Autoxidation of Methyl Linoleate in Freeze‐Dried Model Systems. I. Effect of Water on the Autocatalyzed Oxidation

Abstract

SUMMARY Oxidation of methyl linoleate was studied in a freeze‐dried model system based on micro‐crystalline cellulose. Oxidation was followed manometrically in samples adjusted to various water activities ranging from approximately 0 to approximately 0.6. Water was found (as determined from induction period and rate data) to have an inhibitory effect on the oxidation reaction, varying with water activity up to values of 0.5. Evaluation of the rate data indicates that the inhibitory effect of water is most pronounced in the initial stages of oxidation, including the period during which the hydroperoxide decomposition follows monomolecular decomposition kinetics. Possible interpretations of the observed water effect and its significance to the general problem of lipid oxidation in dehydrated foods are discussed.

Properties of Soybean‐Corn Mixtures Processed by Low‐Cost Extrusion

“…The large negative entropies of activation are expected from biomolecular (as opposed to monomolecular) reactions because bringing two molecules together results in more ordering (Price and Dwek, 1979). Biomolecular reactions take place during initiation, propagation and termination of lipid oxidation when oxygen is not limiting (Maloney et al, 1966). The effects of temperature and RH on lipid autoxidation have been investigated in several different food products and model systems (Labuza et al'., 1972;Quast and Karel, 1972b).…”

Oxidation of Linoleic Acid Encapsulated with Soluble Soybean Polysaccharide by Spray-drying

“…[1][2][3][4][5] The microencapsulation process involves two steps: one is emulsiˆcation of the core material and dense solution of the wall material, and the other is drying of the resulting emulsion. It would, therefore, be desirable for the wall material to possess both emulsifying and emulsion-stabilizing abilities to produce microcapsules of the core material which iŝ nely coated with the wall material and is hard to oxidize.…”

Ação antioxidante de especiarias face diferentes atividades de água

“…Estes resultados encontram apoio nos de KAREL et al [14], LABUZA, TSUYUKI & KAUL [15] e MALONEY, KAREL & LABUZA [21] que em sistemas semelhantes, contendo catalisadores metálicos, observaram um efeito protetor crescente da água desde Aw 0,00 até Aw 0,30 -0,50, pontos de oxidação mínima.…”

“…De acordo com os resultados obtidos neste trabalho, a explicação mais aceitável é a de MALONEY, KAREL & LABUZA [21], que se baseia na teoria desenvolvida por BOLLAND [4], BATTEMAN [3] e URI [34], segundo a qual, a oxidação é uma reação autocatalizada que ocorre por um mecanismo de radicais livres, em 3 etapas: iniciação, propagação e término.…”