Colloidal Stability Flashcards
Stability over time is greatly in part due to
Colloidal Stability
Wine resilience is affected by
Wine colloids
Role of pH and stability
The lower the pH the higher the stability
3 important compounds
- Polysaccharides
- Polyphenols
- Proteins
Red wine and colloidal stability
Red wines are more colloidally stable because they have more Polysaccharides and phenolics to prevent hazing
White wines and colloidal stability
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
Why Aging on lees for a white wine can increase colloidal stability
Because everything released from yeast are always compounds that are able to increase colloidal stability
(polypeptide and polyphenol binding)
Size of Colloids
We want larger colloids that have a bigger surface area and in turn have a larger area to host compounds
Specific surface
the surface area per unit weight or volume
Types of colloids (Lyophilic) 4
- sols of gum
- gelatin
- starch
- polysaccharides
Frome grapes = not so stable
From lees = more stable
Sols of gum in regard to stability
They are quite stable as they are surrounded by two stability factors: Negative or positive charge and a layer of solvent
Types of Colloids (Lyophobic)
Meaning solvent repelling, these colloids are easily precipitated, less stable, and difficult to reconsitute
Amphiphilic Colloids
At low concentration they exist separately, at high concentration they form aggregates or micelles
3 types of colloids
- lyophilic
- lyophobic
- Amphiphilic
2 optical properties of colloids
- Faraday-Tyndall effect
- light scattering effect
Essentially the more colloids you have the more turbidity
what are turbidity units
NTU’s
Brownian motion
The uneven distribution of the collisions between colloid particle and the solvent molecules.
Colloids and viscosity
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
Electric properties of Colloids
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
Two pathways for the stability of colloids
- Addition of large amounts of electrolytes: To make the separation quicker
- Addition of a less polar solvent (alcohol): to favor sedimentation (we can not do this to wine)
Coagulation for flocculation
the addition of small amount of hydrophilic or hydrophobic colloid to a hydrophobic colloid of opposite charge tend to sensitize (coagulate) the particles.
two main mechanisms for colloid stabilization
- Steric stabilization: Surrounding each particle with a protective solvent
- Electrostatic Stabilization: Providing the particle with an electric charge
Role of stabilization of colloids
To prevent colloids from aggregation
Additives or subtractives?
Use additives that will stay in the wine as they increase the capability of the stability compounds
Protective colloidal action
the addition of large amount of hydrophilic colloid (protective colloid) to a hydrophobic colloid tend to stabilize the system.
