Evolution of Oxidative Values during Kinetic Studies on Olive Oil Oxidation in the Rancimat Test

Elevated nitrogen fertilization differentially affects jojoba wax phytochemicals, fatty acids and fatty alcohols

Jojoba wax is gaining popularity among cosmetics consumers for its skin wound healing and rejuvenation bioactivities, attributed to collagen and hyaluronic acid synthesis. However, information regarding wax phytochemical composition and quality parameters, as well as effect of cultivation practices, and fertilization in particular, on wax quality is limited. The aim of the current work was to study the effect of nitrogen (N) availability to jojoba plants on wax phytochemical composition and beneficial skin-related contents. For this, wax quality from a six-year fertilization experiment with five N application levels was evaluated. The chemical parameters included antioxidant activity, free fatty acid, total tocopherol, total phytosterol and oxidative stability, as well as fatty acid and fatty alcohol profile. Our results reveal that the majority of wax quality traits were affected by N fertilization level, either positively or negatively. Interestingly, while fatty acids were unaffected, fatty alcohol composition was significantly altered by N level. Additionally, fruit load also largely affected wax quality, and, due to jojoba's biennial alternate bearing cycles, harvest year significantly affected all measured parameters. Results shed light on the effects of N application on various biochemical constituents of jojoba wax, and imply that N availability should be considered part of the entire agricultural management plan to enhance wax quality. Some traits are also suggested as possible chemical quality parameters for jojoba wax.

The roles of lipoxygenases and autoxidation during mackerel (Scomberomorus niphonius) dry-cured processing

The roles of enzymatic (Lipoxygenases, LOX) oxidation and autoxidation in the dry-cured processing of mackerel were investigated by adding exogenous substances in this study. Four groups, namely control, chlorogenic acid (inhibiting LOX activity), EDTA-2Na (inhibiting autoxidation), and exogenous LOX (adding eLOX), were assigned. The results showed that lipid oxidation of mackerel was reduced by inhibiting LOX activity and autoxidation, while adding eLOX promoted lipid oxidation. Inhibition of LOX activity and autoxidation suppressed fatty acid accumulation mainly in the air-drying and curing stage, respectively. The total contents of key flavors in the mackerel during dry-cured processing were decreased by inhibiting LOX activity and autoxidation, and the former inhibitory effect was stronger than autoxidation, while it was corresponding increased through adding eLOX, of particular in the later stage of air-drying. Collectively, LOX could promote the flavor formation of the mackerel in the dry-cured processing, which could be applied in the flavor adjustment of aquatic products or some similar fields.

Combination of Dehydration and Expeller as a Novel Methodology for the Production of Olive Oil

An alternative olive oil (OO) production process has been developed based on the combination of olive dehydration, followed by extraction with an expeller press. This procedure eliminates the utilization of water and avoids the malaxation stage. Hence, no water residues are generated. In this study, the mentioned alternative methodology was compared to conventional extraction methods. High extraction yields and oil recovery were obtained with our novel procedure. On the contrary, substantial percentages of by-products were generated with conventional methodology. The quality indexes (acidity and peroxide values) of the oils obtained by the combination of dehydration and expeller (dOO) were 0.4% of oleic acid and 3 meq O2/kg of oil, respectively. Furthermore, none of the applied processes affected the resulting OO's fatty acid composition and lipid profile. Total phenolic content was up to four times higher for dOO than for other olive oils and it showed resistance to oxidation with an oxidative stability index about five times higher than that for conventional olive oils.

Effect of the Freeze-Dried Mullein Flower Extract (Verbascum nigrum L.) Addition on Oxidative Stability and Antioxidant Activity of Selected Cold-Pressed Oils

The aim of the study was to analyze the influence of mullein flower extract addition on the oxidative stability and antioxidant activity of cold-pressed oils with a high content of unsaturated fatty acids. The conducted research has shown that the addition of mullein flower extract increases the oxidative stability of oils, but its addition depends on the type of oil and should be selected experimentally. In rapeseed and linseed oil, the best stability was found for samples with 60 mg of extract/kg of oil, while in chia seed oil and hemp oil, it was found with 20 and 15 mg of extract/kg of oil, respectively. The hemp oil exhibited the highest antioxidant properties, as evidenced by an increase in the induction time at 90 °C from 12.11 h to 14.05 h. Additionally, the extract demonstrated a protective factor of 1.16. Oils (rapeseed, chia seed, linseed, and hempseed) without and with the addition of mullein extract (2-200 mg of extract/kg of oil) were analyzed for oxidative stability, phenolic compounds content, and antioxidant activity using DPPH^• and ABTS^•+ radicals. After the addition of the extract, the oils had from 363.25 to 401.24 mg GAE/100 g for rapeseed oil and chia seed oil, respectively. The antioxidant activity of the oils after the addition of the extract ranged from 102.8 to 221.7 and from 324.9 to 888.8 µM Trolox/kg for the DPPH and ABTS methods, respectively. The kinetics parameters were calculated based on the oils' oxidative stability results. The extract increased the activation energy (Ea) and decreased the constant oxidation rate (k).

Moisture sorption isotherms characteristics for shelf-life prediction of peanuts (Arachis Hypogaea L.)

BACKGROUND

The spring grown peanut varieties J87 and TG37A are prone to quality deterioration as a result of high temperature and relative humidity during harvesting. Thus, the sorption isotherms of peanut varieties were evaluated at 25, 35 and 45 °C and the water activity (a_w ) range of 0.110-0.975 aiming to predict the suitable storage conditions, packaging material and shelf-life.

RESULTS

The equilibrium moisture content (EMC) increased with increased a_w and isotherms of type II were observed. The monolayer moisture content varied between 3.135% and 4.235% for J87 and between 3.906% and 5.640% for TG37A variety. The experimental data were fitted to seven mathematical models. The variations in correlation coefficients were in the range 0.879-0.992 and in root mean square were in the range 0.055-1.988. On the basis of statistical parameters, Guggenheim Anderson de Boer and Double Log Polynomial were considered to be best fitted models. At a_w of 0.6, critical moisture content (CMC) was 7.59%, 7.060% and 5.89% for J87 and 9.06%, 8.904% and 7.80% for TG37A at 25, 35 and 45 °C, respectively. The shelf-life prediction model provided that the aluminum packages had the maximum predicted shelf-life of around 1779 days for TG37A and 1077 days for J87 variety at 25 °C with an initial moisture content of 5.91% and 4.81%, respectively.

CONCLUSION

The EMC and CMC evaluated from sorption study provided the basis for determination of package properties and shelf life. Aluminum packages had the minimum water vapor transmission rate and permeability. Hence, peanuts packaged in these bags and stored at 25 °C and 75% relative humidity had the potential to attain the maximum storage life. © 2023 Society of Chemical Industry.

Simultaneous extraction of sunflower oil and active compounds from olive leaves using pressurized propane

Sunflower is grown in different parts of the world and oil from the grain has many uses, including cosmetics and food. Olive leaves are rich in active compounds with potential for industrial use. The simultaneous extraction of raw materials is an economical and sustainable way of using the same extraction process to obtain products with high added value. The aim of this work was to promote the incorporation of bioactive compounds from olive leaves in sunflower oil by two extraction techniques: pressurized propane (PRO) and Soxhlet (SOX) and to evaluate the increase in oxidative stability and antioxidant activity of oils. The techniques used were useful in producing sunflower oil incorporating olive leaf extract (SFO + OLE); 4.3% 1-octacosanol and 5.8% 1-triacontanol were incorporated, and β-sitosterol increased by at least 90%. Also, SFO + OLE showed an increase in the induction time of 2.7 and 3.7 h compared to SFO for the PRO and SOX methods, respectively. The profile of fatty acids was maintained, with the majority in all samples being oleic and linoleic acids. Consequently, with this procedure is possible to produce SFO + OLE with better antioxidant activity and better nutritional characteristics using PRO and SOX. The scaled-up of the simultaneous extraction process via pressurized propane is economically viable according to the process simulation and economic evaluation.

New insights into the kinetic and thermodynamic evaluations of lipid peroxidation

Simultaneous evaluations over the whole practical range of peroxidation, including the initiation and propagation phases, provide more informative and reliable data than single-parameter analyses being mostly employed only over the course of the initiation phase. Besides an overview on the dominant mechanisms governing the initiation and propagation phases, this article highlights a number of unifying parameters that represent inclusively the two phases. Then, the reliable method to calculate induction period and critical reverse micelle concentration of lipid hydroperoxides as the two interstitial parameters when transitioning from the initiation to the propagation phase is reviewed. Next, a reconsidered form of the conventional methodology on the kinetics of chain-breaking antioxidants is presented. After that, the Arrhenius kinetic and thermodynamic Eyring-Polanyi parameters calculated from the initiation, composite, and decomposition rate constants are compared in order to assess oxidative stabilities. Finally, shelf-life predictions based on a number of proposed end-points of peroxidation are addressed.

The Potential Use of Cold-Pressed Pumpkin Seed Oil By-Products in a Low-Fat Salad Dressing: The Effect on Rheological, Microstructural, Recoverable Properties, and Emulsion and Oxidative Stability

The cold-pressed pumpkin seed oil by-product (POB) was evaluated for its application as a natural fat substitute and stabilizer in the reduced-fat salad dressings. For this aim, the samples were prepared by combining the xanthan gum (0.2–0.4 g/100 g), POB (1.0–5.0 g/100 g), egg yolk powder (3 g/100 g), and sunflower oil (10–30 g/100 g) in 17 different formulations. The optimization was carried out using response surface methodology (RSM) and full factorial central composite design (CCD). Results showed that all samples presented the shear-thinning (or pseudoplastic) flow behavior with 3.75–16.11 Pa·sⁿ and 0.18–0.30, K and n values, respectively. The flow behavior rheological data were fitted to a power-law model (R² > 0.99). The samples with high POB and low oil content showed similar K and n values compared to high oil content samples. Additionally, the dynamic rheological properties and three interval thixotropic test (3-ITT) were determined. The G′ value was larger than G″ in all frequency ranges, indicating viscoelastic solid characteristics in all samples. The optimum formulation was determined as 0.384% XG, 10% oil, and 3.04% POB. The samples prepared with the optimum formulation (POBLF-SD) were compared to low-fat (LF-SD), and high-fat (HF-SD) control salad dressing samples based on the rheological properties, emulsion stability, oxidative stability, zeta potential, and particle size. The oxidation kinetic parameters namely, IP, E_a, ΔS⁺⁺, and ΔG⁺⁺ showed that the oxidative stability of salad dressing samples could be improved by enriched by POB. The results of the present study demonstrated that POB could be considerably utilized as a natural fat substitute and stabilizer in salad dressing type emulsions.

Activated complex theory is a classical theory suitable for food science with appropriate use

Activated complex theory (ACT), apart from Van 't Hoff equation, has long been applying as an alternative tool to connect the kinetics (reaction rate constant, k) and thermodynamics parameters (including standard enthalpy of activation, △H⁺⁺; standard entropy of activation, △S⁺⁺; standard Gibbs free energy of activation, △G⁺⁺). The study mainly focuses on ACT application in food systems, especially oil and fruit juice processing. Considering there are several improper calculations or mistakes often found in papers published recently in 2014-2019, three considerations are presented when applying the ACT, including 1) Understand that the reaction should be a single chemical elementary step; 2) Ensure that the units used should be consistent; 3) Effectively analyze the kinetics and thermodynamic parameters by choosing proper temperatures. This study is expected to further improve the understanding and correct application of this well-known theory in future work.

Critical kinetic parameters and rate constants representing lipid peroxidation as affected by temperature

This study aimed to comparatively investigate the temperature effect on the kinetic parameters and rate constants representing lipid hydroperoxides (LOOH) formation and decomposition during initiation and propagation peroxidations. The initiation phase was characterized by induction period IP, overall initiation rate constant k_IP, initiation oxidizability O_i, and the critical reverse micelle concentration of LOOH, CMC_L. The propagation phase was characterized by its duration t_p, the maximum rate of LOOH accumulation R_max, maximum LOOH concentration [LOOH]_max, propagation oxidizability R_n, composite rate constant k_c, and LOOH decomposition rate constant k_d. O_i and R_n indicated relatively high dependencies on temperature, respectively. Among the rate constants, k_d better highlighted oxidizabilities as affected by temperature. The oxidizabilities had good correspondences with the Arrhenius kinetic (A and E_a) and Eyring thermodynamic (ΔS⁺⁺ and ΔH⁺⁺) parameters. The most endergonic reactions (ΔG⁺⁺>0) were LOOH decompositions, followed by LOOH formations during the propagation and initiation phases, respectively.

Antioxidant properties of two novel lipophilic derivatives of hydroxytyrosol

Two novel lipophilic derivatives of the natural olive oil phenol, hydroxytyrosol (HT), were synthesized using 3,4-dihydroxyphenylacetic acid as starting material. Their antioxidant activities and kinetics compared to HT and TBHQ were assessed by Rancimat, Schaal Oven, 2,2-diphenyl-1-picrylhydrazyl (DPPH) and deep-frying methods. All experiments, including kinetic data analysis based on the Arrhenius equation, utilized in assessing antioxidant activity except the DPPH assay revealed that the new lipophilic HT derivatives exhibited much stronger antioxidant activity than hydroxytyrosol. Tert-butylhydroquinone exhibited stronger antioxidant activity in bulk oil at 65 °C than the new HT derivatives, but showed much lower activity at higher temperatures (>110 °C). This demonstrates that the introduction of bulky alkyl moiety to the ortho-diphenolic structure of HT increased its antioxidant activity. It can be concluded that the new lipophilic HT derivatives satisfy industrial demands for bioactive compounds with strong antioxidant potential at high temperatures.

Protective effect of hydroxytyrosol and rosemary extract in a comparative study of the oxidative stability of Echium oil

The oxidative stability of Echium oil has been studied by two accelerated oxidation methodologies namely Rancimat and differential scanning calorimetry at selected temperatures in the range 50-110 °C. Kinetic analyses have provided Arrhenius parameters, oxidative stability indexes (OSI), temperature coefficients (t_coef), Q₁₀ and OSI at 20 °C (OSI₂₀) for both methodologies focussing on secondary and tertiary oxidation products. Peroxide, p-anisidine and polar compounds values have been measured to characterize from primary to tertiary oxidation products. In general, susceptibility of this oil to oxidation has been found to be larger than for other vegetable oils, according to the OSI₂₀ values estimated by Rancimat and differential scanning calorimetry. However, the values of t_coeff and Q₁₀ are found to be similar to those described for vegetable oils. In addition, a study of the influence of two antioxidants, namely hydroxytyrosol and rosemary extract on the oxidative stability of Echium oil has been carried out using both methodologies. Protective effects over oxidation by up to a threefold increase of OSI₂₀ values have been found for both antioxidants at the highest dose utilized.

Use of Iranian Milkweed Seed Oil to Increase Oxidative Stability of Olive Cultivar Roghani Oil

This study aimed to evaluate fatty acid composition and physicochemical properties of Iranian milkweed seed oil (IMSO) and olive cultivar Roghani oil (OCRO). The extraction yield and unsaturated fatty acids content of IMSO were 21.9 % (dry basis) and 65 %, respectively. The monounsaturated fatty acids/polyunsaturated fatty acids ratio, calculated oxidizability, peroxide value, unsaponifiable matter, total tocopherol content, total phenolic content, total sterol, wax content, carbonyl value, conjugated diene value and oxidative stability index of IMSO and OCRO were measured. The results indicated that oxidation stability (OS) of IMSO (6.46 h) was significantly higher than OS of OCRO (5.53 h). In addition, application of IMSO to OCRO resulted in higher OS that was the greatest after 10 % addition of IMSO.