The relationship between the oxidative polymers of soybean oil and flavor reversion

Abstract

Summary The polymers formed during the autoxidation of soybean oil at 60°C. were isolated by a solvent‐extraction method, using diethyl ether and pentanehexane as solvents. The more polar polymer fraction was further oxidized by air at 30°C., and the volatile material obtained was fractionated and characterized. It contained the same carbonyl compounds as the volatile material which has previously been obtained from reverted soybean oil, namely acetaldehyde, propionaldehyde, n‐hexanal, and 2‐pentenal. The more polar polymer fraction contained 21.04% of oxygen and degraded to volatile carbonyl compounds under vacuum as well as under oxygen‐free nitrogen. Depolymerization and ethanolysis of these polymers were carried out in ethyl alcohol which had been adjusted to a normality of 3.5 with anhydrous hydrogen chloride. The polymeric substance formed on the filter presses of a soybean oil refinery could be depolymerized in a similar manner. It is therefore evident that oxidative polymers could be unintentionally introduced into soybean oil in various ways and serve as precursors of reversion compounds.

CARBONYLS IN OXIDIZING FAT III. THE DISTRIBUTION OF’VOLATILE and NON‐VOLATILE CARBONYLSa

“…Volatile and free carbonyls. Differences between comparable methods were due to the degree of decomposition of hydroperoxides (9,23) and/or complex secondary oxidation products (6,7). A comparison of vacuum distillation, steam distillation, and Pool and Klose values is shown in Figure 1 (21.1 a C).…”

“…It is evident that much of the carbonyl was released in some manner by the Girard reagent and reaction conditions. The carbonyls may be present in bound forms or arise from oxidative polymers (6,7) or partial decomposition of hydroperoxides.…”

Characterization of Biodiesel Oxidation and Oxidation Products

“…The fact that oxygen is incorporated in the oxidative polymerization has been demonstrated by the oxidation of soybean oil and the isolation and analysis of the resulting polymeric compounds. The polymers contained 21.4% O compared to 11.8 for the non-oxidized soybean oil 14 . Not surprisingly, increased levels of polyunsaturated fatty acid chains enhance oxidative polymerization in fatty oils.…”

“…Kinematic viscosity appears to be the most often used procedure 18,50,96,100 , although absolute viscosity could also be used. Several studies have used refractive index as a way to show the formation of polymers 13,14,16,18 . The fact that fatty oil or ester polymers have higher refractive indices is undoubtedly the reason why a refractive index detector is used in the BS EN ISO 16931 procedure.…”

Autoxidation of Fish Oils. I. Identification of Volatile Monocarbonyl Compounds from Autoxidized Salmon Oila, b, c

“…Isolation and characterization of the autoxidation products of fats and oils have been the subject of considerable research in the past decade (Badings, 1959;Brekke and MacKinney, 1950;Chang and Kummerow, 1954;Gaddis and Ellis, 1959b ;Johnson et al, 1953 ;Swift et al, 1945Swift et al, , 1949. The reagent 2,4dinitrophenylhydrazine (DNP) forms crystalline derivatives with aldehydes and ketones, with characteristic melting points.…”