Water

Question 1

T or F. Specific heat of water is larger than specific heat of oil.

Answer 1

True

Question 2

T or F. Molecule of carbon dioxide is polar.

Answer 2

False

Question 3

T or F. Percentage of water molecules bound by hydrogen bonds increases with increasing temperature.

Answer 3

False

Question 4

T or F. Water in food may act as a reactant in some reactions.

Answer 4

False

Question 5

T or F. If the temperature of a food product increases, its water activity will decrease.

Answer 5

False

Question 6

How much volume of water increases during (slow) freezing?

Answer 6

9%

Question 7

Agitation during freezing of water ( or liquid food with high content of water) will cause what?

Answer 7

Formation of a large number of small crystals

Question 8

Water activity of a food product can be expressed as:

Answer 8

Aw = RH/100

Question 9

Hysteresis of sorption isotherms is common in:

Answer 9

tissue products

Question 10

Microorganisms cannot grow in food with water activity of what?

Answer 10

0.6 and lower

Question 11

Define water activity.

Answer 11

indicator of available water in a product (available for microorganisms and chemical reactions)

Question 12

Prolamins are proteins soluble in what?

Answer 12

Alcohol

Question 13

At pH = pI, proteins are generally:

Answer 13

least soluble in aqueous solutions

Question 14

Water content in fresh fruits and vegetables is what percent?

Answer 14

more than 80%

Question 15

What will reduce water activity more (considering 10% aq. solution for each?

a. Starch (MW>1 MDa)
b. Sucrose (MW = 342 Da)
c. Glucose (MW = 180 Da)
d. Fructose (MW= 180 Da)
e. Salt (MW=58.5 Da)

Answer 15

e. Salt (MW=58.5 Da)