Test Kit Technologies

VERI-FRY® TPM Test with Color Cards

As frying oil breaks down with use, the color of the oil deepens from near colorless to deep reddish-brown. However, the color of the oil is not directly related to the color of, or degree of quality of the fried food. The color development and quality of the food arise solely from heat and mass transfer among the equipment, heated and oxidized oil, and fluid coming from and entering into the cooking food. Color in the oil is rarely greater than 2% of the mass of the oil, and a thin layer of oil on the food is colorless to the eye.

The VERI-FRY® TPM test sums up all the degradation in frying oil and also includes darkly colored suspended ultra fine silt, food "juices", and also polymeric materials. The test is applicable to all oils in the range of 3.2-32.0% polar breakdown materials in the oil sample. The values were established with an international collaborative study among corporate, government, and university laboratories, monitored by the US Food and Drug Administration (FDA) and U.S. Department of Agriculture (USDA).. Independent studies within individual foreign agencies and testing laboratories individually confirmed the major study.

The technical studies were performed using a spectrophotometer set at 590nm, so the results were independent of operator. In situations where a spectrophotometer is not suitable, a plastic color card can be used to interpret the general results for the VERI-FRY® TPM Test. The translucent color areas on the card permit holding the completed TPM test vial next to the color card while looking through them at either an indoor light or sunlit sky. The ranges of actual % polar materials represented by the color on the card have to be established for a specific, or representative case involving the type of fryer, oil, and food in the fryer being tested. The color card comparison can then be used to generally describe oil condition for the intended target system. To calibrate the color card readings to actual % Polar Compounds and other, interfering substances in the oil, requires specific samples of the target oil to be tested by a column chromatography method in a laboratory. This calibration procedure assures a correlation between color card readings, spectrophotometric readings, and % total polar materials in the target oil. The color card then can be used to approximate TPM in related frying situations.

A printed color chart provided with some versions of the TPM Test Kits works by matching reflected light, rather than transmitted light as with the plastic VERI-FRY® TPM color card. Reflected light color matching is especially useful in throwaway situations, but it is less reliable for both accuracy and precision than the plastic color card.

A final caution, a person handicapped in color discrimination (also called "colorblindness) cannot distinguish some of the color information from transmitted or reflected light, and therefore should not use the color system.

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