Why a Comprehensive Study Is Key to Quality Frying

Research personnel should also be available throughout the study to assist and help keep the study on track. This is especially important when working in a restaurant or a food processing facility. The study should continue until you reach the endpoint established prior to initiating the work. This could be poor food quality or one of the chemical markers of oil degradation.

Types of Frying Tests

So, what do the different tests mean? Let’s take a look at a few of them.

Free fatty acids (FFA). Free fatty acids by themselves have no impact on the oil or fried food flavor. In fact, it is possible to fry foods in 100% free fatty acid mixtures. Fatty acids are, however, more prone to oxidation reactions, which create problems in foods and cooking oils. They are easy to measure, so they are often used as a quality indicator in frying operations, especially in snack foods such as potato chips.

Soaps. Soap is produced in the oil during chemical refining. This is subsequently removed completely from the refined oil using special adsorbents that remove the soap, along with the trace metals and residual phosphatides, from the oil. In frying oils, soaps will form through the reaction of free fatty acids and metals in the presence of water. These metals include calcium, magnesium, sodium, and potassium. Sources of metals are food and residual caustic from cleaning operations. Soaps are surfactants and will be absorbed onto frying food. Many active filter media are designed to reduce soaps in oils. Soap is a detergent. Presence of soap causes rapid rise in FFA in the oil during frying and also causes more rapid oxidation in the oil.

Total polar materials (TPM). The simplest definition for total polar materials is all non-triglyceride materials soluble in, emulsified in, or suspended in oil. Fresh oil typically contains 2 to 4 percent polar compounds but may contain less. Once oil is exposed to frying conditions, conversion of trigylcerides is initiated and is irreversible during the frying process. Proper oil management can slow polar material formation and extend the life of the oil. There are many who consider polar materials the single most important test for degrading restaurant cooking oils. In fact, Spain, Portugal, Italy, Belgium, France, and various states/cantons in Switzerland and Germany have established regulatory limits for polar materials in restaurant frying oils. In 2000, the DGF (German Society for Fat Research) stated that polar materials and polymeric triglycerides were the best indicators of oil abuse. This statement was made as part of the published summary of the 3rd International Symposium on Deep-Fat Frying held in Hagen, Germany. Unfortunately, testing for TPM requires a skilled technician, and the test itself is expensive.

Polymeric triglycerides. Polymers are the single largest class of degradation materials in frying oils. They include dimers, trimers, polymers, tetramers, and others, and are formed through both oxidative and thermal reactions. They manifest themselves as lacquers or brown buildup on fryers or in oil. Polymers are complex and generally indigestible. As noted above, polymeric triglycerides, along with polar materials, are excellent indicators of oil abuse.

Para-anisidine value (pAV). For every molecule of peroxide that breaks down, twice the equivalent amount of anisidines are formed; however, some of these will disappear through further oxidation reactions, forming dimers and trimers. This test is valuable for the detection of reprocessed edible oils. If an oil producer further processes their oils to reduce levels of free fatty acids, the end result will be an increased anisidine value.

Once the baseline data has been compiled and reviewed, the operator should have a good idea of how the oil degrades over time. The sensory data and chemistry can also be reviewed, and one or more of the chemical markers of oil degradation may now be selected as endpoint indicator. Operators will also have a good picture of how their frying systems run, giving them the background data to properly evaluate any proposed changes aimed at system optimization.

Frying Studies for System Optimization

Once a food processor or restaurant operator has established a solid baseline for frying performance, they are set up to properly evaluate any change to their frying system. As noted above, the change can be anything, including a different filter system, a change in food formulation, or the addition of an oil additive. The procedure for evaluating the change will mirror that used to establish the baseline data. The only change between the baseline study and the system or material being evaluated will be what is being evaluated. The sampling schedule will remain the same, the test protocol will remain the same, and the way that the data is analyzed will remain the same.