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Flashcards in Water and Food Dispersions Deck (272)
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1

What are 3 common roles of water in food systems?

1. A carrier of nutrients and wastes
2. A reactant and a reaction medium
3. A stabilizer of biopolymer configuration (poteins and COHs)

2

Water makes up what % of tomatoes and lettuce?

95

3

Water makes up what % of apple juice/milk?

87

4

Water makes up what % of potatoes?

78

5

Water makes up what % of meats?

65-70

6

Water makes up what % of bread?

35

7

Water makes up what % of honey?

20

8

Water makes up what % of rice/wheat flour?

12

9

Water makes up what % of shortening?

0

10

The amount of water, its location and its interaction with the chemical components in a food product is extremely important from the standpoint of _________and ________.

1. acceptability
2. STABILITY

11

What is texture often associated with? Example?

Moisture

Ex: freeze-dried orange vs. fresh orange

12

Because water is a major reactant and serves as a reaction medium, many of our food processing and preservation methods involve the control of water content to:

slow down deteriorative reactions

13

What 3 factors all reduce the water activity (Aw) of a system?

1. Freezing
2. Concentration
3. Dehydration

14

What is one of the most abundant molecular species on Earth?

Water

15

Water is the only _____ liquid and the most _______ solid.

1. common
2. abundant

16

Comparing water (hydrate of oxygen) to the hydrates of other atoms:

a) Across the periodic table (CH4, NH3, HF - all ____ at room temp)
b) Down the periodic table (H2S, H2Se, H2Te - all _____)

Gases

17

How many electrons does H2O have? How many are valence? How many electrons does each Hydrogen have?

8, 6, 2

18

The __ __ orbital(s) and the __ __ orbital(s) of the oxygen atom are combined to form __ __ _____ orbitals.

1. three 2p
2. one 2s
3. four sp3 hybrid

19

How many of oxygen's 6 valence electrons are used up in the two covalent bonds that form between H and O? What is the net result?

2

Net result: there are 2 oxygen lone electron pairs left in two of the sp3 orbitals

20

What makes oxygen highly electronegative in a water molecule?

Its 2 lone electron pairs

21

Water molecules can be viewed as having two ________ regions and two ________ regions situated ________.

1. electron-rich
2. electron-poor
3. tetrahedrally

22

In the presence of other water molecules, the electron-rich/poor regions of H2O will associate in order to do what?

To minimize the overall free energy of the system.

23

What is hydrogen bonding?

The associations due to differential electron density between hydrogen and other electronegative atoms

24

The tetrahedral nature of the spatial arrangement of these regions of electron density in H2O molecules promotes the ability to form a _________________.

3D association/network

25

How strong are hydrogen bonds? Is this strong?

~10 kcal/mol

Not very strong

26

Hydrogen bonding is the basis for what in the atmosphere? What does this lead to?

Water vapor accumulation. Leads to the accumulation of clouds

27

What is capable of forming due to waters ability to hydrogen bond in 3D?

local regions of structure

28

What structure does water have in the liquid phase? What is this termed?

"Transitional" structure

Termed: "flickering clusters"

29

What do flickering clusters do?

They continually form and break up

30

What is the lifetime of flickering clusters?

10^-10 to 10^-11 seconds