Quantification of carbonyl compounds in oxidized fats as trichlorophenylhydrazones

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It is generally agreed that the high linolenate (18:3) content of soybean oil (SBO) contributes to its flavor instability. In this study, the oxidative stability of five SBO of various fatty acid (FA) compositions was compared by using peroxide values, conjugated dienoic acid values and sensory panel scores. Three of the oils were from common commercial varieties representing the range of 18:3 content normally found in SBO. The other two oils were from seed developed in a mutation breeding program. One of these oils from the line A5 had an 18:3 content of 3.5%, and the other from the line A6 had a stearate (18:0) content of 24%. Seed from the five soybean varieties was cold pressed, refined and deodorized without additives under laboratory conditions. Two oxidation experiments were conducted. In the first, the oils were stored at 28 C for 67 days. In the second, the oils were stored at 60 C for eight days. Sensory comparisons were done by using the AOCS Flavor Intensity Scale. The A5 and A6 oils were more stable than the commercial varieties as measured by chemical tests, but the sensory data were inconclusive. Oils with similar 18:3 contents did not have similar rates of oxidation. The differences between the oils were not as distinct in the 60 C test as in the 28 C test.

Section: Percentages Of Conjugated Dienoic Acid A-d Inmentioning

confidence: 92%

Oxidative stabilities of low‐linolenate, high‐stearate and common soybean oils

White

Miller

1988

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“…White and Hammond (12) reported that the reaction of hydroperoxide with the reagent during the formation of the TCPHs resulted in the formation of a small additional amount of carbonyl. To avoid including any carbonyls formed from the hydroperoxides during derivatization in our analytical results, either the hydroperoxides were incubated long enough so that decomposition was complete before the samples were reacted to form derivatives, or the results were corrected.…”

Section: Resultsmentioning

confidence: 99%

Quantification of carbonyls produced by the decomposition of hydroperoxides

Saidia

Hammond

1989

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Carbonyls produced by the decomposition of cyclohexene hydroperoxide and various hydroperoxides of linoleic and linolenic acids and their methyl esters were determined by gas chromatography of the 2,4,6‐trichlorophenylhydrazones. The effect of temperature, iron and copper ions, ethanol and several antioxidants on the rate of decomposition, the nature of the products and their yield was observed. The hydroperoxides of methyl esters decomposed more slowly than those of free fatty acids. Ethanol slowed, and metal ions accelerated the rates of decomposition. Metal ions, especially copper, increased the yield and complexity of the carbonyls formed, but ethanol decreased carbonyl yields. Antioxidants and decomposition temperatures changed the relative yields of carbonyls produced. The 9‐ and 13‐hydroperoxides of linoleic acid gave similar carbonyls, but those of linolenic acid did not. The carbonyl mixtures produced from autoxidized fatty acid methyl esters were more complex than those produced from lipoxygenase‐treated fatty acids.

“…× 26-cm column filled with 10 g Florisil in pentane/ether (99:1). Hydrocarbons were eluted with 15 mL pentane/ether (99:1), and the carbonyls were eluted with 15 mL ether (4).…”

Section: Methodsmentioning

confidence: 99%

Volatile compounds produced during deodorization of soybean oil and their flavor significance

Kao

Hammond

White

1998

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Freshly deodorized soybean oil has a characteristic nutty flavor but often yields no detectable headspace volatiles. The cause of this flavor was investigated by deodorizing soybean oil in an apparatus with a double cold trap that allowed the volatile compounds formed from the initial decomposition of hydroperoxides to be collected separately from those produced during the normal deodorization process. The chief volatile components from the normal deodorization process were hydrocarbons, which contributed little to no odor to the oil. The compounds with the greatest odor were carbonyls, especially heptanal and cis‐4‐heptenal. Although these components should accumulate at some steady‐state concentration in an oil during its deodorization, none seemed to account for the flavor of the deodorized oil. By using a particle detector, it was shown that small particles could be generated in the human mouth that could provide a mechanism to bring oil with nonvolatile flavor components into contact with the olfactory organ. Attempts to separate possible nonvolatile flavors in deodorized oil from triacylglycerides by chromatography on alumina or reaction with 2,4‐dinitrophenylhydrazine were unsuccessful. Possibly, the flavor is caused by the glycerol esters themselves.