Scientists are encouraging the use of vegetable oils instead of fats to prevent cardiovascular diseases. However, using low-quality oil can be just as harmful. Distinguishing between good and bad oils is not an easy task.
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(Photo: VNN) |
To avoid purchasing counterfeit blended oils or low-quality oils, consumers need to have certain knowledge and utilize sensory methods to assess the smell, texture, color, and more.
Evaluating the Smell of Oil
First, wash your hands thoroughly, avoiding scented soap to prevent foreign odors from interfering with your assessment. Take a clean chopstick, dip it into the oil, then place a drop in the palm of your left hand. Use your right index finger to spread the oil across your palm and bring it to your nose to smell. High-quality oil should have a normal scent that is characteristic of the specific type of oil, with no rancid, unpleasant, burnt, or strange odors.
Tasting the Oil
Using a clean chopstick, place 1-2 drops of oil in the hollow of your palm. Use your tongue to sample the oil for any unusual taste. High-quality oil will have a normal flavor, not bitter, sour, or astringent, but rather a distinct taste characteristic of the product, depending on the type of oil. After tasting, spit it out and rinse your mouth thoroughly.
Assessing the Clarity of Oil
If the oil is of high quality, it will be clear with minimal water and impurities. If it is not clear, depending on the level of cloudiness, you can assess whether the oil is of lower or higher quality based on the amount of water and impurities present.
Observe the color of the oil to distinguish between types and qualities. Good quality oil typically has a dark yellow color, while oil of average quality appears light yellow. For canola oil, a hint of green may be present in the yellow, while peanut oil tends to be light yellow or pale orange; cottonseed oil is lighter still.
Detecting Blended Oils
To detect cooking oil mixed with cheaper oils, take a small amount of oil and place it in a test tube. Add a few drops of sulfuric acid and heat it in a water bath at 60 degrees Celsius for 15 minutes. If cheaper oil is present, the solution will form cloudy flakes; if the amount is excessive, it will clump together.
To detect the addition of starch to cooking oil, add a few drops of iodine to a sample of the oil, and observe for a blue color.
Sesame oil is a premium oil, which, when freshly produced, has a pinkish-yellow color. When held up to the light, it appears clear with no sediment at the bottom, no layering, and a distinct aroma. If it has been blended, even a mere 0.5% water can be detected: the oil will not be very clear, will not be as viscous as pure oil, may separate, and may have an off-putting scent or taste due to degradation, oxidation, or spoilage.
