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Regulation of used frying fats and validity of quick test for discarding the fats

DOI:10.3989/gya.1998.v49.i3-4.735
Authors:
M. C. Dobarganes
M. C. Dobarganes
Gloria Márquez-Ruiz at Spanish National Research Council
Gloria Márquez-Ruiz
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Abstract

During deep-fat frying, a complex series of reactions takes place resulting in hydrolysis, oxidation and polymerization of the oil. As quality of fried foods is affected by that of the oil, regulations or guidelines have been established in many countries to guarantee high quality foods. In this lecture, present regulations mainly focusing on oil deterioration and setting limits to alteration compounds are reviewed. Among analytical methods to control oil quality, polar compound and polymer determinations stand out. Studies carried out in different countries indicate the need for improving the quality of frying oil to produce more nutritious fried foods. Practical deep-fat frying can be divided in industrial and fast-food segments, characterized by the use of continuous and discontinuous fryers, respectively. From the analysis of a high number of samples it is deduced that the present situation is very different in both segments and that the main problem is to determine when the fat or oil has to be replaced where there are no laboratory facilities. Hence, simple rapid analytical tests to substitute for official methods are neccesary to monitor oil quality in restaurants and fried food outlets. Data of validity of rapid tests will be presented with particular emphasis on the utility of commercialized kits like Oxifrit-Test and Veri-Fry to improve the quality of frying fats and oils.
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... The FOS instrument, designed in 1979 and commercialized by the Northern Instrument Corp., was considered to be the earliest prototype based on this principle (Graziano, 1979). In the early stages, Paradis and Nawar (1981), Hein, Henning, and Isengard (1998) and Dobargarnes and Marquez-Ruiz (1998) reported a good correlation between FOS readings and chemical results (R 2 = 0.9847-9940). However, the range of FOS readings was from 0 to 10, and a FOS value of 4 was used as the discarding point, whose unit was different from the percentage (%) used in chemical results. ...
... The validity of the rapid test was evaluated with respect to the legislation criteria using the same method reported by Dobargarnes and Marquez-Ruiz (1998). The dataset was separated to four parts of correct results (TPC rapid ≤ internal control and TPC conventional ≤ regulation control), correct results (TPC rapid > internal control and TPC conventional > regulation control), false-negative results (TPC rapid ≤ internal control and TPC conventional > regulation control), and false-positive results (TPC rapid > internal control and TPC conventional ≤ regulation control) by counting the number of samples within the selected range. ...
... According to the regulations of frying oil, the maximum content of TPC has been set at 27% in Australia, China, Switzerland, 25% in Belgium, France, Portugal, Italy, Spain and 24% in Germany (Hosseini et al., 2016). So as estimated in Supplementary material Table S-2, the validity of the rapid test for TPC was evaluated with respect to the legislation criteria using the method reported by Dobargarnes and Marquez-Ruiz (1998). Results showed that, for three mentioned limitations, the rapid result of TPC 22%, 21%, and 20% was recommended as the internal control index in restaurants, respectively. ...
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... Different countries have set different maximum limits of FFA%. In general, it is in the range of 0.5-2.5% depending on each country's legislations (Dobargarnes et al., 1998;Firestone, 1993). ...
... The final FFA content ranged from 0.68 to 3.95. The maximum accepted level of FFA varied from one country to another and ranged from 0.5 to 2.5% (Dobargarnes et al., 1998;Firestone, 1993). ...
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... Also, the gradual increase of the water in the oil caused more acrylamide formation by positively affecting the heat transfer properties of the oil (Gertz and Klostermann, 2002;Gertz et al., 2003;Lim et al., 2014). The successive frying sessions can increase the number of polar compounds in frying oil, and the limit for total polar compounds is 25 % in frying oils (Dobarganes and Márquez-Ruiz, 1998;Hammouda et al., 2019). Karakaya and Ş imşek (2011) showed that the polar compound ratio increased significantly in all oil types in their research on different frying oils. ...
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... For a safety use, the regulation suggested that the presence of TPC and the content of FFA in the oil should Food Engineering, Materials Science, & Nanotechnology Palm olein degradation during frying . . . not be more than 25.00% and 2.50%, respectively (Dobarganes & Marquez-Ruiz, 1998). ...
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