Lecture 6

Question 1

What is a buffer?

Answer 1

a solution that can resist pH change (w/ the addition of an acidic or basic component; able to neutralize small amounts [of added acid or base], thus maintaining the pH of the solution relatively stable.

-Important for specific or stable pH
-Wine has a lot of buffering capacity due to all the different ions (acids and Na+/K+)​

Question 2

Protein solubility is reduced in the presence of ___________?

Answer 2

protein solubility is reduced in the presence of alcohol​

Question 3

(Al2O3·4SiO2)(H2O) is _________ ?

Answer 3

Bentonite: Aluminum silicate anions (bento fining)

Question 4

Bento aluminum is neutralized by _________ such as ______, ______, _____

Answer 4

Neutralized by cations such as Ca, Na, K, Mg​

Question 5

What is NTU???​

Answer 5

Nephelometric Turbidity Units​

Turbidity is the amount of cloudiness in a liquid​ (NTU measurement = wine clairity)

Question 6

How can heat stability can be tested?

Answer 6

either chemical or heating methods (heat method gives the most accurate picture of heat-unstable proteins)​

Question 7

Why preform bento trials?

Answer 7

We will perform Bento trials to determine the minimum bentonite addition required to achieve Heat Stability

Question 8

What is cold stability??​

Answer 8

Tartrate stability

Question 9

What are tartrates?​

Answer 9

Tartaric acid (H2T)​

Bitartrate ion (HT-)​

Tartrate ion (T2-)

Question 10

Potassium bitartrate precipitates to form _______________

Answer 10

Potassium bitartrate precipitates to form ‘wine crystals’​

Question 11

What affects the tartrate stability?​

Answer 11

Solubility of KHT:
Temperature​ (Low)
Ethanol​
pH
Wine Matrix

Question 12

How does tartrate formation affect pH?

Answer 12

As tartrates precipitate TA decreases…
below pH 3.65 = Competing equilibrium is with H2T
Above pH 3.65​ = Competing equilibrium is with T2

Question 13

3 Ways to cold stab

Answer 13

How can we cold stabilize wines?​

Chill wines to 0-4 ° C for extended period​
-Rack off tartrate crystals while wine is still cold​

Chill wines to 0 °C and seed with crystal​
-Small crystals of KHT will introduce nucleation points to promote further crystallization​

Add crystallization inhibitors​
-Metatartaric acid (temporary effect, hydrolyses to tartaric acid)​
-Carboxymethylcellulose (CMC)​

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Question 14

What are some cold stab testing methods?

Answer 14

Qualitative methods​

Freezer test: Freeze wine completely​

Do crystals redissolve into solution?​

Fridge test: Store wine at 4 °C for predetermined period of time (ie.7 days)​

Do crystals form?​

​

Quantitative method​

Conductivity testing​

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Question 15

What is Electrical Conductivity?​

Answer 15

Electrical conductivity is the current or the quantity of electricity passing per second…

Question 16

How does KHT precipitation affect the conductivity?​

Answer 16

Conductivity will decrease as the ions are precipitated from the solution​

K+ ions are removed as KHT precipitates​

Question 17

Tartrate stability is especially important for sparkling wine, why??​

Answer 17

Any tartrate crystals will act as nucleation points for bubbles ​

Larger bubbles, or gushing at disgorging​