The AOCS recommended practice Cc 17-79 measures titratable alkalinity (soaps) at the low parts per million level in fresh, alkalirefined vegetable oils. This method indicated that titratable alkalinity is present at levels equivalent to many parts per million of "soap" in used frying oils. A colorimetric quick test was developed to show the presence and semi-quantitative concentration of alkaline contaminant materials (ACM), such as soap, in two types of fresh and used frying oils. The quick test works with fresh and used vegetable and animal/vegetable oil blends where it is not possible to use Cc 17-79.

Alkaline contaminant materials are formed in frying oils during cooking. The ACM can be eluted from the same International Union of Pure and Applied Chemists-Association of Official Analytical Chemists (IUPAC-AOAC) silica gel column used to determine polar materials in frying oils. The ACM are eluted with methanol after "non-polar" and "polar" fractions already have been eluted from the column. A residue of silica gel in the methanol eluate must be insolubilized before the ACM can be identified and quantitated. IR was used to identify sodium oleate as the major constituent of ACM from a set of restaurant generated frying oil samples.A previous paper (1) described a quick test solution for determining the amount of alkaline contaminant materials {ACM) in used frying oils. ACM include soaps and other highly surfactant materials. These ACM are formed during use of a frying oil along with other polar chemicals. Unlike fatty acids, such alkaline materials are expected to lower the interfacial tension around frying food {2). A decrease in interfacial tension between oil and food corresponds to an increase in the amount of pickup of heated oil on fried food.The column chromatography method of Guhr and Weibel (3) has been adopted as an internationally used test (4} to determine the amount of polar materials formed in frying oils as a result of cooking. Polar materials are retained on a silica gel column while non-polar materials are eluted. The difference between the weight of applied oil and the weight of eluted non-polar materials is used to determine the amount of polar materials in the applied oil for regulatory purposes. For research purposes, the polar materials can be eluted from the column to determine the efficiency of the technique.The more severely degraded oils deposit 1% to 2% nonelutable polar materials on the column (5). While the column chromatography method for determining polar materials in used frying oils is not perfect (6), it has been accepted by some regulatory agencies to judge the degree of use and abuse of frying oils.Elutable non-polar and polar fractions of both fresh and used vegetable oil samples (Mel-Fry, Durkee} were examined. It was found that neither type of fraction reacted with the ACM Quick Test Solution (1}, even though the whole oil, before chromatography, did react to indicate the presence of alkaline materials. This suggested that ACM are among the non-elutable polar materials which remain on the silica gel column after the recommended procedures are followed. We then developed a method for isolating and identifying ACM from the "non-elutable" polar materials left on the silica gel column. EXPERIMENTAL Sample preparation.A premium vegetable oil consisting of partially hydrogenated soybean oil, TBHQ and dimethyl silicone (Mel-Fry, Durkee} was heated in a 20-1 capacity electric fryer. The fryer was operated at 180 + 5 C for 12 hr/day, seven days/week at a fast food restaurant. Foods fried were potatoes {75%} and breaded chicken, fish, clams and vegetables {25%}, for a total of about...

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