MODELING of TRIGLYCERIDE DISTRIBUTION and YIELD of ANHYDROUS MILK FAT IN A CONTINUOUS SUPERCRITICAL CARBON DIOXIDE EXTRACTION SYSTEM

A mathematical model was developed for continuous extraction of multicomponent mixture anhydrous milk fat (AMF) with supercritical carbon dioxide (SC-CO₂) as its solvent. At a constant temperature and pressure, the triglyceride mixture was separated into vapor and liquid fractions. the composition distribution (indicated by acyl carbon number), mass distribution and yield of AMF were calculated by the model based on thermodynamic equilibrium and material balance. the feed composition and distribution coefficient were required information in this model. the experimental values for the extract were in good agreement with the model used. the results for the raffinate were not as precisely modeled. the main factors which affected the model were temperature, pressure, solvent/feed ratio and extract fraction.     

HIGH HYDROSTATIC PRESSURE EXTRACTION OF SALIDROSIDE FROM RHODIOLA SACHALINENSIS

A nonthermal process, high hydrostatic pressure (HHP), was used as a new extraction technique to obtain salidroside from Rhodiola sachalinensis. The leaching rates of salidroside were measured under different treatment conditions. When the material was treated under 500 MPa of hydrostatic pressure with 50 times of volume 60% (v/v) of ethanol solution as the extracting solvent, the leaching rate of salidroside was up to 0.401% in 3 min, while that of ultrasonic extraction was at 0.288% in 30 min and that of reflux extraction was at 0.302% in 120 min. The HHP extraction technique showed high efficiency in extracting salidroside at room temperature using moderate ethanol concentration.

PRACTICAL APPLICATIONS

Rhodiola is prevalently used as a safe and effective antifatigue drug and as an adaptogen around the world. But the common extraction methods used to yield commercial products are still traditional ones, which could easily lead some thermosensitive ingredients to lose their biologic activities. The nonthermal extraction method is the key point of the realization of herb modernization. The high hydrostatic pressure (HHP) technique can be operated at room temperature and can shorten processing time. The extract produced by the method has proved to be of higher extraction yield than traditional varieties. In addition, the HHP technique only consumes electric energy without exhaust emission, which is an environment-friendly method. In the future, we will cooperate with those far-seeing companies to achieve its industrialization. The annual sale of herbs in the whole world has reached 30 billion. We do not doubt the prospect of this technique.     

HIGH PRESSURE DESTRUCTION KINETICS of INDIGENOUS MICROFLORA and ESCHERICHIA COLI IN RAW MILK AT TWO TEMPERATURES

Raw milk with a high count of indigenous microflora, with and without inoculated Escherichia coliK‐12 (ATCC‐29055), was subjected to high pressure treatment (250–400 MPa) for various holding times (0–80 min) at two temperatures (3 and 21C). From the microbial survivor data, an instantaneous pressure kill value (IPK) which represented the effect of a pressure pulse, and kinetic parameters (rate constant, D‐value, z‐value and activation volume) were evaluated based on pressure hold‐time first order kinetics. Both IPK and D values were dependent on pressure level and temperature. Higher pressures, longer holding times and lower temperatures resulted in larger destruction of microorganisms, and E. coli was more pressure sensitive than indigenous microflora. Pressure dependency of kinetic parameters was well described by both pressure death time and Eyring‐Magee models. At 3 and 21C, the z_p values were 227 and 240 MPa and λV# values were ?2.32 and ?2.34 (x 10^?5 m³ mole^?1), respectively, for indigenous microflora, and 179 and 205 MPa (z_p) and ?2.95 and ?2.75 (x 10^?5 m³ mole^?1) (λV#), respectively, for E. coli.     

FIBER OPTIC SENSOR RESPONSE TO LOW LEVELS OF FAT IN SKIM MILK

A fiber optic transmission technique using single fibers to deliver and receive light was investigated for measuring the milkfat content of homogenized skim milk. Light transmission through skim milk for wavelengths of 400 to 1000 nm was measured using a fiber optic spectrophotometer. Transmission was measured for distances of 0.5, 1, 2, 3, 4 and 5 mm and for milk containing 0.05 to 0.21 wt% milkfat. Skim milk was centrifuged, and the resulting fractions mixed to yield samples with 5 different milkfat levels. Three optical responses were tested for correlation with milkfat content. One used a light intensity measurement at a single transmission distance of 4 mm, the second used the light intensity ratio of two wavelengths at a single transmission distance of 4 mm, and the third used six different transmission distances to determine a light extinction coefficient at a single wavelength. The calibration equations from all three methods were able to predict sample milkfat content with a RMSE of 0.008 to 0.012 wt%. Statistical analysis did not find a significant difference between the three methods. Hence, for simplicity using a single transmission distance is attractive for further sensor design.     

超高压对牛乳纤溶酶和脂肪酶的钝化效应研究

以牛乳中纤溶酶和脂肪酶为研究对象，在40MPa～900MPa压力下结合几种施压介质温度、施压时间和施压方式处理鲜乳，分析了各因素对牛乳中纤溶酶和脂肪酶活性的影响。研究结果表明，在40MPa～80MPa处理条件下，乳中纤溶酶和脂肪酶的活性都有所提高，但压力对提高酶活性的作用不显著（P〉0．05）。在室温、500MPa～900MPa施压条件下，900MPa处理4min能使纤溶酶和脂肪酶完全钝化。在室温、350MPa～850MPa施压条件下，纤溶酶和脂肪酶的最小钝化压力均在450MPa～500MPa，850MPa和750MPa施压条件可使纤溶酶和脂肪酶完全钝化。压力对两种酶的钝化效应极显著（P〈0．01），而施压时间和施压方式对酶的钝化效应不显著（P〉0．05）。在不同的施压方式下，间歇式施压对酶的钝化效应明显。钝化纤溶酶的最佳工艺参数为850MPa、间歇式加压处理4min，钝化脂肪酶的最佳工艺参数为750MPa、间歇式加压处理8min。     

超高压技术在低过敏大米中的应用

对大米过敏原进行了简介,阐述了超高压消除大米过敏原的机理,最后论述了超高压消除大米过敏原的影响因素和处理条件.     

脂肪酶的固定化及其水解天然黄油研究

利用吸附法、交联法和包埋法将脂肪酶固定在5种载体上，由吸附法制备的固定化脂肪酶活性最大，用其催化天然黄油的水解反应，短时间内水解率可达到20％左右。且有较高的可操作性，重复利用5次，活性依然保留为原来的96％。     

超高压在蔬菜加工中的应用

应用超高压技术能使蔬菜中酶的活性降低、杀灭微生物、保留蔬菜的风味和营养成分等。综述超高压加工的基本原理及特点、超高压技术在蔬菜加工中的应用以及超高压技术在蔬菜加工中的应用前景。     

高效液相色谱法测定奶粉中泛酸

建立了利用HPLC法测定奶粉中泛酸的方法：色谱柱：Zorbax SB-C18;流动相：乙腈∶0.02mol/LKH2PO4=4∶96;流速：1mL/min;进样量：20μL;DAD检测器,波长200nm。方法在1μg/mL-20μg/mL之间线性良好,泛酸的回收率在86%-102.87%之间,RSD值在0.44%-3.23%之间。对市场上几种奶粉的检测发现,泛酸含量均符合要求,有的产品中泛酸含量远高于标示值。     

有机溶剂浸提番茄红素的工艺优化

采用有机溶剂浸提法从番茄中提取番茄红素.先确定研究的因素,再采用单因素试验确定试验因素的最好条件,最后采用L9(34)正交试验,确定提取的最佳溶剂及最佳工艺条件.在单因素试验中得到皂化温度、乙醇处理时的料液比和二氯甲烷振荡提取时间的各因素的最佳条件,而在正交试验中得到提取番茄在皂化温度、乙醇处理时的料液比和二氯甲烷振苏提取时间的最佳工艺条件:皂化温度为50℃;乙醇处理时料液比为1∶3;二氯甲烷振荡提取时间为35 min.     

DROMEDARY MILK FAT: BIOCHEMICAL, MICROSCOPIC AND RHEOLOGICAL CHARACTERISTICS

Structural and physicochemical characteristics of dromedary milk fat were investigated and compared with those of cow's milk fat. The fatty acid composition of dromedary milk fat showed the presence of very small amounts of short-chain fatty acids (C4–C12) and a higher content of 16:1 and 18:0. The microscopic study showed a discontinuous phase of globules with a smaller size but presenting a relatively thicker membrane layer. The rheological and the melting studies showed that dromedary milk fat on the one hand had a relatively higher fusion point, a higher fusion enthalpy and a higher apparent viscosity and on the other hand a relatively lower value of storage modulus (G'). These various characteristics correlated with the results obtained by microscopy and chromatography.     

RELATIONSHIP BETWEEN VISCOSITY AND FAT CONTENT OF MILK AND CREAM

A comparison of the published data on the flow behaviour of milk and cream at higher shear rates reveals conflicting results which can be explained partly by differences in experimental conditions. Among others, cold agglutination and churning effects appear to play a role. In the absence of these effects and at not very low shear rates, milk behaves as a Newtonian liquid. Excellent agreement is obtained between measured viscosity (η) as a function of fat content (ø f ) and theoretical relations between η; and the volume fraction of dispersed particles, but only if the volume occupied by the protein particles and sugar molecules in the milk is taken into account.     

EFFECT OF DIETARY MILK CREAM AND EGG YOLK FAT ON SERUM AND LIVER LIPID PROFILE IN RATS

Influence of dietary fat from milk and egg yolk on serum and liver lipid profile was studied in rats. Rats fed milk fat at 5% level for 8 weeks showed a 17% decrease in serum cholesterol and 31% decrease in triacylglycerol compared to the control group of rats fed groundnut oil (GNO). Liver cholesterol was decreased by 20% in the milk fed group. There was no difference in serum cholesterol concentration of rats fed egg yolk compared to the control animals. However, triacylglycerol and phospholipids in serum of rats fed egg yolk were decreased by 20 and 24%, respectively. In another set of experiments animals were rendered hypercholesterolemic by feeding a diet containing 0.5% cholesterol. Addition of milk fat in the diet decreased serum and liver cholesterol by 11 and 17%, respectively, compared to rats fed on a control diet. Similarly, triacylglycerols were decreased by 23 and 8%, respectively, in serum and liver of animals given     

INACTIVATION OF ESCHERICHIA COLI IN SKIM MILK BY HIGH INTENSITY PULSED ELECTRIC FIELDS

The inactivation of microorganisms is the most important function in the processing of milk and dairy products. Traditionally, this purpose is realized by thermal treatment, but heat produces alterations to flavor and taste in addition to nutrient loss. The high intensity pulsed electric field (PEF) treatment should be a good alternative to heat because demonstrations have shown PEF can reduce the Escherichia coli survival fraction in aqueous solutions and model foods. In this study, PEF treatment was found to inactivate E. coli in skim milk (inoculum 10⁹ CFU/mL) at 15C. The microorganism inactivation satisfied Hülsheger's model following a first order kinetic for both the electric field intensity and number of pulses when skim milk inoculated with E. coli was treated in a static or continuous flow chamber. PEF treatment in a continuous system when the critical electric field (E_c) and minimum number of pulses (n_min) were 12.34 kV/cm and 2.7 at 30 kV/cm and 30 pulses (0.7–1.8 μs pulse width) inactivated more microorganisms than in a static system. It has also been proven that increasing the pulse duration increases the E. coli inactivation. The inactivation of E. coli using PEF is more limited in skim milk than in a buffer solution when exposed to similar treatment conditions of field intensity and number of pulses due to the complex composition of skim milk, its lower electrical resistivity and the presence of proteins.     

高温灭菌奶的生产

以牛乳为原料,通过正交试验确定生产灭菌奶的工艺条件为：115℃、20min,磷酸盐3.0/万,复合乳化稳定剂0.15%.