- Model studies on the pattern of volatiles generated in mixtures of amino acids, lipid-oxidation-derived aldehydes, and glucose
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The development of flavor and browning in thermally treated foods results mainly from the Maillard reaction and lipid degradation but also from the interactions between both reaction pathways. To study these interactions, we analyzed the volatile compounds resulting from model reactions of lysine or glycine with aldehydes originating from lipid oxidation [hexanal, (E)-2-hexenal, or (2E,4E)-decadienal] in the presence and absence of glucose. The main reaction products identified in these model mixtures were carbonyl compounds, resulting essentially from amino-acid-catalyzed aldol condensation reactions. Several 2-alkylfurans were detected as well. Only a few azaheterocyclic compounds were identified, in particular 5-butyl-2-propylpyridine from (E)-2-hexenal model systems and 2-pentylpyridine from (2E,4E)-decadienal model reactions. Although few reaction products were found resulting from the condensation of an amino acid with a lipid-derived aldehyde, the amino acid plays an important role in catalyzing the degradation and further reaction of these carbonyl compounds. These results suggest that amino-acid-induced degradations and further reactions of lipid oxidation products may be of considerable importance in thermally processed foods.
- Adams, An,Kitryte, Vaida,Venskutonis, Rimantas,De Kimpe, Norbert
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experimental part
p. 1449 - 1456
(2011/10/05)
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- Deshydratation des diols-1,2α,β-ethyleniques IV: role de la stereomutation des carbocations allyliques α-hydroxyles sur l'orientation des reactions observees
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The allylic carbocations formed during the dehydration of diols of type A are found to react by five different processes: three nucleophilic attacks (by solvent at the β or δ positions, or by the intramolecular hydroxyl group at δ), a degradation reaction between Cα and Cβ and the classical pinacol rearrangement.Nucleophilic attack at the carbon δ is a very efficient reaction and sometimes (for monosubstituted substrates in β, γ or δ) gives quasi-exclusive products: a ketone for the reaction with H2O in δ or a 2,5-dihydrofuran product for the intramolecular reaction.In the case of γ and δ disubstituted carbocations, the selectivity is less and we show that it is possible to analyze the different steric effects commanding the stereomutation equilibrium of the allylic carbocation and so determining the orientation in the dehydration.
- Dana, Gilbert,Gharbi-Benarous, Josyane,Thuan, Sa Le Thi
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p. 1451 - 1462
(2007/10/02)
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