乌桕类可可脂结晶过程中表现体积变化

为了解乌桕类可可脂(CTCBE)缓冷结晶横向胀罐爆裂原因，研究CTCBE结晶过程中的膨胀特性，采用流体静力法测试了不同等温结晶条件下CTCBE结晶形成的表观密度和表观体积及其横纵向膨胀状况。结果表明，CTCBE缓冷结晶后形成外部和中部两个晶区。在5-25℃的各等温结晶范围内，当结晶温度增加时，外部结晶区域减小、表观密度变化不大；中部结晶区域增大、表观密度明显减小，CTCBE的表观体积、横向、纵向膨胀率均增大，膨胀横向大于纵向。进一步表明CTCBE在自然缓冷固化的表观体积根本上由其结晶温度决定。为有效防止横向胀罐，自然缓冷固化温度应低于10℃。     

A differential scanning calorimetry method to determine the isothermal crystallization kinetics of cocoa butter

This research aimed to reduce the variability on the data obtained from differential scanning calorimetric (DSC) analysis of the isothermal crystallization kinetics of cocoa butter.

To enable transformation of the DSC crystallization peak to a sigmoid crystallization curve, the DSC peak area has to be integrated. Usually, the start and end points of the crystallization peak are determined visually. The result of this visual determination appeared to be very much dependent on the operator, but also differed considerably when the same operator performed the integration several times. By proposing an objective calculation algorithm to determine the start and end points of integration, the variability caused by the operator during the integration procedure could be eliminated. Furthermore, sample preparation and the DSC heating protocol to melt the sample prior to crystallization were studied. Three heating protocols (65 °C for 15 min, 65 °C for 30 min and 80 °C for 15 min) were compared and it was shown that holding at 65 °C for 15 min was sufficient to eliminate any influence of sample history. Two different sample preparation procedures were compared and it appeared that a change in sample preparation procedure had a significant influence on the measured crystallization process. It is thus important to keep this method constant to eliminate the variability caused by it.     

GC/MS法分析奶油中的脂肪酸

利用气相色谱/质谱/计算机联用技术分析人造奶油、天然奶油和新西兰奶油中的脂肪酸,从中鉴定出7种酸:棕榈酸、棕榈油酸、硬脂酸、油酸、亚油酸、亚麻油酸及花生酸。人造奶油含亚油酸比天然奶油含的高。     

Structure elucidation of triglycerides by chromatographic techniques. Part 1: Capillary GC of ozonized triglycerides

Structure determination of triglycerides according to their number of unsaturated fatty acids (N.U.F.A.) is more easily achieved after ozonolysis of their mixtures (fats and oils) than by capillary gas chromatographic analysis of the mixture as such. Analyses performed before and after ozonolysis of cocoa buttel, hazelnut oil, and a mixture of both fats illustrate the potential of this approach to the structure elucidation of triglycerides by chromatographic techniques.     

Thermostability and polymorphism of theobroma oil and palm kernel oil as suppository bases

Thermal stability of pharmaceutical ingredients is an important aspect. In this study, we adopted differential scanning calorimetry (DSC) to investigate thermal stability of suppository bases, theobroma oil (cocoa butter) and a palm kernel oil (PKO) blend. The study shows theobroma oil possesses six polymorphic forms whilst the palm kernel oil blend has three. Upon rescanning, the PKO blend does not show changes in the enthalpy of fusion and the melting point with time, whilst the theobroma oil shows significant reduction, and only regained its thermal stable state after 10 days. This indicates that PKO blend possesses better thermal stability.     

Investigation of the complex thermal behavior of fats

The thermal behavior of three ural fats (displaying very different composition), cocoa butter (CB)², lard, and a stearin obtained from anhydrous milk-fat (AMF) fractionation, were studied by both DSC and X-ray diffraction as a function of temperature (XRDT). To perform temperature explorations between –30C and +80C, at rates identical to those used for DSC and ranging from 0.1 K min^–1 to 10 K min^–1, a new set of X-ray sample-holders, temperature-controlled by Peltier effect, has been developed. It is shown that the three more stable polymorphic forms of CB were easily characterized by either X-ray diffraction or DSC, and existence of two -3L forms was confirmed. On the contrary, the more complex polymorphism of lard and AMF required combined examination by DSC and XRDT and the brightness of the synchrotron source for studies at the highest heating rates. Quantitative analysis of the long spacings of XRDT recordings is invaluable for interpretation of thermal events. For instance, it was found that the simultaneous formation of two polymorphic forms, of apparent long spacing of 34 and 42 å, at the onset of lard crystallization might explain the difficulty of its fractionation.Special thanks to Courtney P. Mudd (NIH, Bethesda) for his pertinent advice on the mounting and use of thermoelectric devices. The study of lard crystallization was initiated by Valerie Portalier and suggested by Jean-Luc Vendeuvre of CTSCCV (Maisons-Alfort). For the AMF part of this study, stearin was fractionated by ADRIA Normandie, while characterization of its thermal properties was performed as part of a research program funded by ARILAIT Recherches and the French Ministry of Research and Technology.     

Melting Properties of Butter Fat and The Consistency of Butter. Effect of modification of cream ripening and fatty acid composition

The cold unspreadable consistency of butter after taking it out of the refrigerator is a rightful objection on behalf of consumers. The possibilities to improve the cold spreadability of butter are: the enrichment with low melting point triglycerides and the application of a good cream-ripening method. In our investigations milk fat fractions of different low melting points and plant oils of low melting points obtained by cold pressing and extraction have been used to change the original fatty acid composition of milk fat. The cream-ripening, the traditional method and the heat-step ripening method, which seemed to be the most effective to our earlier research, have been applied. The consistency of butter was examined by penetration measurements and its thermal characteristics by differential scanning calorimetric (DSC) method. The cold unspreadable consistency of butter can only be improved by the combination of the heat-step cream ripening and enrichment with low melting point triglycerides to get stable consistency at room temperature. The milk fat fraction of melting point below 5°C made the spreadability better but the spreadable consistency of margarine still cannot be attained. Plant oils with melting point below 0°C improved the cold spreadability of butter to a significantly higher degree than the former did. In the case of the same melting point the plant oil obtained by a cold method (pressing) was more effective. There is a close relationship between the consistency of butter and its product characteristics. From DSC curves the cold spreadability and room temperature stability of butter can be directly concluded. This revised version was published online in July 2006 with corrections to the Cover Date.     

Detection of recombined butter by DSC

DSC can be used to quickly determine if a product labeled as butter is actually a recombined butter made without milk. Recombined butter is manufactured from anhydrous milk fat, skim milk powder, water, salt, and lecithin. Melting profiles of tempered samples of natural butter and recombined butter were alike, but DSC curves from 5 to 25°C of untempered refrigerated samples revealed that the enthalpy of the melting transition around 17–20°C was much higher for natural butter than for recombined butter. The procedure for differentiating the two products can be completed in less than 20 min.Mention of brand or firm names does not constitute an endorsement by the U.S. Department of Agriculture over others of a similar nature not mentioned.The authors thank Dr. Thomas Foglia for helpful discussions and Donna Lu for assisting in butter extractions.     

Preparation of Low-Diacylglycerol Cocoa Butter Equivalents by Hexane Fractionation of Palm Stearin and Shea Butter

Herein, we prepared 1,3-dipalmitoyl-2-oleoyl glycerol (POP)-rich fats with reduced levels of diacylglycerols (DAGs), adversely affecting the tempering of chocolate, via two-step hexane fractionation of palm stearin. DAG content in the as-prepared fats was lower than that in POP-rich fats obtained by previously reported conventional two-step acetone fractionation. Cocoa butter equivalents (CBEs) were fabricated by blending the as-prepared fats with 1,3-distearoyl-2-oleoyl glycerol (SOS)-rich fats obtained by hexane fractionation of degummed shea butter. POP-rich fats achieved under the best conditions for the fractionation of palm stearin had a significantly lower DAG content (1.6 w/w%) than that in the counterpart (4.6 w/w%) prepared by the previously reported method. The CBEs fabricated by blending the POP- and SOS-rich fats in a weight ratio of 40:60 contained 63.7 w/w% total symmetric monounsaturated triacylglycerols, including 22.0 w/w% POP, 8.6 w/w% palmitoyl-2-oleoyl-3-stearoyl-rac-glycerol, 33.1 w/w% SOS, and 1.3 w/w% DAGs, which was not substantially different from the DAG content in cocoa butter (1.1 w/w%). Based on the solid-fat content results, it was concluded that, when these CBEs were used for chocolate manufacture, they blended with cocoa butter at levels up to 40 w/w%, without distinctively altering the hardness and melting behavior of cocoa butter.