Week 3

Question 1

Moisture sorption isotherm `

Answer 1

The moisture sorption isotherm is a chart that tells you how a food will behave at different water activities. It has 3 different zones which each describe a different behavior that water molecules possess at different moisture levels.

Question 2

Constitutional water

Answer 2

Water molecules that are completely bound to a hydrated crystal

Question 3

Hydration shell

Answer 3

This is the single layer of water molecules that covers a particle or droplet

Question 4

Bulk-phase water

Answer 4

Water molecules that are in large quantities and behave in the native form. They do not cling to/interact with other molecules. It is water molecule interacting with water molecule

Question 5

Bound water

Answer 5

These are water molecules that are chemically bound to something so that they are not available for reactions in other areas.

Question 6

Hysteresis

Answer 6

This is the phenomenon in which the dehydration and the hydration lags behind each other. The Dehydrated food will behave differently at the same moisture content than the hydrated food would

Question 7

Interfacial tension

Answer 7

This is basically surface tension, this is where the water molecules at an interfacial surface grab on to each other really tightly and create a strong surface

Question 8

Surfactant

Answer 8

This is a molecule that reduces surface tension at an interfacial surface by interrupting the bonding pattern of the substance

Question 9

Amphipile

Answer 9

A substance that has both an hydrophilic portion and a hydrophobic portion

Question 10

Hydrophile-lipophile balance HLB

Answer 10

A emulsifier blend that emulsifies different mixtures of oil and water, polar and non-polar substances. 7 is neutral, lower numbers emulsify highly oil mixtures and the higher numbers emulsify more water soluble mixtures

Question 11

Steric repulsion

Answer 11

Molecules have charges to them. When large molecules that have large charges come together, they repel one another

Question 12

Emulsion

Answer 12

A mixture that allows two opposite substances to be dispersed in one another. The surface tension is reduced and that is how this accomplished. The smaller the droplet, the more stable the emulsion.

Question 13

Water in oil

Answer 13

An emulsion made with a base of oil and water is mixed in. Would require an emulsifier with an HLB lower than 7

Question 14

Oil in water

Answer 14

An emulsion made with a base of water with oil mixed in . This would require and emulsifier with and HLB of 7or higher

Question 15

Train

Answer 15

This is the loops of the protein molecule that is used as an emulsifier.

Question 16

tail

Answer 16

This is the long tail of a protein molecule that would sit on the surface of droplet or particle and extend into the opposite substance. amphiphilic

Question 17

Continuos phase

Answer 17

This is the phase where one substance is stably suspended into another. Droplets are emulsified

Question 18

Discontinuous phase

Answer 18

this is where the particles are separating out of the primary substance, not stable

Question 19

Droplet size

Answer 19

the larger the droplet, the less stable the emulsion. More coalescence happens when the droplets are bigger. Smaller droplet sizes require more energy but they make the emulsion more stable

Question 20

Volume fraction

Answer 20

This is the ratio of the substance over the total volume

Question 21

Surface layer

Answer 21

Phase boundary between two substances

Question 22

Gibbs-Marangoni effect

Answer 22

This is the phenomenon where solutes rush to one side when two molecules come together and then water rushes in. Like pepper and dish soap

Question 23

Bancrofts rule

Answer 23

this is where an emulsifier is more soluble in the continuous phase than in any of the individual phases