A kinetic model for co‐oxidation of β‐carotene with oleic acid

Abstract

Oxidation experiments with β-carotene in a lipid solution were conducted under various conditions of temperature, oxygen composition, and lipid content. The experimental results were compared with those using n-decane reported previously. Under all conditions, the oxidation rate in oleic acid was faster than that in n-decane. A novel kinetic model for the co-oxidation of carotene with a lipid was proposed based on the reaction mechanism, which consisted of the oxidation of carotene, the oxidation of oleic acid, and the cross-reaction of carotene with oleic acid. The model quantitatively described the oxidation behavior of carotene over a wide range of temperatures, oxygen compositions, and lipid contents.β-Carotene (β-Car) is an active oxygen quencher and an antioxidant (1,2). However, β-Car is very susceptible to oxidation in air and loses its biological activities. In order to utilize β-Car in a food system, prevention of oxidation during processing and long-term storage is very important. Understanding the oxidation kinetics of β-Car can be a useful tool for predicting oxidation behavior and for providing effective operating conditions. In our previous study (3), a novel kinetic model for the oxidation of β-Car in n-decane was proposed. This model was based on an autocatalytic free-radical chain reaction mechanism that included the reactions concerned with the hydroperoxide or the β-Car radical. The model described well the oxidation behavior under various conditions of temperature and oxygen composition.β-Car is commonly dissolved in a lipid when used as a food additive. The lipid is also susceptible to oxidation; hence, the oxidation of β-Car in such a system proceeds via a complicated co-oxidation mechanism accompanying the oxidation of the lipid. Several researchers have investigated the oxidation of β-Car in solution containing lipids (4-10). Most of them have discussed the antioxidative effect of β-Car on the oxidation of the lipid (4-8). However, Budowski and Bondi (9) and Ramakrishnan and Francis (10) have investigated the oxidation of β-Car in an organic solution containing a lipid such as cottonseed oil or methyl linoleate. In their studies, the oxidation rate of β-Car increased with the lipid content in solution. They suggested that the product generated by the oxidation of the lipid affected the oxidation rate of β-Car. However, the co-oxidation mechanism of β-Car with a lipid is still unclear, and a kinetic model based on the reaction mechanism has never been constructed.In this study, the oxidation experiments of β-Car were conducted in an organic solution containing the lipid oleic acid. A novel kinetic model was proposed that could describe quantitatively the kinetics of the co-oxidation of β-Car with a lipid. The kinetic and equilibrium constants in the model were estimated by fitting the model with the experimental results obtained under various conditions of temperature and oxygen composition. EXPERIMENTAL PROCEDURESOleic acid was chosen as the model lipid solvent because it has a simple str...

Degradation of β-carotene during fruit and vegetable processing or storage: reaction mechanisms and kinetic aspects: a review

“…The authors observed that, when oleic acid was the solvent of the reaction, internal oxygen mass transfer from the atmosphere into the oil had to be taken into account, probably because, in this case, oleic acid also consumed oxygen due to its own oxidation, and thus oxygen transfer was the limiting factor. Internal oxygen transfer was thus included in the proposed kinetic model, which was based on the reaction mechanism consisting of the oxidation of β-carotene (7 reactions), the oxidation of oleic acid (2 reactions), and the cross-reaction of β-carotene with oleic acid (1 reaction), i.e., a total of 10 reactions [62]. In a last study [63], oxidation experiments with β-carotene were also performed in oleic acid solvent but with the addition of α-tocopherol.…”

Mechanistic model to couple oxygen transfer with ascorbic acid oxidation kinetics in model solid food

“…Among them, two studies considered permeation as limiting mass transfer phenomena not taking into account diffusion of oxygen within the food sample of study (modelled by Fick's law): either permeation through the packaging coupled to oxygen consumption by ascorbic acid oxidation in orange juice represented by first order kinetics (Ahrne et al, 1997); or oxygen permeation through whey protein coating coupled to oxygen consumption due to lipid oxidation of peanuts described by an apparent zero/first order kinetics (Mate and Krochta, 1998). Two other studies dealt with oxygen diffusion within food (modelled by Fick's law) coupled to b-carotene oxidation in oleic acid, with a kinetic model developed using 10 elementary reactions (Takahashi et al, 2001) or 25 elementary reactions in presence of a-tocopherol (Shibasaki-Kitakawa et al, 2004). Finally, three studies integrated oxygen permeation through packaging, diffusion through food and oxidation reaction.…”

Oxidation kinetics of β‐carotene in oleic acid solvent with addition of an antioxidant, α‐tocopherol

“…Like the previous studies (3-6), the constants are expressed using the pre-exponential factor, B i , and the activation energy, E i , as These constants, B i and E i , were estimated by fitting Equations 27 and 42 with five sets of the experimental results for the β-carotene oxidation in oleic acid solvent with addition of α-tocopherol. The fitting procedure was the same as that reported previously (3)(4)(5)(6). The experimental and fitted results are shown in Figure 2 by the symbols and the solid lines, respectively.…”

“…In this study, a kinetic model describing β-carotene oxidation in oleic acid solvent with addition of α-tocopherol was proposed by combining the previous two models (3,4). Validity of the proposed kinetic model was verified by comparing the experimental and calculated results.…”

“…In our previous study (3), we proposed a kinetic model for the co-oxidation of β-carotene in oleic acid as a lipid solvent based on a reaction mechanism that consisted of β-carotene oxidation, oleic acid oxidation, and the cross-reaction of β-carotene and oleic acid. A model for β-carotene oxidation in the presence of the antioxidant α-tocopherol also was constructed, in which not only the antioxidation of β-carotene by α-tocopherol but also the co-oxidation and radical-exchange reaction of β-carotene and α-tocopherol were incorporated (4).…”