Changes in Quality Indices,Phenolic Content and Antioxidant Activity of Flavored Olive Oils during Storage

The chemical characteristics, phenolic content and antioxidant activity of olive oils flavored with garlic, lemon, oregano, hot pepper, and rosemary were evaluated during 9 months of storage. At the end of the storage period, the unflavored and the garlic-flavored oils maintained their chemical parameters within the limits fixed for extra-virgin olive oils. After 9 months of storage, a noticeable decrease in phenolic content was observed in all the oils. The highest (35.0 ± 3.9 mg/kg oil) and the lowest (6.3 ± 0.4 mg/kg) phenolic contents were detected in the unflavored and garlic-flavored oils, respectively. Compounds such as 3,4-DHPEA-EDA (3,4-dihydroxyphenylethyl 4-formyl-3-formylmethyl-4-hexenoate, the dialdehydic form of decarboxymethyl elenolic acid linked to hydroxytyrosol) and p-HPEA-EDA (dialdehydic form of the decarboxymethyl elenolic acid linked to tyrosol) were the most abundant in both unflavored and lemon-flavored oils up till 6 months of storage. At the end of the storage period, increases in 3,4-DHPEA (hydroxytyrosol) and p-HPEA (tyrosol) were measured in almost all the oils. During storage, the antioxidant activity coefficients of the phenolic extracts, calculated according to the β-carotene bleaching assay, significantly decreased and, after 9 months, were in a decreasing order: rosemary (51.3 ± 4.2), hot pepper, lemon, oregano, unflavored, and garlic (8.5 ± 0.7).     

Performance of Regular and Modified Canola and Soybean Oils in Rotational Frying

Canola and soybean oils both regular and with modified fatty acid compositions by genetic modifications and hydrogenation were compared for frying performance. The frying was conducted at 185 ± 5 °C for up to 12 days where French fries, battered chicken and fish sticks were fried in succession. Modified canola oils, with reduced levels of linolenic acid, accumulated significantly lower amounts of polar components compared to the other tested oils. Canola oils generally displayed lower amounts of oligomers in their polar fraction. Higher rates of free fatty acids formation were observed for the hydrogenated oils compared to the other oils, with canola frying shortening showing the highest amount at the end of the frying period. The half-life of tocopherols for both regular and modified soybean oils was 1–2 days compared to 6 days observed for high-oleic low-linolenic canola oil. The highest anisidine values were observed for soybean oil with the maximum reached on the 10th day of frying. Canola and soybean frying shortenings exhibited a faster rate of color formation at any of the frying times. The high-oleic low-linolenic canola oil exhibited the greatest frying stability as assessed by polar components, oligomers and non-volatile carbonyl components formation. Moreover, food fried in the high-oleic low-linolenic canola oil obtained the best scores in the sensory acceptance assessment.     

The Behaviour of Phenolic Antioxidants,Synergists and their Mixtures in Two Vegetable Oils

Tertiary butylhydroquinone (TBHQ), hydroquinone (HQ), propyl gallate (PG), butylated hydroxytoluene (BHT) and butylated hydroxyanisole (BHA) had much higher antioxidant activity in crude safflower oil than in a commercial brand vegetable oil (Bint oil). The following active oxygen (AOM, hours at 97.8° C) and storage stability (days at 45° C) values for each antioxidant in safflower oil were; (27.9, 105.0), (21.2, 44.8), (15.3, 45.5), (9.8, 36.8) and (7.9, 33.5) respectively compared with (6.8, 31.5) for the control. Ascorbyl palmitate (AP), ascorbic acid (AA) and citric acid (CA) were found to improve the AOM stability of both oils. The same values in Bint oil were: (9.0, 34.3), (9.0, 28.3), (9.4, 41.0), (7.3, 28.5) and (6.2, 2.5) respectively compared with (5.3, 23.3) for the control. Ascorbyl palmitate (AP), ascorbic acid (AA) and citric acid (CA) were found to improve the AOM stability of both oils. AP was more effective and CA least effective in safflower oil, whereas the reverse was true in Bint oil. The five antioxidants were individually blended with the three synergists (0.01 % of each) and the 15 combinations added to each oil and compared with the antioxidant controls at 0.02 %. Safflower oil stability was greater with pure TBHQ, HQ and PG than with any of the synergist mixtures whereas the BHA, BHT-synergist mixtures were found equal or superior to that treated with BHA or BHT alone. Bint oil treated with CATBHQ or CA-HQ mixtures showed improved stability compared to oils treated with these antioxidants alone. However, the AOM method alone suggested CA-PG, CA-BHA and CA-BHT mixtures improved the stability compared to the oil-antioxidant controls. Chelation of metals by CA was assumed to be the primary cause of this synergism, whereas AP and AA behaved more like weak antioxidants.     

槲皮素-3-O-乙酸乙酯的合成及清除自由基活性研究

以芦丁为原料,利用苄基选择性保护羟基,脱去芦丁糖,再经Williamson反应及脱苄基,合成了标题化合物,总收率63.8%。其结构经IR、~1HNMR、~(13)CNMR及MS进行了表征。分别采用邻二氮菲法和DPPH法测定了标题化合物对羟基自由基和DPPH自由基的清除作用。结果显示,标题化合物较槲皮素具有更强的清除羟基自由基及DPPH自由基活性。     

Anti-Rancidity Effects of Sesame and Rice Bran Oils on Canola Oil During Deep Frying

In this study, the effect of sesame oil (SEO) and rice bran oil (RBO) on the rancidity of canola oil (CAO) during the process of frying potato pieces at 180 °C was investigated. The SEO and RBO were added to the CAO at levels of 3 and 6%. Frying stability of the oil samples during the frying process was measured on the basis of total polar compounds (TPC) content, conjugated diene value (CDV), acid value (AV), and carbonyl value (CV). In general, frying stability of the CAO significantly (P < 0.05) improved in the presence of the SEO and RBO. The positive effect of the SEO on the stability of the CAO was more than that of the RBO. Increasing the amounts of SEO and RBO from 3 to 6% led to decreases in the TPC and AV, and increases in the CDV and CV of the CAO during the frying process. The best frying performance for the CAO was obtained by use of 3% of both SEO and RBO together (CAO/SEO/RBO, 94:3:3 w/w/w).     

The Location of Phenolic Antioxidants and Radicals at Interfaces Determines Their Activity

To characterize parameters influencing the antioxidant activity at interfaces a novel ESR approach was developed, which facilitates the investigation of the reaction stoichiometry of antioxidants towards stable radicals. To relate the activity of antioxidants towards the location of radicals at interfaces NMR experiments were conducted. Micellar solutions of SDS, Brij and CTAB were used to model interfaces of different chemical nature. The hydrophilic Fremy’s radical was found to be solubilized exclusively in the aqueous phase of SDS micellar solution but partitioned partly into the hydrophilic headgroup area of Brij micelles. In contrast the hydrophobic galvinoxyl was exclusively located in the micellar phase with the increasing depth of intercalation in the order SDS < Brij < CTAB. Gallates revealed a higher stoichiometric factor towards galvinoxyl in CTAB systems, which is accounted to a concentration effect of antioxidant and radical being both solubilized in the palisade layer. In contrast, in SDS solutions hardly any reaction between galvinoxyl and gallates was found. SDS acted as a physical barrier between radical (palisade layer) and antioxidant (stern layer). The influence of the hydrophobic properties of the antioxidant was clearly seen in Brij micelles. Elongation of the alkyl chain in gallate molecule resulted in increasing stoichiometric factors in the presence of galvinoxyl being located in the deeper region of the bulky headgroup area. The reverse trend was found in the presence of Fremy’s radical being located in the hydrated area of the micelles.     

Phenolic Composition and Antioxidant Activity of Monovarietal and Commercial Portuguese Olive Oils

Olive oil composition has been investigated using chemical approaches, since the composition has a direct impact on its quality and safety and it may be used for certification purposes. In this paper, eleven monovarietal and twelve commercial Portuguese olive oils were analyzed to determine spectrophotometrically their total polyphenol content, ortho-diphenols and antioxidant activity. The phenolic profiles of these olive oils were also studied by high performance liquid chromatography. The lowest phenolic content and antioxidant activity were observed for monovarietal olive oils, however, among these group, ‘Cobrançosa’ and ‘Redondil’ cultivars showed the highest values of these two chemical parameters. In commercial olive oils, the concentration of polyphenols, determined according to the Folin–Ciocalteu method, and the antioxidant activity (ABTS method) ranged from 97.37 ± 1.10 to 219.7 ± 1.50 mg GAE/kg of oil and from 387.2 ± 20.00 to 997.5 ± 30.90 µmol Trolox/kg, respectively. The study of the phenolic profile demonstrated that the highest concentrations of the most abundant compounds in olive oil (tyrosol, hydroxytyrosol and oleuropein) are present in commercial olive oils. The correlation coefficient between total phenolics and antioxidant activity was statistically significant (r = 0.95, p < 0.0001). The same was observed for ortho-diphenol content and antioxidant capacity (r = 0.94, p < 0.0001).     

Frying Performance of Canola Oil Triacylglycerides as Affected by Vegetable Oils Minor Components

The endogenous minor components from canola, rice bran, sesame and palm oils including selected phospholipids, and various combinations of tocopherol isomers were tested during frying using canola oil triacylglycerols as the frying medium. Thermo-oxidative degradation was assessed by measurement of the total polar components, the rate of volatile carbonyl compounds and 4-hydroxynonenal formation. All the tested minor components protected to a different extent canola triacylglycerides from thermo-oxidative degradation during frying. No significant differences were observed in the protection of the triacylglycerides among all the tested tocopherol isomers and their mixtures. Irrespective of the composition of tocopherol homologous, an increase in the added amounts above 1,000 μg/g did not improve protection. Minor components isolated from rice bran and sesame oils offered better protection during canola triacylglycerides frying than endogenous minor components isolated from canola oil. When 0.2% phosphatidylcholine or phosphatidylethanolamine was added to the canola triacylglycerides, the amount of formed polar components decreased twice as compared to the tocopherol isomers. Accordingly, by optimizing the composition and the concentration of the endogenous minor components, the frying performance of oil can be significantly enhanced.     

The Effects of Microwave Frying on Physicochemical Properties of Frying and Sunflower Oils

Deep fat frying is a method of food preparation which has been popular for quite a number of years. During deep frying, the quality of oil and the finished product decreases as the result of heat treatment of the oil exposed to air at high temperature. Application of heat by microwave as an alternative to the conventional method of frying has become popular in recent years. In this research, the effects of microwave frying on the changes in the quality indices of used oil have been investigated. To achieve this, potato slices were fried in both frying and sunflower oils by application of medium power microwave (550 W) for 20 min, three times a day, for five consecutive days, and oils were sampled for analysis. The results obtained from the chemical tests demonstrated that used frying oil had lower polar compounds, a higher induction period, and more saturated fatty acids than sunflower oil. The interesting point observed was that peroxides formed as the result of oxidation chain reactions were not broken down and were built up due to the lower temperature and shorter period of frying. Therefore microwave frying might be considered as a suitable alternative to the conventional frying due to less degradation of the oil and consequently a lower production of artifacts.     

Rapid Assessment of Frying Performance Using Small Size Samples of Oils/Fats

A rapid, effective test mimicking actual frying was developed to assess the frying performance of oils and fats using small size samples. To a small volume of the oil to be tested, a formulated food consisting of gelatinized potato starch, glucose and silica gel (4:1:1 w/w) were added and content heated at 185 ± 5 °C with mixing for 2 h. Thermo-oxidative degradation of the oil was assessed by the measurement of the total amount of polar components and their composition, including degradation of tocopherols. The developed fast test accurately mimics actual frying done using an institutional fryer as assessed by the accumulation and composition of total polar components and the amount of residual tocopherols. The validity of the test was assessed using the following oils: regular canola, high oleic– low linolenic canola, and high oleic sunflower. Comparison of data between the fast frying test and institutional frying revealed a lack of significant differences. The developed frying test provides reliable quantitative and qualitative data describing the performance of the frying oil/fat. The rapid frying procedure allows assessment of the frying performance of oils at the early stages of development where usually only small amounts of the sample are available and when a large number of samples have to be tested assessing effects of oil additives.     

赶黄草中清除1,1-二苯基-2-苦肼基自由基活性物质的研究

通过单因素试验、正交试验、大孔吸附树脂(HP2MGL)的分离纯化试验,以赶黄草提取组分清除1,1-二苯基-2-苦肼基(DPPH)自由基的能力为指标,得到最佳工艺参数为超声时间40 min、超声温度50℃和提取乙醇质量分数为95%,与质量分数为25%乙醇洗脱物、质量分数为50%乙醇洗脱物、质量分数为75%乙醇洗脱物相比,无水乙醇的大孔吸附树脂的洗脱物的清除DPPH自由基的能力最强。对照试验表明,在一定抗氧化剂浓度范围内,优化得到的赶黄草中植物活性物质清除DPPH自由基的能力大于槲皮素、没食子酸,小于抗坏血酸。利用高效液相色谱——Q Exactive质谱(HPLC-MS)技术对最佳洗脱组分进行分析发现化合物的种类较多,未知化合物较多。     

受阻酚类抗氧剂的研究进展

综述了受阻酚类抗氧剂的研究概况、分类、作用机理、抗氧剂效率的影响因素和着色机理,介绍了几种受阻酚类抗氧剂的典型产品,并预测了受阻酚类抗氧剂的发展趋势。     

聚烯烃中受阻酚类抗氧剂的应用

综述了受阻酚类抗氧剂的作用机理,并对在聚烯烃中与其它辅抗氧剂的复配进行了简要的介绍。     

Comparison of the Frying Performance of High Oleic Oils Subjected to Discontinuous and Prolonged Thermal Treatment

Frying is a popular practice because of its unique sensory characteristics and low cost. The high temperature reached with this cooking method alters molecules present in the oil. The deterioration of the oil depends primarily on its chemical composition. The aim of this study was to evaluate the thermal stability of high oleic sunflower oil (HOSO), sunflower oil (SO) and mixed oil (MIX) during deep frying of French fries. Octanoic acid and unsaturated fatty acid (UFA)/saturated fatty acid (SFA) ratio showed a good correlation with total polar compounds (TPC) for all frying samples analyzed. HOSO and MIX were characterized by reduced levels of thermal degradation, while SO resulted in the highest values of oxidation products (highest TPC values). SO was also the oil more retained by the food matrix, whereas MIX was the least absorbed. HOSO and MIX, having a high oleic acid content (77.58 and 59.92 %, respectively) and a low linoleic acid content (13.42 and 25.70 %, respectively), showed the best characteristics for the frying process.     

Kinetic Study of the Scavenging Reaction of the Aroxyl Radical by Eight Kinds of Vegetable Oils in Solution

A detailed kinetic study was performed for the reaction of the aroxyl radical (ArO?) with eight vegetable oils 1–8, which contain different concentrations of α‐, β‐, γ‐, and δ‐tocopherols and ‐tocotrienols (‐Tocs and ‐Toc‐3s). The second‐order rate constants (k_s) and aroxyl radical absorption capacity (ARAC) values for the reaction of ArO? with vegetable oils 1–8 (rice bran 1, perilla 2, rapeseed 3, safflower 4, grape seed 5, sesame 6, extra virgin olive 7, and olive oils 8) were measured in ethanol/chloroform/D₂O (50:50:1, v/v/v) solution at 25 °C using stopped‐flow spectrophotometry. The k_s value (16.1 × 10^?3 L g^?1 s^?1) of rice bran oil 1 with the highest activity was 8.0 times larger than that (2.02 × 10^?3) of olive oil 8 with the lowest activity. The concentrations (in mg 100 g^?1) of α‐, β‐, γ‐, and δ‐Tocs and ‐Toc‐3s contained in the vegetable oils 1–8 were determined using high performance liquid chromatography‐mass spectrometry/mass spectrometry (HPLC‐MS/MS). From these results, it was clarified that the ArO?‐scavenging rates (k_s) (i.e., the relative ARAC value) obtained for the vegetable oils 1–8 may be well explained as the sum of the product of the rate constant () and the concentration ([AOH‐i]/10⁵) of AOH‐i (Tocs and Toc‐3s) included in vegetable oils. The results suggest that the ARAC assay method might be used in the evaluation of antioxidant activity of general food extracts.     

Rapid Determination of Degradation in Frying Oils with Near-Infrared Spectroscopy

Measures of free fatty acids (FFA), total polar materials (TPM), and conjugated dienoic acids (CDA), typical indices of oil degradation, were analyzed in daily oil aliquots taken from soybean oils with different linolenic acid concentrations used to fry French fries. The oils also were scanned with a reflectance near-infrared spectrometer using a wavelength range of 350–2,500 nm. By using partial least squares and one-out cross validation, calibrations were developed to quantitatively determine FFA, TPM, and CDA by near-infrared spectroscopy (NIRS). The coefficients of determination (R ²) when compared to the standard methods were 0.973 for FFA, 0.984 for TPM, and 0.902 for CDA. NIRS was an accurate and fast method to determine FFA, TPM, and CDA in oxidized oils. The ability to obtain different parameters simultaneously makes NIRS a potentially valuable tool for food quality assurance.     

Radical Scavenging Activity of Lipophilized Products from Lipase-Catalyzed Transesterification of Triolein with Cinnamic and Ferulic Acids

Lipase-catalyzed transesterification of triolein with cinnamic and ferulic acids using an immobilized lipase from Candida antarctica (E.C. 3.1.1.3) was conducted to evaluate the antioxidant activity of the lipophilized products as model systems for enhanced protection of unsaturated oil. The lipophilized products were identified using ESI-MS. Free radical scavenging activity was determined using the DPPH radical method. The polarity of the solvents proved important in determining the radical scavenging activity of the substrates. Ferulic acid showed much higher radical scavenging activity than cinnamic acid, which has limited activity. The esterification of cinnamic acid and ferulic acid with triolein resulted in significant increase and decrease in the radical scavenging activity, respectively. These opposite effects were due to the effect of addition of electron-donating alkyl groups on the predominant mechanism of reaction (hydrogen atom transfer or electron transfer) of a species with DPPH. The effect of esterification of cinnamic acid was confirmed using ethyl cinnamate which greatly enhances the radical scavenging activity. Although, compared to the lipophilized cinnamic acid product, the activity was lower. The radical scavenging activity of the main component isolated from lipophilized cinnamic acid product using solid phase extraction, monocinnamoyl dioleoyl glycerol, was as good as the unseparated mixture of lipophilized product. Based on the ratio of a substrate to DPPH concentration, lipophilized ferulic acid was a much more efficient radical scavenger than lipophilized cinnamic acid.     

Effects of Cultivars and Location on Quality, Phenolic Content and Antioxidant Activity of Extra-Virgin Olive Oils

Quality characteristics of extra-virgin olive oils depend on several factors. In order to study the effects of genotype and growing location on olive oil quality, olives from cv. Coratina, Nocellara, Ogliarola, and Peranzana, picked in four locations of the Apulia region (Italy), were crushed by a three-phase system to produce mono-cultivar extra virgin olive oils that were analyzed for acidity, peroxide value, spectrophotometric indices, total phenolic content, phenolic profile and antioxidant activity. The experimental data concerning peroxide value, spectrophotometric indices, phenolic content and profile and antioxidant activity showed great variability among the cultivars grown in the same location and also among the oils produced with olives of the same cultivar but grown in different locations. For each cultivar, no significant differences were found among locations in terms of acidity and ΔK whereas peroxide value, K₂₃₂, and K₂₇₀ differ significantly among locations for both Ogliarola and Peranzana cv. Concerning the phenolic content of Ogliarola cv., no differences were highlighted between the locations whereas the phenolic contents of Peranzana significantly changed as a function of the place of growing. On the basis of these results, the statistical multivariate analysis did not allow the classification into homogeneous groups neither of the oils belonging to the same cultivar nor of those obtained from olives picked in the same location.