Effects of variation in the palm stearin: Palm olein ratio on the crystallisation of a low-trans shortening

Changes in the rheological properties during crystallisation and in the crystal size and morphology of blends containing rapeseed oil with varying percentages of palm stearin (POs) and palm olein (POf) have been studied. The crystals formed from all three blends were studied by confocal laser scanning microscopy, light microscopy and environmental scanning electron microscopy, which revealed the development of clusters of 3–5 individual elementary “spherulites” in the early stages of crystallisation. The saturated triacylglycerol content of the solid crystals separated at the onset of crystallisation was much greater than that in the total fat. Fat blends with a higher content of palm stearin had a more rapid nucleation rate when observed by light microscopy, and this caused an earlier change in the rheological properties of the fat during crystallisation. Using a low torque amplitude (0.005 Pa, which was within the linear viscoelastic region of all samples studied) and a frequency of 1 Hz, the viscoelastic properties of melted fat during cooling were studied. All samples, prior to crystallisation, showed weak viscoelastic liquid behaviour (G″, loss modulus >G′, storage modulus). After crystallisation, a more “solid like” behaviour was observed (G′ similar to or greater than G″). The blend having the highest concentration of POs was found to have the earliest onset of crystallisation (27% w/w POs; 12 mins, 22% w/w POs; 13.5 mins, 17% w/w POs, 15 mins, respectively). However, there were no significant differences in the time to the point when G′ became greater than G′ among the three blends.     

温度变化对薄荷油增溶量的影响

本文从定量方面对薄荷油的胶束增溶体系进行了研究，做了有关温度变化对增溶量的影响，并绘制了不同条件下的三元相图。     

基于维生素E组成的植物油掺棕榈油鉴别研究

目的 建立基于维生素E组成的植物油掺棕榈油鉴别方法。方法 采用正相高效液相色谱-荧光检测方法测定大豆油、菜籽油、葵花籽油、橄榄油、玉米油、棕榈油等植物油中α-、β-、γ-、δ-生育酚和α-、β-、γ-、δ-生育三烯酚8种维生素E组成,使用主成分分析（principal component analysis, PCA）构建植物油品种识别和掺假油鉴别模型。结果 不同种类植物油中的生育酚和生育三烯酚的组成差异很大,棕榈油中含高水平的生育三烯酚,这成为其区别于其他5种植物油的一个重要特点。结合PCA可以将棕榈油、葵花籽油、大豆油、橄榄油等相互区分开来。采用PCA建立了针对菜籽油、大豆油、橄榄油、葵花籽油、玉米油中掺棕榈油的鉴别模型,当棕榈油掺杂浓度大于等于25%时,模型可准确识别出掺假油。结论 采用正相液相色谱-荧光检测方法测定植物油中α-、β-、γ-、δ-生育酚和α-、β-、γ-、δ-生育三烯酚8种维生素E组成,结合化学计量学法,可实现对常见植物油掺棕榈油的鉴别。     

Heat-oxidation stability of palm oil blended with extra virgin olive oil

Rancimat induction time of palm oil (PO), several extra virgin olive oils (EV) and their binary blends have been determined at three different temperatures (120, 130 and 140°C). Analytical composition and oxidation stability of PO/EV blends were found to be a linear combination of the oil partners. Induction time of pure PO was always higher than those of EV oils and blends, in which induction time increased proportionally with the percentage of PO. However, induction time of 80% PO blend was similar to that of pure PO. Fatty acid composition appeared to be the most important factor affecting heat-oxidation stability and a saturated/unsaturated ratio near 1 was the optimally stable composition. Conversely, total phenols had a zero or negative role on the oxidative stability of the blends. Finally, in heat-oxidised oils significant losses of polyunsaturated fatty acids and formation of short-chain fatty acids were recorded.     

Rheological behaviour of aerated palm kernel oil/water emulsions

The interactions between emulsion droplets containing solid fat are important for the rheology and functionality of the emulsion as a whole, particularly for aerated emulsion systems where partial coalescence plays a role in the overall structure of the product. In this study, the interactions between emulsion droplets appeared to be sensitive to the relative amounts of solid fat and liquid oil, thus changing the rheology of the whole system. Incorporation of air had a major effect on these interactions as it appeared to force the emulsion to adopt a stronger structure by encouraging partial coalescence. The rheological behaviour of a non-aerated emulsion and an aerated emulsion was compared. Non-aerated samples did not show major changes in viscosity with increasing temperature. In contrast, the aerated emulsion seemed to be considerably more temperature sensitive, showing a dramatic increase of viscosity as the temperature was increased above a critical value. The effect of temperature ramp rates was investigated. Higher temperature ramp rates resulted in delayed changes in viscosity. The phase behaviour of the fat is both time and temperature dependent; therefore, a faster temperature ramp means that a higher temperature could be reached before critical phase changes in the fat could take place. The rheological behaviour of the emulsions was also dependent on the shear rate applied during the experiment.     

The effect of palm oil or canola oil on feedlot performance,plasma and tissue fatty acid profile and meat quality in goats

Twenty-four entire male Kacang kid goats were fed diets containing 3% canola (n = 12) or palm oil (n = 12) supplements for 16 weeks. The goats had an initial live weight of 14.2 ± 1.46 kg and were fed a mixed ration ad libitum (10.4 MJ/ME and 14% crude protein). There was no difference in feedlot performance due to diet. Inclusion of canola oil reduced (P < 0.05) kidney fat weight and increased (P < 0.05) linolenic acid (18:3n − 3) concentration in the blood plasma, m. longissimus lumborum (LL), liver, and kidney. The palm oil diet increased (P < 0.05) myristic (14:0) and palmitic (16:0) acid content in the blood, but this did not alter these fatty acids in the LL muscle. Lipid oxidative substances in the liver and LL from palm oil fed kids were higher (P < 0.05) than those from canola supplemented kids. The incorporation of canola oil into the goats' diet increased muscle omega-3 fatty acid content, but lipid oxidation was lowered in the blood and muscle LL.     

Interpretation of triacylglycerol profiles of palm oil,palm kernel oil and their binary blends

The effects of lipase-catalyzed interesterification (IE) on changes in the chemical composition of palm oil (PO), palm kernel oil (PKO) and their binary blends at 3:1, 1:1 and 1:3 (w/w) ratios, using both 1,3 specific Rhizomucor miehei, (Lipozyme™) and non-specific Pseudomonas sp. lipases were evaluated. IE of the native PO and PKO showed very distinct chemical composition changes. Catalysis of PO, using both lipases, caused synthesis of more medium and long chain triacylglycerols (TAG), with MMM/OLL, MMP, OOO and PPP (M, myristic acid; O, oleic acid; L, linoleic acid; P, palmitic acid) increasing in concentration. In contrast, IE of PKO resulted in the formation of more short and medium chain TAG, with LaLaO and LaMO (La, lauric acid; C, capric acid) experiencing noteworthy increments. Both Rhizomucor miehei and Pseudomonas sp. lipases showed high affinity in hydrolyzing PO fatty acids, resulting in high TAG losses and formation of high percentages of partial glycerides while these lipases were found to enhance the synthesis process in IE of PKO. Catalysis of the three binary blends caused similar TAG compositional changes where the synthesis process focussed on the medium chain TAG, while hydrolysis was observed in the short and long chain TAG that showed corresponding decreases. Catalysis of the three blends was influenced by the major fraction of these blends. Among these blends, PO: PKO at a 1:1 ratio exhibited the highest degree of IE. The diversity and quantity of available TAG are postulated to be the main causes of the different catalytic activities in these binary blends with Pseudomonas sp. lipase showing a higher degree and rate of IE than R. miehei.     

Crystallization kinetics of palm oil in blends with palm-based diacylglycerol

Crystallization kinetics of palm oil (PO) in the presence of different concentrations (2, 5, 10, 30 and, 50% w/w) of palm-based diacylglycerol (PB-DAG) were investigated over different ranges of crystallization temperatures. Addition of 30 and 50% (w/w) of PB-DAG (high concentrations) increased significantly (P < 0.05) the melting point and crystallization onset while addition of 2 and 5% PB-DAG did not have significant (P > 0.05) effect. PO and PO blends with 2 and 5% of PB-DAG showed crystal transformation at crystallization temperatures (T_Cr) of 26, 26, 26.5 °C, respectively as reflected in corresponding changes of the Avrami parameters at below and above these T_Cr. This was especially evident for the blends containing 2 and 5% of PB-DAG. Individual comparison of induction time (T_i), Avrami exponent (n), Avrami constant (k) and half-time of crystallization (t_1/2) of blends classified under various supercooling ranges based on the supercooling closeness (± 0.1 °C), showed that addition of 5% of PB-DAG in most of the supercooling ranges significantly (P < 0.05) reduced nucleation rate as well as crystal growth velocity of PO. This was reflected in the significantly (P < 0.05) higher T_i and t_1/2 and lower k. Although the presence of 2% of PB-DAG was found to have inhibitory effect on PO crystallization, this effect was not significant (P > 0.05). Mode of crystal growth attributed to n was changed significantly only in presence of 5% of PB-DAG. Furthermore, presence of 10% PB-DAG showed ??'-stabilizing effect on PO. On the other hand, high concentrations of PB-DAG were found to significantly (P < 0.05) reduce T_i as well as t_1/2 and also increase k suggesting their promoting effects on nucleation and crystallization rate of PO even with the close supercoolings. In addition, they changed crystal growth mode of PO. Amongst the different concentrations of PB-DAG investigated, blend containing 50% of PB-DAG as compared to PO, not only, have healthier benefits but also, may have greater potential applications in plastic fat products due to its unique physical properties.     

棕榈油干式分提工艺结晶回温的原因及解决办法

简要说明了棕榈油干式分提工艺结晶回温的害处,并详细分析了回温的原因。回温是由于RBD棕榈油熔点偏高或偏低,或者是结晶菜单不适合造成的。针对不同的回温原因,分别提出了不同的解决办法:当RBD棕榈油熔点偏低时,结晶菜单主结晶段设置温度应下调、时间应减少;当RBD棕榈油熔点偏高时,结晶菜单主结晶段设置温度应上调,时间应增加;当结晶菜单设置不合适时,可归类于RBD棕榈油熔点偏低或偏高进行调整。     

Effect of refining processes on antioxidant capacity,total contents of phenolics and carotenoids in palm oils

Antioxidant capacity (AC), total phenolic content (TPC) and total carotenoid content (TCC) in palm oils at various stages of the refining process from two technological modes were determined. The obtained mean FRAP and DPPH values for the methanolic extracts of palm oils from mode 1 (19.5–102.8 μmol TE/100 g and 18.8–103.0 μmol TE/100 g) were lower than for oils from mode 2 (25.6–134.8 μmol TE/100 g and 25.4–135.4 μmol TE/100 g). The total phenolics (4.1–12.4 mg GA/100 g) and carotenoids (0.18–45.8 mg/100 g) in the studied oils were correlated with their antioxidant capacities determined by FRAP and DPPH methods (r = 0.6623–0.9878). During the refining process, for both technological modes resulted in a loss of AC by 80%, TPC by 26–55% and TCC by 99%. The bleaching step caused the highest losses of AC as determined by FRAP 41% and 46%, DPPH by 43% and 48%, while TPC loss was 45% and 23% and loss of carotenoids was 49% and 56%, in mode 1 and mode 2, respectively.     

高温煎炸棕榈油体系抗氧化剂的选择

研究了茶多酚、植酸、维生素E3种天然抗氧化剂对棕榈油煎炸过程中过氧化值、酸值、羰基值、P-茴香胺值等品质劣变指标的控制效果,同时与人工合成抗氧化剂TBHQ作比较,旨在找到能够替代TBHQ的复合型天然抗氧化剂.结果表明:4种抗氧化剂的抗氧化效果次序为TBHQ＞维生素E＞植酸＞茶多酚;3种天然抗氧化剂的最佳复配组合为0.02％茶多酚+0.016％植酸+0.65％维生素E.     

Effect of repeated frying on the viscosity, density and dynamic interfacial tension of palm and olive oil

The effect of deep-fat frying on the viscosity, density and dynamic interfacial tension (against air and water) of palm oil and olive oil was investigated. Repeated frying (up to 40 batches) at two different potato-to-oil ratios (1/7, 1/35 kg_potatoes/L_oil) was examined. Results were compared to those from simple heating the oils at the same temperatures. Viscosity increased during repeated frying for both oils. However, only palm oil viscosity was sensitive to potato-to-oil ratio. Due to the novelty of dynamic interfacial characterization of such systems a discussion was made about the appropriate timescales and deformation types for interfacial measurements. Significant effects of repeated frying on the dynamic interfacial tension at the oil/water interface were observed. Contrarily, changes in density were not significant. Results were assessed with respect to the evolving chemical profile of the oils determined in previous works. Possible implications of the determined properties on the frying process were discussed.     

Tripalmitin and monoacylglycerols as modifiers in the crystallisation of palm oil

An exhaustive analysis of the crystallisation behaviour of palm oil was performed using low-resolution magnetic pulsed nuclear resonance, differential scanning calorimetry, polarised light microscopy and X-ray diffraction. The aim of this study was to characterise the changes induced in the crystallisation of palm oil by the addition of two different levels of tripalmitin and two different types of monoacylglycerols. The addition of monoacylglycerols led to the formation of a large number of crystallisation nuclei without changing the final solids content, accelerating the process of crystal formation, leading to the formation of smaller crystals than those found in the refined palm oil. Higher levels of tripalmitin produced crystals with larger dimensions, reducing the induction period and resulted in a higher level of solids at the end of the crystallisation period. The addition of monoacylglycerols and tripalmitin induced the formation of a polymorphic β-form.     

Effects of parameters on yield for sub-critical R134a extraction of palm oil

Extraction of palm oil from its palm mesocarp using sub-critical 1,1,1,2-tetrafluoroethane (R134a) as an alternative solvent to supercritical CO₂ was studied. The effects of pressure, temperature, flowrate and sample pre-treatment method on extraction yield were examined. Dynamic method was used to determine palm oil solubility at flowrate between 0.5 and 5.0 ml/min. Extraction was performed at pressures between 45 and 100 bar which was lower than those required by CO₂ solvent, and at temperatures between 40° and 80 °C. The results show that extraction yields using R134a increased with pressure and temperature, and that temperature effect (p-value = 0.0000) on palm oil solubility prevailed over that of pressure (p-value = 0.0087). The maximum yield of 66.06 w/w% was obtained at 100 bar and 80 °C which was the best pressure and temperature. Substantial oil yields at relatively lower pressure proved that sub-critical R134a is a viable alternative to CO₂ for extraction of palm oil.     

温度对大豆压榨油稳定性的影响

实验探讨用4种表征参数,单表征参数(CP):电导率、过氧化值、等容燃烧热和酸值,综合描述温度(T)对大豆压榨油(SSO)稳定性的影响,比较各CP表征结果的异同性。在相对湿度40%、氧分压21 kPa、光照度800 lx、初始顶空率50%的固定条件下,调控T分别为30、40、50、60和70℃,长时间连续密闭氧化SSO试样,多次同时测定不同氧化时间(t)的4种CP,绘制CP^t关系曲线,回归其动力学方程并求算速率常数(k)和表观活化能,建立变质时间预测模型并验证其符合率。结果表明,CP随T升高和t延长变化显著;SSO的氧化酸败具有简单级数反应特征,其变质时间预测模型符合度较高;CP不同,k差异较大。SSO之大豆压榨油稳定性宜用多元CP综合描述。     

Structured lipids obtained by chemical interesterification of olive oil and palm stearin

Interesterification of palm stearin (PS) with liquid vegetable oils could yield a good solid fat stock that may impart desirable physical properties, because PS is a useful source of vegetable hard fat, providing β′ stable solid fats. Dietary ingestion of olive oil (OO) has been reported to have physiological benefits such as lowering serum cholesterol levels. Fat blends, formulated by binary blends of palm stearin and olive oil in different ratios, were subjected to chemical interesterification with sodium methoxide. The original and interesterified blends were examined for fatty acid and triacylglycerol composition, melting point, solid fat content (SFC) and consistency. Interesterification caused rearrangement of triacylglycerol species, reduction of trisaturated and triunsaturated triacylglycerols content and increase in diunsaturated-monosaturated triacylglycerols of all blends, resulting in lowering of melting point and solid fat content. The incorporation of OO to PS reduced consistency, producing more plastic blends. The mixture and chemical interesterification allowed obtaining fats with various degrees of plasticity, increasing the possibilities for the commercial use of palm stearin and olive oil.     

Structural characteristics of crystals formed in palm oil using sorbitan tristearate and sucrose stearate

The formation and stabilization of fat crystals in palm oil (PO) by the templating effects of sorbitan tristearate (STS) and sucrose stearate (S-370) were examined. We observed that the crystallization mechanism occurred via heterogeneous nucleation, which was induced by co-crystallization or seeding, after the addition of STS or S-370, respectively. Overall, both emulsifiers, STS and S-370, caused an increase in the hardness of PO, which was related to changes in the microstructure. In addition, the intensity of this effect was shown to be dependent on the emulsifiers concentration. In differential scanning calorimetry analysis, S-370 proved to be associated predominantly to the crystallization of high-melting triacylglycerols (TAGs), while STS showed to actuate the crystallization of high and low-melting TAGs. Moreover, the addition of STS improved the polymorphic stability of the PO, while the use of S-370 resulted in a soft texture at lower temperatures.     

核桃油贮藏过程抗氧化能力的研究

以核桃油为试验原料,研究了核桃油在氧化过程中的抗氧化活性的变化。结果表明:未曾氧化的核桃油抗氧化活性较好,核桃油对DPPH·自由基的抑制率随着核桃油样品浓度的增加而不断增强,147.0 mg/m L质量浓度的核桃油清除DPPH·自由基能力为50%;340.83 mg/m L质量浓度的核桃油清除羟基自由基的能力为50%;1.0 mg/m L质量浓度的核桃油对超氧阴离子自由基的平均清除率与1.0 mg/m L质量浓度的Vc相当。而经氧化后的核桃油清除DPPH·自由基和·OH自由基的能力明显降低,相同浓度不同氧化时间的核桃油样品对超氧阴离子自由基的清除能力,随着氧化时间的增长而逐渐下降,但氧化时间越短核桃油对O2-·的抑制率越好,当氧化时间为30天时,核桃油对O2-·的平均抑制率从55.53%降到15.43%。总之,未曾氧化的核桃油的抗氧化物活性较好,随着氧化时间的增加核桃油对以上三种自由基的清除能力逐渐降低。     

Utilization of interesterified oil blends in the production of frankfurters

Ten treatments of frankfurters were produced with interesterified oil and oil blends (palm oil, palm stearin, cottonseed oil, hazelnut oil and their mixtures) and were compared to control, produced with all animal fat. Addition of interesterified oil and oil blends affected (p < 0.05) the moisture and fat content and pH values of frankfurters. According to the colour measurements, the brightness value (L^∗) of most of the samples with interesterified oil and oil blends were higher (p < 0.05) than the control. The fatty acid composition of frankfurters was modified. The PUFA/SFA values of frankfurters were increased due to the presence of interesterified oil and oil blends in the formulation. Frankfurters with 100% interesterified cottonseed oil or with interesterified oil blends with 66.6% and 83.4% cottonseed oil had PUFA/SFA ratio higher than 0.4 and are considered better than all others from the health point of view. Frankfurters produced with 100% interesterified cottonseed and hazelnut oil or with interesterified hazelnut oil blends had the same (p > 0.05) scores for sensory attributes with the control, while all other treatments were also acceptable.     

High performance liquid chromatographic separation of interesterified palm oil with tributyrin

Short-chain triacylglycerol, tributyrin (glyceryl-sn-1,2,3-tri-butyric acids), was interesterified with palm oil to produce mixtures of structured triacylglycerol (SL-TAG) species as a low-calorie lipid. Lipozyme RM IM from Rhizomucor miehei, known as a 1,3-regioselective immobilized lipase, was used as a catalyst. During 24 h reaction, the reaction mixture was analyzed with Hypersil^®BDSCPS high performance liquid chromatography (HPLC) column to determine neutral lipids composition. Also, the compositional changes of TAG, as well as monoacylglycerol (MAG)/diacylglycerol (DAG) as by-products, were determined. After 24 h, 5.8 g/100 g DAG was found in the reaction mixture, while 89.5 g/100 g TAG was observed. The reaction mixture was also analyzed with Nova-Pak^® C18 and Chrompack Si60 columns for separation of SL-TAG species. It was found that the normal-phase (NP)-HPLC with Chrompack Si60 column readily separated SL-TAG species composed of short- and long-chain acyl residues. Further, mass spectrometer was employed for identifying the separated SL-TAG molecules. SL-TAG containing two butyryl and one long-chain acyl residue (e.g., PBB and OBB) were most abundant in the interesterified product.