Differential Scanning Calorimetry Analysis of Goat Fats: Comparison of Chemical Composition and Thermal Properties

The physical–chemical properties, fatty acid composition and thermal properties of goat subcutaneous (SF), tallow (TF) and intestinal (IF) fats were determined. SF differed from other fat types with respect to its lower melting (41.6 °C), lower saponification (190.3 mg KOH/g) and higher iodine (40.4) values as compared to those of other fats. Goat fat types contained palmitic acid (C_16:0), stearic acid (C_18:0), oleic acid (C_18:1ω9) and linoleic acid (C_18:2ω6) as the major components of the fatty acid composition (23.06–23.52, 22.95–39.03, 21.94–36.16 and 1.96–2.22%, respectively). A differential scanning calorimetry (DSC) study revealed that two characteristic peaks were detected in both crystallization and melting curves. Major peaks (T _peak) of TF and IF were similar and determined as 34.02–35.24 and 9.95–10.72 °C, respectively for the crystallization peaks and 15.11–18.26 and 50.70–52.76 °C, respectively for the melting peaks in the DSC curves; but those of SF (27.14 and 4.36 °C for crystallization peaks and 8.39 and 44.93 °C for melting peaks) differed remarkably from those of other fat types.     

Application of palm olein in the production of zero‐trans Iranian vanaspati through enzymatic interesterification

The utilization of palm olein in the production of zero‐trans Iranian vanaspati through enzymatic interesterification was studied. Vanaspati fat was made from ternary blends of palm olein (POL), low‐erucic acid rapeseed oil (RSO) and sunflower oil (SFO) through direct interesterification of the blends or by blending interesterified POL with RSO and SFO. The slip melting point (SMP), the solid fat content (SFC) at 10–40 °C, the carbon number (CN) triacylglycerol (TAG) composition, the induction period (IP) of oxidation at 120 °C (IP₁₂₀) and the IP of crystallization at 20 °C of the final products and non‐interesterified blends were evaluated. Results indicated that all the final products had higher SMP, SFC, IP of crystallization and CN 48 TAG (trisaturated TAG), and lower IP₁₂₀, than their non‐interesterified blends. However, SMP, SFC, IP₁₂₀, IP of crystallization and CN 48 TAG were higher for fats prepared by blending interesterified POL with RSO and SFO. A comparison between the SFC at 20–30 °C of the final products and those of a commercial low‐trans Iranian vanaspati showed that the least saturated fatty acid content necessary to achieve a zero‐trans fat suitable for use as Iranian vanaspati was 37.2% for directly interesterified blends and 28.8% for fats prepared by blending interesterified POL with liquid oils.     

Combined Short-Path Distillation and Solvent-Assisted Crystallization of Beef Fatty Acid Methyl Esters

Solvent‐assisted crystallization has previously been employed to remove long‐chain saturated fatty acids (≥ 18 carbons) from animal fat to improve its cold temperature biofuel properties. The same technology can be used for removing long‐chain saturated fatty acids (SFA) from animal fats for human consumption, but SFA remaining (i.e., 14:0 and 16:0) are more atherogenic than longer chain SFA. In the present study, an easy and efficient method was developed using short‐path distillation prior to solvent‐assisted crystallization for the more complete removal of SFA from beef tallow, and for the first time reports the distillation and crystallization behavior of polyunsaturated fatty acid biohydrogenation products (PUFA‐BHP). Shorter chain SFA methyl esters (i.e., 14:0 and 16:0) were efficiently removed at 90 °C, 9.3 Pa, with a rotor speed of 70 rpm and either two cycles of distillation at 90 drops/min or three cycles at 110 drops/min. Stearic acid (18:0) was then effectively removed by crystallization at ?20 °C using a sample to methanol ratio of 1:10. The remaining fraction enriched with PUFA‐BHP (i.e., rumenic acid, c9,t11‐18:2, and its precursor vaccenic acid, t11‐18:1) have potential use in disease model (i.e., cell culture and animal) studies to help further elucidate their bioactivity and mode of action, and may in the future have functional food or nutraceutical potential.     

Interaction of self‐nucleation and the addition of a nucleating agent on the crystallization behavior of isotactic polypropylene

The relationship between heterogeneous or homogeneous nucleation and self‐nucleation of polypropylene (PP) and PP nucleated by an organic phosphate salt (PPA) was studied by DSC. For pure PP, it homogeneously nucleated during cooling after melting at the selected temperature (T_s) of 170–200°C for 3 min, but at the T_s of 160–168°C self‐nucleation occurred; PPA only nucleated heterogeneously at the T_s of 168–200°C, and there existed self nucleation at the T_s of 160–168°C. The double melting peaks of PP and PPA at the T_s of 162°C were observed. Once the self‐nucleation occurred, the change of the crystallization temperature and heat of fusion of PP is more significant than that of PPA with the change of the T_s, depending upon the crystallization conditions. Results were explained by homogeneous nucleation, heterogeneous nucleation, self‐nucleation, and annealing crystallization. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 78–84, 2001     

Effects of silver nanoparticles on the dynamic crystallization and physical properties of syndiotactic polypropylene

The effects of silver (Ag) nanoparticles on the physical properties of syndiotactic PP (sPP) were investigated concentrating on the isothermal melt crystallization behavior under shear. sPP with 5 wt % Ag nanoparticles presented higher crystallization temperature (T_c) and heat of crystallization (ΔH_c) than pure sPP. At 90°C, the Ag nanoparticles had little effect on the induction time of crystallization but a little increased the half‐time (t_1/2) for the crystallization. At 100°C, however, the induction time was decreased with increasing the Ag content and the t_1/2 was decreased up to the Ag content of 0.5 wt %. DSC melting endotherms exhibited double melting peaks when crystallized at 90°C under shear but a single melting peak when crystallized at 100°C. The WAXD patterns exhibited that the presence of Ag nanoparticles did not produce any change in the crystal structure of sPP. The tensile strength of sPP is little changed up to the Ag content of 0.1 wt % but it was decreased with further addition. In addition, the introduction of less than 0.1 wt % Ag increased the elongation at break, but further addition decreased it abruptly. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Crystallization kinetics and melting behavior of poly[(trimethylene terephthalate)‐co‐(29 mol % ethylene terephthalate)] copolyester

The copolyester was characterized as having 71 mol % trimethylene terephthalate units and 29 mol % ethylene terephthalate units in a random sequence according to the NMR spectra. Differential scanning calorimeter (DSC) was used to investigate the isothermal crystallization kinetics in the temperature range (T_c) from 130 to 170°C. The melting behavior after isothermal crystallization was studied using DSC and temperature‐modulated DSC by varying the T_c, the crystallization time, and the heating rate. The DSC thermograms and wide‐angle X‐ray diffraction patterns reveal that the complex melting behavior involves melting‐recrystallization‐remelting and different lamellar crystals. As the T_c increases, the contribution of recrystallization gradually falls and finally disappears. A Hoffman‐Weeks linear plot yields an equilibrium melting temperature of 198.7°C. The kinetic analysis of the growth rates of spherulites and the change in the morphology from regular to banded spherulites indicate that a regime II→III transition occurs at 148°C. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Nonisothermal crystallization kinetics and morphology of self‐seeded syndiotactic 1,2‐polybutadiene

Subsequent melting behavior after isothermal crystallization at different temperatures from the isotropic melt and nonisothermal crystallization kinetics and morphology of partially melting sPB were carried out by differential scanning calorimetry (DSC), polarized light microscopy (POM), respectively. Triple melting‐endothermic peaks were observed for the polymer first isothermally crystallized at temperatures ranging from 141 to 149°C, respectively, and then followed by cooling at 10°C/min to 70°C. Comparing with the nonisothermal crystallization from the isotropic melt, the nonisothermal crystallization for the partially melting sPB characterized the increased onset crystallization temperature, and the sizes of spherulites became smaller and more uniform. The Tobin, Avrami, Ozawa, and the combination of Avrami and Ozawa equations were applied to describe the kinetics of the nonisothermal process. Both of the Tobin and the Avrami crystallization rate parameters (K_T and K_A, respectively) were found to increase with increase in the cooling rate. The parameter F(T) for the combination of Avrami and Ozawa equations increases with increasing relative crystallinity. The Ziabicki's kinetic crytallizability index G_Z for the partially melting sPB was found to be 3.14. The effective energy barrier Δ? describing the nonisothermal crystallization of partially melting sPB was evaluated by the differential isoconversional method of Friedman and was found to increase with an increase in the relative crystallinity. At the same time, Hoffman‐Lauritzen parameters (U and K_g) are evaluated and analyzed from the nonisothermal crystallization data by the combination of isoconversional approach and Hoffman‐Lauritzen theory. The K_g value obtained from DSC technique was found to be in good agreement with that obtained from POM technique. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1479–1491, 2006     

Melting behavior of blends of milk fat with hydrogenated coconut and cottonseed oils

The melting behavior of milk fat, hydrogenated coconut and cottonseed oils, and blends of these oils was examined by nuclear magnetic resonance (NMR) and differential scanning calorimetry (DSC). Solid fat profiles showed that the solid fat contents (SFC) of all blends were close to the weighted averages of the oil components at temperatures below 15°C. However, from 15 to 25°C, blends of milk fat with hydrogenated coconut oils exhibited SFC lower than those of the weighted averages of the oil components by up to 10% less solid fat. Also from 25 to 35°C, in blends of milk fat with hydrogenated cottonseed oils, the SFC were lower than the weighted averages of the original fats. DSC measurements gave higher SFC values than those by NMR. DSC analysis showed that the temperatures of crystallization peaks were lower than those of melting peaks for milk fat, hydrogenated coconut oil, and their blends, indicating that there was considerable hysteresis between the melting and cooling curves. The absence of strong eutectic effects in these blends suggested that blends of milk fat with these hydrogenated vegetable oils had compatible polymorphs in their solid phases. This allowed prediction of melting behavior of milk-fat blends with the above oils by simple arithmetic when the SFC of the individual oils and their interaction effects were considered.     

Thermal properties and morphology of noncrosslinking linear low‐density polyethylene‐grafted acrylic acid

Noncrosslinking linear low‐density polyethylene‐grafted acrylic acid (LLDPE‐g‐AA) was prepared by melt‐reactive extrusion in our laboratory. The thermal behavior of LLDPE‐g‐AA was investigated by using differential scanning calorimetry (DSC). Compared with neat linear low‐density polyethylene (LLDPE), melting temperature (T_m) of LLDPE‐g‐AA increased a little, the crystallization temperature (T_c) increased about 4°C, and the melting enthalpy (ΔH_m) decreased with an increase in acrylic acid content. Isothermal crystallization kinetics of LLDPE and LLDPE‐g‐AA samples were carried out by using DSC. The overall crystallization rate of LLDPE was smaller than that of grafted samples. It showed that the grafted acrylic acid monomer onto LLDPE acted as a nucleating agent. Crystal morphologies of LLDPE‐g‐AA and LLDPE were examined by using SEM. Spherulite sizes of LLDPE‐g‐AA samples were lower than that of LLDPE. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2626–2630, 2002     

Crystallization kinetics and melting behaviour of microbial poly(3‐hydroxybutyrate‐co‐3‐hydroxyhexanoate)

Isothermal and non‐isothermal crystallization kinetics of microbial poly(3‐hydroxybutyrate‐co‐3‐hydroxyhexanoate) [P(3HB‐3HHx)] was investigated by differential scanning calorimetry (DSC) and ¹³C solid‐state nuclear magnetic resonance (NMR). Avrami analysis was performed to obtain the kinetic parameters of primary crystallization. The results showed that the Avrami equation was suitable for describing the isothermal and non‐isothermal crystallization processes of P(3HB‐3HHx). The equilibrium melting temperature of P(3HB‐3HHx) and its nucleation constant of crystal growth kinetics, which were obtained by using the Hoffman–Weeks equation and the Lauritzen–Hoffmann model, were, respectively, 121.8 °C and 2.87 × 10⁵ K² when using the empirical ‘universal’ values of U* = 1500 cal mol^?1. During the heating process, the melting behaviour of P(3HB‐3HHx) for both isothermal and non‐isothermal crystallization showed multiple melting peaks, which was the result of melting recrystallization. The lower melting peak resulted from the melting of crystals formed during the corresponding crystallization process, while the higher melting peak resulted from the recrystallization that took place during the heating process. Copyright © 2005 Society of Chemical Industry     

Nonisothermal crystallization kinetics of poly(butylene terephthalate)/poly(ethylene terephthalate)/glass fiber composites

The influences of the glass fiber (GF) content and the cooling rate for nonisothermal crystallization process of poly(butylene terephthalate)/poly(ethylene terephthalate) (PBT/PET) blends were investigated. The nonisothermal crystallization kinetics of samples were detected by differential scanning calorimetry (DSC) at cooling rates of 5°C/min, 10°C/min, 15°C/min, 20°C/min, 25°C/min, respectively. The Jeziony and Mozhishen methods were used to analyze the DSC data. The crystalline morphology of samples was observed with polarized light microscope. Results showed that the Jeziony and Mozhishen methods were available for the analysis of the nonisothermal crystallization process. The peaks of crystallization temperature (T_p) move to low temperature with the cooling rate increasing, crystallization half‐time (t_1/2) decrease accordingly. The crystallization rate of PBT/PET blends increase with the lower GF contents while it is baffled by higher GF contents. POLYM. COMPOS. 36:510–516, 2015. © 2014 Society of Plastics Engineers     

Isothermal melt crystallization and melting behaviour of syndiotactic polypropylene

The lamellar morphological information and subsequent melting behaviour of syndiotactic polypropylene (s‐PP) samples isothermally crystallized at crystallization temperatures ranging from 30 to 95 °C have been investigated using a combination of wide‐angle X‐ray diffraction (WAXD), small‐angle X‐ray scattering (SAXS) and differential scanning calorimetry (DSC) techniques. Three known methods for determining the equilibrium melting temperature T_m°, namely the Gibbs–Thomson extrapolation, the linear Hoffman–Weeks extrapolation and the non‐linear Hoffman–Weeks extrapolation, have been employed to evaluate this important thermodynamic parameter, and the results obtained are compared. Finally, an estimate of the equilibrium melting temperature for a perfect s‐PP sample (T_m°)_100% is given. © 2000 Society of Chemical Industry     

Multiple melting and partial miscibility of ethylene‐vinyl acetate copolymer/low density polyethylene blends

Multiple melting behaviors and partial miscibility of ethylene‐vinyl acetate (EVA) copolymer/low density polyethylene (LDPE) binary blend via isothermal crystallization are investigated by differential scanning calorimetry (DSC) and wide angle X‐ray diffraction (WAXD). Crystallization temperature T (°C) is designed as 30, 50, 70, 80°C with different crystallization times t (min) of 10, 30, 60, 300, 600 min. The increase of crystallization temperature and time can facilitate the growth in lateral crystal size, and also the shift of melting peak, which means the completion of defective secondary crystallization. For blends of various fractions, sequence distribution of ethylene segments results in complex multiple melting behaviors during isothermal crystallization process. Overlapping endothermic peaks and drops of equilibrium melting points of LDPE component extrapolated from Hoffman–Weeks plots clarify the existence of partial miscibility in crystalline region between EVA and LDPE. WAXD results show that variables have no perceptible influence on the predominant existence of orthorhombic crystalline phase structure. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Thermophysical properties of bacterial poly(3‐hydroxybutyrate): Characterized by TMA,DSC, and TMDSC

The melting, isothermal and nonisothermal crystallization behaviors of poly(3‐hydroxybutyrate) (PHB) have been studied by means of temperature modulated differential scanning calorimetry (TMDSC) and conventional DSC. Various experimental conditions including isothermal/annealing temperatures (80, 90, 100, 105, 110, 120, 130, and 140°C), cooling rates (2, 5, 10, 20, and 50°C/min) and heating rates (5, 10, 20, 30, 40, and 50°C/min) have been investigated. The lower endothermic peak (T_m1) representing the original crystals prior to DSC scan, while the higher one (T_m2) is attributed to the melting of the crystals formed by recrystallization. Thermomechanical analysis (TMA) was used to evaluate the original melting temperature (T_melt) and glass transition temperature (T_g) as comparison to DSC analysis. The multiple melting phenomenon was ascribed to the melting‐recrystallization‐remelting mechanism of the crystallites with lower thermal stability showing at T_m1. Different models (Avrami, Jeziorny‐modified‐Avrami, Liu and Mo, and Ozawa model) were utilized to describe the crystallization kinetics. It was found that Liu and Mo's analysis and Jeziorny‐modified‐Avrami model were successful to explain the nonisothermal crystallization kinetic of PHB. The activation energies were estimated in both isothermal and nonisothermal crystallization process, which were 102 and 116 kJ/mol in respective condition. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42412.     

Crystallization and melting behavior of polyester/clay nanocomposites

Polyester/clay nanocomposites were prepared by melt compounding with different clay loadings. Comparing against neat polyester resins, the crystallization and multiple melting behavior of the nanocomposites was investigated by differential scanning calorimetry (DSC) and X‐ray diffraction (XRD). Nanoclay filler is an effective heterogeneous nucleating agent, as evidenced by a decrease and an increase in the crystallization temperature for both cold and melt crystallization of polyesters, respectively. The degree of crystallinity was found to increase with increasing clay content, due to heterogeneous nucleation effects by the addition of a nanofiller. For the annealed samples, multiple melting peaks were always observed for both neat polyester and its nanocomposites. The origins of the multiple melting behavior are discussed, based on the DSC and XRD results. Interestingly, an ‘abnormal’ high‐temperature endothermic peak (T_{m, 3}) at about 260 °C was observed when the nanocomposite samples were annealed at higher temperatures (eg ≥240 °C). The constrained polyester crystals formed within intercalated clay platelets due to confinement effects were probably responsible for this melting event at these higher temperatures. Copyright © 2004 Society of Chemical Industry     

Structuring of Chicken Fat by Monoacylglycerols

In this study, we investigated the effect of monoacylglycerol (MAG) as a structuring agent on the physicochemical, microstructure and rheological properties of chicken fat. The fatty acid composition, oxidative stability, free fatty acids (FFA), slip melting point (SMP), solid fat content (SFC), kinetics of crystallization, microstructure and rheological properties of the samples were evaluated. The addition of MAG at a 0.5 % level did not affect the fatty acid composition, induction period of oxidation at 110 °C (IP_ox110), SFC curve or rheological properties of chicken fat (p > 0.05). However, structured samples containing 3.0 and 5.0 % MAG had higher saturated fatty acid (SFA) content, SFC, SMP, FFA content and IP_ox110 (p < 0.05). The addition of MAG led to a reduction in the IP of oxidation at 60 °C (IP_ox60) and increased the oxidation rate of fats, as measured by the Schaal oven test. Samples containing 3–5 % MAG had higher SFC content, higher loss, storage and complex moduli, higher complex viscosity, and a lower induction period of crystallization (IP_cryst) and tan δ than chicken fat. Investigations by polarized light microscopy confirmed the presence of increased crystal content in samples containing higher MAG levels. These results show that structured chicken fats have the potential for application in the production of soft tub margarine and Iranian vanaspati.     

Synthesis and characterization of poly(ε‐caprolactone)‐b‐poly(ethylene glycol)‐b‐poly(ε‐caprolactone) triblock copolymers with dibutylmagnesium as catalyst

Two series of poly(ε‐caprolactone)‐b‐poly(ethylene glycol)‐b‐poly(ε‐caprolactone) triblock copolymers were prepared by the ring opening polymerization of ε‐caprolactone in the presence of poly(ethylene glycol) and dibutylmagnesium in 1,4‐dioxane solution at 70°C. The triblock structure and molecular weight of the copolymers were analyzed and confirmed by ¹H NMR, ¹³C NMR, FTIR, and gel permeation chromatography. The crystallization and thermal properties of the copolymers were investigated by wide‐angle X‐ray diffraction (WAXD) and differential scanning calorimetry (DSC). The results illustrated that the crystallization and melting behaviors of the copolymers were depended on the copolymer composition and the relative length of each block in copolymers. Crystallization exothermal peaks (T_c) and melting endothermic peaks (T_m) of PEG block were significantly influenced by the relative length of PCL blocks, due to the hindrance of the lateral PCL blocks. With increasing of the length of PCL blocks, the diffraction and the melting peak of PEG block disappeared gradually in the WAXD patterns and DSC curves, respectively. In contrast, the crystallization of PCL blocks was not suppressed by the middle PEG block. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Enzymic hydrolysis of animal fats in organic solvents at temperatures below their melting points

Lipase fromCandida rugosa catalyzed the hydrolysis of inedible beef tallow and pork lard (edible and inedible) in the presence of organic solvents at temperatures below the melting point of the fat. Reactions were carried out at 50% substrate with 180 lipase units per gram of fat in a two-liter reactor. In the presence of isooctane (5-10%) beef tallow yielded 94% hydrolysis in 24 hr both at 37° and 31°C. Edible pork lard yielded 97% hydrolysis under these conditions and at temperatures as low as 25°C, while inedible lard gave hydrolysis intermediate between the other two fats.     

Sonocrystallization of a Tristearin‐Free Fat

The objective of this study was to fractionate a purified interesterified fat to eliminate tristearin (SSS) and to evaluate the crystallization behavior of the tristearin‐free fat. The fractionated sample was crystallized with and without the application of high‐intensity ultrasound (HIU) by supercooling the sample at 2 °C. In the absence of SSS, the crystallization process was driven by low‐melting‐point triacylglycerols (TAG) such as OSS and OOS (O, oleic; S, stearic acid). There were no differences observed in the crystallinity in the sample based on the solid fat content (P > 0.05) along with any microstructural differences. In addition, an increase in the enthalpy of melting was observed upon sonication, indicating higher crystallinity (P < 0.05). Stronger intramolecular forces were formed in the sonicated samples as evidenced by increased viscoelastic parameters such as the elastic modulus (G′) and storage modulus (G″) (P < 0.05). G′ values increased from 138.25 ± 41.30 to 939.73 ± 277.45 Pa while the G″ values increased from 39.15 ± 8.98 to 149.77 ± 16.00 Pa (P < 0.05). Change in viscosity was not observed as a consequence of sonication (P > 0.05). This study showed that HIU was effective in changing the crystallization behavior of SSS‐free fats with low‐melting TAG.     

Physicochemical and Rheological Characterization of Roll-in Shortenings

The composition and physical properties of roll‐in shortenings, commonly rich in trans and saturated fatty acids, were investigated and compared to other specialty fats, to provide insights into the physico‐chemical origins of their functionality. Triacylglycerols and fatty acid composition, polymorphic and melting behavior, solid fat content and large deformation rheological properties were determined. Roll‐in shortenings contained higher amounts of trisaturated and unsaturated triacylglycerols (12–27 %; 47–62 %) than other shortenings (9–11 %; 6–44 %). However, all exhibited high levels of saturates and trans fatty acids and similar crystal characteristics: β′ or mixed β′ and β, irrespective of their end use. Roll‐in shortenings had comparable melting peaks (42–52 °C) but sharper melting endotherms with higher enthalpies (38.6–43.3 J/g) than other bakery fats (18.7–25.4 J/g). This was in accordance with their well‐defined short spacings, indicative of smaller crystallites with more‐ordered packing. Solid fat profiles of roll‐in shortenings were akin to all purpose and cake interesterified shortenings, but not to all‐purpose and icing shortenings which displayed substantial melting as temperature rises. Differences in large deformation rheology (yield stress: σ^*, apparent Young modulus: E_app, yield value: C) were marginal and inconsistent with their solid fat content. Roll‐in shortenings exhibited E_app, σ and C in the order of 1–2 × 10⁶, 4–7 × 10⁴, and 7–29 × 10⁴ Pa, respectively. Particularly, the σ*and C, previously established as major parameters to specify the functionality of roll‐in shortenings, were not significantly different (p > 0.05). Overall, roll‐in shortening differed from other samples in regard to molecular makeup but not greatly in their physical parameters, suggesting that triacylglycerol composition has important implications on their functionality.