Analysis of Edible Oil Oxidation Based on Changes in the Electrical Conductivity of the Extracted Aqueous Phase

Abstract

A novel and rapid method is developed to analyze oxidation in edible oils by using electrical conductivity (EC). The extent of edible oil oxidation is confirmed using the American Oil Chemists’ Society (AOCS) standard method as a reference. Analytical conditions, including temperature, oscillating time, and water–oil (v/v) ratio, are optimized to determine ECs. A model is established based on EC changes in the aqueous phase extracted from several water–oil mixtures. This model is used to predict the oxidation degree of the samples, and its results are validated by the AOCS standard methods. Results show that the analytical conditions exert no significant effects on EC determination. The model is developed using a water–oil (v/v) ratio of 5. Three regions are classified according to the ECs of the samples. Oils with ECs less than 6.9 µS cm−1 are found to be non‐oxidized oils, samples with ECs within 6.9–8.9 µS cm−1 are suspected oils, and samples with ECs exceeding 8.9 µS cm−1 correspond to oxidized oils. The total identification rate of the model in validation samples is 94.1%. The results of the present study clearly indicate that the proposed method can be used as an alternative to conduct qualitative discrimination of the oxidation degree of edible oils. Practical applications: A method based on EC changes in the aqueous phase is used to determine the extent of edible oil oxidation. A total of 151 oil samples are used and assigned to two groups for calibration (n = 83) and validation (n = 68) oil samples. In the EC method, determination of ECs is independent of analytical conditions, which provides great flexibility in the selection process. The method requires no spectral pre‐treatments or data processing methods, which simplifies the experiment process. Furthermore, the EC instrument is less than 40 $ USD, which is more affordable and portable in a small scale. These characteristics make the proposed method convenient for inspection departments to accomplish on‐site testing of edible oils. The EC method can be applied to determine edible oil oxidation. A method based on EC changes in the aqueous phase extracted from water–oil mixture is used to determine the extent of edible oil oxidation. At a water–oil (v/v) ratio of 5, the EC model can be divided into three regions: ECs of less than 6.9 µS cm−1 representing non‐oxidized oils, ECs within 6.9–8.9 µS cm−1 representing suspected oils, and ECs of over 8.9 µS cm−1 representing oxidized oils. The total identification rate of the model in validation samples is 94.1%.

Identification of olfactory characteristics of edible oil during storage period using metal oxide semiconductor sensor signals and ANN methods

“…Parameters that increase oil oxidation include long-term storage in adverse environmental conditions such as light exposure, high temperature, or oxygen. Moreover, oxidation is one of the main factors reducing edible oil quality and often determines its shelf life (Wang et al, 2019).…”

Colorimetric Sensing of the Peroxide Number of Milk Powder Using CsPbBr3 Perovskite Nanocrystals

“…According to ISO 3976:2006, spectrophotometry is a widely used method for the determination of the peroxide number of milk powder, but there are still several limitations, such as: (1) the preparation process for the determination is relatively complex and time-consuming; (2) the test solutions need to be prepared fresh; and (3) the sensitivity is still unsatisfactory. Recently, several approaches for the analysis of edible oil oxidation or type based on electrical conductivity [ 14 ] and surface-enhanced Raman spectroscopy (SERS) [ 15 , 16 , 17 ] have been reported, which provide new routes for the rapid determination of the peroxide number using a device. In addition, simple and rapid colorimetric sensing approaches could also be considered.…”

Optical Determination of Solid Fat Content in Fats and Oils: Effects of Wavelength on Estimated Accuracy

“…On the other hand, portable embedded sensor systems based on microcontrollers, field programmable gate arrays (FPGAs) or modern smartphones, are very attractive since they can carry out in-situ measurements using less expensive electronics, thus providing near real-time results at very low cost, making this technique rapid and affordable for small food industries. Some examples of sensors and sensor systems recently proposed in the literature for food analysis include evaluation of the microbial content in raw milk; [9] real-time detection of bovine milk adulteration; [10] estimation of fish freshness using impedance sensors; [11] characterization and control of ice cream properties with electrical impedance; [12,13] detection of freshness of chicken meat; [14] assessment of lycopene content in tomatoes; [15] detection of bacterial contamination in meat; [16] quality analysis of olive oil; [17][18][19] rapid non-destructive testing of fruit firmness; [20] low-cost analysis of edible oil oxidation using electrical conductivity measurements; [21] handheld near-infrared spectroscopy analysis for characterization of extra virgin olive oil. [22] A technique to estimate SFC in fats and oils, based on single wavelength (near-infrared) optical measurements during a thermal cycle, has been previously developed.…”