Test Method for Smoke Point of Vegetable Oils and Fats
Vegetable oils and fats are natural oils extracted from plant seeds, fruits or germs, whose main components are compounds of fatty acids and glycerol. Most of them are liquid at room temperature (e.g., soybean oil, peanut oil), while a few are semi-solid or solid (e.g., coconut oil). They are mainly classified into two categories: edible vegetable oils (e.g., soybean oil, rapeseed oil) and industrial oils (e.g., tung oil, castor oil); as well as three types based on drying properties: drying oils (e.g., tung oil), semi-drying oils (e.g., sesame oil) and non-drying oils (e.g., coconut oil).
Common types are as follows:
Edible oils: soybean oil, peanut oil, rapeseed oil, sesame oil, corn oil, olive oil, etc.
Industrial oils: tung oil, castor oil, etc.
Vegetable oils and fats are not only used in cooking, but also widely applied in the production of industrial products such as soap, paint and lubricating oil.
Purpose of the Experiment
The main purposes of the experiment for testing the smoke point of vegetable oils and fats are as follows:
1.Evaluate thermal stability of oils and fats: The smoke point refers to the temperature at which an oil starts to emit a steady stream of blue smoke, which directly reflects its heat resistance. The higher the smoke point, the more stable the oil is during high-temperature cooking, and the less likely it is to decompose and produce harmful substances.
2.Ensure food safety: During high-temperature cooking, smoking of oils and fats will release carcinogens such as acrolein. Smoke point testing helps screen safer edible oils and reduce health risks.
3.Unify testing standards: The national standard GB/T 20795-2006 specifies the method for determining smoke point, ensuring the comparability of data from different laboratories and avoiding quality disputes caused by testing differences.
4.Guide production and consumption:
Production side: Assist enterprises in optimizing production processes and improving the thermal stability of oils and fats.
Consumption side: Provide a basis for consumers to make choices. For example, oils with high smoke points are more suitable for frying.
Experimental Samples and Instruments
Experimental samples: Vegetable oils and fats
Experimental instruments: ST123 Oil Smoke Point Tester, which complies with the standard AOCS Cc 9a-48
Experimental Procedures：
Sample preparation：Filter the vegetable oil sample to be tested to remove impurities (such as solid particles or moisture); ensure the sample is free of turbidity or precipitation, and centrifuge for clarification if necessary.
2.Instrument calibration：Calibrate the thermometer or digital sensor to ensure the accuracy meets the requirements (±1℃); check that the heating device and air circulation device are functioning properly.
3.Sample heating：Pour approximately 50 mL of vegetable oil into a clean and dry container; place the container on the heating device, turn on the heating and start temperature recording. Initial heating rate: heat up at a rate of about 1℃/min (achievable by adjusting heating power).
4.Observation and recording
Temperature range: Heat the sample from room temperature (about 20-25℃) until the oil starts to smoke.
Smoke identification: Record the temperature when continuous, stable blue smoke (not transient steam) appears on the surface of the oil. Note to distinguish between water vapor (transient, white) and oil smoke (continuous, blue).
Environmental control: Maintain air circulation in the laboratory to avoid local overheating or overcooling; prevent direct strong light or air current from interfering with smoke observation.
Repeat experiment：Repeat the experiment at least 3 times for each sample, and take the average value as the final smoke point. If the results differ significantly (e.g., by more than ±5℃), check the sample purity or instrument status.
Experimental Results
Soybean oil: Smoke point is 230℃, suitable for high-temperature cooking such as frying and baking (smoke point ≥230℃).
Peanut oil: Smoke point is 226℃, suitable for medium-to-high temperature cooking such as stir-frying and quick-frying (smoke point ≥220℃).
Olive oil: Smoke point is 230℃, only suitable for cold dressing and low-temperature cooking (smoke point ≤190℃).