Lecture 4 - Sucrose Inversion & Residual Sugar Flashcards
(36 cards)
What are amino acids?
-are the building blocks for peptides and Proteins
consist of an amine group and a carboxylic acid
What are L-amino acids?
L-amino acids are more common in nature; and are the building blocks of proteins
The ionization state of amino acids isdependent of what?
The ionization state of amino acids is pH dependent:
If the solution is…
acidic = amino groups(ionized) + carboxyl group (not)
neutral solutions = both ionized
basic = amino groups(neutral) + carboxyl group(ionized)
If the wine is acidic what is the ionization state of the amino acids?
In an acidic solution (pH 0-7) the:
amino groups= ionized (net negative)
carboxyl groups= net positive
In a basic (7-14pH) solution, is the carboxyl group net positive or negative?
basic = amino groups(neutral) + carboxyl group(ionized)
What pH would your wine have to be for both amino groups and carboxyl groups to be ionized?
neutral solutions = both ionized, pH of 7
What is a Zwitterion? Name an example
A ZwitterION = a functional group molecule
that has (at least) one positive electrical charge and one negative electrical charge
Amino Acids (ex) a group of amines (basic) and a group of carboxyls (acidic)
How are peptide bonds formed?
Peptide bonds are formed when =
the amino group from one amino acid is linked to the carboxyl group of another amino acid forming the AMIDE functional group
What is the glucose:fructose concentration in grape juice/must?
~1:1 concentration of
glucose:fructose
What is the order of sweetest to least sweet perception at same concentration?
fructose > sucrose > glucose
Do most S. cerevisiae strains are fructophilic (prefer fructose) or glucophilic (prefer glucose)
most = glucophilic (prefer glucose)
Name 3 methods of RS (Residual Sugar Testing) determination.
Rebelein method
Enzymatic testing
FOSS
FermenTEST
What must happen to red wine before testing with the Rebelein Method?
Red wine must be decolorized prior to testing (bc endpoint is cream colour)
What form are the amino groups at wine pH?
at wine ph the amino groups exists in the catION form
Protein content can increase/decrease significantly through the fermentation process. True or False + How?
TRUE!
Increase:
-Yeast secrete proteins into the wine
-Yeast autolysis after fermentation releases protein into wine
Decrease:
-metabolism
-Bind to lees
Solubility of proteins in wine depends on ______ + _______?
pH of wine
Isoelectric point (pI) of proteins (usually ~4-6)
Proteins are most soluble at their pI and so wine pH (~3-4) in terms of protein charge and stability: true or false
false (least soluble)
What is fining wine? Why would you do it?
Adding ingredients to wine that will remove components
-Remove off-flavors
-Improve stability
-Heat stability
-Cold stability
Fining agents react with components in wine by _________
binding Chemically+Physically
What properties are necessary to allow noncovalent interaction with proteins?
-Negatively charged compounds, bind by electrostatic interactions
-Compounds can form H-bonds w/ protein NH or OH groups
What is the most important factor for how well Bentonite works??
swelling
Can you add too much bentonite??
YES, you could remove desirable wine components – flavour and aroma
Bentonite fining trials:
Test a range of bentonite reactions with your wine to determine the minimum required for protein stability
What is Silica Gel Fining?
Aqueous suspension of silica dioxide
silicate particles are negatively-charged, interact with positively charged proteins, also can H-bond
What is NTU???
Nephelometric Turbidity Units
Turbidity is the amount of cloudiness in a liquid
