pH & Titratable Acidity

Question 1

Titratable acidity

Answer 1

Total acid concentration within a food sample

Determined by titration

Question 2

Organic acids

Answer 2

Citric
Malic
Lactic
Tartaric
Acetic

Question 3

Inorganic acids

Answer 3

Phosphoric (lower pH)
Carbonic (beverages)

Question 4

Apples acid

Answer 4

Malic

Question 5

Grapes acid

Answer 5

Tartaric
(& malic)

Question 6

Citrus fruit acid

Answer 6

Citric acid

Question 7

Mushroom acid

Answer 7

Fumaric

Question 8

Dairy product acid

Answer 8

Lactic

Question 9

Vinegar acid

Answer 9

Acetic

Question 10

Potentiometric titration

Answer 10

End point = a target pH

Question 11

Colorimetric titration

Answer 11

End point = color change of a certain dye

Question 12

Molarity

Answer 12

mol solute/L solution

Question 13

Normality

Answer 13

Eq solute/L solution

Represents the mol of H+ and OH- per liter that will be exchanged in neutralization

Question 14

Equilivant

Answer 14

amount of a substance that reacts with an amount of another substance in a chemical reaction

Question 15

SA + SB End Point

Answer 15

pH 7
All acid and base dissolves into solution

Question 16

WA + SB End point

Answer 16

For foods
pH 8.2-8.3

Question 17

% TA Equation

Answer 17

(100 x N titrant x V titrant x EW acid) / (mass sample)

Question 18

Automatic titrators

Answer 18

Fast and accurate
Has a pH probe built in
Pump dispenses base
Stops titration around 8.2

Question 19

Automatic titrators cons

Answer 19

Need specific titrator for certain concentration ranges
Have to buy NaOH from them

Question 20

Volatile acidity

Answer 20

Evaporates from the food

Question 21

Fixed acidity

Answer 21

doesn’t evaporate from the food

Question 22

Calculate volatile acidity

Answer 22

Do 2 titrations: before and after boiling off the acid

Volatile = total - fixed

Question 23

HPLC

Answer 23

Does not differentiate between A and CB

Separates individual acids

Need to create standard curve for each acid

Question 24

pH

Answer 24

Convenient measurement of acidity
In aq solution

Question 25

Litmus paper

Answer 25

Acidic = red
Basic = blue
Not quantitative

Question 26

pH Indicator strips

Answer 26

Simple
Rapid
Inexpensive
Paper is bound with indicator dyes

Question 27

pH meter

Answer 27

Two combined electrodes (known vs unknown pH)

Measured voltage is related to concentration of the ions in solution

Question 28

pH caveats

Answer 28

Must calibrate with buffers

Have to adjust for temp (pH is temp dependent)

Question 29

pH Error

Answer 29

High or low concentration of ions affects the accuracy

At very high pH → alkaline error → pH reading is lower than actual

At very low pH → reading is higher than actual

Question 30

NaOH standardization

Answer 30

Working solution is made by diluting stock base
KHP used to standardize titrant

Question 31

Normality equation

Answer 31

mass Acid (mg) / Volume base * EW Acid

Question 32

Equilivant weight

Answer 32

Molecular weight / # of equivalents