What is the best way for a restaurant to determine when the end of the fry life of a zero trans fat oil has been reached?
Unquestionably the taste, odor and texture of the product. The color of the oil is not a good indicator. Many oils darken quickly, but they perform perfectly well regardless of the color. Click here for more information about oil color and fry life. Using 3M strips to determine free fatty acids is a rough indicator used by many restaurants but not reliable. Some restaurants use digital measuring probes such as an Ebro oil monitor or a Testo 265 that they dip in the oil. Such devices indicate the Total Polar Materials (TPM) in the oil which is the most reliable indicator. However, most oils develop off-flavors and off-odors long before the accepted 24% TPM limit is reached.
