The liberation of free fatty acids in potato slices at low temperature

Free fatty acids (FFA) are liberated in the first stages of potato granule production. In this study, the liberation of FFA was examined in model experiments. Potato slices were exposed to conditions resembling the first stages of the industrial process, which was of the “add-back type”. The slices were kept at 9°C in the dark and, after various periods of time (up to two hours), the amount and composition of the FFA liberated at the surface and in the middle of the potato slices were analyzed by gas chromatography. The liberation of FFA was more pronounced at the surface of the slices than in the middle. The polyunsaturated fatty acids, linoleic acid and linolenic acid, were liberated to a greater extent than the saturated fatty acids. The experiment was repeated at 4°C and the results obtained were very similar. The lower temperature did not decrease the rate of FFA liberation. But, in thin potato strips, which have a larger total surface of damaged membranes than the potato slices, considerably more FFA were liberated. The amount and composition of FFA also were analyzed in potato slices from the industrial process for potato granule production. Before the blanching bath (76°C for 12–15 min) only minor amounts of FFA were liberated but during the blanching there was a substantial liberation of FFA at the surface of the potato slices. After the blanching bath there were no more FFA liberated at the surface of the slices but in the middle of the potato slices the liberation of FFA continued until the potato slices reached the steamcooking bath.