Lecture 14: Preservation

Question 1

What are the ways that food can go bad?

Answer 1

• Oxidation (especially fatty acids and proteins)
• Hydrolysis = loss of texture (especially in milk)
• Loss or migration of moisture (sogging out, drying out)
• Crystallization = retrogradation of starch (honey, jams)

Question 2

How do low temps preserve foods?

Answer 2

• Refrigeration impedes bacterial growth

- Freezing stops bacterial growth and impedes chemical changes

Question 3

How do high temps preserve foods?

Answer 3

Kills microorganisms

Question 4

What does a low water activity mean?

Answer 4

Bacteria (especially pathogens) won’t grow

Question 5

How can we lower water activity?

Answer 5

• Dry the food (sun dried, beef jerky)
• Add salt (brine)
• Add sugar (jams, jellies, preserves)

Question 6

Osmosis

Answer 6

Water flows from region of high concentration to region of low concentration

Question 7

What does pH measure?

Answer 7

Acid content

Question 8

What is the pH limit for safety?

Answer 8

4.6

Question 9

What water activity and pH are safer for foods?

Answer 9

High acidity and low water activity

Question 10

How is salami cured?

Answer 10

Ferment with lactic acid-producing bacteria

Question 11

What is pickling?

Answer 11

Preservation of foods by adding acid

Question 12

What are the 2 ways one can pickle foods?

Answer 12

• Fermentation

- Direct addition or infusion of acidity

Question 13

What is the most common acid for infusions?

Answer 13

Vinegar (acetic acid)

Question 14

What acids are mosts commonly used for fermentation?

Answer 14

Lactic acid or carbonic acid

Question 15

What do yeasts do during fermentation?

Answer 15

• Lowers pH
• Removes fermentable carbohydrates
• Makes alcohol

Question 16

How does smoking foods aid in preservation?

Answer 16

• Drying seals the surface of foods and keeps flies, germs, and maggots away
• Incomplete combustion products have antimicrobial activity

Question 17

What processes reduce bacterial count in foods?

Answer 17

• Pasteurization
• Filtration
• Irradiation

Question 18

What are irradiated foods exposed to?

Answer 18

X-rays or gamma rays

Question 19

How are irradiated foods identified?

Answer 19

• Food must be identified with international symbol (colored green)
• Must also be labeled “Treated with Radiation” or “Treated by Irradiation”

Question 20

What cause breads and cakes rise?

Answer 20

Production and expansion of CO2 gas produced by yeast or acid plus baking soda

Question 21

Aseptic packaging

Answer 21

Sterilize product by placing it in a sterile container

Question 22

What is the measure of water most relevant to food safety?

Answer 22

Water activity

Question 23

What are the ways in which acid may be added to food?

Answer 23

• Inoculation with lactic acid bacteria
• Addition of vinegar
• Addition of citric acid