Quality control frying oils

Most countries in Europe and Chile have adopted some form of regulations to control the quality of frying oil at the restaurants. Most of these countries have decided that the oil reaches the end point when the polar material in the oil exceeds a certain level. This level is somewhat different for different countries. This regulation compels the restaurant personnel to learn the techniques of testing fryer oil for quality and to determine when to discard it. Table 4 lists the regulatory limits on the restaurant oil quality (3). 

Free fatty acids are probably the most widely used characteristic of oil quality control (AOCS Ca 5a-40). Deodorized oUs, generally, have a free fatty acid level of less than 0.05%. During use for frying, there is a buildup of free fatty acids. In the initial... 

A number of routine methods have been used to evaluate the extent of oxidative and thermal damage to frying fats. These methods can be divided into those that can be used later on oil samples collected some time after frying, those employed immediately after frying for quality control, and those applied to fried foods. 

In most controlled frying studies, total polar material (TPM) has proven to be a reliable measure of the oil quality. At least TPM has shown to be more consistent than free fatty acids, per oxide value, colour or oil viscosity. In some EU countries, 24% TPM is considered to be the end point of the fry oils. However, it cannot be stated conclusively that in all frying operations TPM above 24% will result in less than acceptable quality of the fried food. In addition, several companies sell fast reacting dip strips which prove helpful in some operations but not others. 

Hydrogels are used in the refining of edible oils to adsorb phospholipids, trace metals, and soaps (103). The adsorption capacity depends on the ease of hydration of the adsorbates, so best performance demands careful control of moisture content in the system (104). Silica hydrogel in combination with alumina has been found to be useful for purifying used cooking oils in order to extend their life and enhance the quality of the fried food (105). 

The finish frying zone which starts as the product approaches the end of the submerger belt and continuous until the product is removed from the fryer by the carry out conveyor. Finish frying is very important for the quality of the product and must be carefully controlled. If the product is removed from the fryer before finish frying is completed it would have poor flavor, light color, poor textural characteristics, and low oil content. It is the final dehydration and temperature rise that support chemical reactions generating much of the flavor and color of the products and create the desired texture. 

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