Crystallisation kinetics of palm stearin,palm kernel olein and their blends

The kinetics of isothermal crystallisation of palm stearin, palm kernel olein and their blends (20–80 g/100 g palm stearin with 20 g/100 g increment) were determined using differential scanning calorimetry (DSC). The mechanism of crystallisation (n) was calculated by applying the Avrami equation using the crystallisation curves obtained at 10, 15 and 20 °C. The DSC isothermal crystallisation data at 10, 15 and 20 °C fitted well into the Avrami equation over the entire fractional crystallisation with correlation coefficient always greater than 0.98. Based on the Avrami exponent obtained, the palm stearin and palm kernel olein have different nucleation and growth mechanisms. The suggested mechanism for palm kernel olein was high nucleation rate at the beginning of crystallisation, which decreased with time, and plate-like growth (n = 2). On the other hand, the mechanism for palm stearin was instantaneous heterogeneous nucleation followed by spherulitic growth (n = 3). For blends of palm stearin and palm kernel olein, the mechanisms of crystallisation were 2 and 3 depending on the composition of the blends and crystallisation temperatures.     

Influence of diglycerides on crystallisation of palm oil

Palm oil diglycerides and pure synthetic diglycerides of 1,2‐(2,3‐) and 1,3‐dipalmitoylglycerol, dioleoylglycerol and palmitoyloleoyl glycerol were added to purified triglycerides of palm oil. The crystallisation kinetics of the samples were studied by spectrophotometry, NMR analysis of the solid fat content and by X‐ray diffraction of the crystals obtained at 20°C. Palm oil diglycerides inhibited the nucleation process and retarded the crystal growth rate of palm triglycerides. The effect was less pronounced at a higher degree of supercooling. The extent of inhibition depended on the nature of the diglycerides and the concentration. © 1999 Society of Chemical Industry     

Characterisation of Crystals in Palm Olein

The composition of the crystals obtained during the storage of palm olein between 28 and 10°C were analysed by gas–liquid and high-performance liquid chromatography. The crystals were of the β form, and consisted of a high-melting component and a low-melting component. The high-melting component melts at 65°C and consist of a high concentration of diglycerides, mainly the 1,3-dipalmitin. The low-melting component is probably the palm olein liquid entrapped between the crystals. The high tripalmitin and dipalmitin content in the crystals suggest that these glycerides need to be removed if the olein were to remain clear under fluctuating temperature conditions.     

Preparation of palm olein enriched with medium chain fatty acids by lipase acidolysis

Medium chain (MC) fatty acids, caprylic (C8:0) and capric (C10:0) were incorporated into palm olein by 1,3-specific lipase acidolysis, up to 36% and 43%, respectively, when added as mixtures or individually after 24 h. It was found that these acids were incorporated into palm olein at the expense of palmitic and oleic acids, the former being larger in quantity and reduction of 18:2 was negligible. The modified palm olein products showed reduction in higher molecular weight triacylglycerols (TGs) and increase in concentration of lower molecular weight TGs compared to those of palm olein. Fatty acids at sn-2 position in modified products were: C10:0, 4%; C16:0, 13%; C18:1, 66%; and C18:2, 15.4%. DSC results showed that the onset of melting and solids fat content were considerably reduced in modified palm olein products and no solids were found even at and below 10 °C and also the onset of crystallisation was considerably lowered. The cloud point was reduced and iodine value dropped from 55.4 to 38 in modified palm olein. Thus, nutritionally superior palm olein was prepared by introducing MC fatty acids with reduced palmitic acid through lipase acidolysis.     

Crystallisation of palm olein under the influence of sucrose esters

This work studied the effects of three sucrose esters (S170, P170 and L195) on the crystallisation of palm olein (PO). The effect of the emulsifiers on the crystallisation behaviour, crystallisation curves, microstructure and polymorphism was investigated. Both S170 and P170 accelerated the early stages, via template effects, but suppressed the later stages of PO crystallisation. The effect on the latter stages was stronger with P170 than S170. In contrast, L195 suppressed PO crystallisation at all time points. Through DSC, S170 and P170 only associated with the high-melting fraction of PO whereas L195 showed little influence. All SEs exhibited no effect on polymorphism. S170 and P170 greatly reduced PO crystal size but increased crystal number while the L195 increased the crystal size but decreased the crystal number especially at low concentration. Overall, S170, P170 and L195 influence PO crystallisation kinetics but the effect was dependent on the emulsifier concentration.     

Interactions between tocopherols,tocotrienols and carotenoids during autoxidation of mixed palm olein and fish oil

Electron spin resonance (ESR) and spin trapping detection of radical formation showed that the oxidative stability of palm olein/fish oil mixtures increased with the amount of palm olein. Mixtures with red palm olein were less stable than were mixtures with yellow palm olein. Addition of ascorbyl palmitate and citric acid gave further reduction of radical formation, whereas no effect was observed by adding lecithins. Storage of palm olein/fish oil mixtures (4:1) at 30 °C confirmed that red palm olein mixtures were less stable than were yellow palm olein mixtures. Ascorbyl palmitate together with citric acid improved the stability in both cases. The concentrations of α-tocopherol and α-tocotrienol decreased during storage, whereas β-, γ-, and δ-tocotrienols were unaffected. Ascorbyl palmitate reduced the losses of α-tocopherol and α-tocotrienol. The rate of loss of carotenoids was independent of the presence of fish oil and, except for an initial fast drop, also of the presence of ascorbyl palmitate.     

Discrimination of palm olein oil and palm stearin oil mixtures using a mass spectrometry based electronic nose

To discriminate mixing ratios for mixtures of palm olein oil and palm stearin oil, an electronic nose based on mass spectrometer (MS-electronic nose) and GC were used. The intensities of each fragment from the palm olein oil and palm stearin oil by the MS-electronic nose were used for discriminant function analysis (DFA). When palm olein oil is mixed with palm stearin oil, more than 3% of stearin oil can be estimated by DFA. The obtained data were used for DFA. DFA plot indicated a significant separation of pure palm olein oil and palm stearin oil. The added concentration of palm stearin oil to palm olein oil was highly correlated with the first discriminant function score (DF1). When palm stearin oil was added to palm olein oil, it was possible to predict the following equation; DF1= −0.112×(conc. of palm stearin oil)+0.416 (r²=0.95). When palm stearin oil was added to palm olein oil, peak area of GC was correlated to DF1 by MS-electronic nose with ratio of palm olein oil vs palm stearin oil. The MS-electronic nose system could be used as an efficient method for the authentication of oil.     

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.     

巧克力涂层基料油的理化性质及其相容性研究

选用棕榈油中间分提物(PMF)、全氢化棕榈仁液油(HPKOL)、可可脂(CB)作为巧克力涂层的基料油,对其理化性质及其相容性进行分析。结果表明,当两相体系PMF-HPKOL中PMF含量在30%以下时,共晶现象较弱。PMF和HPKOL混合可以作为涂层油脂配方,用于开发无反式脂肪酸巧克力涂层。添加可可脂会导致三相体系(PMF-HPKOL-CB)严重的共晶现象,因此在代可可脂涂层配方中不宜再添加可可脂。     

Physico-chemical properties of various palm-based diacylglycerol oils in comparison with their corresponding palm-based oils

Palm-based diacylglycerol (P-DAG) oils were produced through enzymatic glycerolysis of palm kernel oil (PKO), palm oil (PO), palm olein (POL), palm mid fraction (PMF) and palm stearin (PS). High purity DAG (83–90%, w/w) was obtained and compared to palm-based oils (P-oil) had significantly (P < 0.05) different fatty acid composition (FAC), iodine value (IV) and slip melting point (SMP). Solid fat content (SFC) profiles of P-DAG oils as compared to P-oils had less steep curves with lower SFC at low temperature range (5–10 °C) and the higher complete melting temperatures. Also, P-DAG oils in contrast with P-oils showed endothermic as well as exothermic peaks with higher transition temperatures and significantly (P < 0.05) higher crystallisation onsets, heats of fusion, and heats of crystallisation. Crystal forms for P-DAG oils were mostly in the β form.     

四种棕榈油结晶速度的研究

报道了棕榈油、棕榈软脂、棕榈硬脂及氢化棕榈油在0℃,10℃,20℃条件下的结晶速度,指出它们在结晶速度方面的差异,这些资料对人造奶油和起酥油生产具有实用意义。     

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.     

Effects of chemical interesterification on physicochemical properties of blends of palm stearin and palm olein

Chemical interesterification is an important technological option for the production of fats targeting commercial applications. Fat blends, formulated by binary blends of palm stearin and palm olein in different ratios, were subjected to chemical interesterification. The following determinations, before and after the interesterification reactions, were done: fatty acid composition, softening point, melting point, solid fat content and consistency. For the analytical responses a multiple regression statistical model was applied. This study has shown that blending and chemical interesterifications are an effective way to modify the physical and chemical properties of palm stearin, palm olein and their 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 palm olein.     

食用棕榈油卫生标准的研制

报告了食用棕榈油国家卫生标准的研制经过和结果，讨论了食用棕榈油脂肪酸构成的特殊性，其生产工艺过程及有关卫生问题，并将本标准的各项技术指标同ＦＡＯ／ＷＨＯ食品法典食用棕榈油标准ＣＯＤＥＸＳＴＡＮ１２５—１９８１及马来西亚食用棕榈油的卫生标准ＭＳ８１７—８９和我国现行精炼食用植物油卫生标准ＧＢ１５１９７—９４作了分析比较。标准的研制将对口岸食用棕榈油的把关检验和国内市场食用棕榈油的卫生监督提供执法的依据     

棕榈油基沙拉酱的制备工艺

利用棕榈液油部分替代传统沙拉酱中的大豆油制备棕榈油基沙拉酱。研究产品配方和加工工艺条件。通过单因素实验和正交实验确定,将30%棕榈液油和70%大豆油混合制备沙拉酱,最佳配方和乳化条件:选用复合乳化剂海藻酸丙二醇酯和黄原胶(等比例),乳化剂添加量0.22%,水的加入量10%,变性淀粉添加量0.8%,乳化时间10min。在此条件下制备的沙拉酱感官性质及功能性质良好,0℃条件下存放3个月乳化体系稳定,无油水分离现象发生。对棕榈油基沙拉酱进行质构分析,结果表明该产品乳化体系稳定,其质构特征与全部用大豆油制备的沙拉酱样品相近。     

Copper bioavailability in rats fed unused palm olein and palm olein used in frying

The influence of the consumption of unused and used (in repeated potato frying operations) palm olein on copper bioavailability was investigated. Three diets containing respectively 8% olive oil (O), palm olein (P) and palm olein from 80 repeated potato frying operation without turnover (PF), which nearly reached the limit of 25% polar compounds allowed by law, were given to rats for 28 days. No differences were found in food intake and body weight. The liver mass index was higher in PF than in P rats. No significant differences were observed in copper apparent absorption or in liver, skin, erythrocyte, serum and carcass copper contents. Therefore consumption of palm olein, whether unused or used in frying, does not alter copper bioavailability in growing rats. Copyright © 2004 Society of Chemical Industry     

Intake of unused palm olein and palm olein used in frying does not affect calcium and phosphorus bioavailability in rats

Palm oil is widely used as a cooking medium. This study was undertaken to examine whether extensive use leading to the formation of polar compounds has any effect on calcium and phosphorus balances. Three isocaloric diets containing 8% olive oil (O), palm olein (P) and palm olein from 80 repeated potato frying uses (PF) without turnover, and which nearly reached the limit of 25% polar compounds allowed by law, were prepared and given to three groups of growing rats during a study period of 28 days. Body weight and food intake were monitored and faeces and urine were collected to calculate calcium and phosphorus balances during the last week of the study. At the end of the experiment the animals were killed and their livers, serum and carcases stored. No differences were observed between food intake, body weight and food efficiency of rats which consumed palm olein, whether unused or used in frying, and the control group (O). The liver mass index was higher in PF than O rats. No significant differences were observed in apparent absorption and retention of calcium and phosphorus. Faecal calcium (p = 0.065) and the percentage of phosphorus absorbed (p = 0.084) showed a tendency to increase in rats fed diets with both unused and used palm olein and could be due to the known higher affinity of fat for Ca than P. No variations in serum calcium and carcase calcium and phosphorus levels were seen. The conclusion of this study was that consumption of palm olein, whether unused or used in frying, does not alter calcium and phosphorus bioavailability. © 2000 Society of Chemical Industry     

RECOVERY OF PALM CAROTENE FROM PALM OIL AND HYDROLYZED PALM OIL BY ADSORPTION COLUMN CHROMATOGRAPHY

Crude palm oil and crude palm olein were hydrolyzed with lipase from Candida rugosa to produce a free fatty acid (FFA) rich oil. The percentages of FFA produced and carotene degradation after the hydrolysis process were determined. The palm oil and hydrolyzed palm oil were subsequently subjected to column chromatography. Diaion HP-20 adsorbent was used for reverse phase column chromatography at 50C. Isopropanol or ethanol, and n-hexane were used as the first and second eluting solvents, respectively. The objective of hydrolyzing the palm oil was to produce more polar FFA-rich oil in order to enhance the nonpolar carotene bind to the nonpolar HP-20 adsorbent in the column chromatography process. Hydrolyzing palm oil with lipase from Candida rugosa gave 30- and 60-fold, respectively, of FFA in the crude palm oil and crude palm olein in 24 h at 50C. Approximately, 15.56 and 17.48% of carotene degraded in crude palm oil and crude palm olein, respectively. For column chromatography, using isopropanol or ethanol as the first eluting solvent, unhydrolyzed oil and hydrolyzed oil showed the carotene recovery infraction two (carotene-rich fraction) of about 36–37 and 90–96%, respectively. Over 90% of carotene recovery was obtained from     

Differential scanning calorimetric analysis for monitoring the oxidation of heated oils

A simple and reliable differential scanning calorimetric (DSC) method was developed for monitoring the oxidation in heated oils. Three different types of edible oils, namely, corn oil (CO), refined, bleached and deodorised palm olein (RBDPO) and soybean oil (SO) were used in this study. The DSC method was based on the cooling thermogram of oil samples at a scanning rate of 1°C/min from −30 to −85°C. The cooling thermogram of oil showed a well-defined single crystallisation peak. Two DSC parameters of this single crystallisation peak, namely peak temperature and enthalpy were determined. In addition to the DSC method, the deterioration of heated oils was also quantified by means of seven chemical methods. A statistical comparative study was carried out on the DSC and chemical methods. The results show that there is good correlation between the DSC method and other standard chemical methods. In conclusion, the DSC method offers an alternative for the monitoring of the oxidation of heated oil due to its appreciable time-saving, use of small samples with minimal preparation, and absence of toxic chemicals.     

大豆油调和不同熔点棕榈液油的冷藏试验

为了制备适应不同储存温度的豆油-棕榈液油调和油,以大豆油与不同熔点棕榈液油为原料,采用冷藏试验方法优化抑晶剂种类、用量和调和油配方。结果表明,羟基硬脂精是效果最佳的抑晶剂,其最佳添加量为0.025%;调和油1(豆油70%+10℃棕榈油30% +羟基硬脂精0.025%)在0℃环境下储存可保持16h以上澄清透亮,在5℃条件可保持72h以上澄清透亮;调和油2(豆油70%+18℃棕榈油30%+羟基硬脂精0.025%)在10℃环境下可保持30h以上澄清透亮;调和油3(豆油60%+18℃棕榈油40%+羟基硬脂精0.025%)在15℃环境下可保持20h以上澄清透亮;调和油4(豆油60%+24℃棕榈油40%+羟基硬脂精0.025%)在20℃环境下可保持10h以上澄清透亮。