Lecture 5

Question 1

Protein solubility is reduced in the presence of alcohol​. True or False

Answer 1

True

Question 2

Bentonite Fining: name 3 ways

Answer 2

sodium bentonite​:
-used to be most common​
-bad precipitation​
-more surface area, need less​

calcium bentonite​:
-better lees compaction, but plates separate​
-less surface area for protein binding, need more​

calcium/sodium bentonite​:
now most common​!!!!

Question 3

What is denaturation?

Answer 3

loss of biological activity

(from a normal protein; heavy scribble to a denatured protein; a light, spaced-out scribble)

Question 4

What are Chemical Heat Stab Tests?

Answer 4

Addition of acid to wine, which reacts with all proteins (denatures proteins)
i.e. Trichloroacetic acid or Phosphomolybdic acid (bento test)​​

Question 5

What is a BENTO test?

Answer 5

-test by chemical denaturation
-[leads to] overestimate bento dose rate requirements (*heat test is most specific)

Question 6

What causes the undesirable haze in wine?

Answer 6

Proteins in wine: precipitate causing an undesirable haze​

Question 7

What charge are proteins at wine pH?

Answer 7

Proteins are positively charged at wine pH and interact with negatively charged molecules​

Question 8

What are bento additions for?

Answer 8

Bentonite additions can be used to remove proteins to achieve heat stability​

Question 9

How to measure wine clarity?

Answer 9

Wine clarity can be measured as NTU (Nephelometric Turbidity Units)​

Question 10

Why [preform BENTO trials?

Answer 10

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

Question 11

How to test Heat stability?

Answer 11

Heat stability can be tested by either chemical or heating methods (heat method gives the most accurate picture of heat unstable proteins)​

Question 12

What is cold stability??

Answer 12

Tartrate stability

Question 13

What are tartrates?

Answer 13

Tartaric acid (H2T)​

Bitartrate ion (HT-)​

Tartrate ion (T2-)

Question 14

What are wine crystals?

Answer 14

Potassium bitartrate precipitates to form ‘wine crystals’

Question 15

What affects the tartrate stability?

Answer 15

Solubility of KHT

Temperature​
-Low temperature decrease solubility​

Ethanol​
-Ethanol decreases the solubility​

pH​
-Highest concentration at pH=3.65 (least cold stable)​

Wine matrix components​
-Ie. K+ ions, other charged molecules​

Question 16

What household item is KHT

Answer 16

cream of tartar

Question 17

How does tartrate formation affect pH at above 3.65?

Answer 17

Above pH 3.65​

-As tartrates precipitate TA decreases​

-Competing equilibrium is with T2-, so [H+] is decreased with KHT precipitation (raising pH)​

Question 18

How does tartrate formation affect pH at below 3.65?

Answer 18

Below pH 3.65​

As tartrates precipitate TA decreases, ​

Competing equilibrium is with H2T, so [H+] is increased with KHT precipitation (lowering pH)​

Question 19

How can we cold stabilize wines?
​

Answer 19

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

2.Chill wines to 0 °C and seed with crystal​
3.Add crystallization inhibitors​

Question 20

Cold Stab Testing MethodS:

Answer 20

Qualitative methods​

Freezer test: Freeze wine completely​
Do crystals redissolve into solution?​

Fridge test: Store wine at 4 °C for a predetermined time (ie.7 days)​
Do crystals form?​

Quantitative method​

Conductivity testing​

Question 21

How does KHT precipitation affect the conductivity?​

Answer 21

Conductivity will decrease as the ions are precipitated from solution

Question 22

What is Electrical Conductivity?​

Answer 22

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

Question 23

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

Answer 23

Any tartrate crystals will act as nucleation points for bubbles ​

Larger bubbles, or gushing at disgorging​

Question 24

Potassium Bitartrate (KHT) can precipitate over time, causing _________.

Answer 24

crystal formation in wine.​

Question 25

Wines are cold stabilized to avoid ___________

Answer 25

crystal formation in bottle.

Question 26

Two ways wines can be cold stabilized

Answer 26

Wines can be cold stabilized at low temperatures (KHT can be added to induce crystal formation) OR with by added crystallization inhibitors​

Question 27

The bitartrate solubility is affected by ____________.

Answer 27

Wine pH affects the bitartrate solubility (Lowest solubility at pH=3.65)​

Question 28

What would decrease KHT solubility?

Answer 28

Low temperatures and alcohol content decrease KHT solubility​