Colloidal Stability

Question 1

Stability over time is greatly in part due to

Answer 1

Colloidal Stability

Question 2

Wine resilience is affected by

Answer 2

Wine colloids

Question 3

Role of pH and stability

Answer 3

The lower the pH the higher the stability

Question 4

3 important compounds

Answer 4

1. Polysaccharides
2. Polyphenols
3. Proteins

Question 5

Red wine and colloidal stability

Answer 5

Red wines are more colloidally stable because they have more Polysaccharides and phenolics to prevent hazing

Question 6

White wines and colloidal stability

Answer 6

It is more difficult to achieve colloidal stability in white wines, but we can age them on lees to increase stability, without this method we miss the roundess and mouth feel of the wine

Question 7

Why Aging on lees for a white wine can increase colloidal stability

Answer 7

Because everything released from yeast are always compounds that are able to increase colloidal stability
(polypeptide and polyphenol binding)

Question 8

Size of Colloids

Answer 8

We want larger colloids that have a bigger surface area and in turn have a larger area to host compounds

Question 9

Specific surface

Answer 9

the surface area per unit weight or volume

Question 10

Types of colloids (Lyophilic) 4

Answer 10

1. sols of gum
2. gelatin
3. starch
4. polysaccharides

Frome grapes = not so stable
From lees = more stable

Question 11

Sols of gum in regard to stability

Answer 11

They are quite stable as they are surrounded by two stability factors: Negative or positive charge and a layer of solvent

Question 12

Types of Colloids (Lyophobic)

Answer 12

Meaning solvent repelling, these colloids are easily precipitated, less stable, and difficult to reconsitute

Question 13

Amphiphilic Colloids

Answer 13

At low concentration they exist separately, at high concentration they form aggregates or micelles

Question 14

3 types of colloids

Answer 14

1. lyophilic
2. lyophobic
3. Amphiphilic

Question 15

2 optical properties of colloids

Answer 15

1. Faraday-Tyndall effect
2. light scattering effect

Essentially the more colloids you have the more turbidity

Question 16

what are turbidity units

Answer 16

NTU’s

Question 17

Brownian motion

Answer 17

The uneven distribution of the collisions between colloid particle and the solvent molecules.

Question 18

Colloids and viscosity

Answer 18

We want viscosity from colloids because it is very low and gives the wine a roundness. Wine is like a Newtonian flow (similar to water) must is more like pseudo-plastic flow with more friction

Question 19

Electric properties of Colloids

Answer 19

They can either be positive or negative. What is important are negative charges. We want more negative charges for stability (we also prefer lower pH) More neagative charges make the wine more stable

Question 20

Two pathways for the stability of colloids

Answer 20

1. Addition of large amounts of electrolytes: To make the separation quicker
2. Addition of a less polar solvent (alcohol): to favor sedimentation (we can not do this to wine)

Question 21

Coagulation for flocculation

Answer 21

the addition of small amount of hydrophilic or hydrophobic colloid to a hydrophobic colloid of opposite charge tend to sensitize (coagulate) the particles.

Question 22

two main mechanisms for colloid stabilization

Answer 22

1. Steric stabilization: Surrounding each particle with a protective solvent
2. Electrostatic Stabilization: Providing the particle with an electric charge

Question 23

Role of stabilization of colloids

Answer 23

To prevent colloids from aggregation

Question 24

Additives or subtractives?

Answer 24

Use additives that will stay in the wine as they increase the capability of the stability compounds

Question 25

Protective colloidal action

Answer 25

the addition of large amount of hydrophilic colloid (protective colloid) to a hydrophobic colloid tend to stabilize the system.