Cryoscopy
Definition
Measurement of milk freezing-point depression (AOAC 961.07). Pure bovine milk freezes at -0.530 to -0.560°C; added water raises (makes less negative) the freezing point; added urea or salts lower it. The combination of added water plus urea can give a misleadingly normal cryoscopy result.
- Standard method
- AOAC 961.07
- Pure bovine milk range
- -0.530 to -0.560 degrees Celsius
- Added water effect
- Raises the freezing point (less negative)
- Detection gap
- Added urea can mask water dilution
Common questions
Why can added water go undetected by a simple cryoscopy reading alone?+
Water dilution raises the freezing point away from the expected pure-milk range, but if urea or another solute is added at the same time to lower it back down, the combined result can land back within the normal range, giving a falsely reassuring reading.
How is this masking typically caught in a full adulteration investigation?+
Cryoscopy is paired with other tests, such as measuring urea, total solids, or specific conductivity, because an adulterant combination that fools one test rarely produces a consistent result across all of them simultaneously.
Related terms
- ATR-FTIR
- Attenuated Total Reflectance Fourier-Transform Infrared Spectroscopy: a non-destructive mid-infrared method that analyses a single drop of milk pressed against an ATR crystal....
- Bromocresol Green (BCG) Test
- A colorimetric rapid test for surfactant detergents in milk: BCG at pH 4 partitions into surfactant micelles, shifting from yellow to blue-green...
- Codex Alimentarius
- The FAO/WHO joint food standards programme that sets international reference limits. Its 2012 action levels for melamine (2.5 mg/kg in infant formula,...
- Diacetyl Monoxime (DAM) Test
- A FSSAI-approved colorimetric rapid test for urea: urea reacts with DAM under acidic conditions to produce a yellow-to-orange chromophore readable at 540...
- FSSAI
- Food Safety and Standards Authority of India, established under the Food Safety and Standards Act 2006 as the central food regulatory body,...
- Kjeldahl Method
- The reference method for protein determination in food: sulphuric acid digestion converts all nitrogen to ammonium sulfate, which is titrated after distillation....
- LC-MS/MS MRM
- Liquid chromatography with triple-quadrupole tandem mass spectrometry operated in multiple reaction monitoring mode. The most sensitive confirmatory method for melamine (primary MRM...
- Melamine
- 1,3,5-triazine-2,4,6-triamine (C3H6N6), a nitrogen-rich compound (66.7% N by mass) used industrially in resins and laminates, illegally added to milk and dairy products...
- Melamine-Cyanuric Acid Co-Crystal
- A 1:1 insoluble complex formed when melamine and cyanuric acid co-occur in acidic renal urine. The co-crystal precipitates inside renal tubules, causing...