Effect of the Simultaneous Interaction among Ascorbic Acid, Iron and pH on the Oxidative Stability of Oil-in-Water Emulsions

Abstract

The objective of this study was to demonstrate how different factors can simultaneously influence the oxidative stability of an oil-in-water emulsion, and how these factors can be used to enlarge the variation range of oxidation markers, expressed as peroxide value (PV) and TBARS. Initially, a Plackett-Burman design was used to screen seven factors (temperature, pH, and iron, copper, ascorbyl palmitate, ascorbic acid, and sodium chloride concentrations). A temperature elevation of 30 to 60 °C reduced PV and TBARS, a pH change from 3.0 to 7.0 increased PV and reduced TBARS, and the presence of ascorbic acid (1 mmol/L) had no significant effect on PV but increased TBARS (p < 0.05). Thus, the temperature was fixed at 30 °C, and an emulsion was formulated with different combinations of ascorbic acid, iron, and pH according to a central composite rotatable design. Regression models were fitted to PV and TBARs responses and optimized to get the higher values of both markers of oxidation. The optimized emulsion contained 1.70 mmol/L AH (ascorbic acid) and 0.885 mmol/L FeSO(4) · 7H(2)O (1.0 mmol/L Fe(2+)) at pH 5.51 and 30 °C. The range of variation observed for oxidation markers in the optimized emulsion model (PV, 0-4.27 mequiv/L; TBARS, 0-13.55 mmol/L) was larger than the variation observed in the nonoptimized model (PV, 0-1.05 mequiv/L; TBARS, 0-1.00 mmol/L). The antioxidant activity of six compounds (Trolox, α-tocopherol, caffeic acid, gallic acid, catechin, and TBHQ) was evaluated using the optimized emulsion conditions. After application of the Tukey HSD post hoc statistical test, the samples that were not different (p < 0.05) in the nonoptimized emulsions showed a significant difference in the optimized emulsions. Considering the importance of the interactions on oxidation studies, our model represents a significant improvement in a direct methodology that can be applied to evaluate natural compounds under different combination of factors.

Lipid Oxidation in Oil‐in‐Water Emulsions: Involvement of the Interfacial Layer

“…An increased oxidation, when decreasing pH, was also found in Tween 80 and Citrem‐stabilized emulsions (Sorensen and others ), and in sodium dodecyl sulfate (SDS)‐stabilized emulsions (Mei and others ). Similar results were found by Branco and others (): in SDS‐stabilized emulsions, changing the pH from 3.0 to 7.0 reduced the decomposition of primary oxidation products (peroxides) and the formation of secondary oxidation products (TBARS). The higher solubility of iron at low pH levels was suggested to be partly responsible for the increased oxidation.…”

“…Recent studies also report lipid oxidation in emulsions incubated in simulated digestive conditions (Kenmogne‐Domguia and others , ). Even though some studies have been performed without any intentional addition of oxidation initiator, iron has been widely used to accelerate lipid oxidation in emulsions (Donnelly and others ; Mei and others , 1998b; Fomuso and others ; Haahr and Jacobsen ; Guzun‐Cojocaru and others ), even if other metals such as copper have been sometimes encountered (Fomuso and others ; Osborn‐Barnes and Akoh ; Branco and others ). Water‐soluble azo initiators such as 2,2′‐azobis(2‐amidinopropane)‐dihydrochloride (AAPH) or 2,2′‐azobis[2‐(2‐imidazolin‐2‐yl)propane] (ABIP) have also been shown to promote efficiently lipid oxidation in O/W emulsions or fatty acid dispersions (Hanlon and Seybert ; Kubouchi and others ; Gotoh and others ).…”

“…Ferrous iron can then be involved in the formation of ROS (reactions 3 and 5) and in the decomposition of hydroperoxides (reaction 7). Accordingly, ascorbate favored oxidation in fish‐oil‐enriched mayonnaise and in SDS‐stabilized emulsions (Jacobsen and others ; Branco and others ). Conversely, when ascorbate concentration exceeds to a large extent that of metals, ascorbate has an antioxidant role through the direct scavenging of hydrophilic free radicals (Buettner and Jurkiewicz ; Halliwell ).…”

Factors affecting formulation characteristics and stability of ascorbic acid in water‐in‐oil creams

“…In the recent past, interest in the topical use of AA has gained considerable importance due to its scavenging activity against reactive oxygen species (ROS) produced on exposure to sunlight and thus delaying the effect of ageing [16]. Various workers have formulated different AA topical preparations [1][2][3][4][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32] but still the stability of AA remains a major concern. Derivatives of AA like sodium ascorbate, ascorbyl palmitate, etc.…”

The effects of antioxidants and shelf life conditions on oxidation markers in a sunflower oil salad dressing emulsion (SOSDE)

“…Most studies have evaluated the effects of one factor at a time (Branco, Rodrigues, Gioielli, & Castro, 2011). For example the Arrhenius equation has been used to relate temperature of storage with reaction velocity (Córdova, Quezada, & Saavedra, 2011).…”