder, spices (ex. cinnamon), honey

Question 26

How should dried foods be stored?

Answer 26

At room temperature in a cool, dark, dry place

Question 27

Briefly describe how you would rehydrate dried vegetables. When cooking with dried vegetables, when would you salt?

Answer 27

Soak in the fridge for several hours. Add salt near the end of cooking

Question 28

How much moisture may be left in dried foods?

Answer 28

6-10%

Question 29

Where is pectin normally found?

Answer 29

In fruit, acts as the cement to hold the cell walls of fruit together. More concentrate in the skin and cores of the fruit.

Question 30

T or F: Fruit that contain less pectin are more suitable for jam and jelly recipes. Why?

Answer 30

F: fruit that contain more pectin are better for jams and jellies
Because they contain more natural pectin to help gel the jellies and jams.

Question 31

How can we tell when a jam is ready? (3)

Which one of the 3 is used for jellies?

Answer 31

1. The temperature test: Use a candy thermometer. should be 4 C above boiling water temp
2. The plate test: Should gel on a frozen plate
3. The spoon test (for jellies): the jelly should join as they drop or drop as a sheet, when a cold metal spoon is placed in the jelly.

Question 32

Commercial pectin is made from

Answer 32

extracting pectin from apple pomace (residue once juice is extracted) or citrus products.

available in powder or liquid form

Question 33

When using the standard commercial pectin, the product is designed to be used with enough sugar so that the final sugar concentration of the jelly is ___

Answer 33

60%

Question 34

In little to no sugar jams, what kind of pectin is in there?

Answer 34

This pectin forms a gel without sugar in the presence of divalent ions, like calcium. Contains locust bean gum and xantham gum. An artificial sweetener can be used.