Antioxidative Properties of Stearoyl Ascorbate in a Food Matrix System.

Stearoyl ascorbate or 6-O-stearoyl l-ascorbate is a lipophilic derivative of l-ascorbic acid and is commercially used in foods as a fat-soluble antioxidant and surfactant to overcome the disadvantages of using l-ascorbic acid. The objective of this research is to evaluate the antioxidative ability of stearoyl ascorbate, in the presence of wheat starch or gluten as a matrix, by measuring the unoxidized methyl linoleate available in the mixture of them after oxidation under accelerated conditions compared to that when using ascorbic acid. We observed that stearoyl ascorbate and ascorbic acid exhibited mutually adjacent antioxidative ability against oxidation of the methyl linoleate at a molar ratio of 0.0001 in presence of either wheat starch or gluten. In addition, the oxidation process in the mixture containing either stearoyl ascorbate or ascorbic acid was significantly slower than that in the mixture without stearoyl ascorbate or ascorbic acid. Moreover, by altering the initiation and propagation periods of the oxidation process, the mixture containing the stearoyl ascorbate and gluten as the matrix exhibited conspicuously slower oxidation than the mixture containing either the wheat starch or stearoyl ascorbate alone. However, increase in the ratio of stearoyl ascorbate to methyl linoleate to 0.001 or higher resulted in adverse effects due to acceleration of the oxidation process.

Suppressive ability of defatted rice bran against lipid oxidation in cookies containing iron.

Cookies containing iron, defatted rice bran, and several oils were prepared, and their oxidative stability evaluated. Oxidation was suppressed by the defatted rice bran, but a limit to the suppressive effect was observed. The maximum peroxide values obtained with defatted rice bran were low, and similar, regardless of the degree of unsaturation of the oils. A chemical analysis suggested that proteins and polyphenols in the defatted rice bran contributed to the suppressive effect. Cookies without the defatted rice bran showed decreasing maximum peroxide value as the relative humidity increased. No such dependence was observed for the cookies containing defatted rice bran. The water sorption isotherm of defatted rice bran indicated that the weak dependence was due to low water sorption.