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Food Analysis > pH & Titratable Acidity > Flashcards

pH & Titratable Acidity Flashcards

1
Q

Titratable acidity

A

Total acid concentration within a food sample

Determined by titration

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2
Q

Organic acids

A

Citric
Malic
Lactic
Tartaric
Acetic

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3
Q

Inorganic acids

A

Phosphoric (lower pH)
Carbonic (beverages)

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4
Q

Apples acid

A

Malic

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5
Q

Grapes acid

A

Tartaric
(& malic)

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6
Q

Citrus fruit acid

A

Citric acid

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7
Q

Mushroom acid

A

Fumaric

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8
Q

Dairy product acid

A

Lactic

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9
Q

Vinegar acid

A

Acetic

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10
Q

Potentiometric titration

A

End point = a target pH

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11
Q

Colorimetric titration

A

End point = color change of a certain dye

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12
Q

Molarity

A

mol solute/L solution

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13
Q

Normality

A

Eq solute/L solution

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

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14
Q

Equilivant

A

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

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15
Q

SA + SB End Point

A

pH 7
All acid and base dissolves into solution

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16
Q

WA + SB End point

A

For foods
pH 8.2-8.3

17
Q

% TA Equation

A

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

18
Q

Automatic titrators

A

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

19
Q

Automatic titrators cons

A

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

20
Q

Volatile acidity

A

Evaporates from the food

21
Q

Fixed acidity

A

doesn’t evaporate from the food

22
Q

Calculate volatile acidity

A

Do 2 titrations: before and after boiling off the acid

Volatile = total - fixed

23
Q

HPLC

A

Does not differentiate between A and CB

Separates individual acids

Need to create standard curve for each acid

24
Q

pH

A

Convenient measurement of acidity
In aq solution

25
Q

Litmus paper

A

Acidic = red
Basic = blue
Not quantitative

26
Q

pH Indicator strips

A

Simple
Rapid
Inexpensive
Paper is bound with indicator dyes

27
Q

pH meter

A

Two combined electrodes (known vs unknown pH)

Measured voltage is related to concentration of the ions in solution

28
Q

pH caveats

A

Must calibrate with buffers

Have to adjust for temp (pH is temp dependent)

29
Q

pH Error

A

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

30
Q

NaOH standardization

A

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

31
Q

Normality equation

A

mass Acid (mg) / Volume base * EW Acid

32
Q

Equilivant weight

A

Molecular weight / # of equivalents

Food Analysis (19 decks)

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