ABSTRACT: The feasibility of applying methods developed by Safety Associates, Inc., to monitor oil degradation products, in- cluding malondialdehydes (AldeSafe TM ), FFA (FASafe TM ), and peroxides (PeroxySafe TM ), in fresh and heat-abused deep-fat fry- ing oil was evaluated. Based on performance qualification stud- ies, the AldeSafe method was the most suitable SafTest TM assay for monitoring the quality of frying oil because of its high accu- racy, precision, linearity, and reproducibility, and low detec- tion/quantitation limits. A strong correlation (r = 0.924) between the AldeSafe method and its counterpart, AOCS Official Method Cd 19-90, also supported the suitability of the SafTest method for monitoring oil quality. Moreover, the FASafe method had a mod- erately strong relationship with AOCS Official Method Ca 5a-40 (r = 0.761). Our studies suggest that this test can be applied for monitoring frying oil; however, certain method performance lim- itations must be considered for routine analysis purposes. In con- trast, the PeroxySafe method probably should not be used to mon- itor heat-abused oil without further development because of high variability, low accuracy, and low correlation (r = 0.062) with the AOCS Official Method Cd 8-53 assay. Paper no. J11254 in JAOCS 83, 15–20 (January 2006). KEY WORDS:Assay correlation, deep frying, free fatty acids, method qualification, malondialdehyde, oil degradation prod- ucts, oil quality indicators, peroxides. Controlling deep-fat frying processes is crucial in the food in- dustry, as oil degradation products can compromise the qual- ity of the oil over time and may be harmful to human health (1–6). Peroxides and malondialdehyde (MDA) are applicable indicators of oil quality, as these oxidation by-products are produced from several frying parameters, i.e., light, elevated temperatures, oxygen, water in the food, and the like (7,8). FFA are another oil quality indicator because these molecules are cleaved from TAG when steam reacts with oil at the ele- vated temperatures typically used in a deep-fat frying process (2). Although AOCS official methods are available for moni- toring the cited indicators of degraded oil, several disadvan- tages exist in their application (9–11). For example, haz- ardous chemicals are needed for some of the tests; therefore, appropriate safety equipment and additional waste disposal must be considered. Bias and manual errors can also occur when performing the titration-based methods for FFA and peroxides. To complete the MDA-AOCS method, 2-thiobar bituric acid (TBA) is combined with the test sample and a pigment is formed in the presence of MDA, which can the be monitored at a wavelength of 530 nm (8,12). However, TBA reacts with other molecules, including ketones, ketos teroids, acids, esters, sugars, imides and amides, amino a oxidized proteins, pyridines, and pyrimidines (13). In addi tion, solution and/or standard preparation requirements in crease the time required to complete the AOCS assays. Methods developed by Safety Associates, Inc., (Tempe, AZ) under the brand name of SafTest TM may be promising al- ternatives to the official AOCS assays for monitoring fryin oil quality because peroxides, MDA, and FFA can easily be detected (14). Samples are prepared for this system by so bilizing the food matrix with a proprietary preparation sol tion, separating the quality indicator from other food com nents when necessary, and reacting the ensuing extract w proprietary reagents. The quality indicators are detected an optical reader programmed to quantitate the molecule interest against a previously established calibration curve the test reagents, calibration standards, controls, membra packs, and so on are available in kits specific to the qualit indicator of interest. As a result, the SafTest system gener less waste, does not require timely standardized solut preparations, and is capable of higher sample analyses th the AOCS methods. Despite internal studies conducted by the manufacturer showing the successful application of the SafTest methods various food systems, these assays have not been used ext sively in the food industry. The purpose of these studies w to determine the feasibility of using the SafTest system to monitor the quality of frying oil heated for extended perio of time. Assay qualification studies were initially performe to evaluate the basic performance characteristics of t SafTest assays. These methods were then compared with official AOCS counterparts. MATERIALS AND METHODS Reagents and solutions. AldeSafe TM , FASafe TM , and Peroxy- Safe TM kits were purchased from Safety Associates, Inc. Ea kit contained the following items: preparation solution, an lyte reaction reagents, positive controls (low, high, an medium), and 3 to 5 standards of known concentrations. T reagents purchased to complete the AOCS test consisted o acetic acid, 1 N sodium hydroxide, glacial acetic acid (J.T. Copyright © 2006 by AOCS Press 15 JAOCS, Vol. 83, no. 1 (2006) *To whom correspondence should be addressed at Department of Food Sci- ence and Technology, 143 Filley Hall, University of Nebraska, Lincoln, NE 68583-0919. E-mail: vlschleg@unlnotes.unl.edu Evaluation of SafTest TM Methods for Monitoring Frying Oil Quality Swee Yee Foo, Susan Cuppett, and Vicki Schlegel* Department of Food Science and Technology, University of Nebraska, Lincoln, Nebraska 68583-0919