Development of a Measure Cell to Assess by Amperometry Dissolved Oxygen in Vegetable Oils

Abstract

Dissolved oxygen in vegetable oils is an important component of oil degradation over time. Various methods for the determination of dissolved oxygen in oils are proposed in the literature leading to very variable results. An amperometric method associated with a cell of measurement in dynamic mode makes it possible to determine the conditions of stability of the measurements of the relative dissolved oxygen concentration (RDOC, mg L −1 ) and the electrolysis current intensity (ECI) (nA) in seed oils and virgin olive oils. The effects of oxygenation/deoxygenation time and temperature on RDOC measurements are investigated. For virgin olive oils, the RDOC in bottles closed for eight weeks varies from 0 to 0.9 mg L −1 . The nature of the fruitiness and the filtration of the oils have no influence on the RDOC. The monitoring of RDOC and ECI during the flow of virgin olive oil in a column open to air, simulating an industrial tank, shows differences in dissolved oxygen concentration due to a faster flow of oil in the center of the column than at the walls. This result is validated by a similar experiment with nitrogen inerting the column and by a numerical simulation. Practical applications: Knowledge of the oxygen dissolved in vegetable oils is an important factor in limiting the autoxidation phenomenon to increase their shelf life. The development of a cell for measuring the relative dissolved oxygen concentration (RDOC) in vegetable oils and its conditions of use, provides a tool for the RDOC applicable to the different stages of the manufacturing process and during storage or packaging. The RDOC measurement is particularly useful during long storage in tanks whether inerted or not.

Postextraction monitoring of dissolved oxygen in virgin olive oil

“…Moreover, the authors showed that the extent of the mechanical action applied during the oil extraction does not allow to reach the theoretical solubility value of oxygen in the oil. Accordingly, the maximum DO concentration recorded in that work was of about 8-9 mg L -1 , close to the values of Ninfali et al, [16] as well as the highest values reported by Fakhri et al [15] Interestingly, the latter authors This is in agreement with Parenti et al, [20] which found a faster oxidative decay of VOO with a greater initial content of DO during a controlled 18 months storage.…”

“…These data fit well with the results reported by Ninfali et al, [16] where DO values ranged from 2 to 7 mg L -1 in bottled VOO samples collected from the market. Fakhri et al [15] measured substantially lower DO concentrations in VOO samples stored for several weeks in unopened bottles, with values ranging from 0 to 0.9 mg L -1 . This finding is corroborating because of the expected inverse relationship between oxygen solubility and temperature, also confirmed by Fakhri et al [15] The next step in data analysis has been the application of a general linear model where the source of variation are both the unit-operation factor (7 levels) and the operation-effect (2 levels), and their interaction.…”

“…Fakhri et al [15] measured substantially lower DO concentrations in VOO samples stored for several weeks in unopened bottles, with values ranging from 0 to 0.9 mg L -1 . This finding is corroborating because of the expected inverse relationship between oxygen solubility and temperature, also confirmed by Fakhri et al [15] The next step in data analysis has been the application of a general linear model where the source of variation are both the unit-operation factor (7 levels) and the operation-effect (2 levels), and their interaction. The analysis of variance of the model gives significance only for the two main effects (p ≤ 0.05) (Table 2).…”

“…[8,9] Despite this body of knowledge, the measurement, monitoring, and management of DO during virgin olive oil (VOO) processing and storage through bottling are practices whose dissemination and study are rather limited, and the issue of DO is generally neglected. Data on oxygen solubility and measurement systems in VOO date back to the period between 1952 and 1983, [10][11][12][13][14] with the exception of Fakhri et al [15] who recently proposed a current-based measurement method. Ninfali et al [16] studied the antioxidant capacity of VOO by ORAC assay.…”

“…Data on oxygen solubility and measurement systems in VOO date back to the period between 1952 and 1983, [ 10–14 ] with the exception of Fakhri et al. [ 15 ] who recently proposed a current‐based measurement method. Ninfali et al.…”