Composition of oils extracted from potato chips by supercritical fluid extraction

There have been many studies involving frying of potato chips in various vegetable oils in order to observe the quality of the fried product [1-6]. Frying oils are exposed to extreme environmental conditions (air, water or steam, high temperatures of 140-200 °C), trace metals that result in degradation of the frying oil triacylglycerols by oxidation, polymerization, isomerization, cyclization and hydrolysis reactions [4-6]. These reactions affect the flavor quality of foods fried in the oils. Frying produces oils that are complex mixtures of unaltered triacylglycerols, triacylglycerols with conjugated diene and trans fatty acids, volatile compounds such as aldehydes, triacylglycerol oxidation products such as alkoxy, epoxy, keto monomeric compounds, higher molecular weight oxidation products, thermal degradation products such as oligomeric triacylglycerols or triacylglycerols with cyclized fatty acids and hydrolysis products such as diacylglycerols [6]. Additionally, frying oils, which have cooled to room temperature, contain triacylglycerol monohydroperoxides, that are only fleetingly present at frying oil temperatures [6]. A large number of the oxidation products have not been identified yet [6]. Many of the triacylglycerol oxidation products, which are formed, would be expected to be decomposed to volatile compounds during frying or heating [6]. While major quantities of the volatiles are steam-distilled out of the frying oil, some quantities of the volatiles remain in the oil and in the fried foods affecting flavor and odor of the food. To better control the production of undesirable flavor and odors, the respective volatile precursors or the molecular markers for the undesired volatile compounds need to be identified. Most reported studies of frying oil degradation products, which affect flavor, have involved various analyses of the fryer oil but not the oil absorbed by the fried food such as potato chips [4-6]. Very little work has been reported on the oil extracted from food products. Since the absorbed oil directly affects the flavor of the fried food, it is important to study the degradation products in this oil. Most extractions of lipids from foods use a labor-intensive and time-consuming process with large amounts of product extracted by hexane [7-10]. For analytical work, the hexane has to be removed; however, removal of hexane can produce artifacts, that can give misleading analytical results for degradation products. Also, hexane is an undesirable solvent and an environmentally unfriendly compound. Recently, supercritical fluid extraction has become more extensively utilized in the extraction of fats from foods using supercritical carbon dioxide, a nontoxic material [11-19]. Thus, a fat extract is obtained with little or no deterioration and with no solvent residue. HowWilliam E. Neff, Fred Eller, Kathleen Warner