Increasing the oxidative stability of soybean oil through fortification with antioxidants

Vegetable oils high in polyunsaturated fatty acids (PUFA), like soybean oil (SO), are known for lowering the risk of consumers for contracting cardiovascular disease as well as improving cognitive health. However, they are more susceptible to lipid oxidation than recently introduced high‐oleic cultivars like high‐oleic sunflower oil (HOSFO). Thus, the objective of this study was to increase the stability of PUFA oils to maintain the aforementioned health benefits by supplementing them with industrially relevant antioxidant compounds that prevent or delay oxidation during food production and storage. Herein, a variety of synthetic and natural antioxidants tested alone or in mixtures was screened to bring the stability of SO closer to that of HOSFO. Oils were stored under accelerated conditions (35 °C) in the dark for 28 weeks, and the evolution of primary (hydroperoxides) and secondary (hexanal) lipid oxidation products was monitored. Oxidative stability index data showed that addition of 300 ppm of ascorbyl palmitate (AP) stabilised SO to the greatest magnitude. Further, a combination of AP (300 ppm) and M‐TOC (1000 ppm) was able to limit hydroperoxide and hexanal formation in SO at 35 °C for 12 weeks. It was demonstrated that assessing multiple quality parameters for lipid stability are a necessary undertaking.     

A multivariate approach to optimise the synergistic blend of oleoresin rosemary (Rosmarinus officinalis L.) and ascorbyl palmitate added into sunflower oil

The simultaneous optimisation of a synergistic blend of oleoresin rosemary (ROS) and ascorbyl palmitate (AP) in sunflower oil (SO) was performed using central composite and rotatable design coupled with principal component analysis (PCA) and response surface methodology (RSM). The physicochemical parameters, viz. peroxide value, anisidine value, induction period, total polar matter, UV absorbances (232 and 270 nm) and antioxidant capacity were considered as response variables. PCA reduced the original set of correlated responses to few uncorrelated principal components (PC). The PC1 (eigenvalue, 6.08; data variance explained, 86.97%) was selected for optimisation using RSM. The quadratic model described the data (R² = 0. 93, P < 0.05), and lack of fit was insignificant (P > 0.05). The contour plot of PC 1 score indicated the optimal synergistic combination of 1309.62 and 129.29 ppm for ROS and AP, respectively. In conclusion, the versatility of PCA–RSM approach has resulted in an easy interpretation in multiple response optimisations.     

Assessment of thermo‐oxidative rancidity in sunflower oil and fried potato chips stabilised with oleoresin sage (Salvia officinalis L.) and ascorbyl palmitate by altered triglycerides and electronic nose

Oleoresin sage (Salvia officinalis) (SAG) (200–1500 mg kg^?1), ascorbyl palmitate (AP) (100–300 mg kg^?1) and TBHQ (200 mg kg^?1) were assessed for delaying the thermo‐oxidation in sunflower oil (SO) during 18 h of frying (180 °C). Electronic nose compared the global aroma fingerprints of potato chips fried in oils. The chemical rancidity indices viz., fatty acids, total polar compounds (TPC), altered triglycerides (dimers, polymers, oxidised monomers, diglycerides), free fatty acids, conjugated dienes and induction periods were monitored along with physical indices viz., viscosity and colour. SO_SAG+AP (1309.62 + 270.71 mg kg^?1) outperformed SO_TBHQ by preserving polyunsaturated fatty acids (60.48% vs. 56.23%), retarding TPCs (28.16% vs. 29.91%), triglyceride dimers (90.24 vs. 95.82 mg g^?1) and polymers (25.40 vs. 26.98 mg g^?1) concomitantly extending the oil disposal time (basis 25% TPC) (15.9 vs. 14.7 h). The postfrying viscosity, colour values and global aroma fingerprints of fried chips indicate a close match between SO_SAG+AP and SO_TBHQ.     

Heating,microwave and UV irradiation effects on oxidative stability of Sardasht red grape (Vitis vinifera cultiv. Sardasht) seed oil

In the current study, for the first time, the oxidation stability of the extracted edible oil from Sardasht red grape at three different accelerated deteriorative conditions (oven, microwave and ultraviolet (UV) irradiation) was investigated. In this context, the peroxide value (PV), conjugated diene value (CDV), carbonyl value (CV), radical scavenging activity (RSA) and oil/oxidative stability indices, as well as fatty acid composition and total tocopherol content, were evaluated. Sardasht grape seed oil as a rich oil in unsaturated fatty acid (about 87%) contains linoleic acid in terms of the principal fatty acid (70.4 ± 1.8%). The excessive oxidative stability of crude oil can be correlated with the extreme content of natural antioxidants (tocopherols and tocotrienols). The findings showed that Sardasht red grape seed oil could be approached as new source of edible oil with acceptable oxidative stability.     

不同贮存条件对海藻油氧化稳定性影响

以过氧化值为指标,考察空气、温度、光照等环境条件对海藻油稳定性影响,然后采用Schall烘箱加速氧化法,以POV和DHA含量为指标,通过L9(34)正交试验,从抗氧化剂TBHQ、VE、Vc棕榈酸酯优选海藻油复合抗氧化剂;及研究充N2保护、充N2保护结合添加抗氧化剂对海藻油稳定性影响。结果表明:空气,高温及光照均可显著加速海藻油氧化,降低海藻油稳定性;抗氧化剂TBHQ、VE、Vc棕榈酸酯能明显延缓海藻油氧化,影响顺序为Vc棕榈酸酯TBHQVE,最佳抗氧化剂组合为0.01%Vc棕榈酸酯+0.02%TBHQ+0.50%VE;充N2保护也能提高海藻油氧化稳定性,但效果比最佳复合抗氧化剂为差;充N2保护结合添加抗氧化剂能有效提高海藻油氧化稳定性。     

Enzymatic Synthesis of Ascorbyl Palmitate in Organic Solvents: Process Optimization and Kinetic Evaluation

This work is focused on the optimization of reaction parameters for the synthesis of ascorbyl palmitate catalyzed by Candida antarctica lipase in different organic solvents. The sequential strategy of experimental designs proved to be useful in maximizing the conditions for product conversion in tert-butanol system using Novozym 435 as catalyst. The optimum production were achieved at ascorbic acid to palmitic acid mole ratio of 1:9, stirring rate of 150 rpm, 70 °C, enzyme concentration of 5 wt.% at 17 h of reaction, resulting in an ascorbyl palmitate conversion of about 67%. Reaction kinetics for ascorbyl palmitate production showed that very satisfactory reaction conversions (∼56%) could be achieved in short reaction times (6 h). The kinetic empirical model proposed showed ability to satisfactory represents and predict the experimental data.     

Effects of lipophilic and hydrophilic antioxidants in oil-in-water emulsions under chlorophyll photosensitization

Antioxidative or prooxidative properties of α-tocopherol, Trolox, ascorbic acid, and ascorbyl-palmitate at the concentration of 0.1 and 1.0 mM were determined in oil-in-water (O/W) emulsions under chlorophyll photosensitization. Headspace oxygen depletion, lipid hydroperoxides, and headspace volatile analyses were conducted to determine the oxidative stability of O/W emulsions. For 32 h visible light irradiation, depleted headspace oxygen content in O/W emulsions were in the order of samples containing Trolox, ascorbic acid, ascorbyl palmitate, α-tocopherol, without antioxidants under light, and samples in the dark, which implies that all the added compounds acted prooxidant. These prooxidative properties of added compounds can be observed in the results of lipid hydroperoxides and headspace volatiles. Samples containing ascorbic acid and ascorbyl palmitate retained higher chlorophyll content than those containing Trolox up to 16 h. Increases of concentration of Trolox, ascorbic acid, and ascorbyl palmitate from 0.1 to 1.0 mM increased the lipid oxidation products whereas α-tocopherol decreased the degree of lipid oxidation implying α-tocopherol may not share the same prooxidant mechanisms compared to other compounds in chlorophyll sensitized O/W emulsions.     

Cytooxidative effects of α‐tocopherol and ascorbyl palmitate on thermal oxidation of canola oil

Canola oil, with and without added α‐tocopherol and ascorbyl palmitate, was used to deep‐fat frying potatoes once per day for 10 day or once per week for 10 weeks. Changes in chemical and physical properties were monitored. Refractive index, free fatty acids and absorbance at 232 and 270 nm increased with frying time. Smoke point, ‘L’ color index, iodine value and the C_18 : 2/C_16 : 0 ratio in the oil decreased with the frying time. According to smoke point, which shows the time of the oil should be discarded, canola oil without antioxidant (control) can be used safely 8 times daily or 7 times weekly. For canola oil with antioxidant (oil + α‐tocopherol + ascorbyl palmitate( the smoke point did not decrease below 170°C in both daily and weekly fryings. This showed that canola oil with antioxidant could be used safely at least 10 times for both frying intervals. In both daily and weekly fryings, the addition of 200 ppm α‐tocopherol and 200 ppm ascorbyl palmitate increased the oxidative stability of canola oil.     

3种抗氧化剂对菜籽油氧化稳定性的影响

为探究抗坏血酸棕榈酸酯、迷迭香提取物和茶多酚棕榈酸酯及其复合物对菜籽油氧化稳定性的影响,采用Schaal烘箱加速氧化实验法对菜籽油进行氧化稳定性评价,并采用响应面实验优化复配抗氧化剂的配方。结果表明：3种抗氧化剂均能显著提高菜籽油的氧化稳定性（P＜0.05）,其中茶多酚棕榈酸酯抗氧化效果最为理想,添加量为0.01%和0.05%时,菜籽油过氧化值比空白对照分别降低了61.76%和68.79%;响应面实验得到最优复配抗氧化剂配方为0.02%抗坏血酸棕榈酸酯、0.03%迷迭香提取物、0.03%茶多酚棕榈酸酯,在此配方下加速氧化13 d时菜籽油过氧化值为6.017 mmol/kg。该复配抗氧化剂能有效减缓菜籽油的氧化速度,且能够保护菜籽油不易受高浓度抗氧化剂的促氧化作用。     

Antioxidant capacities of α-tocopherol,trolox, ascorbic acid,and ascorbyl palmitate in riboflavin photosensitized oil-in-water emulsions

Antioxidant capacities of α-tocopherol, trolox, ascorbic acid, and ascorbyl palmitate at 0.01, 0.1, and 1.0 mM in riboflavin photosensitized oil-in-water (O/W) emulsions were determined using headspace oxygen depletion, lipid hydroperoxide, and headspace volatile analyses. After 32 h visible light irradiation, headspace oxygen in O/W emulsions without adding antioxidants, with 1.0 mM α-tocopherol, trolox, ascorbic acid, and ascorbyl palmitate decreased to 18.50%, 18.85%, 16.01%, 17.92%, and 19.88%, respectively, whereas those samples in the dark were 20.74%. Trolox and ascorbic acid acted as prooxidants while their lipophilic counterparts, α-tocopherol and ascorbyl palmitate, respectively showed antioxidant properties. Similar antioxidative or prooxidative properties of the tested compounds can be observed in the results of lipid hydroperoxides and headspace volatiles. However, the prooxidant and antioxidant properties of the tested compounds were not clearly shown at 0.01 and 0.1 mM concentration. Both the type and concentration of antioxidants influenced the antioxidant capacities in riboflavin photosensitized O/W emulsions.     

4 种天然抗氧化剂对纯油和人造奶油氧化稳定性的影响

对脂溶性天然抗氧化剂迷迭香、VE、抗坏血酸棕榈酸酯和水溶性天然抗氧化剂表没食子儿茶素没食子酸酯,在以棕榈油为主体的纯油产品和油包水型人造奶油产品中的抗氧化效果进行研究。结果表明：亲水亲油性不同的抗氧化剂在两种体系中的抗氧化性有明显差异。在人造奶油体系中,0.02%水溶性表没食子儿茶素没食子酸酯的抗氧化性最好。在纯油体系中,0.07%脂溶性迷迭香的抗氧化性最好。人造奶油体系的氧化稳定性明显低于纯油体系。     

Interactions between tocopherols,tocotrienols and carotenoids during autoxidation of mixed palm olein and fish oil

Electron spin resonance (ESR) and spin trapping detection of radical formation showed that the oxidative stability of palm olein/fish oil mixtures increased with the amount of palm olein. Mixtures with red palm olein were less stable than were mixtures with yellow palm olein. Addition of ascorbyl palmitate and citric acid gave further reduction of radical formation, whereas no effect was observed by adding lecithins. Storage of palm olein/fish oil mixtures (4:1) at 30 °C confirmed that red palm olein mixtures were less stable than were yellow palm olein mixtures. Ascorbyl palmitate together with citric acid improved the stability in both cases. The concentrations of α-tocopherol and α-tocotrienol decreased during storage, whereas β-, γ-, and δ-tocotrienols were unaffected. Ascorbyl palmitate reduced the losses of α-tocopherol and α-tocotrienol. The rate of loss of carotenoids was independent of the presence of fish oil and, except for an initial fast drop, also of the presence of ascorbyl palmitate.     

Influence of sn‐1,3‐lipase‐catalysed interesterification on the oxidative stability of soybean oil‐based structured lipids

The oxidative stability of structured lipids (SLs) synthesised by specific sn‐1,3‐lipase catalysed interesterification of soybean oil (SBO) with caprylic acid (CA) in a stirred batch reactor was studied. SLs contained considerable amounts of tocopherol (TOH) isomers, although they lost almost 25% of endogenous TOHs during production. The effects of the addition of different TOH homologues (α, β, γ, δ), ascorbyl palmitate (AP, 200 ppm), lecithin (Le, 1000 ppm), butylated hydroxytoluene (BHT, 100 ppm) and butylated hydroxyanisole (BHA, 100 ppm) on the oxidative stability of SLs were investigated. Induction time (IT) of SBO, determined by the Rancimat method, decreased from 8.4 to 5.8 h at 110 °C after the modification. On the other hand, purified SLs and purified SBO had the same IT due to the tocopherol reduction during silica purification. No significant difference was observed between IT of SLs and SLs plus different α‐tocopherol concentrations (50, 100, 150, 200, 300, 500 and 1000 ppm) (P > 0.05). However, the addition of Le and/or AP significantly improved oxidative stability of purified SLs and SBO. The ternary blend containing δ‐TOH, AP and Le had higher IT than ternary blends of α‐TOH, β‐TOH or γ‐TOH. Furthermore, ternary blend containing BHA, AP and Le had higher IT than ternary blends of BHT, AP and Le. In addition, there was an increase in peroxide value (PV), conjugated diene (CD) content and p‐anisidine value (AV) during oxidation of oils at 60 °C. Antioxidant mixtures of α‐TOH (50 ppm) and δ‐TOH (500 ppm) with AP and Le decreased PV, CD and AV effectively. Copyright © 2006 Society of Chemical Industry     

泠榨制取与超临界CO2萃取核桃油的氧化稳定性比较研究

核桃油中的不饱和脂肪酸含量很高,因而比较容易氧化。为了比较冷榨制取与超临界CO2萃取的核桃油的氧化稳定性,测定了它们在黑暗和光照条件下的过氧化值,并进行了感官品评。研究发现:黑暗条件下,冷榨制取的核桃油的氧化稳定性高于超临界CO2萃取的核桃油的氧化稳定性;光照条件下,超临界CO2萃取的核桃油的氧化稳定性高于冷榨制取的核桃油的氧化稳定性。根据它们氧化稳定性的不同可以选择不同的材料对产品进行包装。     

Classification of Sunflower Oil Blends Stabilized by Oleoresin Rosemary (Rosmarinus officinalis L.) Using Multivariate Kinetic Approach

The sunflower oil–oleoresin rosemary (Rosmarinus officinalis L.) blends (SORB) at 9 different concentrations (200 to 2000 mg/kg), sunflower oil–tertiary butyl hydroquinone (SO_TBHQ) at 200 mg/kg and control (without preservatives) (SO_control) were oxidized using Rancimat (temperature: 100 to 130 °C; airflow rate: 20 L/h). The oxidative stability of blends was expressed using induction period (IP), oil stability index and photochemiluminescence assay. The linear regression models were generated by plotting ln IP with temperature to estimate the shelf life at 20 °C (SL₂₀; R² > 0.90). Principal component analysis (PCA) and hierarchical cluster analysis (HCA) was used to classify the oil blends depending upon the oxidative stability and kinetic parameters. The Arrhenius equation adequately described the temperature‐dependent kinetics (R² > 0.90, P < 0.05) and kinetic parameters viz. activation energies, activation enthalpies, and entropies were calculated in the range of 92.07 to 100.50 kJ/mol, 88.85 to 97.28 kJ/mol, ?33.33 to ?1.13 J/mol K, respectively. Using PCA, a satisfactory discrimination was noted among SORB, SO_TBHQ, and SO_control samples. HCA classified the oil blends into 3 different clusters (I, II, and III) where SORB₁₂₀₀ and SORB₁₅₀₀ were grouped together in close proximity with SO_TBHQ indicating the comparable oxidative stability. The SL₂₀ was estimated to be 3790, 6974, and 4179 h for SO_control, SO_TBHQ, and SORB₁₅₀₀, respectively. The multivariate kinetic approach effectively screened SORB₁₅₀₀ as the best blend conferring the highest oxidative stability to sunflower oil. This approach can be adopted for quick and reliable estimation of the oxidative stability of oil samples.     

Physical,chemical and oxidative changes in raw peanuts: Effect of relative humidity

Peanuts are susceptible to oxidative deterioration due to various factors during storage. This research studied the proximate composition (lipid, protein, total sugar, moisture and ash.), composition and content of amino acids and fatty acids, peroxide value (PV), carbonyl value (CV), malondialdehyde content (MDA), protein composition and structure changes in the peanuts stored for 320 days under different relative humidity (RH; 50%, 65% and 80%) conditions. Lipid oxidation was delayed at low RH (50% and 65%) storage conditions. At high RH (80%), the contents of unsaturated fatty acids, amino acids, protein and lipids decreased significantly during storage (P < 0.05), whereas the PV, CV and MDA contents increased significantly (P < 0.05). The CV values of YH-9326 and YH-22 increased by 14.46 and 17.48 times respectively. In addition, the protein structure changed throughout the whole storage period (P < 0.05). This research provides a theoretical reference for maintaining storage quality and extending shelf life.     

Effects of antioxidants on peanut oil stability

Several antioxidants including phospholipids (PL), ascorbyl palmitate (AP), rosemary (ROS), tocopherol (TOC) and catechin (CAT) were chosen to study the effects on peanut oil stability. Among these antioxidants, catechin alone and composites of catechin with other antioxidants showed significant increases in oil stability as compared to control oil. A response surface design was used to study the effects of three antioxidant composites on the peanut oil stability. Results showed the OSI (Oxidation Stability Index) values are significantly influenced by CAT (p<0.0001), followed by ROS (p<0.05) and PL (p<0.5). TOC was the least significant (p>0.5) in the increase of OSI value. By considering cost, handling and minimum usage of antioxidants, the OSI value of peanut oil would reach 15–16 h by the addition of 1500 ppm of CAT and a maximum level of either 400 ppm of ROS or PL.     

Cross‐linking of bovine and caprine caseins by microbial transglutaminase and their use as microencapsulating agents for n‐3 fatty acids

Bovine and caprine caseins were cross‐linked with microbial transglutaminase (mTG). The mTG‐cross‐linked bovine or caprine casein dispersion, mixed with 14.5% maltodextrin (DE = 40), was used to prepare emulsions with 10.5% algae oil. Oxidative stability of emulsions was evaluated by peroxide values (PVs) and anisidine values. Adding liposoluble rosemary extract rich in carnosic acid and δ‐tocopherol lowered the formation of hydroperoxides and their subsequent decomposition products in emulsions. Emulsions stabilised with liposoluble rosemary extract rich in carnosic acid and δ‐tocopherol were spray‐dried at 180/95 °C. Algae oil microencapsulated with mTG‐cross‐linked bovine casein reduced PV by ≈ 34%, while the algae oil microencapsulated with mTG‐cross‐linked caprine casein with low levels of α_s1‐casein reduced PV by ≈ 42% at 4 weeks of storage at 30 °C. The investigation suggests that liposoluble rosemary extract rich in carnosic acid and δ‐tocopherol effectively protected algae oil during the coating process with mTG‐cross‐linked bovine and caprine caseins. The above results clearly indicated that the choice of milk caseins (bovine vs. caprine) cross‐linked with mTG impacts the oxidative stability of spray‐dried algae oil emulsions (microcapsules) enriched with n‐3 fatty acids.     

Activity and thermal stability of antioxidants by differential scanning calorimetry and electron spin resonance spectroscopy

Heat flux differential scanning calorimetry (DSC) and electron spin resonance spectroscopy (ESR) were used to assess the activity and the thermal stability of antioxidants in four vegetable oils. Sunflower oil (SO) and high oleic sunflower oil (HOSO), both rich in diunsaturated fatty acids (FA), low trans oil (LT) and partially hydrogenated palm oil (PHPO), both containing monounsaturated FA, were analyzed by isothermal heat flux DSC, with or without 300 mg/kg of antioxidant: ascorbyl palmitate (AP), α-tocopherol (αT), δ-tocopherol (δT) and propyl gallate (PG). DSC experiments showed that δT is the most effective antioxidant for SO and PG for the less unsaturated oils. SO and PHPO were also analyzed by ESR at 120 and 145 °C, respectively. ESR results confirm the strongest antioxidant activity of δT and PG for SO and PHPO, respectively. Therefore, the present study demonstrates that DSC and ESR are valuable technologies to study activity and stability of antioxidants at high temperature. Moreover, experiments performed in the presence of the spin-trap N-tert-butyl-α-phenylnitrone (PBN), suggest that δT delay lipid oxidation through a different reaction mechanism when compared to αT. A different mechanism between tocopherols isomers in delaying lipid oxidation has been hypotized.     

Contribution of Chlorophyll to Photooxidation of Soybean Oil at Specific Visible Wavelengths of Light

Photosensitizers in foods and beverages are important considerations when selecting packaging materials. Chlorophyll is found at low concentrations in many food products. The objective of this study was to determine the photosensitizing effect of chlorophyll on soybean oil (SO) using broad‐spectrum light and 3 visible wavelength regions of light. SO with added chlorophyll (0, 1, or 2 μg chlorophyll added/mL SO) was exposed to 5 light conditions, using a photochemical reactor (10 °C; 4 h). Light treatments included broad‐spectrum (BS; no filter; 157.6 ± 4.7 mW intensity), 430 nm (10 nm; 1.8 ± 0.7 mW), and 660 nm (10 nm; 0.332 ± 0.05 mW) wavelengths compared to a no‐light control. Chlorophyll a (but not b) absorbs light in the selected visible wavelength regions. Chlorophyll degradation was evaluated. Oxidative changes in SO were assessed by peroxide value (PV) and thiobarbituric acid‐reactive substances (TBARS) assay, which measures malondialdehyde (MDA). Chlorophyll was completely degraded at BS and 430 nm conditions and degraded to 36% of original concentration at 660 nm wavelength. PV and MDA concentration significantly increased with chlorophyll addition (1 μg/mL) at BS and 430 nm wavelengths compared to no‐light control. Lower light intensity at 660 nm initiated oxidation reactions as measured by PV, but not significantly. There were differences in PV (BS, 430 nm) and TBARS (BS) between the no‐light and light‐exposed SO without chlorophyll added. There was very little effect at 450 nm. This study suggests that broad‐spectrum light and at least light wavelengths at or near 430 nm and 660 nm excite chlorophyll, resulting in initiation of oxidation reactions. Packaging material selection for foods and beverages should consider blocking excitation wavelengths of photosensitizing molecules, including chlorophyll, to protect product quality.