HIRANUMA APPLICATION DATA

Jun 6,
2017

Date No. A11

Automatic Titrator

Acid value measurement of orange juice

FOOD

1. Abstract
An example for acid value measurement of orange juice performed by neutralization titration isintroduced here.
Dispense the sample and add pure water. Titrate with sodium hydroxide standard solution until the pHreaches 8.1 using a glass electrode (neutralization titration). Acid value is calculated by the standard solution
volume titrated until the pH reaches 8.1 as the citric acid content.
Reaction between citric acid and sodium hydroxide is described by the following formula (1).

CH2COOH∣C(OH)COOH∣CH2COOH+3NaOH→CH2COONa∣
C(OH)COONa∣
CH2COONa+3H 2O･･･(1)2. Configuration of instruments and Reagent(1) Configuration：

Main unit

Hiranuma Automatic Titrator COM series

Electrodes ：Glass electrode GE-101B
Reference electrode RE-201Z
Thermistor electrode TE-403＊The glass/reference combination electrode is usable instead of glass electrodeand reference electrode. The glass/reference combination electrodes are listedbelow.
・GR-501BZ (Fixed sleeve type)・GR-511BZ (Movable sleeve type )(2) Reagent
Titrant：

0.1 mol/L sodium hydroxide standard solution

3. Measurement procedure(1) pH calibration
The pH calibration should be performed with neutral phosphate (pH 6.86) and borate (pH 9.18) pH
standard solution.
(2) Acid measurementi) Dispense 1~5 g of the sample into a 200 mL beaker and accurately weigh it.
ii) Add pure water to make about 100 mL of solution.
iii) Immerse the electrodes and start to titrate with sodium hydroxide standard solution. Perform it until thepH reaches 8.1.
iv) Measure the blank in a similar way to the above procedure without sample.

4. Measurement condition and Results
Example of titration condition
Measurement of blank
Cndt No.
MethodBuret No.
Amp No.
D. Unit
S-Timer
C.P. mL
Direction
D.P. mL
End Point pH
Over mL
Max.Vol.

1
Set
1
1
pH
50
↑
0.0
8.10
0.0
1

sec
mL
mL
pH
mL
mL

ConstantNo.
SizeBlank
Molarity
Factor
KL

1
0.0
0.0
0.1
1.005
0.0
0.0

Unit
FormulaDigitsAuto In Pram.

mL
D3g
mLmol/L

Mode No.
Pre Int
Del K
Del Sens
Int Time
Int Sens
Brt SpeedPulse

140003328Mode No.
Pre Int
Del K
Del Sens
Int Time
Int Sens
Brt SpeedPulse

505033240sec
mV
sec
mV

Non

Measurement of sample
Cndt No.
MethodBuret No.
Amp No.
D. Unit
S-Timer
C.P. pH
Direction
D.P. pH
End Point pH
Over mL
Max.Vol.

2
Set
1
1
pH
10
6.0
↑
6.5
8.10
0.10
20

ConstantNo.
SizeBlank
Molarity
Factor
K
L

sec
pH
pHpH
mL
mL

Unit
FormulaDigitsAuto In Pram.

22.6328
0.02
0.1
1.005
640.0g
mL
mol/L

sec
mV
sec
mV%(D-B)*K*F*M/(S*10)
3
NonMeasurement results
Measurement of blank
Number ofmeasurement

Measurement of sample

Size

123
Average（Blank)

(g)
―――

Titer (mL)
0.020
0.019
0.021
0.020 mL

Number ofmeasurement
12
3

Size

Titer(g)(mL)

2.62102.782
2.58532.743
2.5920
2.751
AverageStandard deviation
Coefficient of variation

Acidvalue
(%)
0.678
0.677
0.678
0.678
0.001
0.085

Blank measurement

Sample measurement

Examples of titration curves

5. Note(1) pH calibration
The pH calibration is quite important because pH 8.1 is detected as the endpoint by set-endpoint
detection on the acid value measurement. It must be calibrated before the measurement one time per a dayat least.
The pH is sensitive to the temperature, the use of a thermistor electrode for temperaturecompensation is recommended to measure pH more accurately.
(2) Reduction of measurement time
When using the function “CP pH”, the titrant is continuously added until the pH reaches the set value(pH 6.0 here). The measurement time can be reduced by this function.
For example, the measurement time was about 4 minutes without using CP pH on this measurement.
However, it was 2 minutes when using CP pH. CP pH availability depends on the sample, pleaseappropriately use it considering the sample.
Keyword：Acid value, Orange Juice, Neutralization Titration, Fruit drink, pH calibration*Some measurement would not be possible depending on optional configuration of system.