Chemical Properties and Oxidative Stability of Perilla Oils Obtained From Roasted Perilla Seeds As Affected by Extraction Methods

Abstract: The chemical properties and oxidative stability of perilla oils obtained from roasted perilla seeds as affected by extraction methods (supercritical carbon dioxide [SC‐CO₂], mechanical press, and solvent extraction) were studied. The SC‐CO₂ extraction at 420 bar and 50 °C and hexane extraction showed significantly higher oil yield than mechanical press extraction (P < 0.05). The fatty acid compositions in the oils were virtually identical regardless of the extraction methods. The contents of tocopherol, sterol, policosanol, and phosphorus in the perilla oils greatly varied with the extraction methods. The SC‐CO₂‐extracted perilla oils contained significantly higher contents of tocopherols, sterols, and policosanols than the mechanical press‐extracted and hexane‐extracted oils (P < 0.05). The SC‐CO₂‐extracted oil showed the greatly lower oxidative stability than press‐extracted and hexane‐extracted oils during the storage in the oven under dark at 60 °C. However, the photooxidative stabilities of the oils were not considerably different with extraction methods.     

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 roasting conditions on the physicochemical properties and volatile distribution in perilla oils (Perilla frutescens var. japonica)

Abstract: Perilla seeds have more than 60% of α‐linolenic acid, one of omega‐3 essential fatty acids. Headspace volatiles and physicochemical properties including color, fluorescence intensity, and the oxidation products in perilla oil (PO) from perilla seeds roasted at different conditions were analyzed. Roasting temperature was 150, 170, 190, and 210 °C, and roasting time was 15 and 30 min at each roasting temperature. PO from higher roasting temperature and longer roasting time had lower L* values, higher a*, b*, and chroma values, more brown pigments and fluorescence intensity, and more conjugated dienoic acids. Pyrazines were major volatiles in PO, and furans, sulfur‐containing compounds, and hydrocarbons were also detected by a solid phase microextraction gas chromatography/mass spectrometry. In PO, 2,5‐Dimethylpyrazine and 2‐furancarboxaldehyde were 2 major volatiles. The principal component analysis of volatiles showed the 1st principal component (PC1) and the 2nd principal component (PC2) express 56.64% and 22.72% of the volatile variability in PO, respectively, which can differentiate PO prepared from roasting conditions clearly. Some physicochemical properties especially brown pigment and volatiles were positively correlated with each other in PO. Practical Application: Perilla oil (PO) from perilla seeds possesses more than 60% of α‐linolenic acid, one of omega‐3 fatty acids. Roasting process has been used to extract oil from perilla seeds. Understanding physicochemical properties of PO from diverse roasting conditions are important steps to produce PO in food industry. Roasting process induces darkening of color, increase of fluorescence intensity, and brown pigments in PO. Pyrazines and furans are major headspace volatiles in PO roasted above 170 °C. The results of this study can help to produce PO in industrial scales with desired headspace volatiles, colors, and oxidative state.     

Optimization of Hull‐Less Pumpkin Seed Roasting Conditions Using Response Surface Methodology

Abstract: Response surface methodology (RSM) was applied to optimize hull‐less pumpkin seed roasting conditions before seed pressing to maximize the biochemical composition and antioxidant capacity of the virgin pumpkin oils obtained using a hydraulic press. Hull‐less pumpkin seeds were roasted for various lengths of time (30 to 70 min) at various roasting temperatures (90 to 130 °C), resulting in 9 different oil samples, while the responses were phospholipids content, total phenols content, α‐ and γ‐tocopherols, and antioxidative activity [by 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) free‐radical assay]. Mathematical models have shown that roasting conditions influenced all dependent variables at P < 0.05. The higher roasting temperatures had a significant effect (P < 0.05) on phospholipids, phenols, and α‐tocopherols contents, while longer roasting time had a significant effect (P < 0.05) on γ‐tocopherol content and antioxidant capacity, among the samples prepared under different roasting conditions. The optimum conditions for roasting the hull‐less pumpkin seeds were 120 °C for duration of 49 min, which resulted in these oil concentrations: phospholipids 0.29%, total phenols 23.06 mg/kg, α‐tocopherol 5.74 mg/100 g, γ‐tocopherol 24.41 mg/100 g, and an antioxidative activity (EC₅₀) of 27.18 mg oil/mg DPPH. Practical Application: A well‐defined roasting process is very important for the food industry to be able to produce pumpkin seed oil with desirable nutritive and chemical characteristics of this unique salad oil, which changes during the roasting. This study contributes to the knowledge of a product design process for the roasting conditions of naked pumpkin seeds based on results that have demonstrated that an increase in roasting temperature significantly increased the biochemical values and antioxidant properties of the obtained virgin oils.     

Oxidation stability and compositional characteristics of oils from microwave roasted pumpkin seeds during thermal oxidation

The oxidative stability and compositional characteristics of the pumpkin seed oil (PSO) exposed to microwaves were studied during heating at 170°C. The oxidative indices such as free fatty acid (FFA), peroxide value (PV), p-anisidine value (p-AV), TOTOX, specific extinctions and thiobarbituric acid (TBA) value of oils were significantly increased, and the increments were found to be significantly higher (P < 0.05) in unroasted seed oil as compared to roasted seed oil. The relative contents of polyunsaturated fatty acids (PUFAs) were decreased to 84.7%, and saturated fatty acids (SFAs) were increased to 119.5% in unroasted sample, after 9 h of heating. On the other hand, in 12 min roasted samples, the relative contents of PUFAs were decreased to 97.0%, and SFAs were increased to 102.6% after 9 h of heating. The triacylglycerol species LLL and OLL levels were decreased as a consequence of increased heating time, and the reduction tended to be significantly higher in unroasted samples as compared to roasted ones. The oxidation products formed were also investigated by FTIR. The present results indicated that microwave roasting of pumpkin seeds markedly enhanced the oxidative stability of the oils during heating.     

Temperature Dependence of Autoxidation of Perilla Oil and Tocopherol Degradation

Abstract: Temperature dependence of the autoxidation of perilla oil and tocopherol degradation was studied with corn oil as a reference. The oils were oxidized in the dark at 20, 40, 60, and 80 °C. Oil oxidation was determined by peroxide and conjugated dienoic acid values. Tocopherols in the oils were quantified by HPLC. The oxidation of both oils increased with oxidation time and temperature. Induction periods for oil autoxidation decreased with temperature, and were longer in corn oil than in perilla oil, indicating higher sensitivity of perilla oil to oxidation. However, time lag for tocopherol degradation was longer in perilla oil, indicating higher stability of tocopherols in perilla oil than in corn oil. Activation energies for oil autoxidation and tocopherol degradation were higher in perilla oil (23.9 to 24.2, 9.8 kcal/mol, respectively) than in corn oil (12.5 to 15.8, 8.8 kcal/mol, respectively) indicating higher temperature-dependence in perilla oil. Higher stability of tocopherols in perilla oil was highly related with polyphenols. The study suggests that more careful temperature control is required to decrease the autoxidation of perilla oil than that of corn oil, and polyphenols contributed to the oxidative stability of perilla oil by protecting tocopherols from degradation, especially at the early stage of oil autoxidation.     

辣椒籽油的制备及其挥发性香味物质的研究

利用亚临界低温萃取技术对经过炒制前处理的辣椒籽进行萃取制备得到辣椒籽油,并采用同时蒸馏结合GC-MS法,分析了不同的炒制温度(120~200℃)和炒制时间(5~25 min)对辣椒籽油中的挥发性成分和脂肪酸成分的影响。在炒制时间为5 min,炒制温度低于140℃时,芳樟醇、月桂烯、双戊烯是辣椒籽油的主要香气物质,当温度高于140℃时,吡嗪类化合物和2-戊基呋喃是辣椒籽油的主要香气物质。在炒制温度为140℃,炒制时间为5 min时,辣椒籽油中的芳樟醇、月桂烯、双戊烯的含量分别达到最大值,随着炒制时间的增加,辣椒籽油中的2,3,5,6-甲基四吡嗪和2-戊基呋喃的含量在20 min时达到了最大值。辣椒籽油中主要的脂肪酸成分是棕榈酸(11.57%)、油酸(76.16%)和亚油酸(7.14%)。     

Tocopherol content,peroxide value and sensory attributes in roasted peanuts during storage

The objective of this study was to determine changes in tocopherol content, peroxide value (PV) and sensory attributes from roasted peanuts during storage at 40 °C. There were no differences in tocopherol contents between roasted and raw peanuts except in α‐tocopherol content that decreased after roasting. All tocopherol contents decreased during storage. On the contrary, lipid oxidation indicators such as PV and the intensity ratings of oxidised and cardboard flavour increased during storage. On the other hand, the intensity ratings of roasted peanutty flavour decreased with storage time. Good correlations were observed between tocopherol contents and PVs. Tocopherol contents could be used as indicator of oxidative state in peanut products.     

Physicochemical properties and oxidative stabilities of mealworm (<Emphasis Type="Italic">Tenebrio molitor</Emphasis>) oils under different roasting conditions

Physicochemical properties and oxidative stabilities of mealworm (Tenebrio molitor) oils under different roasting conditions were investigated. Oils were extracted using n-hexane from mealworms roasted at 200°C for 0, 5, 10, and 15 min and physicochemical properties and oxidative stabilities of oils were analyzed. Roasting increased the color intensity and the oleic acid and δ-tocopherol contents, but decreased linoleic acid, and α- and γ-tocopherol contents. An improvement in oxidative stability was observed in roasted mealworm oils, demonstrated by induction time and peroxide values. Mealworm oil contained abundant essential fatty acids and exhibited a superior oxidative stability.     

Effects of seed roasting temperature and time on the quality characteristics of sesame (Sesamum indicum) oil

The quality characteristics and composition of sesame oils prepared at different roasting temperatures (160–250°C) from sesame seeds using a domestic electric oven were evaluated as compared to an unroasted oil sample: only minor increases (P<0·05) in characteristics, such as peroxide value, carbonyl value, anisidine value and thiobarbituric acid reactive substances, of sesame oils occurred in relation to increasing roasting temperature and time between 160 and 200°C, but colour units of oils increased markedly over a 220°C roasting temperature. Significant decreases (P<0·05) were observed in the amounts of triacylglycerols and phospholipids in the oils prepared using a 250°C roasting temperature. The amounts of γ-tocopherol and sesamin still remained over 80 and 90%, respectively, of the original levels after roasting at 250°C. In the oil prepared using a 250°C roasting temperature, sesamol was detected at 3370 mg per kg oil, but sesamolin was almost depleted after 25 min of roasting. Burning and bitter tastes were found in the oils prepared at roasting temperatures over 220°C. The results suggested that a high-quality product would be obtained by roasting for 25 min at 160 or 180°C, 15 min at 200°C and 5 min at 220°C when compared with the other samples. © 1997 SCI.     

美藤果油、亚麻籽油和紫苏籽油氧化稳定性对比研究

以共轭二烯烃、共轭三烯烃、过氧化值、羰基值平均增长速率以及110℃的氧化诱导时间为指标,对比研究了美藤果油、亚麻籽油和紫苏籽油的氧化稳定性,同时探讨了在60℃加速氧化过程中3种植物油主要微量组分以及脂肪酸组成的变化。结果表明:3种植物油中共轭二烯烃、共轭三烯烃、过氧化值、羰基值平均增长速率为美藤果油<亚麻籽油<紫苏籽油,氧化诱导时间为美藤果油>亚麻籽油>紫苏籽油;甾醇、多酚的损失率为紫苏籽油>美藤果油>亚麻籽油,维生素E的损失率为紫苏籽油>亚麻籽油>美藤果油;多不饱和脂肪酸损失率和饱和脂肪酸增加率为亚麻籽油>紫苏籽油>美藤果油。因此,认为美藤果油氧化稳定性最强,亚麻籽油次之,紫苏籽油最弱。     

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     

Effects of storage conditions on oxidative stability of soybean oil

Soybean oil in the presence or absence of 200 µg g^?1 tert‐butyl hydroquinone (TBHQ) was subjected to accelerated oxidative storage at 60 °C for 10 days or stored at room temperature for 12 months. Tocopherol contents of the oil decreased, whereas the headspace volatiles and peroxide values (PV) increased as the storage time increased. During accelerated storage, TBHQ was effective in retarding the formation of hydroperoxides and headspace volatiles in the oil. TBHQ also protected tocopherols, especially α‐tocopherol, from oxidation. During long‐term room‐temperature (LTRT) storage, the changes in PV between the oils with and without TBHQ were similar, but the oil with TBHQ had lower headspace volatile contents than that without TBHQ. Headspace volatile analysis was more suitable than PV measurement for predicting the oxidative stability of soybean oil during LTRT storage. The contents of hexanal or (E)‐2‐heptenal in the oil at 1–5 days of accelerated storage could be used to predict those of the corresponding compound in the oil at 0–4 weeks of LTRT storage. Copyright © 2005 Society of Chemical Industry     

Changes in Volatile Compounds of Black Cumin (Nigella Sativa L.) Seed Oil During Thermal Oxidation

This study examined the oxidation stability and volatile compounds in samples of black cumin seed oil at 60 and 100°C. Oxidative changes of black cumin oils followed by periodic determination of its conjugated dienes and trienes during accelerated conditions (60 and 100°C). Black cumin oil showed high resistance to oxidation during thermal oxidation (60 and 100°C). In addition to oxidative stability, volatile compounds in the oil were determined by headspace solid phase microextraction with gas chromatography-mass spectrometry analysis technique. The major componenent of the oil was p-cymene (44.77%) followed by thymoquinone (28.62%). Some volatile compounds were lost rapidly during thermal oxidation at the end of storage. Levels of thymoquinone, 4-terpineol, α-longipinene, carvacrol, and isolongifolene reduced slowly and remained more stable during storage at two temperatures (60 and 100°C).     

Effects of Roasting Conditions on the Changes of Stable Carbon Isotope Ratios (δ13C) in Sesame Oil and Usefulness of δ13C to Differentiate Blended Sesame Oil from Corn Oil

Abstract: Differentiating blended sesame oils from authentic sesame oil (SO) is a critical step in protecting consumer rights. Stable carbon isotope ratios (δ¹³C), color, fluorescence intensity, and fatty acid profiles were analyzed in SO prepared from sesame seeds with different roasting conditions and in corn oil blended with SO. Sesame seeds were roasted at 175, 200, 225, or 250 °C for 15 or 30 min at each temperature. SO was mixed with corn oil at varying ratios. Roasting conditions ranging from175 to 250 °C at the 30 min time point did not result in significant changes in δ¹³C (P > 0.05). Values of δ¹³C in corn oil and SO from sesame seeds roasted at 250 °C for 15 min were −17.55 and −32.13 ‰, respectively. Fatty acid ratios, including (O + L)/(P × Ln) and (L × L)/O, where O, L, P, and Ln were oleic, linoleic, palmitic, and linolenic acids, respectively, showed good discriminating abilities among the SO blended with corn oil. Therefore, using different combinations of stable carbon isotope ratios and some fatty acid ratios can allow successful differentiation of authentic SO from SO blended with corn oil. Practical Application: Adulteration of sesame oil with less expensive oils such as corn oil or soybean oil to reduce cost is a common unethical practice in Korea. Due to the unique and strong flavor of sesame oils that may mask other weaker flavors, however, differentiating authentic sesame oils from blended oils is difficult. This study showed that the roasting process did not significantly affect the ratios of the stable carbon isotope (δ¹³C) in sesame oils. δ¹³C was confirmed to be a reliable parameter. Moreover, some fatty acid ratios were designed to discriminate between blended sesame oil with corn oil and authentic sesame oil.     

Effect of processing on the quality of edible argan oil

Sensory quality of edible oil is essential to get the consumer acceptance. Modifications during processing can alter edible oil sensory quality. The storage stability and sensory quality of argan oil prepared from (1) mechanically pressed unroasted kernels, (2) mechanically pressed roasted kernels, (3) hand-pressed roasted kernels, and (4) hand-pressed roasted kernels coming from goat-digested fruits was studied at room temperature and under accelerated conditions (60 °C). The roasting process had a positive effect on storage stability of the resulting oils, while argan oil prepared from mechanically pressed roasted kernels provides the optimum storage stability. Oil from hand-pressed roasted kernels originating from goat-digested fruits was not suitable for human consumption because of the unpleasant taste and odoûr. Only oil from mechanically pressed roasted kernels did not produce negative sensory attributes like fusty or Roquefort cheese.     

Tocols in caneberry seed oils

The compositional analysis of tocols in oils extracted from Korean caneberry seeds was compared with commercial soybean, corn, olive, canola, perilla, and grape seed oils. The oils from caneberry seeds of six different species were extracted using either a chloroform–methanol–water system or hot hexane. Tocols from all of the oils were analysed using isocratic HPLC. The contents of total tocopherols in the caneberry seed oils were about 75–290 mg/100 g oil, whereas tocotrienols were not detected. γ-Tocopherol was the most abundant tocopherol (31.8–239 mg/100 g oil) in the caneberry seed oils, followed by α-tocopherol (7.6–58.2 mg/100 g oil). The contents of total tocols in soybean, corn, olive, canola, perilla, and grape seed oils were 99.9, 61.1, 28, 27, 45.4, and 52.2 mg/100 g oil, respectively. Total tocol content was higher in most of the caneberry seed oils including the refined ones than in the commercial vegetable oils.     

Effects of temperature during processing with wine on chemical composition,antioxidant capacity and enzyme inhibition activities of Angelica Sinensis Radix

The effects of temperature (100 °C, 150 °C, 250 °C) during processing with wine on chemical composition, oil oxidative stability, inhibitory activities on acetylcholinesterase (AChE) and pancreatic lipase (PL) of Angelica Sinensis Radix (ASR), and the feasibility of melanoidins as a colour index to control the roasting intensities were investigated for the first time. The results showed that there were the highest content of ferulic acid, total flavonoids and antioxidant activity of sample roasted at 150 °C, and the sample roasted at 250 °C had the highest content of polysaccharide and total phenolics. A continued reduction in volatile content has occurred in progressive roast. The oxidant stability of oil has a slight increase along with the strength of the roasting intensities, which was higher than unprocessed ASR. Inhibitory activities on acetylcholinesterase and pancreatic lipase were decreased firstly and then increased. Melanoidins can be used as a colour indicator for controlling the thermal processing.     

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.     

Effects of added phenolics on the storage stability of avocado and coconut oils

This study investigated the effects of added phenolics on the storage stability of avocado and coconut oils. Avocado and coconut oils in the absence (control oil) and presence (treated oil) of caffeic acid (CA) or p‐coumaric acid (pCA) were stored at 20 and 60 °C for 50 days. The total phenolic content, peroxide value, p‐anisidine value (p‐AV), free fatty acids (FFAs) and FA composition of the obtained oils were examined on days 0, 7, 15, 23, 35 and 50. Results showed that storage at 60 °C accelerated oil oxidation, and the CA or pCA helped preserve avocado and coconut oils to different extents. CA and pCA protected some desirable unsaturated fatty acids at 60 °C, but facilitated the hydrolysis of triglycerides. Substantially extractable phenolics were still detected in the treated oils after either storage. Incorporation of phenolics into oil products is feasible and beneficial for increasing oil stability and nutritional value.