基于不同波段近红外光谱的原料奶主要成分品质检测研究

试验采用不同波段的近红外光谱对原料奶的主要成分进行品质检测。使用2种近红外光谱仪采集原料奶的透反射和漫反射光谱,建立牛奶中蛋白含量、脂肪含量和乳糖含量的定量分析模型。结果表明,蛋白含量、脂肪含量、乳糖糖含量的相关系数(r)分别达到0.9311、0.9218、0.8288,预测误差均方根(RMSEP)分别为1.9144、2.0143、2.804,测量值与浓度参考值之间有着良好的相关性。结果表明,基于近红外光谱的原料奶主要成分品质快速检测准确度高,具有很高的实用价值。     

Technical note: Milk composition in mice—Methodological aspects and effects of mouse strain and lactation day

Analysis in individual mouse milk samples is restricted by small sample volumes and hindered by high fat contents. Miniaturized methods were developed for the analysis of dry matter (DM), crude fat, crude protein (CP), and lactose in individual samples of ≤200 μL of fresh or previously frozen mouse milk and used to compare milk from the mouse strain DU6, the largest growth-selected mouse line worldwide, with unselected mice (CON) on lactation d 3, 14, and 18. Individual milk samples were collected by means of a self-constructed milking machine. Aliquots of 10 μL of milk were used to measure DM [coefficient of variation (CV) <2.1%], which was subsequently used to analyze nitrogen for calculation of CP (CV 2.7%). Crude fat was determined in 100 μL via a miniaturized Röse-Gottlieb method (CV 2.8%). An HPLC protocol was used to analyze lactose in 20 μL of diluted whey (CV 5.3%). The miniaturized methods gave similar results compared with conventional approaches. Homogenization was the most important factor affecting milk composition and its reproducibility. Milk storage at −20°C had no effect on composition. Irrespective of the mouse strain, maximum values of 45.5% DM, 29.8% fat, and 12.7% CP were observed at d 14. The greatest lactose contents were found on d 18 (2.41%). Milk lactose concentration at d 3 was lower in DU6 (1.13 ± 0.10%) than CON (1.67 ± 0.18%). The method provides an accurate assessment of mouse milk composition.     

IPTG与乳糖联合诱导重组大肠杆菌右旋糖酐蔗糖酶表达

研究异丙基硫代-β-D-呋喃半乳糖苷（isopropyl-β-D-1-thiogalactopyranoside,IPTG）与乳糖联合诱导重组大肠杆菌右旋糖酐蔗糖酶表达的效果。在利用IPTG和乳糖分别作为诱导剂对右旋糖酐蔗糖酶工程菌Escherichia coliBL21（DE3）/pET28-dexYG进行诱导表达的基础上,尝试将此两种诱导剂联合使用,在降低成本的同时获得较好的表达效果。在获得最佳培养基的基础上,考察菌体IPTG与乳糖的联合加入量、菌体浓度、诱导时间对右旋糖酐蔗糖酶表达的影响。在菌浓（OD600 nm）达到3.0时,加入0.1 mmol/L IPTG 95 μL＋2.5 g/L乳糖,25 ℃混合诱导培养4 h,酶活力最高,达到40.44 U/mL。IPTG与乳糖联合诱导重组大肠杆菌右旋糖酐蔗糖酶表达可行。     

β‐Galactosidase immobilization into poly(hydroxyethyl methacrylate) membrane and performance in a continuous system

The activity of β‐galactosidase immobilized into a poly(2‐hydroxyethyl methacrylate) (pHEMA) membrane increased from 1.5 to 10.8 U/g pHEMA upon increase in enzyme loading. The K_m values for the free and the entrapped enzyme were found to be 0.26 and 0.81 mM, respectively. The optimum reaction temperatures for the free and the entrapped β‐galactosidase were both found to be 50°C. Similarly, the optimum reaction pH was 7.5 for both the free and the entrapped enzyme. The immobilized β‐galactosidase was characterized in a continuous system during lactose hydrolysis and the operational inactivation rate constant (k_iop) of the entrapped enzyme was found to be 3.1 × 10⁻⁵ min⁻¹. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1367–1373, 1999     

硫酸氢钠催化合成氯乙酸异戊酯的研究

以NaHSO4.H2O为催化剂,通过氯乙酸和异戊醇反应合成了氯乙酸异戊酯。较适宜的反应条件为:氯乙酸50 mmol,n(氯乙酸)∶n(异戊醇)=1∶1.2,NaHSO4.H2O用量为1.5%,环己烷5.0 mL,于98~126℃反应1.5 h,酯收率可达98.45%。     

New narrow tube spray dryer for precise drying history control

Of all the operating conditions in a spray dryer, temperature of the drying medium holds the key parameter in affecting the degree of crystallinity in spray-dried particles. Previous experiments only focus on controlling the drying temperature at the inlet or outlet of drying chamber to delineate the drying history of particles, precluding any detailed studies on particle development throughout the drying duration. Hence, the objective of this work is to address the current limitation by introducing a modified narrow tube spray dryer which enables in situ control of drying history. Essentially, the drying chamber consists of 10 narrow copper tubes with an internal diameter of 1.7?cm. Each individual copper tube can be heated independently to create a unique controlled drying history. Scanning electron microscopy images demonstrate the significant impact of drying history on lactose morphology with possible crystallization by even slight variations in the drying history, which further accentuates the sensitivity of degree of crystallization to temperature. With this newly developed equipment, the detailed drying history conditions can be designed and manipulated to engineer the desired particle properties.     

A study of foam granulation and wet granulation in a twin screw extruder

This research investigated a new technique known as foam granulation for the continuous manufacturing of pharmaceuticals by a twin screw extruder. Six grades of hypromellose were compared as binders in the trials, using two addition methods: foam injection by auxiliary side stuffer feeder and liquid injection directly into the extruder. The produced granules were tested for particle size, Carr compressibility index and characteristic fracture strength. It was found that granulation using foam injection improved powder lubrication inside the extruder and wetting uniformity of the lactose, as well as produced granules having lower Carr indices. © 2012 Canadian Society for Chemical Engineering     

硫酸氢钠催化合成乙酸异丁酯

以冰醋酸和异丁醇为原料,在一水合硫酸氢钠的催化作用下合成乙酸异丁酯,探讨了酸醇物质的量比,反应时间及催化剂用量对酯化率的影响。实验结果表明:一水合硫酸氢钠具有较好的催化活性,酸醇物质的量比为1:2.5,反应时间为150min,催化剂用量为1.2g,酯化率达92.33%。     

一水合硫酸氢钠催化合成柠檬酸三丁酯

以一水合硫酸氢钠作为催化剂合成柠檬酸三丁酯，其优化工艺条件为：催化剂用量为总加料量的4.0％～4．5％，柠檬酸与正丁醇加料比为1：4．5～5．0，反应终点温度145～150℃。所得产品可达到国家优级品标准，酯化率达99％以上；催化剂价廉易得，可重复使用4次，再生容易，无腐蚀，环境污染小。