奶牛采食量检测仪的设计与技术研究

为了及时、准确地测量出奶牛的采食量，本文根据奶牛在采食、反刍和吞咽时的行为表现，本文提出了通过传感器实时检测奶牛颞窝部位的运动规律来反映牛只采食量大小的原理，并根据此原理研制了一种基于单片机控制和检测的奶牛采食量自动检测仪。该检测仪能够准确地测量并计算出奶牛的吞咽次数，然后根据奶牛吞咽时食团质量的大小计算出奶牛的采食量，并且可将一定时期内的采食量进行回归分析制定出相应的营养方案。本检测仪实现了快速、方便和精确的采食量测定目的。     

固相萃取-离子色谱法测定乳与乳制品中可致癌物硝酸盐的研究

研究了采用固相萃取-离子色谱法测定乳与乳制品中可致癌物硝酸盐.将制备好的样品加入适量乙酸沉淀蛋白,离心,取上清液以4mL/min的流速通过DIONEX OnGuard Ⅱ RP固相萃取柱去除脂肪等疏水性化合物后,直接进样测定.用30mM的KOH溶液等度淋洗,流速为1.0mL/min,采用AS11-HC型阴离子色谱柱进行分析.在此检测条件下,硝酸盐有很好的线性（r=0.9999）,回收率为85.5%～108%.实验结果表明,该方法简便、快速,且检测结果准确.     

Contribution oftrans-18∶1 acids from dairy fat to european diets

Twelve commercial samples of French butter, purchased in October–November, and 12 other samples, purchased in May–June, were analyzed with particular attention to theirtrans-octadecenoic acid contents. The isomeric fatty acids were quantitated by a combination of gas-liquid chromatography (GLC) of total fatty acids as isopropyl esters on a polar capillary column (CPSil 88) and of silver nitrate-impregnated thin-layer chromatography followed by GLC of the pooled saturated (used as internal standards) andtrans-octadecenoic acid fractions. Autumn butters contained 3.22±0.44%trans-octadecenoic acids (relative to total fatty acids), whereas those collected during the spring contained 4.28±0.47% (P<0.01). Minimum and maximum values for the two sets of butters were 2.46 (autumn) and 5.10% (spring), respectively. The annual mean value for thetrans-octadecenoic acid content in all butter samples was 3.8% of total fatty acids (ca. 2% for thetrans-11 18∶1 acid). This value allows calculation of the daily individual intake oftrans-octadecenoic acids from dairy products by populations of member states of the European Economic Community (EEC). It varies from 0.57 g (Portugal) to 1.66 g (Denmark). The mean value for the twelve countries of the EEC is 1.16 g/person/d, which is close to data published for the United States. In France, the consumption oftrans octadecenoic acids from dairy fat is higher than that from margarines (ca. 1.5 vs. 1.1 g/person/d).     

A new short-path distillation system applied to the reduction of cholesterol in butter and lard

A molecular distillation plant, built particularly to increase the separation efficiency and to obtain safer working conditions, was tested to remove cholesterol from anhydrous butter and lard. A preliminary experiment was carried out with butter to evaluate the fractionation obtained at temperatures between 190 and 250°C and residual pressures between 10⁻³ and 10⁻⁴ torr. A second experiment was carried out at 185°C and at the maximum operational vacuum, evaluating the fractionation achieved within a time scale between 30 and 180 min. Cholesterol was almost completely removed during the second hour with minimal loss of low-molecular weight triglycerides. An experiment was carried out with lard at 250°C and maximum achievable operational vacuum (10⁻⁴ Torr), lasting approximately 6 h, and cholesterol was removed almost completely during the second hour without significant modifications in the triglyceride composition. This situation remained constant throughout the duration of the test.     

基于卟啉传感器的三聚氰胺检测研究

针对传统三聚氰胺检测方法成本高、分析时间长等不足之处,根据卟啉阵列与液体中分子或离子结合产生光谱变化的基本原理,设计了一种基于卟啉化学传感器的三聚氰胺检测系统.针对系统的软硬件设计,研究了光谱信号、模式识别、通过图像处理获得目标物质的特征信息,经过匹配识别,从而实现目标物质的检测.结合实例,运用该装置对牛奶中三聚氰胺进...     

应用FIAstar5000和透析膜测定牛奶及乳制品中的亚硝酸盐和硝酸盐

样品在热萃取缓冲溶液中,是悬浊液。离心分离并快速冷却分离出脂肪。脱脂后的溶液注射到流动注射分析系统中。系统内透析膜用来除去蛋白质和残余脂肪。通过镉将硝酸根离子还原至亚硝酸根离子。在一个酸性的对氨基苯磺酰胺溶液中,亚硝酸根形成偶氮化合物。它与N-（1-萘基）-乙二胺二盐酸盐（NED）结合形成紫色的含氮染料,在540nm处进行测定。此方法为测定牛奶亚硝酸盐和硝酸盐的常规方法,检出限可达0．02mg／kg,RSD〈10,回收率〉90％。     

Thermal analysis of isothermal crystallization kinetics in blends of cocoa butter with milk fat or milk fat fractions

The kinetics of isothermal crystallization of binary mixtures of cocoa butter with milk fat and milk fat fractions were evaluated by applying the Avrami equation. Application of the Avrami equation to isothermal crystallization of the fats and the binary fat blends revealed different nucleation and growth mechanisms for the fats, based on the Avrami exponent. The suggested mechanism for cocoa butter crystallization was heterogeneous nucleation and spherulitic growth from sporadic nuclei. For milk fat, the mechanism was instantaneous heterogeneous nucleation followed by spherulitic growth. For milk fat fractions, the mechanism was high nucleation rate at the beginning of crystallization, which decreased with time, and plate-like growth. Addition of milk fat fractions did not cause a significant change in the suggested nucleation and growth mechanism of cocoa butter.     

Chemical and physical characteristics of cocoa butter substitutes, milk fat and malaysian cocoa butter blends

Two ternary systems of confectionery fats were studied. In the first system, lauric cocoa butter substitutes (CBS), anhydrous milk fat (AMF), and Malaysian cocoa butter (MCB) were blended. In the second system, high-melting fraction of milk fat (HMF42) was used to replace AMF and also was blended with CBS and MCB. CBS contained high concentrations of lauric (C_12:0) and myristic (C_14:0) acids, whereas palmitic (C_16:0), stearic (C_18:0), and oleic (C_18:1) acid concentrations were higher in MCB. In addition, AMF and HMF42 contained appreciable amounts of short-chain fatty acids. CBS showed the highest melting enthalpy (143.1 J/g), followed by MCB (138.8 J/g), HMF42 (97.1 J/g), and AMF (72.9 J/g). The partial melting enthalpies at 20 and 30°C demonstrated formation of a eutectic along the binary blends of CBS/MCB, AMF/MCB, and HMF42/MCB. However, no eutectic effect was observed along the binary lines of AMF/CBS and HMF42/CBS. Characteristics of CBS included two strong spacings at 4.20 and 3.8 Å. MCB showed a strong spacing at 4.60 Å and a weak short-spacing at 4.20 Å. On the other hand, AMF exhibited a very weak short-spacing at 4.60 Å and two strong spacings at 4.20 and 3.8 Å, while HMF42 showed an intermediate short-spacing at 4.60 Å and also two strong short-spacings at 4.20 and 3.8 Å. Solid fat content (SFC) analyses at 20°C showed that CBS possessed the highest solid fat (91%), followed by MCB (82.4%), HMF42 (41.4%), and AMF (15.6%). However, at 30°C, MCB showed the highest SFC compared to the other fats. Results showed that a higher SFC in blends that contain HMF does not necessarily correlate with a stronger tendency to form the β polymorph.     

Relation of fat bloom in chocolate to polymorphic transition of cocoa butter

A special chocolate with spray-dried sugar (50:50 w/w sucrose/20 Dextrose Equivalent corn syrup solids) was made to study the polymorphic changes in cocoa butter crystals using X-ray diffraction. Anhydrous milk fat (AMF) and high-, middle-, and low-melting milk fat fractions were used to replace 2% (w/w) of cocoa butter. Chocolates were tempered, and the consistency of temper among chocolate samples was verified by a temper meter. Chocolates were cycled between 19 and 29°C at 6-h intervals to induce fat bloom. The special chocolates were analyzed by X-ray spectroscopy and colormeter. X-ray analysis on the special chocolates showed polymorphic transition from the βV to the βVI form of cocoa butter. After a lag phase, the percentage of the βVI form rapidly increased. However, the sample made with the high-melting milk fat fraction transformed slowly to βVI. Visual bloom appeared rapidly on the special chocolates made with AMF, middle- and low-melting fractions, whereas visual bloom was very slow to appear on the special chocolates made with high-melting milk fat fraction and on the cocoa butter control. The commercial chocolate responded consistently; the control bloomed rapidly, the AMF exhibited some bloom resistance, and the high-melting fraction inhibited bloom. Despite the βV to βVI transition, the control chocolates with amorphous sugar did not bloom. Since the only difference in the chocolates was sugar microstructure, differences in bloom formation were caused by the microstructure, not the polymorphic transition.