Antioxidant efficiency and oxidizability of mayonnaise by oximetry and isothermal calorimetry

Oxidation kinetics of fats from meat and meat products by isothermal calorimetry

Lipid oxidation significantly affects the nutritional value and sensory properties of processed meat products. This study aimed to apply isothermal calorimetry to analyze the oxidation kinetics of fats from chicken, pork, lamb and speck at 40 °C in presence of 2,2'-Azobis(2-methylpropionitrile) (AIBN) radical initiator. Isothermal calorimetry allowed for continuous monitoring of the heat flow developed during the oxidation reaction determining key kinetic parameters such as the induction time (τ), rates of inhibited (Rinh) and uninhibited (Runi) periods, and oxidizability index (O.I.). The calorimetric data were validated using oximetry and peroxide value measurements (R2 = 0.99). Chicken fat exhibited longest τ followed by pork > speck > lamb. The results correlated with the concentration of antioxidants, mainly tocopherols, present in the samples. Furthermore, the O.I. of the fat samples varied significantly (p < 0.05) due to the different fatty acid compositions. Overall, isothermal calorimetry provided valuable kinetic insights while enabling the simultaneous analysis of multiple samples.

Advancing the assessment of oxidative stability in co-stabilized zein nanoparticles and xanthan gum Pickering emulsions using isothermal calorimetry

This study aims to apply isothermal calorimetry to investigate the oxidative stability of Pickering emulsions made with zein nanoparticles (ZNPs) and xanthan gum. The ZNPs were fabricated using an anti-solvent precipitation method, resulting in nanoparticles with a particle size of 168.4 ± 38.9 nm and a zeta potential of +27.8 ± 7.3 mV. Xanthan gum was incorporated to enhance the physical stability by increasing the viscosity of the continuous phase. The emulsions oil phase consisted of different plant-based oils such as sunflower, corn, olive, and soy. Pickering emulsions physical stability was characterized using a multiple light scattering technique. Kinetic parameters of emulsions oxidative stability, including induction time (τ), rates of inhibited (Rinh) and uninhibited (Runi) periods, and oxidizability index (O.I.) were determined by isothermal calorimetry. Pickering emulsions exhibited a different oxidative stability depending on the oils used, with olive oil-based emulsions showing the longest induction time, highest antioxidant efficiency (A.E. = 9.35 ± 0.07), and lowest oxidizability index (2.25 ± 0.02 (M·h)-0.5). The results correlated with the total phenolic content and antioxidant activity of the oils. The findings provide valuable insights into designing emulsion-based formulations, emphasizing the role of oil type in enhancing Pickering emulsion oxidative stability.

Sequential extraction of antioxidants from Citrus aurantium L. flower and kinetic evaluation of their effect on oil microparticle oxidative stability

This study applied supercritical CO2 and ultrasound-assisted ethanol extraction (UAE) to obtain apolar and polar antioxidant fractions from Citrus aurantium flowers. HPLC-HRMS revealed distinct phytochemical profiles, with the polar extract showing higher phenolic content and antioxidant activity. Linseed oil was co-encapsulated with these extracts at varying concentrations (1, 2, and 5 mg/g of oil) using the Particles from Gas Saturated Solution (PGSS) technique, and the oxidative stability was assessed using isothermal calorimetry. Key kinetic parameters, such as induction time (τ), oxidation rates (R inh , R uni ), and antioxidant efficiency (A.E.), were measured. The polar extract demonstrated superior A.E., further confirmed by the DPPH stopped-flow assay. Co-encapsulation of both extracts produced an additive effect, surpassing the synthetic antioxidant BHT (200 μg/g). This study highlights Citrus aurantium flower extracts as natural antioxidants, enhancing the oxidative stability of encapsulated oils, while offering a sustainable method for bioactive compound recovery for food applications.

Advancements in Biosensors for Lipid Peroxidation and Antioxidant Protection in Food: A Critical Review

This review highlights the progress made in recent years on biosensors aimed at detecting relevant analytes/markers of food peroxidation. Starting from the basic definition of biosensors and the chemical features of peroxidation, here we describe the different approaches that can be used to obtain information about the progress of peroxidation and the efficacy of antioxidants. Aptamers, metal-organic frameworks, nanomaterials, and supported enzymes, in conjunction with electrochemical methods, can provide fast and cost-effective detection of analytes related to peroxidation, like peroxides, aldehydes, and metals. The determination of (poly)phenols concentrations by biosensors, which can be easily obtained by using immobilized enzymes (like laccase), provides an indirect measure of peroxidation. The rationale for developing new biosensors, with a special focus on food applications, is also discussed.

Continuous fluorescence-based quantitative antioxidant assay using vegetable oil as an oxidizable substrate

Several spectrophotometric assays, such as 1,1-diphenyl-2-picrylhydrazyl (DPPH) and oxygen radical absorbance capacity (ORAC), are commonly used to assess antioxidant activity. However, these methods often lack real-world relevance as they do not inhibit autoxidation in actual food substrates. Although direct measurement of oxygen consumption or peroxide formation during inhibited autoxidation offers certain advantages, it is labor intensive and requires specialized equipment. In this study, we introduce a small-volume inhibited autoxidation approach that utilizes a standard microplate reader and a food-derived oxidizable substrate, specifically stripped sunflower oil (SSO), and styrene-conjugated BODIPY (STY-BODIPY) chromophores that oxidizes with the substrate, enabling straightforward monitoring of the reaction progress without interfering with it. The rate of initiation (Ri) was controlled by using azobis(isobutyronitrile) (AIBN) at 30 °C (Ri = 8.6 ± 0.5 × 10-10 M s-1) to accurately determine the rate constant of antioxidant reaction with peroxyl radicals (kinh). The method was standardized using the synthetic α-tocopherol analogue 2,2,5,7,8-pentamethyl-6-chromanol (PMC) as a reference antioxidant and was successfully applied to evaluate its synergistic interactions with γ-terpinene, quercetin, and caffeic acid. The rate constant for the reaction of peroxyl radicals with STY-BODIPY was determined, kST = 890 ± 52 M-1 s-1. Induction time (τ) of PMC increased in a concentration-dependent manner by the synergistic interactions of PMC/γ-terpinene, PMC/quercetin, and PMC/caffeic acid. The kinh value for PMC in SSO at 30 °C remained constant at 1.5 × 106 M-1 s-1. The validity of this approach was further confirmed using isothermal calorimetry, demonstrating its potential as a reliable and accessible tool for antioxidant testing in food systems.

Real-time monitoring of vegetable oils photo-oxidation kinetics using differential photocalorimetry

This study introduced differential photocalorimetry (DPC) as a method for real-time monitoring of the photo-oxidation kinetics of vegetable oils. DPC measures the heat flow generated during the oxidation of oils upon light exposure. Experiments conducted with stripped linseed oil (SLSO), an oil depleted from its natural antioxidants, showed no induction time (τ). Conversely, spiking SLSO with increasing concentrations of trans-ferulic acid resulted in an induction time (τ) proportional to the antioxidant concentration (R2 = 0.99). A comparative study among different vegetable oils revealed that rice bran oil exhibited the highest resistant to photo-oxidation, followed by corn, soybean, and sunflower oils. The results are discussed in terms of sample oxidizability and antioxidant efficiency (A.E.), and validated through high-performance liquid chromatography with diode array detection (HPLC-DAD). Furthermore, the measured heat flow enabled the determination of the rates of inhibited (Rinh) and uninhibited (Runi) periods, as well as the rate constant of propagation (kp) and inhibition (kinh) reactions.

Analysis of the Efficiency of Antioxidants in Inhibiting Lipid Oxidation in Terms of Characteristic Kinetic Parameters

In this work, we aim to find physical evidence demonstrating the crucial role that the effective concentration of antioxidants (AOs) present at the interfacial region of emulsions has in controlling the inhibition of the lipid oxidation reaction. We prepared a series of antioxidants of different hydrophobicities derived from chlorogenic and protocatechuic acids. We first monitored, in intact emulsions, the (sigmoidal) production of conjugated dienes and determined the corresponding induction times, tind. Independently, we determined the effective concentrations of the antioxidants in the same intact emulsions. Results show that both the length of the induction periods and the antioxidant interfacial concentrations parallel each other, with a maximum at the octyl-dodecyl derivatives. The ratio between the interfacial antioxidant concentrations and the induction periods remains constant for all AOs in the same series, so that the rates of initiation of lipid oxidation are the same regardless of the hydrophobicity of the antioxidant employed. The constancy in the rate of initiation provides strong experimental evidence for a direct relationship between interfacial concentrations and antioxidant efficiencies. Results suggest new possibilities to investigate lipid peroxidation under non-forced conditions and are of interest to formulators interested in preparing emulsions with antimicrobial properties.

Early detection of acrolein precursors in vegetable oils by using proton transfer reaction - mass spectrometry

Acrolein is a toxic volatile compound derived from oxidative processes, that can be formed in foods during storage and cooking. This study employs proton transfer reaction mass spectrometry (PTR-MS) to detect acrolein precursors in vegetable oils by focusing on the m/z (mass-to-charge ratio) 57. To this purpose, hempseed, sesame, walnut, olive and linseed oils were stored for 168 h at 60 °C in presence of 2,2'-azobis(2-metilpropionitrile) (3 mM) radicals initiator. The evolution of m/z 57 by PTR-MS was also compared with traditional lipid oxidation indicators such as peroxide value, conjugated diene, oxygen consumption and, isothermal calorimetry. The obtained results were explained by the fatty acid composition and antioxidant capacity of the oils. Hempseed fresh oil presented a very low total volatile organic compounds (VOCs) intensity (5.6 kncps). Nonetheless, after storage the intensity increased ∼70 times. A principal component analysis (PCA) confirmed the potential of m/z 57 to differentiate fresh versus rancid hempseed oil sample. During an autoxidation experiment oils high in linolenic and linoleic acids showed higher m/z 57 emissions and shorter induction times: linseed oil (38 h) > walnut oil (47 h) > hempseed oil (80 h). The m/z 57 emission presented a high correlation coefficient with the total VOC signal (r > 0.95), conjugated dienes and headspace oxygen consumption. A PCA analysis showed a complete separation of the fresh oils on the first component (most significant) with the exception of olive oil. Walnut, hempseed and linseed oil were placed on the extreme right nearby total VOCs and m/z 57. The results obtained highlight the potential of PTR-MS for the early detection of oil autoxidation, serving as a quality control tool for potential acrolein precursor emissions, thereby enhancing food safety in the industry.