QUANTITATION AND DISTRIBUTION OF POLAR COMPOUNDS IN AN EXTRA VIRGIN OLIVE OIL USED IN FRYINGS WITH TURNOVER OF FRESH OIL

The alteration of an extra virgin olive oil used in 75 repeated and in termittent deep-fat fryings of potatoes (with a frequent turnover of f resh oil) was measured by column and high-performance size-exclusion c hromatography (HPSEC), Total polar content increased slightly but cont inuously in the fryer's oil during the first 30 fryings from 2.76 +/- 0.01 mg/100 mg oil (mean +/- SD) to 6.60 +/- 0.00 mg/100 mg used oil, followed by a tendency to reach a near steady state after a large numb er of fryings. Compounds related to thermoxidative alteration also inc reased significantly in the oil used 75 times to fry potatoes. Triglyc eride dimers increased from 0.03 +/- 0.01 mg/100 mg unused oil to 1.65 +/- 0.05 mg/100 mg oil at the thirtieth fryings while triglyceride po lymers and oxidized triglycerides did so during the first 60 fryings ( 0.07 +/- 0.01 mg/100 mg oil and 0.56 +/- 0.03 mg/100 mg oil in the unu sed oil respectively to 0.38 +/- 0.01 mg/100 mg oil or 2.95 +/- 0.15 m g/100 mg oil in the used oil, respectively). Both of these changes wer e followed by a tendency of these polar compounds to reach a near stea dy state in later successive fryings. Nevertheless, diglycerides and f ree fatty acids related to hydrolytic alteration remained quite stable throughout the frying process. Data from this study indicate that rep eated fryings of potatoes in extra virgin olive oil with a frequent tu rnover of fresh oil throughout the frying slightly increased the level of polar material in the fryer oil during the first fryings followed by minor changes and by a tendency to reach a near steady state in suc cessive fryings.