Determination of Oil in Fried Potato Products by Differential Scanning Calorimetry

Abstract

Differential scanning calorimetry (DSC) was used to determine the oil uptake of commercial frozen par-fried potatoes after frying at 180 °C in colza/soybean oil. The enthalpy and temperature range of the crystallization peak for the pure frying oil were 47.2 J/g and −44 to −50 °C, respectively. DSC was performed by cooling samples of crust and core of fried potatoes from 10 to −60 °C at 1 °C/min and the oil content calculated from the peak area. The crust contained almost 6 times as much oil as the central core (23.6% vs 4%, dry weight basis), as visualized by light microscopy. Only 87% of the oil in the intact crust can be removed by solvent extraction, the rest being extractable only after grinding. Deviation between DSC and Soxtec extraction methods was less than 3%. The DSC method is fast, specific, and reliable, does not use solvents, requires smaller samples (<100 mg) than conventional solvent extraction methods, and can also detect freezable water. Keywords: Differential scanning calorimetry; oil; frying; fried potatoes; microstructure