Comparison of pulsed NMR and ultrasonic velocity techniques for determining solid fat contents

An ultrasonic velocity technique has been compared with pulsed NMR'weight' and 'direct' methods of determining solid fat contents (SFC). Measurements were made at 18°C using samples 0–20% of rapidly cooled tristearin in paraffin oil, tristearin in sunflower oil and tripalmitin in paraffin oil. Correlations between the amount of triglyceride added and the SFC predicted by each of the techniques were always better than 0.995 ( n ± 13). The precisions of the ultrasonic technique (0.2%) and the weight method (0.3%) were significantly better than that of the direct method (0.7%). The ultrasonic technique may therefore offer a suitable alternative or adjunct to the established pulsed NMR technique for SFC determinations; it has considerably lower capital cost and a faster sampling rate.     

Influence of Surface Structure on Cholesterol Oxidation in Model Food Powders

Three milk-resembling powders having different oil phases were prepared and stored for six months at room temperature. Samples were taken monthly for estimation of the surface composition by ‘electron spectroscopy for chemical analysis’ (ESCA) and analyses of the level of cholesterol oxides by gas chromatography. The highest fat coverage was obtained with technical tristearin as the oil phase. This preparation had around 75% of the powder surface covered by fat; during storage this coverage decreased. This powder also had the largest increase in cholesterol oxides during storage, the final level being 159 μg g⁻¹ cholesterol. The powder containing high-melting pure tristearin had a low surface coverage of fat, originally about 25%, which decreased during the storage period. Little increase in cholesterol oxides was observed, the final level being 52 μg g⁻¹ cholesterol. The third powder containing liquid triolein as oil phase, had a surface coverage of about 50% throughout the storage period. The cholesterol oxidation rate was in between that of the two tristearin powders, the final level of oxides being 75 μg g⁻¹ cholesterol. The results for the investigated powders indicate that the surface composition is of major importance for the oxidation of cholesterol. No correlation between cholesterol oxidation and solvent extractable fat (free fat) was found.     

Enzymatic Synthesis of Refined Olive Oil‐Based Structured Lipid Containing Omega ‐3 and ‐6 Fatty Acids for Potential Application in Infant Formula

Structured lipids (SLs) containing palmitic, docosahexaenoic (DHA), and gamma‐linolenic (GLA) acids were produced using refined olive oil, tripalmitin, and ethyl esters of DHA single cell oil and GLA ethyl esters. Immobilized Lipozyme TL IM lipase was used as the biocatalyst. The SLs were characterized for fatty acid profile, triacylglycerol (TAG) molecular species, solid fat content, oxidative stability index, and melting and crystallization profiles and compared to physical blend of substrates, extracted fat from commercial infant formula (IFF), and milk fat. 49.28 mol% of palmitic acid was found at the sn‐2 position of SL TAG and total DHA and GLA composition were 0.73 and 5.00 mol%, respectively. The total oleic acid content was 36.13 mol% which was very close to the 30.49% present in commercial IFF. Comparable solid fat content profiles were also found between SLs and IFF. The SLs produced have potential for use in infant formulas.     

过氧化氢酶固体脂质纳米粒制备和鉴定

利用双乳化和溶剂蒸发技术制备过氧化氢酶固体脂质纳米粒(CAT-SLN),通过单因素试验和响应面分析,确定最佳合成工艺条件为:将浓度为20 mg/mL酶溶液(内水相)加入至含TG和PC(PC:TG=15.24%)的二氯甲烷/丙酮(1/1)(油相),油相:内水相=5,超声作用20s乳化形成W/O乳状液;再加入1.5% Poloxmer188水溶液(第二相)中,W/O乳状液:第二相=1:4,超声作用30s乳化形成W/O/W型乳状液。所制备CAT-SLN为球型,没粘连,粒径大小较一致,平均粒径为274 nm,Z电位为-37.1 mV,多分散系数为0.273,包封率为74.51%。     

Energy Value of a Fat High in Stearic Acid

A fat containing 92.1% stearic acid (tristearin) was evaluated for energy value using shortening (9 kcal/g) and mineral oil (0 kcal/g) as controls and young rats as the test model. Energy value was calculated based on efficiency of conversion of estimated gross energy intake to carcass energy over a 3-wk period. Rats fed the shortening-based diet deposited more than double the fat and significantly more protein in the carcass than rats fed the tristearin-based diet. Rats fed the tristearin-based diet deposited significantly more fat and protein than rats fed the mineral oil-based diet. Based on these observations, the estimated energy value of tristearin was calculated as 3 kcal/g.     

Mutual effect of fat and β-carotene on fat crystal network structure and carotenoid bleaching

In this study the mutual effect of fat type and β-carotene on fat crystallization behavior and carotenoid bleaching was investigated. To this aim, β-carotene was added to tripalmitin (PPP), tristearin (SSS) and saturated monoglycerides (MG). Phase transition properties of fats with and without β-carotene were studied by differential scanning calorimetry, synchrotron X-ray diffraction and polarized light microscopy. The color fading of β-carotene containing fat matrices was followed by measuring color changes during storage at 20 °C.Structural information acquired at different length scales highlighted that the presence of β-carotene in fats greatly affected crystal morphology, crystal network structure and thermal properties of the lipid matrices. Depending on fats molecular characteristics, β-carotene participated (PPP and SSS) or withdrew (MG) from the fat crystallization. The presence of β-carotene probably altered the triacylglycerol crystal morphology through its incorporation into the solid phase. Contrarily, β-carotene formed clusters inside the solid matrix when added to MG. Results appear of considerable interest in the attempt to improve the stability of β-carotene in lipid containing foods as well as to design efficient delivery systems, for which the choice of the lipid carrier could be crucial. In fact, preliminary results showed that the kinetics of β-carotene bleaching were higher in PPP and SSS than in MG, suggesting that β-carotene location inside the crystal network as well as lipid structure organization might affect the carotenoid chemical stability.     

Enzymatic production of infant milk fat analogs containing palmitic acid: optimization of reactions by response surface methodology

Infant milk fat analogs resembling human milk fat were synthesized by an enzymatic interesterification between tripalmitin, coconut oil, safflower oil, and soybean oil in hexane. A commercially immobilized 1,3-specific lipase, Lipozyme RM IM, obtained from Rhizomucor miehei was used as a biocatalyst. The effects of substrate molar ratio, reaction time, and incubation temperature on the incorporation of palmitic acid at the sn-2 position of the triacylglycerols were investigated. A central composite design with 5 levels and 3 factors consisting of substrate ratio, reaction temperature, and incubation time was used to model and optimize the reaction conditions using response surface methodology. A quadratic model using multiple regressions was then obtained for the incorporation of palmitic acid at the sn-2 positions of glycerols as the response. The coefficient of determination (R²) value for the model was 0.845. The incorporation of palmitic acid appeared to increase with the decrease in substrate molar ratio and increase in reaction temperature, and optimum incubation time occurred at 18 h. The optimal conditions generated from the model for the targeted 40% palmitic acid incorporation at the sn-2 position were 3 mol/mol, 14.4 h, and 55°C; and 2.8 mol/mol, 19.6 h, and 55°C for substrate ratio (moles of total fatty acid/moles of tripalmitin), time, and temperature, respectively. Infant milk fat containing fatty acid composition and sn-2 fatty acid profile similar to human milk fat was successfully produced. The fat analogs produced under optimal conditions had total and sn-2 positional palmitic acid levels comparable to that of human milk fat.     

甘三酯立体专一分析的研究：（Ⅱ）甘三酯立体专一分析方法初探

在第一部分综合讨论的基础上对甘三酯立体专一分析方法作了初步探讨。以液体油(菜油)及固体脂(猪脂)为基质,系统地研究了这一分析方法,取得了经验并补充了一些具体验证方法。分析液体油的结果与文献数据相一致,分析猪脂的结果欠佳,还存在一些问题需待进一步研究。     

人乳替代脂鲳鱼油和巴沙鱼油的脂肪酸、甘油三酯 组成及含量分析

为寻找与中国人乳脂脂质组成高相似的天然人乳替代脂，分析比较了3种鱼油(金鲳鱼油、银鲳鱼油和巴沙鱼油)的总脂肪酸、sn-2位脂肪酸、甘油三酯组成和含量。结果表明：金鲳鱼油中棕榈酸、油酸和亚油酸含量分别为24.93%、25.61%和26.52%,其中sn-2位棕榈酸的含量为39.71%,占总棕榈酸比例为53.10%;在3种鱼油中，金鲳鱼油总脂肪酸组成最接近中国人乳脂；甘油三酯组成分析结果证实，金鲳鱼油中富含1-油酸-2-棕榈酸-3-亚油酸甘油三酯(OPL,24.36%),其含量显著高于其他两种鱼油，且其1,3-二油酸-2-棕榈酸甘油三酯(OPO)的含量(16.79%)接近报道的中国人乳脂的平均含量(15.84%)。因此，金鲳鱼油是理想的中国婴儿配方奶粉专用油脂基料油，在人乳替代脂中具有良好的发展前景。     

A novel nanoemulsification method of stirring at the Θ-point with the tocopherol-based block co-polymer nonionic emulsifier PPG-20 Tocophereth-50

Nanoemulsions have recently become increasingly important as potential vehicles for the controlled delivery of cosmetics and for the optimized dispersion of active ingredients in particular skin layers. The preparation of conventional nanoemulsions requires mainly high‐pressure homogenization, which is unproductive and requires high energy due to its lower efficiency, limiting their practical applications. In order to solve these problems novel nanoemulsions were studied using a model system of pseudo‐ternary water/emulsifier/paraffin oil. Nanoemulsions were prepared by stirring a mixture of the tocopherol‐containing block co‐polymer emulsifier PPG‐20 Tocophereth‐50, paraffin oil, and distilled water at the Θ‐point using weight fractions of the dispersed phase (φ) of 0.31 to 0.82 and an emulsifier content of 1.0 to 9 wt.%. The emulsifying property of PPG‐20 Tocophereth‐50 in nanoemulsions was compared with that of the conventional emulsifiers Tocophereth‐43, a mixture of polysorbate 60 and sesquioleate (3/1), and phospholipids. Also the emulsifying property of PPG‐20 Tocophereth‐50 in the more hydrophilic oils caprylic/capric triglyceride and octyldodecanol was compared with that in paraffin oil. The stability and morphology of the resulting nanoemulsions were studied by visual inspection, optical microscopy, particle size analysis, and cryo‐scanning electron microscopy. In the nanoemulsion systems containing caprylic/capric triglyceride and octyldodecanol, respectively, as an oil phase PPG‐20 Tocophereth‐50 showed emulsification properties similar to those in paraffin oil. The conventional emulsifiers Tocophereth‐43, a mixture of polysorbate 60 and sesquioleate (3/1), and phospholipids did not give nanoemulsions with high‐speed stirring. The block co‐polymer nonionic emulsifier PPG‐20 Tocophereth‐50 was found to produce stable nanoemulsions of mean droplet diameters ranging from 204 to 499 nm. The emulsification method of high‐speed stirring at the Θ‐point using PPG‐20 Tocophereth‐50 was found to be very effective for the preparation of stable nanoemulsions useful for applications in skincare cosmetics, cosmeceuticals, and drugs.     

Increasing the fat content of pancakes augments the digestibility of starch in-vitro

Carbohydrate foods that breakdown rapidly during digestion are known to have the highest glycemic index (GI) values. It is known that lipid-starch complexes can form in foods; however how this may enhance the resistance of starch to enzyme hydrolysis is unknown. The aim of this study was to examine the effect of adding different fats to a carbohydrate rich food on the digestibility of starch in-vitro. Three sets of carbohydrate-lipid emulsion (CLE) batters in the form of pancakes were prepared as 1) low fat (20.3% mass as fat), 2) medium fat (32.7% mass as fat) and 3) high fat (45.1% mass as fat). For each set of CLE a control (containing no added fat), saturated fat (butter), polyunsaturated fat (sunflower oil), monounsaturated fat (olive oil) and medium chain triglyceride saturated fat (MCT oil) was prepared. The CLEs were digested in-vitro and sugars released measured. The results indicated that increasing the concentrations of fat in the CLE augmented sugar release (p < 0.001). The results also showed that there were differences between the different types of fats in the CLE (p < 0.001). The primary differences existed between the control and all the other CLEs, as well as between the MCT CLE and all other CLEs. Correlation analysis showed an inverse relationship between the amount of remnants remaining after digestion and the sugars released from the CLE (p = 0.004 and p = 0.014). This research indicates that adding fat to a carbohydrate food will increase the digestibility of starch and release of sugars from the food which may impact on glycemic response.     

Dietary Effects of Frankfurters with Added Beef Fat and Peanut Oil

Beef frankfurters containing 12% or 29% fat, either all beef fat or 40% beef fat plus 60% peanut oil, were fed to rabbits, resulting in a significant increase in serum cholesterol and triglyceride levels compared to rabbits fed rabbit chow. The absolute increase and rate of increase in triglyceride levels were affected by the amount of fat but not by the presence or absence of peanut oil. Cholesterol levels were not significantly different in animals fed frankfurters containing 12% or 29% beef fat except at 4 wk; the inclusion of peanut oil in the frankfurters significantly lowered serum cholesterol levels .at 5 and 6 wk. Overall, frankfurters containing 12% final fat with 60% peanut oil substitution had the least hyperlipidemic effect.     

A Method for the Determination of Diffusion Coefficients of Food Components in Low- and Intermediate Moisture Systems

A simple set-up to measure translational diffusion of components in low moisture systems is described. The tracer technique was tested on the diffusion of ¹⁴C-labeled tripalmitin and palmitic acid in a model system containing paraffin oil, microcrystalline cellulose and gum arabic. Different methods to evaluate the apparent diffusion coefficients from the experimental diffusion curve were compared. Good results were obtained using a curve-fitting procedure based on the sum of least squares. The technique appears to be suitable for measuring diffusion coefficients up to 10^?9 cm²/sec. The procedure offers the possibility to quantify the mobility of chemical components in dried foodstuffs in order to elucidate the mechanisms and kinetics of reactions occurring during storage.     

含山嵛酸低热量油脂的理化特性与功能性质表征

对含山嵛酸低热量油脂的脂肪酸组成、甘油三酯组成、固体脂肪含量(SFC)、熔点、结晶速率、晶型及晶体形态进行研究,结果表明含山嵛酸低热量油脂具有较好的功能特性,不含反式脂肪酸,可作为人造奶油/起酥油的基料油,也可作为烹调油、糖果脂及煎炸油等使用.     

氢氧化钠与甘油催化棕榈基油脂酯交换反应

利用氢氧化钠与甘油催化棕榈液油和棕榈硬脂进行酯交换反应,考察反应温度、氢氧化钠浓度、反应时间、氢氧化钠与甘油比例、搅拌速度对反应产物固体脂肪含量、甘油三酯碳数、酸值、皂化值、熔点的影响。结果表明:在反应温度110℃、反应时间30 min,氢氧化钠浓度0.5%、氢氧化钠与甘油的比例1︰1、搅拌速度150 r/min的条件下,氢氧化钠与甘油混合物的催化效果接近于甲醇钠。     

PARAMETERS THAT DETERMINE TRIPALMITIN CRYSTALLIZATION IN SESAME OIL

The crystallization of tripalmitin (TP) in sesame oil (0.98, 1.80 and 2.62% w/v) was investigated under isothermal conditions using a cooling rate similar to the one achieved by industrial crystallizers (1 K/min) and utilizing a modification of the Avrami equation. It was concluded that z, the crystallization rate constant, and the associated energy of activation (Ea) values determined through Avrami's original equation yield erroneous results. Additional results indicated that the increase in supercooling at constant oil phase viscosity (e.g., 5.25–5.5 dynes/cm²) during crystallization, produced a higher degree of nucleation without an appreciable effect on TP crystal size. In contrast, as viscosity of the oil phase decreased at equal supercooling conditions (e.g., 22.0 - 22.5C) the main crystallization process evaluated through z and Ea was crystal growth. It was also concluded that the characteristic crystallization stages of induction time for nucleation, crystal nucleation and growth, and end of crystallization were evident in the viscosity profile of the solid fraction developed during TP crystallization. The predominance of any of these processes (i.e., nucleation or crystal growth) as a function of supercooling and viscosity of the oil phase determines, to a great extent, the rheological profile during crystallization and the final viscosity value of the crystal suspension.     

Production of lipase‐catalyzed solid fat from mustard oil and palm stearin with linoleic acid by response surface methodology

BACKGROUND: Solid fat was produced from mustard oil and palm stearin through lipase‐catalyzed reaction, in which linoleic acid was intentionally incorporated. For optimizing the reaction condition of melting point and ω6/ω3 fatty acids, response surface methodology (RSM) was employed with three reaction variables such as substrate mole ratio of mustard oil (MO) to palm stearin (PS) (X₁), reaction temperature (X₂) and reaction time (X₃). RESULTS: The predictive model for melting point of solid fat was adequate and reproducible due to no significant lack of fit (P = 0.0764), P‐value (0.0037) of the model, and satisfactory level of coefficient of determination (R² = 0.92). For the ω6/ω3 ratio model, R² and P‐value were 0.89 and 0.0132, respectively, but lack of fit was significant (P = 0.0389). The melting point of the produced solid fat was affected by substrate mole ratio, whereas reaction temperature and time had no significant effect. The ω6/ω3 ratio of solid fat was influenced by substrate mole ratio and reaction temperature but not by reaction time. Based on ridge analysis, lower ω6/ω3 ratio was predicted by decreasing substrate mole ratio and reaction time, and by increasing reaction temperature. CONCLUSIONS: For producing solid fat with a specific melting point of 34.57 °C, a combination of 1:2 (X₁), 65.17 °C (X₂) and 21.46 h (X₃) was optimized, and the optimization was confirmed under the same reaction conditions. The solid fat contained palmitic (37.8%), linoleic (24.8%), oleic (21.3%), and erucic acid (9.7%), and its solid fat content was 30.3% and 10.3% at 20 and 30 °C, respectively. Copyright © 2009 Society of Chemical Industry     

Effect of Solid Fat Content on Structure in Ice Creams Containing Palm Kernel Oil and High-Oleic Sunflower Oil

ABSTRACT: The development of a structural fat network in ice cream as influenced by the solid:liquid fat ratio at the time of freezing/whipping was investigated. The solid fat content was varied with blends of a hard fraction of palm kernel oil (PKO) and high-oleic sunflower oil ranging from 40% to 100% PKO. Fat globule size and adsorbed protein levels in mix and overrun, fat destabilization, meltdown resistance, and air bubble size in ice cream were measured. It was found that blends comprising 60% to 80% solid fat produced the highest rates of fat destabilization that could be described as partial coalescence (as opposed to coalescence), lowest rates of meltdown, and smallest air bubble sizes. Lower levels of solid fat produced fat destabilization that was better characterized as coalescence, leading to loss of structural integrity, whereas higher levels of solid fat led to lower levels of fat network formation and thus also to reduced structural integrity. Practical Application: Blends of highly saturated palm kernel oil and monounsaturated high-oleic sunflower oil were used to modify the solid:liquid ratio of fat blends used for ice cream manufacture. Blends that contained 60% to 80% solid fat at freezing/whipping temperatures produced optimal structures leading to low rates of meltdown. This provides a useful reference for manufacturers to help in the selection of appropriate fat blends for nondairy-fat ice cream.     

Enzymatic interesterification of tripalmitin with vegetable oil blends for formulation of caprine milk infant formula analogs

The structure of triacylglycerols in vegetable oil blends was enzymatically modified, and the blends were incorporated into skim caprine milk to produce goat milk-based infant formula analogs, homologous to human milk. A modified lipid containing palmitic, oleic, and linoleic acids, resembling the composition of human milk fat, was synthesized by enzymatic interesterification reactions between tripalmitin and a vegetable oil blend containing a 2.5:1.1:0.8 ratio of coconut, safflower, and soybean oils. A commercial sn-1,3-specific lipase obtained from Rhyzomucor miehei, Lipozyme RM IM, was used as the biocatalyst. The effects of substrate molar ratio and reaction time on the incorporation of palmitic, oleic, and linoleic acids at the sn-2 position of the triacylglycerols were investigated. The fatty acid composition and sn-2 position of the experimental formulas were analyzed using gas chromatography. Results showed that the highest incorporation of palmitic acid was obtained at 12 h of incubation at 55°C with a substrate molar ratio of 1:0.4 of tripalmitin to vegetable oil blend. However, the modified milk interesterified for 12 h at a 1:1 molar ratio had a greater resemblance to human milk compared with the other formulas. The level of oleic acid incorporation at the sn-2 position increased with the molar ratio of tripalmitin to vegetable oil blend. It was concluded that, unlike the original goat milk and other formulas, the formulated caprine milk with a molar ratio of 1:1 and a 12-h incubation was similar to the fatty acid composition of human milk.