Polymorphism and growth behavior of low-trans fat blends formulated with and without emulsifiers

Polymorphism and growth behavior of blends of a high-melting fraction of milk fat (HMF) and sunflower oil (SFO) formulated with and without the addition of sucrose esters (SE) P-170, P-1670, and S-170 were studied by pulsed ¹H NMR spectroscopy, X-ray diffraction, and polarized light microscopy. The effect of SE on the solid content maximum (S _max) or crystallization rate was observed only at low supercooling (values of ΔT below 15°C). The Avrami k _n decreased as n values increased, indicating that SE inhibited growth and impeded nucleation. Addition of SFO modified the polymorphic behavior of milk fat, most likely owing to the increase in the C₅₄ fraction (mostly 18∶1 cis) in crystals composition. P-170 and S-170 modified the polymorphic behavior of HMF when it crystallized in the α-form or in blends with up to 40% SFO at all crystallization temperatures (T _c ) selected. Addition of P-170 and S-170 favored crystallization in the β′-form, and the appearance of the β-form was delayed. P-1670 had no effect on polymorphism. When HMF and the blends were crystallized under dynamic conditions, addition of P-170 and S-170 markedly decreased crystal sizes. P-1670, however, showed no effect on microstructure.     

Effects of emulsifiers on the oxidative stability of soybean oil TAG in emulsions

The effects of two types of commercial emulsifiers, sucrose FA esters and polyglycerol FA esters, on the oxidation of soybean oil TAG-in-water emulsions were studied. Both emulsifiers influenced the oxidative stability of soybean oil TAG in the emulsion, but they had little effect on the oxidation of TAG in bulk phase. When the TAG were dispersed with sucrose esters having the same FA composition, the oxidative stability increased as their hydrophilic-lipophilic balance (HLB) increased. On the other hand, when the HLB was the same, the oxidative stability increased with increasing acyl chain length of the FA esterified on sucrose ester. However, the effect of the polyglycerol ester could not be explained by the relationship with HLB or the acyl composition. When the stability of TAG in emulsion was compared under the same concentrations of TAG, emulsifier, and oxidation inducer, the TAG dispersed with sucrose esters were oxidatively less stable than with polyglycerol esters. Analysis of the emulsion droplet size suggested that the lower oxidative stability of TAG dispersed with sucrose esters was partly due to their relatively smaller droplet sizes.     

Sucrose esters and sucrose ester/glyceride blends as emulsifiers

The sucrose mono-and diesters of long-chain fatty acids form a class of food-grade emulsifiers with a wide range of hydrophile-lipophile balance (HLB) values. Blends of sucrose mono-_and di-tallowate show a linear relationship between HLB and composition over the HLB range 10–16. Using blends of mixed glycerides and sucrose tallowate, the HLB range from 4 to 16 can be covered. The relationship between HLB water-solubility and composition in the sucrose esters is dependent on three factors: (a) the degree of sub-stitution; (b) the alkyl chain length in the ester group; and (c) the presence of dienoic or trienoic acyl groups. Water-solubility of the esters studied ranged from soluble to insoluble; sucrose esters with C12 or unsaturated acyl groups act as solubilizers. The relationship between fatty acid profile and solubility was studied using sucrose esters prepared from tallow, palm kernel oil, soybean oil and coconut oil. The properties required of a range of emulsifiers designed for use in foods, cosmetics and pharmaceuticals are: (a) that they cover the range of HLB from 2 to 16+; (b) that at high HLB values (16+), they act as solubilizers; (c) low toxicity and irri-tancy. The sucrose esters, and sucrose ester/mixed glyceride blends, have the required combination of properties. The HLB range to 16+ can be covered without forming ethoxylated or propoxylated derivatives.     

Effects of hydrophobic emulsifier additives on crystallization behavior of palm mid fraction in oil-in-water emulsion

Ultrasonic velocity measurements and X-ray diffraction were employed to monitor the crystallization behavior of palm mid fraction (PMF) in oil-in-water emulsions (20 vol%). Three hydrophobic emulsifiers—sucrose oligoesters (SOE) containing palmitic acid (P-170) and stearic acid (S-170) moieties and a polyglycerine ester (DAS-750) containing a stearic acid moiety—were added to PMF in an attempt to increase the rate and extent of crystallization of PMF, which are otherwise suppressed owing to emulsification of the oil phase into many droplets. The results revealed that the hydrophobic emulsifiers accelerate the nucleation of PMF in the emulsion system, while retarding the rate of crystal growth. As a results, the crystallization temperature (T _c) of PMF increased with increasing concentrations of the hydrophobic emulsifiers. The effects of the three additives were different; in particular the addition of DAS-750 remarkably enhanced crystallization at low concentrations. By adding the emulsifiers at higher concentrations, the polymorphic behavior of PMF crystallization was also modified to different degrees, depending on the type of emulsifier. With addition of SOE, PMF crystallized predominantly in the β′ form; with addition of DAS-750, the extent of β′ nucleation was reduced by comparison with that observed with SOE. The results were explained in terms of adsorption of the hydrophobic emulsifier additives at the oil-water interface, which provides a template for acceleration of surface heterogeneous nucleation of PMF in the emulsion system.     

The effect of propylene–ethylene copolymers with different comonomer content on melting and crystallization behavior of polypropylene

The effect of propylene–ethylene copolymers (PEc) with different ethylene‐unit contents on melting and crystallization behaviors of isotactic‐polypropylene (iPP) were investigated by differential scanning calorimetry (DSC) and polarized light microscopy (PLM). The results show that the addition of PEc decreases significantly crystallization temperature (T_c) of iPP, but slightly affects melting temperature (T_m). With increasing the ethylene‐unit content of the propylene–ethylene copolymers, the decrease in crystallization temperature of iPP is smaller. The PLM results show that the spherulite growth rate decreases with increasing crystallization temperature for iPP and iPP/PEc blends. The higher the ethylene‐unit content of the copolymers is, the lower the spherulite growth rate (G) of iPP/PEc blends is. The influence of the PEc on nucleation rate constant (K_g) and fold surface energy (σ_e) of iPP was examined by nucleation theory of Hoffman and Lauritzen. The results show that both K_g and σ_e of iPP/PE20(80/20) and iPP/PE23(80/20) blends are higher than those of iPP, demonstrating that the overall crystallization rate of iPP/PEc blends decreased as compared to that of iPP, resulting from the decrease of the nucleation rate and the spherulite growth rate of iPP. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effect of food emulsifiers on crystal structure and habit of stearic acid

Several food emulsifiers have been found to serve as crystal structure modifiers for stearic acid crystallized from various organic solvents. Stearic acid that usually precipitates under appropriate crystallization conditions as the B- form is converted into the C- form when 1- 5% of sorbitan esters or ethoxylated sorbitan esters of fatty acids are present in the solution. Other emulsifiers such as polyglycerol esters, bdsubstituted monoglycerides and sucrose esters of fatty acids consisting of bulky hydrophilic groups are also effective emulsifiers in preserving the C- form of the crystallized stearic acid. The active emulsifiers modify the external crystal habit of stearic acid. Mass spectrograph analysis indicates that sorbitan monostearate (Span 60) is precipitated with the stearic acid.     

Emulsification properties of polyesters and sucrose ester blends I: Carbohydrate fatty acid polyesters

A number of carbohydrate fatty acid polyesters, potential fat substitutes, were screened for their ability to reduce surface and interfacial tensions alone or as blends with commercial emulsifiers. Commercial sucrose ester emulsifiers (Ryoto, Mitsubishi-Kasei Food Corporation, Tokyo, Japan) were evaluated alone or blended with other sucrose esters or with other carbohydrate fatty acid polyesters, and their surfactant properties were examined in terms of their ability to reduce surface and interfacial tensions at different concentrations and to stabilize oil-in-water (o/w) and water-in-oil (w/o) food emulsions at room and refrigeration temperatures, respectively. In general, when used alone the carbohydrate polyesters were excellent stabilizers of w/o emulsions and poor stabilizers of o/w emulsions. Blending lipophilic carbohydrate polyesters with hydrophilic commercial emulsifiers, such as S-1670, produced stable o/w emulsions and unstable w/o emulsions. Our results suggest that emulsifier blends of potential fat substitutes with FDA-approved commercial sugar ester emulsifiers can be prepared for possible use in low-calorie foods, cosmetics and pharmaceuticals as o/w and w/o emulsifiers.     

Organic reactions in emulsions—Preparation of glycerol and polyglycerol esters of fatty acids by transesterification reaction

Monoglycerol and polyglycerol esters of fatty acids have been prepared in an emulsion medium of polyglycerol in esters of fatty acids. Transesterification between glycerol or polyglycerols and methyl esters of fatty acids is made at relatively low temperatures (95–150 C) in the presence of alkaline catalyst and anionic or nonionic emulsifiers. The reaction system consists of two immiscible phases transformed into a “milky” (macro) or transparent (micro) emulsion throughout the heating process. The product obtained using this technology is not a highly substituted ester since the transesterification reaction is selective. The type and the amount of emulsifier have to be carefully selected. Unsuitable emulsifiers which will not stabilize the emulsion are ineffective in enlarging the contact between the reactants; therefore, the conversion of the reactants is very poor. With suitable emulsifiers, the conversions and the yields improved due to a better contact between reactants.     

Production and Emulsifying Effect of Polyglycerol and Fatty Acid Esters with Varying Degrees of Esterification

Esters with acyl groups can be formed by the esterification of polyglycerol. The purpose of the present study was to produce fatty acid esters [hexanoic (caproic), octanoic (caprylic), decanoic (capric), dodecanoic (lauric), tetradecanoic (myristic), hexadecanoic (palmitic), octadecanoic (stearic)] and polyglycerol (average number‐of degrees of polymerization of 5) with varying degrees of esterification and to examine their emulsifying properties. A number of fundamental catalysts of polyglycerol acylation reactions by methyl esters of carboxylic acid were studied, and sodium methoxide was found to be the best choice. The temperature rate of transesterification increased from 180 to 220 °C with the fatty acid chain alkyl residue. Synthesized mono‐, di‐, tri‐, tetra‐, and heptaesters of various fatty acids and polyglycerol provided the highest hydroxyl values from 15 to 815 mg KOH g^?1 and saponification values from 82 to 321 mg KOH g^?1. The emulsifying properties were assessed for all polyglycerol and fatty acid esters, with results showing maximum emulsifying effect for tri‐ and tetraesters of capric, lauric, and caprylic acids. Regardless of the hydrophilic–lipophilic balance value (HLB) of polyglycerol esters and carboxylic acid, a 4:1 ratio of sunflower oil to water formed a water‐in‐oil type emulsion. When mixing oil and water in a 1:1 ratio, mono‐ and diesters of polyglycerol formed an oil‐in‐water type emulsion, heptaesters formed a water‐in‐oil type emulsion, and tri‐ and tetraesters formed both of types of emulsions, depending on the length of the acid hydrocarbon radicals.     

共聚甲醛的自成核结晶行为

采用自成核的方法研究了共聚甲醛（POM）的结晶过程、结晶行为及其形态结构。结果表明,POM的有效自成核温度（Ts）区间为165.5～167 ℃;POM经自成核处理后可在144～148 ℃内迅速结晶,相对其在210 ℃熔融后的结晶温度（Tc）最大提高了5 ℃;在150～154 ℃内自成核处理后的样品随着等温Tc的升高,结晶速率（G）变慢;根据Arrhenius方程和Lauritzen Hoffman方程可获得样品的各项动力学参数,通过对比发现,自成核处理可有效提高POM的Tc和G;POM经自成核处理后晶型未发生变化,且微晶尺寸细化,球晶尺寸变小;自成核处理可有效促进POM的结晶。     

Factors Affecting Initial Retention of a Microencapsulated Sunflower Seed Oil/Milk Fat Fraction Blend

To study the effect of emulsion stability, particle size, emulsifier, and crystalline fat in the oil phase on initial retention of a low-trans fat encapsulated in a trehalose matrix, six emulsions were prepared. The six emulsions were formulated with 20 wt% trehalose solution as the aqueous phase, a lipid phase either with no crystalline fat, sunflower seed oil (SFO), or with a crystalline phase, a 40% SFO in high-melting fraction of milk fat (HMF) blend, and sodium caseinate (NaCas), a 50 wt% blend of the palmitic sucrose esters (SE) P-170 and P-1670, or a 50 wt% blend of NaCas/SE as stabilizers. Particle size did not change or it changed only slightly during the freeze thaw or freeze drying process when the fat phase was SFO. However, when a crystalline phase was present, the volume-weighted mean diameter (D _4,3) increased dramatically for SE and NaCas/SE stabilizers. Encapsulation properties were determined by the counteracting effects of particle size and distribution, the presence of crystalline material in the droplets and interactions between interface components, fat phase and trehalose. In addition, retention was less related to emulsion stability. The emulsions selected for this study were stable for at least 30 h which was enough for obtaining a high degree of encapsulation.     

Effects of Sucrose Esters on Isothermal Crystallization of Palm Oil‐based Blend

The effects of sucrose esters (SEs) with different acyl chain lengths, namely, lauryl (L‐195), palmitoyl (P‐170), stearoyl (S‐170), oleoyl (O‐170), and erucyl (ER‐190), on isothermal crystallization of a palm oil‐based blend (PO–PS) were studied. From this study, it was found that both α‐ and β′‐crystals coexisted following crystallization of PO–PS from melt to room temperature. Addition of SEs P‐170 and S‐170, which had saturated acyl chains similar to PO–PS, resulted in an accelerating crystallization rate, promoting the appearance of α‐crystals and transition to β′‐crystals and increasing viscosity of PO–PS blend. SE O‐170, which is liquid at room temperature, had little effect on blend crystallization. SEs L‐195 and ER‐190, with an acyl chain dissimilar to PO–PS, inhibited triacylglycerol bonding or further integration to the surface of crystals and reduced the crystallization rate and viscosity of the PO–PS blend. The PO–PS blend with SE L‐195 and ER‐190 contained large crystals and resulted in slower formation of α‐crystals and transformation to β′‐crystals. Results from this study indicate that crystallization of PO–PS was greatly influenced by acyl–acyl interactions between acyl chains of SEs and triacylglycerols.     

Effect of self‐nucleation on the crystallization of segmented copolymer poly(ether ester)

The effect of self‐nucleation on the nonisothermal and isothermal crystallization behaviors of the segmented copolymer poly(ether ester), based on poly(ethylene glycol) as the soft segment and poly(ethylene terephthalate) as the hard segment was investigated by means of differential scanning calorimetry (DSC) and depolarization polarized light (DPL) techniques, respectively. The results demonstrated that self‐nucleation could enhance the crystallization rate in both cases. The experimental conditions of the self‐nucleation procedure studied by DSC were discussed in detail. The isothermal crystallization was analyzed by the Avrami equation, and the Avrami parameters were dependent on the melting temperature. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 498–504, 2001     

Microencapsulation of a Low-trans Fat in Trehalose as Affected by Emulsifier Type

A low-trans fat blend formulated with high linoleic sunflower seed oil (SFO) and a high melting fraction (HMF) of milk fat was encapsulated by freeze-drying emulsions. The selected emulsifiers were a mixed of the palmitic sucrose esters (SE) P-170 and P-1670, sodium caseinate (NaCas) or a blend of SE and NaCas. The ability to retain the core material with time was studied by storing the powders at different water activities (a _w). Efficiency of encapsulation was strongly dependent on emulsifier type. NaCas formulation was more efficient retaining core material during storage. The formulation with a protein and a small surfactant had the lowest performance. The stabilizer also influenced droplet size distribution and matrix crystallinity. For NaCas-stabilized powder volume weighted mean diameter (D _4,3) remained small for up to 2 months of storage (0.56 ± 0.5 μm) and then grew notably in agreement with matrix collapse. There were no significant differences in D _4,3 with water content. For NaCas/SE-stabilized powder, however, D _4,3 was high at the beginning (100 ± 0.5 μm) and then decreased most likely due to particle break-up. Although particle size distribution showed the same behavior for all a _w, retention was strongly dependent on water content. Retention with time was determined by the counteracting effects of these factors.     

Morphology,dynamic mechanical,and electrical properties of bio‐based poly(trimethylene terephthalate) blends,part 2: Poly(trimethylene terephthalate)/poly(ether esteramide)/polycarbonate blends

Bio‐based poly(trimethylene terephthalate) (PTT) and poly(ether esteramide) (PEEA) blends were prepared by melt processing with varying weight ratios (0–20 wt %) of polycarbonate (PC). The blends were characterized by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), polarized light microscopy (PLM), and transmission electron microscopy (TEM). Electrostatic performance was also investigated for those PTT blends since PEEA is known as an ion conductive polymer. DMA suggests that PC is miscible with PEEA and selectively goes into PEEA phase in case of ternary blends of PTT/PEEA/PC. The glass transition temperature (T_g) for PC/PEEA is well predicted by Gordon Taylor equation. Addition of PC retards the electrostatic decay performance of PTT/PEEA blends by restricting the motion of ions in PEEA through increasing the T_g of PEEA. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Crystallization,morphology, and electrical properties of bio‐based poly(trimethylene terephthalate)/poly(ether esteramide)/ionomer blends

Bio‐based poly(trimethylene terephthalate) (PTT) and poly(ether esteramide) (PEEA) blends were prepared by melt processing with varying weight ratios (0–20 wt %) of ionomers such as lithium‐neutralized poly(ethylene‐co‐methacrylic acid) copolymer (EMAA‐Li) and sodium‐neutralized poly(ethylene‐co‐methacrylic acid) copolymer (EMAA‐Na). The blends were characterized by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), polarized light microscopy (PLM), and transmission electron microscopy (TEM). DSC and PLM results showed that EMAA‐Na increased the crystallization rate for PTT significantly, whereas EMAA‐Li did not enhance the crystallization rate at all. Specific interactions between PEEA and ionomers were confirmed by DSC and TEM. Electrostatic performance was also investigated for those PTT blends because PEEA is known as an ion‐conductive polymer. Here, we confirmed that both sodium and lithium ionomers work as a synergist to enhance the static decay performance of PTT/PEEA blends. Morphological study of these ternary blends systems was conducted by TEM. Dispersed ionomer domains were encapsulated by PEEA, which increases the interfacial surface area between PEEA and the PTT matrix. This encapsulation effect explains the unexpected synergy for the static dissipation performance on addition of ionomers to PTT/PEEA blends. This core–shell morphology can be predicted by calculating spreading coefficient for the ternary blends. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Curing behavior and thermal mechanical properties of cyanate ester blends

Cyanate esters are a class of important thermally resistant polymers. To tailor their processability and thermomechanical properties, a series of cyanate ester blends based on a trifunctional novolac cyanate ester (HF‐5), a difunctional bisphenol E cyanate ester (HF‐9), and a reactive catalyst [2,2′‐diallyl bisphenol A (DBA)] were formulated. The effect of the blend composition on the rheology and curing behavior of these cyanate ester blends and the corresponding thermal and mechanical properties of the cured cyanate ester blends was studied. The results showed that HF‐5 contributed to good mechanical property retention at high temperatures because of its trifunctionality, whereas HF‐9 imparted processability by reducing the viscosity and extending the pot life of the formulated cyanate ester blends at the processing temperature. On the basis of the results, an optimal cyanate ester blend suitable for resin transfer molding was determined: the HF‐5/HF‐9/DBA weight ratio of 80 : 15 : 5 exhibited good processability and thermomechanical properties. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4284–4290, 2006     

Improving the cold flow properties of biodiesel from waste cooking oil by surfactants and detergent fractionation

The use of surfactants and detergent fractionation to improve the cold flow properties of biodiesel from waste cooking oil (BWCO) was investigated. The effect of five types of surfactants, including sugar esters (S270 and S1570), silicone oil (TSA 750S), polyglycerol ester (LOP-120DP) and diesel conditioner (DDA) on the reduction of the cold filter plugging point (CFPP) of the BWCO, was evaluated, with the greatest reduction to the CFPP of the BWCO (from −10 °C to −16 °C) being was achieved by the addition of 0.02 wt% of polyglycerol ester (LOP-120P). Detergent fractionation of the BWCO was performed by first mixing partially crystallized biodiesel with a chilled detergent (sodium dodecylsulfate) solution accompanied by an electrolyte (magnesium sulfate), and then separating the mixture by centrifugation to obtain the BWCO liquid. An orthogonal experimental design was utilized to investigate the effects of the various parameters on detergent fractionation. The optimal parameters, as obtained by range analysis, were as follows: detergent loading 0.3 wt%, electrolyte loading 1.0 wt%, and water loading 150 wt%. The CFFP of the liquid biodiesel from waste cooking oil (LBWCO) was −17 °C with a yield of 73.1% when the detergent fractionation was performed under these conditions. A limited number of biodiesel physical and chemical properties were analyzed before and after the addition of surfactants and detergent fractionation.     

Crystallization kinetics and tensile modulus of blends of metallocene short‐chain branched polyethylene with conventional polyolefins

In this study, blends of metallocene short‐chain branched polyethylene (SCBPE) with low‐density polyethylene (LDPE), high‐density polyethylene (HDPE), polystyrene (PS), ethylene–propylene–diene monomer (EPDM), and isotactic polypropylene (iPP) were prepared in weight proportions of 80 and 20, respectively. The crystallization behaviors of these blends were studied with polarized light microscopy (PLM) and differential scanning calorimetry. PLM showed that SCBPE/LDPE, SCBPE/HDPE, and SCBPE/EPDM formed band spherulites whose band widths and sizes were both smaller than that of pure SCBPE. No spherulites were observed, but tiny crystallites were observed in the completely immiscible SCBPE/PS, and the crystallites in SCBPE/iPP became smaller; only irregular spherulites were seen. The crystallization kinetics and mechanical properties of SCBPE were greatly affected by the second polyolefin but in different way, depending on the phase behavior and the moduli of the second components. SCBPE may be phase‐miscible in the melt with LDPE, HDPE, and EPDM but phase‐separated during crystallization. A big change in the crystal morphology and crystallization kinetics existed in the SCBPE/iPP blend. The mechanical properties of the blends were also researched with dynamic mechanical analysis (DMA). DMA results showed that the tensile modulus of the blends had nothing to do with the phase behavior but only depended on the modulus of the second component. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1816–1823;2005     

我国食品乳化剂的现状和展望

介绍了我国几类主要食品乳化剂———甘油脂肪酸酯、蔗糖脂肪酸酯、斯盘和吐温、大豆磷脂、硬脂酰乳酸钠和钙的生产和研究现状 ,并对我国食品乳化剂发展提出了几点建议。