Extraction of Lignan Compounds from Roasted Sesame Oil and their Effects on the Autoxidation of Methyl Linoleate

ABSTRACT:  Lignan compounds were extracted from roasted sesame oil and their effects on the autoxidation of methyl linoleate (ML) were studied. Lignan compounds extracted from roasted sesame oil, sesamol, sesamin, and sesamolin, were added to ML, which was then oxidized at 60 ^oC for 18 h in the dark. Alpha-tocopherol was separately added to ML for a reference antioxidant. Degree of ML oxidation was monitored by conjugated dienoic acid (CDA) contents and p -anisidine value (PAV) by AOCS methods, and ML retention by gas chromatography. CDA contents and PAV of samples increased with the oxidation time at 60 ^oC in the dark, and ML decreased. Sesamol-, sesamin-, or sesamolin-added samples showed lower CDA contents, PAV, and ML loss than the samples without lignans during oxidation in the dark, which indicated that lignan compounds lowered the ML autoxidation. The antioxidant activity of sesamol was significantly higher ( P < 0.05) than that of sesamin, sesamolin, or α-tocopherol. Lignan compounds added to ML were degraded during the autoxidation of ML, and the degradation rate was higher in sesamol- than in sesamin-, or sesamolin-added ML, but was lower than in tocopherol-added samples. As the lignan compounds concentration in ML increased, the degradation rate of lignans decreased, and the inhibition of the ML autoxidation by lignan compounds increased. The results strongly suggested that the autoxidative stability of ML could be improved by the addition of sesamol, sesamin, or sesamolin extracted from the roasted sesame oil.     

Effects of roasting conditions of sesame seeds on the oxidative stability of pressed oil during thermal oxidation

Oxidative stability of sesame oil (SO) prepared from sesame seeds roasted at 213, 230, and 247 °C for each 14, 21, or 28 min was determined at 180 °C heating condition by 2,2-diphenyl-1-picrylhydrazyl (DPPH), conjugated dienoic acid (CDA) value, headspace oxygen analysis, and profile changes of sesamol and sesamolin. As sesame seeds were roasted with longer time and higher temperature, more sesamol was found in SO. SO from sesame seeds roasted at 247 °C for 28 min had the highest oxidative stability based on the results of CDA and headspace oxygen. Absorbance of DPPH from SO roasted at 230 and 247 °C showed different patterns compared to those from SO at 213 °C during thermal oxidation. Sesamol was continuously generated with the decrease of sesamolin in SO from 230 to 247 °C while sesamol in SO from 213 °C did not increase during 180 °C heating. Higher oxidative stability of SO may be related with the continuous generation of sesamol from the degradation of sesamolin during thermal oxidation rather than the initial antioxidant content.     

Effect of Infrared Heating on the Formation of Sesamol and Quality of Defatted Flours from Sesamum indicum L.

ABSTRACT:  Infrared (IR) heating offers several advantages over conventional heating in terms of heat transfer efficiency, compactness of equipment, and quality of the products. Roasting of sesame seeds degrades the lignan sesamolin to sesamol, which increases the oxidative stability of sesame oil synergistically with tocopherols. IR (near infrared, 1.1 to 1.3 μm, 6 kW power) roasting conditions were optimized for the conversion of sesamolin to sesamol. The resultant oil was evaluated for sesamol and tocopherol content as well as oxidative stability. The defatted flours were evaluated for their nutritional content and functionality. IR roasting of sesame seeds at 200 °C for 30 min increased the efficiency of conversion of sesamolin to sesamol (51% to 82%) compared to conventional heating. The γ-tocopherol content decreased by 17% and 25% in oils treated at 200 and 220 °C for 30 min, respectively. There were no significant differences in the tocopherol content and oxidative stability of the oil. Methionine and cysteine content of the flours remained unchanged due to roasting. The functional properties of defatted flours obtained from either IR roasted or conventionally roasted sesame seeds remained the same.
Practical Applications: Sesame oil is stable to oxidation compared to other vegetable oils. This stability can be attributed to the presence of tocopherols and the formation of sesamol, the thermal degradation product of sesamolin—a lignan present in sesame. Roasting of sesame seeds before oil extraction increases sesamol content which is a more potent antioxidant than the parent molecule. The conversion efficiency of sesamolin to sesamol is increased by 31% by infrared roasting of seeds compared to electric drum roasting. This can be used industrially to obtain roasted oil with greater oxidative stability.     

Effects of sesamol, sesamin, and sesamolin extracted from roasted sesame oil on the thermal oxidation of methyl linoleate

This study investigated the effects of lignan compounds extracted from roasted sesame oil, which were sesamol, sesamin, and sesamolin, on oxidation of methyl linoleate (ML) during heating. These compounds were added at 500 or 1000 mg/kg to ML, and α-tocopherol was used as a reference antioxidant. The ML added with lignans or α-tocopherol was heated at 180 °C for 60 min. Thermal oxidation of ML was evaluated by conjugated dienoic acid (CDA) contents, p-anisidine value (PAV), and ML retention. Contents changes of lignan compounds or α-tocopherol in ML during heating were monitored by high-performance liquid chromatography. CDA contents and PAV of samples increased and ML decreased with heating time at 180 °C. Samples added with lignan compounds showed lower CDA contents and PAV but higher ML retention than samples without lignan compounds. The antioxidant activity of sesame oil lignan compounds in ML oxidation during heating tended to be higher than that of α-tocopherol. The contents of lignan compounds in samples decreased with heating time due to their degradation, but the degradation rates were lower than that of α-tocopherol. This study suggested that sesame oil lignan compounds be used as antioxidants in oil at high temperatures for deep-fat frying due to their higher effectiveness and stability than α-tocopherol.     

Oxidative Stability of Soybean and Sesame Oil Mixture during Frying of Flour Dough

ABSTRACT: Effects of roasted sesame seed oil on the oxidative stability of soybean oil during frying of flour dough at 160 °C were studied by determining fatty acid composition and conjugated dienoic acid (CDA), p -anisidine (PA), and free fatty acid (FFA) values. Concentration of sesame oil in frying oil was 0%, 10%, 20%, or 30% (v/v). Tocopherols and lignan compounds in the frying oil were also determined by high-performance liquid chromatography. As the number of fryings performed by the oil increased, linolenic acid content in frying oil decreased, and the decreasing rate was lower in frying oil containing sesame oil than in the oil containing no sesame oil. CDA and FFA values of frying oil increased during frying and their relative values to the initial value were lower in frying oil containing sesame oil than in the oil containing no sesame oil. This indicates that the addition of sesame oil improved thermooxidative stability of frying oil, possibly due to the presence of lignan compounds in sesame oil. Tocopherols and lignan compounds in frying oil decreased during frying. As the amount of sesame oil in frying oil increased, degradation of tocopherols increased and lignan compounds degradation decreased. Tocopherols were suggested to protect lignan compounds in sesame oil from decomposition during frying.     

Effects of Sesame Oil Addition to Soybean Oil During Frying on the Lipid Oxidative Stability and Antioxidants Contents of the Fried Products During Storage in the Dark

ABSTRACT: Effects of sesame oil addition to soybean oil during frying on the lipid oxidative stability and antioxidants contents of fried products during storage in the dark were studied. Flour dough pieces (2 cm × 2 cm × 0.1 cm) were fried at 160 °C for 1 min in sesame oil-added soybean oil. Concentrations of sesame oil in the frying oil were 0%, 10%, and 20% by volume. Fried products were put into a glass bottle, and the bottles were tightly sealed and stored at 60 °C in the dark for 18 d. Lipid oxidation of fried products was determined by fatty acid composition changes and conjugated dienoic acid (CDA) and p -anisidine (PA) values. Tocopherols and lignan compounds in the fried products were determined by high-performance liquid chromatography. Relative content of linolenic acid decreased, and CDA and PA values increased during storage of the fried products in the dark. Fatty acid composition change and CDA and PA values during storage were lower in the products fried in sesame oil-added soybean oil than in the products fried in soybean oil without sesame oil. The results clearly showed that addition of roasted sesame oil to soybean oil at 10% and 20% during frying decreased the lipid oxidation of fried products during storage in the dark for 18 d by extension of induction period and decrease in decomposition of oxidized lipids. Fried products contained 134 to 267 ppm tocopherols and 0 to 148 ppm lignans before storage; however, their contents decreased during storage in the dark. Lignan compounds were more stable than tocopherols, and the rate of tocopherols degradation was lower in the products fried in sesame oil-added soybean oil than in the products fried in soybean oil without sesame oil, which could be because of protection of tocopherols from degradation by lignan compounds.     

The contents of lignans in commercial sesame oils of Taiwan and their changes during heating

Sesame lignans have multiple functions and were recently reported to have potential as sources of phytoestrogens. Sesame oils used in Taiwan are expelled from roasted sesame seeds with dark colour and strong flavour. This study analyzed lignan contents of 14 brands of sesame oils, and found their mean of total lignans to be 11.5 mg/g; 82% and 15% of the lignans were sesamin, and sesamolin, respectively. Sesamol contents were relatively higher in those with darker colour. In use as a cooking oil, heating at 180 °C for 4 min did not change the content of lignans, but the level of sesamol increased after heating at 180 °C for 20 min. Heating at 200 °C for 20 min caused a significant loss of sesamolin and sesamol. From our calculation, ingestion of 10 g of sesame oil is adequate to provide the level of lignans that might benefit cardiovascular health, as found by other studies. Cooking at temperatures above 200 °C will cause loss of some lignans, but sesamin, a source of phytoestrogen, is relatively heat-stable.     

芝麻林素的酸催化反应与抗氧化性分析

采用石油醚、甲醇和乙醇溶解芝麻林素,研究不同溶剂体系芝麻林素酸催化反应的现象;以1,1-二苯基-2-三硝基苯肼（1,1-diphenyl-2-picrylhydrazyl,DPPH）自由基清除能力评价芝麻林素及其分解产物的抗氧化能力;采用磷钨杂多酸（phosphotungstic heteropoly acid,HPW）催化芝麻油中芝麻林素的转化,研究芝麻林素酸催化对冷榨芝麻油氧化稳定性的影响。结果表明：芝麻林素在3 种溶剂体系中酸催化反应的产物不尽相同,芝麻酚是共同产物,石油醚体系产生Semin和芝麻素酚,甲醇和乙醇体系均出现不同未知物;芝麻林素和芝麻素的DPPH自由基清除能力远低于特丁基对苯二酚、丁基羟基茴香醚、丁基羟基甲苯和芝麻酚,但石油醚体系芝麻林素酸催化产物的DPPH自由基清除能力大幅提高,为HPW催化芝麻林素提高冷榨芝麻油氧化稳定性提供了理论依据;随着HPW催化剂添加量的增加,冷榨芝麻油中的芝麻林素含量逐渐减少,芝麻酚和芝麻素酚的含量逐渐升高,同时冷榨芝麻油的氧化诱导时间逐渐延长,氧化稳定性增强。     

Effect of Seed Roasting Conditions on the Antioxidant Activity of Defatted Sesame Meal Extracts

ABSTRACT: Antioxidant activities of defatted sesame meal extract increased as the roasting temperature of sesame seed increased, but the maximum antioxidant activity was achieved when the seeds were roasted at 200°C for 60 min. Roasting sesame seeds at 200°C for 60 min significantly increased the total phenolic content, radical scavenging activity (RSA), reducing powers, and antioxidant activity of sesame meal extract; and several low-molecular-weight phenolic compounds such as 2-methoxyphenol, 4-methoxy-3-methylthio-phenol, 5-amino-3-oxo-4-hexenoic acid, 3,4-methylenedioxyphenol (sesamol), 3-hydroxy benzoic acid, 4-hydroxy benzoic acid, vanillic acid, filicinic acid, and 3,4-dimethoxy phenol were newly formed in the sesame meal after roasting sesame seeds at 200°C for 60 min. These results indicate that antioxidant activity of defatted sesame meal extracts was significantly affected by roasting temperature and time of sesame seeds.     

水酶法芝麻油与其他工艺芝麻油品质差异研究

通过对芝麻油外观品质、理化特性、抗氧化成分及脂肪酸组成进行对比,研究了水酶法芝麻油与其他工艺芝麻油(热榨法芝麻油、冷榨法芝麻油、水代法芝麻油)的品质差异。结果表明:水酶法芝麻油的外观品质好,色泽浅,符合一级成品芝麻油标准;水酶法芝麻油的水分及挥发物的含量介于冷榨法芝麻油和水代法芝麻油之间,酸价、过氧化值、不皂化物含量最低;水酶法芝麻油的抗氧化成分(生育酚、芝麻素和芝麻林素)含量最高,但未检出芝麻酚;与热榨法芝麻油、冷榨法芝麻油、水代法芝麻油相比,水酶法芝麻油的饱和脂肪酸含量最高,不饱和脂肪酸含量最低。     

芝麻油品质检测方法的研究现状与分析

针对近些年来芝麻油掺伪现象日益严重的问题,对目前采用的芝麻油品质检测方法及其研究现状进行了综述分析。主要介绍了常用的显色法、色谱法、光谱法、电子鼻技术以及一些联用的方法在芝麻油掺伪检测中的研究现状,通过检测脂肪酸、甘三酯、芝麻林素、芝麻酚等特征物质来实现芝麻油品质的有效检测。     

The relationship of antioxidant components and antioxidant activity of sesame seed oil

Although sesame seed oil contains high levels of unsaturated fatty acids and even a small amount of free fatty acids in its unrefined flavored form, it shows markedly greater stability than other dietary vegetable oils. The good stability of sesame seed oil against autoxidation has been ascribed not only to its inherent lignans and tocopherols but also to browning reaction products generated when sesame seeds are roasted. Also, there is a strong synergistic effect among these components. The lignans in sesame seed oil can be categorized into two types, i.e. inherent lignans (sesamin, sesamolin) and lignans mainly formed during the oil production process (sesamol, sesamolinol, etc.). The most abundant tocopherol in sesame seed oil is γ‐tocopherol. This article reviews the antioxidant activities of lignans and tocopherols as well as the browning reaction and its products in sesame seed and/or its oil. It is concluded that the composition and structure of browning reaction products and their impacts on sesame ingredients need to be further studied to better explain the remaining mysteries of sesame oil. © 2014 Society of Chemical Industry     

芝麻油生产工艺对细辛素形成的影响研究

通过对不同制油工艺制得的28个芝麻油样中芝麻木酚素组分含量(尤其是细辛素含量)进行的检测分析,研究制油工艺对芝麻油中细辛素含量的影响。结果发现：2个浸出精炼芝麻油样中细辛素含量平均119.45 mg/100g,其他26个油样中仅有3个检测出少量细辛素,分别为17.25 mg/100g、7.43 mg/100g、0.58 mg/100g,冷榨芝麻油中未检出细辛素。对不含细辛素的冷榨芝麻油进行水化脱胶、碱炼脱酸、吸附脱色、蒸馏脱臭等精炼处理,并对处理后的芝麻油进行细辛素含量检测分析。结果表明：添加磷酸进行水化脱胶和添加活性白土进行吸附脱色能造成芝麻油中细辛素的形成,且随脱胶时磷酸添加量和脱色时白土添加量的增加,细辛素含量增加(磷酸添加量1%时为131.22 mg/100g,白土添加量5%时为50.73 mg/100g);碱炼脱酸、活性炭脱色、水蒸汽蒸馏脱臭过程只降低了芝麻木酚素总量,没有细辛素形成。据此,细辛素可作为区别冷榨芝麻油和其他芝麻油尤其是浸出精炼芝麻油的特征指标。     

Influence of seed roasting process on the changes in composition and quality of sesame (Sesame indicum) oil

The composition and quality changes of sesame oils prepared at different roasting temperatures (180–260°C) from sesame seed were evaluated and compared with an unroasted oil sample. There were no apparent differences in characteristics, such as acid value, iodine value, saponification value and refractive index, of sesame oils prepared at a roasting temperature between 180 and 220°C. The colour units and total polar content of oils increased in relation to an increase in roasting temperature. The phospholipid content was reduced from 690 mg kg^?1 in unroasted oil to 0 mg kg^?1 in the oil prepared using a 260°C roasting temperature. The fatty acid content of the oil was reduced markedly, especially in oleic and linoleic acids, when the roasting temperature was over 220°C. The amounts of chlorophyll and sesamolin decreased with increasing roasting temperature. However, the highest level of sesamol and γ-tocopherol was found in oils prepared with a 200–220°C roasting temperature. The sesame oil prepared at a 200°C roasting temperature had the best flavour score when compared with the other samples.     

In vitro studies on antioxidant activity of lignans isolated from sesame cake extract

The antioxidant activity of compounds isolated from a methanolic extract of commercial sesame cake was studied using a peroxidation model and a radical‐scavenging method. Pure compounds were isolated from the extract by preparative high‐performance liquid chromatography (HPLC) and identified and confirmed as sesamol, sesamin, sesamolin, sesaminol diglucoside and sesaminol triglucoside by HPLC, infrared, nuclear magnetic resonance and mass spectrometry. When the rate of inhibition of lipid peroxidation and the superoxide radical‐scavenging power of the individual compounds were evaluated, the compounds showed antioxidant activity to different extents. The antioxidant activity of compounds by the β‐carotene‐bleaching assay followed the order sesamol > sesamolin ≥ sesamin > butylated hydroxytoluene (BHT) > sesaminol triglucoside > sesaminol diglucoside. By the thiocyanate method the inhibition of linoleic acid peroxidation shown by sesamol, sesamin, sesamolin, sesaminol triglucoside, sesaminol diglucoside and BHT at 200 mg l^?1 was 77, 60, 69, 32, 25 and 49% respectively. A concentration–dependent superoxide–scavenging effect was also shown by these compounds. Sesamolin had an appreciable effect at 300 and 500 mg l^?1, while the other compounds were more effective at 100 mg l^?1. The study also established the occurrence of sesamol in the methanolic extract of defatted sesame cake for the first time. Copyright © 2005 Society of Chemical Industry     

Microwave Heating Affects Composition and Oxidative Stability of Sesame (Sesamum indicum) Oil

The effects of microwave heating on antioxidative components and lipid quality of sesame seeds were studied. Amounts of antioxidative components were 576, 18, and 8 mg/kg oil for γ-, δ-, and α-tocopherols; 6,824, 5,642, and 54 mg/kg oil for sesamin, sesamolin, and sesamol, respectively. During microwave treatments, concentrations of tocopherols, sesamin and sesamolin gradually decreased, and ca. 20% of these dominant components was lost after 30 min heating. However, microwave treatments for 16 to 20 min, which would be optimal to prepare sesame oil with better quality, still retained over 85% of the antioxidative components (with few exceptions) and caused no significant chemical changes in lipids.     

芝麻中木脂素的组成、结构及其生理功能

介绍了芝麻中木脂素类物质(lignans):芝麻素、芝麻林素、芝麻酚以及芝麻林素酚等生物活性物质的结构、含量以及其所具有的抗氧化、抗癌、保护肝脏、降低血浆中的胆固醇、调节脂质代谢等诸多生理功能特性.     

The use of sesame oil unsaponifiable matter as a natural antioxidant

Individual components of sesame oil unsaponifiable matter isolated from two different coloured seed varieties (white and brown) were identified and quantified. Unsaponifiables from the brown sesame variety were markedly different in their composition from those of the white variety. The brown variety contained higher amounts of total sterols and tocopherols but lower amounts of sesamin, sesamolin and total hydrocarbons than the white variety. The seeds were roasted at 180 °C for 30 min. Roasting increased some effective antioxidant compounds. These included relatively higher percentages of sesamol, Δ^24,28 ethylidene sterols (Δ⁵ and Δ⁷-avenasterols), squalene, as well as tocopherols and some active browning substances. These antioxidative components are effective via synergistic action. Additionally, unsaponifiable matter from unroasted (USM) and roasted white sesame seeds (RSM) was added individually to sunflower oil at levels of 0.02, 0.05 and 0.1% and their effectiveness was compared with a control (no additives) at 63 °C. Results indicated that both USM and RSM had antioxidant activity which increased with increasing concentration. Compared to USM, the RSM was a better antioxidant in most cases. Moreover, the addition of 0.1% RSM gave a strong antioxidative efficiency and this could be used as an alternative natural antioxidant for food applications.     

Effect of refining on the lignan content and oxidative stability of oil pressed from roasted sesame seed

Oxidative stability of pressed and refined sesame oils during seven consecutive months of storage at room temperature was studied comparatively. Lignans, peroxide value (PV), p‐anisidine value (AV) and total oxidation value (TOTOX) were determined as evaluation indices. PV, AV and TOTOX of sunflower, corn and peanut oils were simultaneously monitored to compare their oxidative storage stabilities with the sesame oils. The total amount of lignans in the pressed and refined sesame oils were 1103 and 790 mg per 100 g respectively. The contents of sesamin and sesemolin in the pressed sesame oil were 734 and 369 mg per 100 g respectively. Sesamin and sesamolin content were reduced by 256 and 159 mg per 100 g, respectively, after refining. Nearly 40% of the sesamin epimerised to asarinin after oil refining. The results indicate that sesame oils pressed from roasted seed have far superior storage stability to oxidation than the other vegetable oils. This difference may be due to much higher sesamin and sesamolin contents in the pressed sesame oils. The results suggest lignan compositions and levels could be used as key indicators for evaluating the oxidative storage stability of sesame oil products as well as to differentiate between pressed and refined sesame oils.     

Carbonaceous materials from seed hulls for bleaching of vegetable oils

Seed hulls, namely cottonseed, peanut, sunflower, soybean, faba bean and lupine were evaluated as carbonaceous materials for the bleaching of crude soybean oil. The six seed hulls were activated by carbonization, steam activation and acid activation. Two reference standards, Fullers earth and Tonsil clay, were used for comparison throughout the whole study. Bleaching of crude soybean oil under vacuum at 100 °C using the treated hulls was carried out. The effect of bleaching with the different hulls on the oil characteristics was evaluated by determining the % free fatty acid, % reduction in peroxide value, % removal of phospholipids, % bleachability and oxidative stability of the bleached oils. Results revealed that bleaching with carbonized hull yielded oils with least free fatty acid content and highest oxidative stability. Bleaching with acid activated hull carbons gave oils with least content of peroxides, phospholipids together with best color. Acid activation of the hulls resulted in highest increase in surface area, pore volume and least pore dimension.