Browsing by Author "Gloria, H"

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    Assessment of the quality of heated oils by differential scanning calorimetry
    (AMER CHEMICAL SOC, 1998) Gloria, H; Aguilera, JM
    Differential scanning calorimetry (DSC) was used to follow changes in the thermal characteristics of commercial frying oils (sunflower seed, colza, and groundnut) during heating at 180 degrees C for up to 10 h. DSC tracings of oils scanned from 10 to -80 degrees C were characterized by a single crystallization peak (CP) at -43 to -48 degrees C. Heating of oils resulted in a progressive shift of the CP to lower temperatures and reduced enthalpies of crystallization (EC). The temperature of the CP decreased as much as 27 degrees C, and the EC was reduced by almost 90% after heating for 10 h. These changes in thermal characteristics correlated well with the appearance of polar compounds, the increase in viscosity, and color changes of the oil. DSC is a fast method of analysis, requires small samples (15-60 mg) with minimal preparation, and may be implemented directly in fried products.
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    Determination of oil in fried potato products by differential scanning calorimetry
    (AMER CHEMICAL SOC, 1997) Aguilera, JM; Gloria, H
    Differential scanning calorimetry (DSC) was used to determine the oil uptake of commercial frozen par-fried potatoes after frying at 180 degrees 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 degrees C, respectively. DSC was performed by cooling samples of crust and core of fried potatoes from 10 to -60 degrees C at 1 degrees 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.