Sensory odour profiling and physical characteristics of edible oil blends during frying

Edible oil blends containing 80 parts of mustard oil (MO) or groundnut oil (GNO) or sunflower oil (SNO) and 20 parts of sesame oil (SO) or refined red palm oil (RPO) or rice bran oil (RBO) were studied to determine the changes in their physical and sensory characteristics during deep fat frying. Odour evaluation by the trained sensory panel revealed that successive fryings subdued the intensity of typical odour notes of the oil blends. Intensity of sulphury, pungent and vinegar (sour) notes of MO, nutty and sweet notes of GNO, sweet and seedy notes of SNO, seedy and earthy notes of SO, husk-like note of RPO and beany and branny notes of RBO decreased significantly by end of the 7th frying. Apparent viscosity of the oil blends increased on successive frying. Colour measured in CIE system indicated that the dominant parameters were a+ (redness) in RPO blends, b+ (yellowness) in blend containing SO or MO and a− (greenness) in RBO blends. The redness component decreased and yellowness increased with successive frying in SNO + RPO blend and GNO and RBO blend, respectively. Applying principal component analysis (PCA) to the data showed seggregation of various oil blends as distinct groups exhibiting their typical and characteristic attributes. PCA also revealed the pathway of change of oils during different frying cycles. MO and blend of MO + RPO were characterised by sulphury, pungent, harsh odour notes and red colour; GNO occupied a quadrant with fresh-oil-like, green and sweet notes, and SNO was characterised by fresh-oil-like, seedy odour and yellow colour. Addition of SO increased earthy note and lightness value, while blends containing RBO had distinct yellow colour, increased heated note and higher apparent viscosity.     

COMPARATIVE STUDIES ON PHYSICAL PROPERTIES OF VEGETABLE OILS AND THEIR BLENDS AFTER FRYING

Physical properties of six commonly used oils and three blends consisting of three oils in each blend were studied after three successive frying of 'poories'(fried snack from flattened dough of refined wheat flour). The changes in viscosity, CIE trans-reflectance color and related parameters, UV-Visible spectra and UV-spectra of oil samples in solvent system (chloroform:methanol; 2:1, v/v) were studied. The results showed that viscosity and color of the oils changed to a much higher extent after first frying than subsequent fryings. The hue angle followed a similar trend. Changes in the UV-spectra in the solvent system indicated an increase in the formation of conjugated compounds after successive fryings. Peroxide values (PV) also increased after frying. Principal Component Analysis (PCA) plots of the data indicated that among oils examined groundnut oil and soy oil in combination with other oils were preferred for frying. Use of small amounts of unrefined oils (filtered) such as mustard oil or sesame oil which have a high content of natural antioxidants was beneficial as formation of conjugated compounds and increase in peroxide value was minimized after successive frying using blended oils.     

SEMI-SOLID FAT BY INTERESTERIFICATION OF RED PALM OIL WITH OTHER VEGETABLE OILS

Interesterification of appropriate blends of vegetable oils offers an alternative method for obtaining semi-solid fats without hydrogenation. Random interesterification was carried out on blends of different oils, namely palm oil and sunflower oil (8:2, 7:3 and 6:4 w/w), palm oil and rice bran oil (8:2 and 7:3 w/w), palm oil and coconut oil (9:1 and 6:4 w/w), as well as palm oil and soybean oil (7:3 w/w), in the presence of sodium methoxide as a catalyst (0.2% w/v). The melting characteristic of the interesterified fat obtained from a blend of refined red palm oil and sunflower oil blend, in the ratio of 4:1 (w/w; slip melting point 41C) indicated that this combination could be an ideal margarine fat base.     

不同工艺芝麻油的挥发性成分分析和感官评价

利用SPME-GC-MS分析6种工艺芝麻油的挥发性物质,建立了芝麻油的感官风味轮,使用直线标度对感官属性强度评分,并利用主成分分析法比较芝麻油的感官差异,列出部分挥发性物质对应的特征气味,以研究加工工艺对芝麻油的挥发性成分和感官品质的影响。结果表明:冷榨芝麻油的挥发性成分以醛类和酸类为主,具有较强的生芝麻味、土腥味、木屑味和青草味;精炼芝麻油中挥发性成分最少;芝麻原油由于含有正己烷,表现出较强的机油味和刺激感;芝麻压榨毛油、压榨成品油和小磨芝麻香油富含吡嗪类、酚类、醛类和酮类等物质,具有较强的炒芝麻味、焦香味、留香较久且风味浓郁。小磨芝麻香油风味最纯正和醇厚,口感最绵柔。     

Stabilization of astaxanthin in edible oils and its use as an antioxidant

Astaxanthin, a ketocarotenoid (3,3′‐dihydroxy‐β,β‐carotene‐4,4′‐dione), is produced in high concentration in the green alga Haematococcus pluvialis. It constitutes 85–88% of total carotenoid and exists in the monoester, diester and free form. Astaxanthin in its ester form is fairly stable in all edible oils such as rice bran, mustard, groundnut, gingelly, coconut and palm oil at room temperature with variation in terms of its loss in content and colour during a 4 month period. Rice bran, gingelly and palm oil retained 84–90% of astaxanthin when heated at 70 °C for 8 h while palm oil was effective in retaining 90% of astaxanthin at 90 °C for 8 h without any change in its ester form in comparison to 90% carotenoid loss in aqueous form. At 120 and 150 °C, carotenoid loss was significant (60–90%) without change in the fatty acid profile of the edible oils. The antioxidant activity of carotenoids stored in oils was comparable to standard butylated hydroxy anisole (BHA). Copyright © 2007 Society of Chemical Industry     

滴定法滴定稻米油酸值的影响分析

研究了谷维素含量、指示剂种类、游离脂肪酸含量、油脂色泽对稻米油滴定酸值的影响规律。结果表明,当以酚酞为指示剂时,随着谷维素含量的增加,新鲜精炼稻米油和一级精炼大豆油的滴定酸值升高;但是当采用溴百里酚蓝为指示剂时,谷维素含量对两种油脂的滴定酸值无明显影响。游离脂肪酸含量以及油脂色泽对滴定酸值无显著影响。     

Detection of oil blends

In case of model blends of groundnut – palm and coconut – groundnut oil quantification of individual oils in the blend was achieved on the basis of computed linear regression equations based on Bellier temperature, cloud point and fatty acid composition of triglycerides. In case of model blends of groundnut – palm and coconut – groundnut oil quantification of individual oils in the blend was achieved on the basis of computed linear regression equations based on Bellier temperature, cloud point and fatty acid composition of triglycerides.     

DEVELOPMENT OF DEEP FRYING EDIBLE VEGETABLE OILS

Refined soybean and rice-bran oils have been selected as base oils for preparation of frying oils. Hexane and acetone fractionation of nontraditional tree seed oils (NTOs) such as sal, mango, mahua and palm fats was carried out at 5–20C. Chemical and chromatographic parameteres were used to fractionate each oil (NTOs) in order to obtain olein-rich and stearin-rich fractions. The stearin fraction obtained at 10 and 15C from hexane and acetone were identical and hence mixed together. The stearin fraction obtained from all the four NTOs were incorporated at 10% level with the conventionally refined (market sample) and physically refined (laboratory sample) soybean and rice-bran oils in order to obtain frying oils. Heat stability parameters of the oils, namely free fatty acids (FFA%), peroxide value (PV), and iodine value (IV) were determined for base oils and frying oils after heating. Values for oil samples changed as follows: A (refined soybean oil and frying oils containing it) % FFA from 0.18 to 0.17–0.19, PV from 3.6 to 4.6–6.0 and IV from 125.3 to 109.2–115.8; B (refined rice-bran oil and frying oils containing it) from 0.21 to 0.19–0.23 for % FFA, 4.0 to 4.6–6.7 for PV and 99.4 to 87.6–92.8 for IV; C (physical refined soybean oil and frying oils containing it) from 0.36 to 0.33–0.36 for % FFA, 5.7 to 7.4–11.2 for PV and 126.9 to 108.9–113.2 for IV; and D (physical refined rice bran oil and frying oils containing it) from 0.79 to 0.75–0.79 for % FFA, 7.1 to 8.2–11.3 for PV and 101.4 to 88.6–93.7 for IV, respectively. However, when base oils were heated as such, their deterioration was much faster. Fatty acid composition, determined by gas chromatography, also supported the results obtained by chemical means. These frying oils showed improved heat stability compared to their base oils.     

稻米油在快餐煎炸中的性能研究

本文通过模拟西式快餐门店的煎炸实验,考察了稻米油在快餐煎炸中应用的可行性。通过油脂理化指标、肪酸组成分析及微量成分分析来比较稻米油与棕榈油和大豆油的差异,通过模拟西式快餐门店168℃下煎炸薯条过程中极性物质和酸价的变化,并对薯条进行感官评价,对比稻米油、大豆油与棕榈油的煎炸性能。结果显示:稻米油所含的饱和脂肪酸和不饱和脂肪酸均介于棕榈油和大豆油之间,并且其含有的维生素E与大豆油接近且明显高于棕榈油;另外稻米油还含有12035.74 mg/kg植物甾醇和4359.17 mg/kg谷维素。在煎炸过程中,稻米油的酸价上升速度远远低于大豆油,接近于棕榈油;尽管其初始极性组分较高,但其极性组分在煎炸后期上升比较平稳,至煎炸终点时其极性组分低于棕榈油和大豆油;同时在煎炸过程中,棕榈油、稻米油、大豆油中的维生素E随煎炸时间的延长明显降低,至第6 d对应的含量分别10.01、8.49与2.11 mg/kg;而稻米油中谷维素和植物甾醇含量也随煎炸时间的延长而减少,但至煎炸终点时,仍有较多的保留,含量分别为1531.98和6618.45 mg/kg。另外,感官评价发现,稻米油炸制的薯条比大豆油、棕榈油更酥脆、风味更好,整体喜好度更高。总之,但稻米油具有良好煎炸性能,其煎炸性能明显优于大豆油,可用作西式快餐煎炸油。     

Vegetable oil blends with α-linolenic acid rich Garden cress oil modulate lipid metabolism in experimental rats

Vegetable oil blends with modified fatty acid profile are being developed to improve n-6/n-3 polyunsaturated fatty acid (PUFAs) ratio in edible oils. The objective of this study is to develop vegetable oil blends with α-linolenic acid (ALA) rich Garden cress oil (GCO) and assess their modulatory effect on lipid metabolism. Sunflower oil (SFO), Rice bran oil (RBO), Sesame oil (SESO) were blended with GCO at different ratios to obtain n-6/n-3 PUFA ratio of 2.3–2.6. Native and GCO blended oils were fed to Wistar rats at 10% level in the diet for 60 days. Serum and liver lipids showed significant decrease in Total cholesterol (TC), Triglyceride (TG), LDL-C levels in GCO and GCO blended oil fed rats compared to native oil fed rats. ALA, EPA, DHA contents were significantly increased while linoleic acid (LA), arachidonic acid (AA) levels decreased in different tissues of GCO and GCO blended oils fed rats. In conclusion, blending of vegetable oils with GCO increases ALA, decreases n-6 to n-3 PUFA ratio and beneficially modulates lipid profile.     

UNSAPONIFIABLE MATTER AND OXIDATIVE STABILITY OF COMMERCIALLY PRODUCED INDIAN RICE BRAN OILS

Chemically and physically refined rice bran oils (RBO) were investigated for their content and composition of unsaponifiable matter and oxidative stability. The chemically and physically refined rice bran oils contained 2.6 and 4.5% unsaponifiable matter, respectively. The content and composition of unsaponifiable matter for chemically and physically refined RBO were phytosterols, 0.96%and 1.40%; 4-methyl sterols, 0.51%and 1.12%; triterpene alcohols, 0.52% and 0.86%; and nonpolar components, 0.61% and 1.13%, respectively. The corresponding oxidative stability for the two oils were 2.80 h and 4.37 h, respectively. The content of unsaponifiable matter was influenced by residual amounts of wax and oryzanol in the refined oil as shown by the model experiments. Thus physical refining of rice bran oil requires a thorough dewaxing step to obtain a refined oil without haziness and with a lower amount of unsaponifiable matter.     

Determination of iodine-bromine numbers of some edible oils with two N-bromoimides

The iodine-bromine numbers of some edible oils such as coconut oil, gingelly oil, groundnut oil, mustard oil, olive oil, palm oil and sunflower oil were determined titrimetrically using the N-bromoimides, N-bromophthalimide (NBP) and N-bromosaccharin (NBSA). The proposed excess-back titration methods were based on quantitative bromination of the glycerides of unsaturated fatty acids present in the oils and both the methods were simple, rapid and accurate.     

A study on monitoring of frying performance and oxidative stability of cottonseed and palm oil blends in comparison with original oils

Blending polyunsaturated oils with highly saturated or monounsaturated oils has been studied extensively; however, in literature there is negligible information available on the blending of refined cottonseed oil with palm olein oil. Blending could enhance the stability and quality of cottonseed oil during the frying process. In the present study, the effects of frying conditions on physicochemical properties of the palm olein-cottonseed oil blends (1:0, 3:2, 1:1, 2:3, and 0:1, w/w) were determined and compared to the pure oils. The frying process of frozen French fries was performed in duplicate at 170 ± 5°C for 10 h without interruption. The oil degradations were characterized during deep-frying applications; peroxide, free fatty acid, and iodine value by standardized methods, fatty acid profile by using a gas chromatography-flame ionization detector, polar and polymeric compounds by using the high-performance size exclusion chromatography/evaporative light scattering detector technique. The present study clearly indicated that the oxidative and frying performances of pure palm olein oil and cottonseed oil significantly improved by blending application. Results clearly indicated that the frying performance of cottonseed oil significantly improved by the blending with palm olein oil. Except that free fatty acid content, all the physicochemical variables were significantly influenced by type of pure and blend oils. By increasing the proportion of palm olein oil in cottonseed oil, the levels of polyunsaturated fatty acids decreased, while saturated fatty acid content increased. The progression of oxidation was basically followed by detecting polar and polymeric compounds. The fastest increments for polar and polymeric compounds were found as 6.30% level in pure cottonseed oil and as 7.07% level in 40% cottonseed oil:60% palm olein oil blend. The least increments were detected as 5.40% level in 40% cottonseed oil:60% palm olein oil blend and 2.27% level in 50% cottonseed oil:50% palm olein oil blend. These levels were considerably below the acceptable levels recommended by the official codex. Therefore, the present study suggested that blending of cottonseed oil with palm olein oil provided the oil blends (50% cottonseed oil:50% palm olein oil and 40% cottonseed oil:60% palm olein oil, w/w) with more desirable properties for human nutrition.     

Effect of blending and lipase catalyzed interesterification reaction on the cholesterol lowering properties of palm oil with rice bran oil in rats

The effect of feeding blended and interesterified oils containing palm oil (PO) and rice bran oil (RBO) on serum and liver lipids was evaluated in rats. The PO and RBO were blended to contain saturated, monounsaturated and polyunsaturated fatty acids in the proportion of 1:1.5:1. The blended oil was subjected to transesterification reaction using immobilized lipase, lipozyme IM‐RM. Rats were fed a diet containing blended or interesterified oils for 8 weeks. Rats fed PO showed significantly higher levels of cholesterol in serum and liver as compared to those given RBO, blended oil of PO with RBO or interesterified oil. Rats fed blended oils showed a significant decrease in serum cholesterol by 51% compared to rats fed PO. Feeding interesterified oil to rats resulted in decrease in serum cholesterol by 56% compared to rats fed PO, which was 10% lower compared to that observed in rats given blended oil. The present study indicated that a combination of PO with RBO can significantly lower serum lipids in rats as compared to those given diet containing PO alone.     

拉曼光谱-聚类分析快速鉴别掺伪芝麻油

目的建立快速鉴别掺伪芝麻油的拉曼光谱-聚类分析方法。方法以不同产地、不同品牌的多批次芝麻油、大豆油、玉米油、菜籽油、精炼棕榈油、精炼棉籽油及精炼地沟油为样品,在780 nm和532 nm激光光源下,扫描和比较其普通、扩展及导数拉曼光谱的形态。结果在532 nm激光光源的扩展光谱及一阶导数光谱中,芝麻油与低价植物油及精炼地沟油光谱的信息量最大,样品间光谱形态的差异显著。基于此全波段光谱信息和形态建立的多步聚类分析模型对芝麻油、低价植物油、仿冒芝麻油和精炼地沟油的判别正确率均为100%;对5%、10%、20%、30%和50%掺假芝麻油的判别正确率分别为72%、92%、100%、100%和100%;对5%、10%和20%掺杂芝麻油的判别正确率分别为97%、100%和100%;对5%、10%和20%掺杂植物油的判别正确率分别为94%、100%和100%。样品测量时无需制备样品及消耗化学试剂,测量和分析一份样品仅耗时5 min左右。结论所建立的拉曼光谱-聚类分析模型既可准确鉴定芝麻油,还可准确鉴定各种类型的掺伪芝麻油,可实现对掺伪芝麻油的快速、无损和准确鉴别。     

稻米油调和油煎炸应用研究

通过与棕榈油对比180℃下炸制薯片以及评估薯片感官喜好度、质构、口感及粘牙性等差异来评价稻米油调和油的煎炸应用性能。结果表明:采用稻米油调和油煎炸的薯片中多不饱和脂肪酸含量显著高于棕榈油(P<0.05),且其薯片的整体感官喜好度、质构口感、酥脆度、粘牙喜好度,均显著优于棕榈油薯片(P<0.05)。在加速氧化条件下,采用稻米油调和油炸制的薯片的酸价、过氧化值均与棕榈油炸制的薯片无显著性差异(P>0.05),且远低于GB 16565-2003的规定。在加速存储过程中,谷维素却得到了很好的保留。总之,稻米油调和油具有良好的煎炸性能。     

RELATIONSHIP BETWEEN INSTRUMENTAL AND SENSORY ANALYSIS OF TEXTURE AND COLOR OF POTATO CHIPS

The instrumental and sensory analysis of the texture and color of commercial potato chips were compared. The instrumental measurement was a puncture test with an Intron Universal Testing Machine, and the parameters used were fracture force, deformation and stiffness. The instrumental color quantification was a computerized video image analysis technique, and the color was expressed as L*a*b* values. Sensory evaluation of texture and color was performed by a sensory panel especially trained in evaluating potato chips. The sensory attributes were "hardness", "chewiness", "crunchiness", and "tenderness" for texture analysis, and "yellow color", "burnt aspect", "sugar colored aspect" and "transparency" for color analysis. The factor analysis of the sensory attributes indicated that texture can be divided into two principal components, one represented by "hardness", "crunchiness" and "chewiness", and the other by "tenderness" alone. The factor analysis of the color can be divided into two principal components, one including "yellow color" and "burnt aspect", and the other "sugar colored aspect" and "transparency". Discriminant analysis showed that "tenderness" and "crunchiness" could predict correctly over 90% of the data. Fracture force correlated well with all of the sensory attributes (R² > 0.76), and L* with the sensory color attributes (R² > 0.79). The "Tenderness" was the individual sensory attribute which had the highest correlation (R²= 0.95) with fracture force.     

Improvement of Chemlali olive oil oxidative stability by blending with Chétoui and Rekhami cultivars

In order to improve the quality of Chemlali olive oil, characterised by a very low stability (2.09 h), blending with two different monovarietal oils in various proportions: Chétoui and Rekhami (known by their higher stability 7.79 and 13.99 h, respectively) was carried out. Results showed that blended oils had an improved oil composition compared to that of Chemlali. In fact, the highest percentage of Chétoui and Rekhami olive oils (90% of blending) can reduce the acidity up to 68.79% and 79.61%, respectively. At 50% blending, oleic acid increased from 53% to 59.54%, while palmitic acid decreased from 20.97% to 14.89% with Chétoui olive oil. At the lowest percentage (10–20%), chlorophylls in Chemlali olive oil underwent significant increase (from 0.18 to 0.47 and 0.65 mg kg⁻¹, respectively). The amount of carotenoids was higher when Chemlali was blended by 20–40% with Chétoui olive oil (from 2.23 to 4.13 and 4.33 mg kg⁻¹). Blending can be used in industrial applications to provide oils with improved composition related to stability, nutrition and functionality and endowed with the characteristics requested by consumers' preferences.     

UTILITY OF CIE TRISTIMULUS SYSTEM IN MEASURING THE OBJECTIVE CRUMB COLOR OF HIGH-FIBER TOAST BREAD FORMULATIONS

The major objectives of this study were to develop high‐fiber toast bread formulations with lighter crumb color and to evaluate the CIE tristimulus system to measure the color of crumb as affected by the addition of various flour mill fractions. The optimized straight‐dough bread making method (AACC method 10‐10B) was used for conducting the baking trials. CIE L* a* b* values of the crumb were measured. Additional color attributes, (whiteness value, redness index (RI), saturation index (SI) and total color difference (ΔE), were calculated from these L* a* b* values. Compared with flour samples, the germ and bran fractions had significantly lower CIE L* a* b* and whiteness values, but higher redness and saturation indices, indicating darker color and hue for the latter. Test bread samples having up to 30% bran and 10% germ, were lighter in crumb color than the control whole wheat flour bread. It was concluded that high‐fiber toast bread, with lighter crumb color than whole wheat flour bread, can be produced by using white flour, and equal proportions of coarse and fine bran at 20%, germ at 5%, and sodium stearoyl‐2‐lactylate at 0.5% levels. The CIE L*a* b* tristimulus system can effectively be utilized for distinguishing crumb color variations in toast bread samples.