Small scale frying of potatoes in sunflower oil: thermooxidative alteration of the fat content in the fried product.

Sets of 500 g of potatoes were fried discontinuously 15 times in 31 of sunflower oil without addition of unused oil. The fat content of fried potatoes increased with the number of fryings. The quality of the extracted oil from the fried potatoes was evaluated by a combination of column and high performance size exclusion chromatography, and compared with their respective fryer oils. Total polar content (mg 100 mg oil-1) increased after 15 fryings from 6.2 +/- 0.35 to 18.7 +/- 0.81 in the oil in the frier and to 21.2 +/- 0.92 in the fries. Triglyceride polymers, triglyceride dimers and oxidized triglycerides (mg 100 mg oil-1) increased progressively and significantly with the number of fryings either in the fryer oil or in the extracted oil, being the content of triglyceride dimers significantly higher in the extracted oil than in the oil in the fryer. Potatoes from the 15th frying contained more total alteration-oil-products, triglyceride polymers, triglyceride dimers and oxidized triglycerides (g 100 g fresh matter-1) than potatoes from the 8th frying (all p < 0.01). This fact may be of special relevance for some people who usually eat large quantities of potatoes fried in oils with a null or low turnover of fresh oil.