GIFSQ Tools · Module 07 — Dairy, Milk, Cheese & Fermented Products · Tool 138 of 500
Track titratable acidity in a fermenting milk from the sodium hydroxide titration, and see how fast the acidity is rising.
Try sample values — fills the form with the worked example below.
–
Acidity (% lactic acid)
–
Change since last reading (pp)
–
Acidity rise (% per hour)
Equation: Acidity (% lactic acid) = titration volume (mL) × normality × 0.090 × 100 ÷ sample (g). Change (pp) = acidity − previous acidity. Rise (% per hour) = change ÷ hours since the previous reading.
Method: Titratable acidity of fermented milk by ISO/TS 11869 (IDF/RM 150): titration with sodium hydroxide to the phenolphthalein end point, expressed as lactic acid (0.090 g per mL of 1 N NaOH).
Assumptions: the end point is the faint permanent pink of phenolphthalein; the sample is well mixed; the previous reading was taken on the same batch.
Limitations: titratable acidity is not pH — a batch can be on acidity and off pH, so check both before cooling; the rise rate is only valid between two readings on the same batch.
Rounding: acidity, change and rate to 2 decimal places; intermediates unrounded.
This is a calculation aid, not a laboratory report — confirm against your accredited method before citing a value.
Method: Titratable acidity of fermented milk by ISO/TS 11869 (IDF/RM 150): titration with sodium hydroxide to the phenolphthalein end point, expressed as lactic acid (0.090 g per mL of 1 N NaOH).
Assumptions: the end point is the faint permanent pink of phenolphthalein; the sample is well mixed; the previous reading was taken on the same batch.
Limitations: titratable acidity is not pH — a batch can be on acidity and off pH, so check both before cooling; the rise rate is only valid between two readings on the same batch.
Rounding: acidity, change and rate to 2 decimal places; intermediates unrounded.
This is a calculation aid, not a laboratory report — confirm against your accredited method before citing a value.
Worked example: 9.0 mL of 0.1 N NaOH for a 10 g sample; previous acidity 0.45% two hours ago. Acidity = 9.0 × 0.1 × 0.090 × 100 ÷ 10 = 0.81%; change = 0.36 pp; rise = 0.18% per hour.
Saved records
Saved on this device only — nothing leaves this browser.
| Saved | Result |
|---|
Enter values above to see results.
Set yogurt is usually cooled at 0.85–0.95% titratable acidity (pH about 4.6); readings are saved on this device only. Tool 138 of 500 — GIFSQ
