高效液相色谱法检测强化牛奶中的维生素A

本文介绍了用高效液相色谱法检测强化牛奶中维生素A乙酸酯的方法。样品经乙醇沉淀蛋白质后用石油醚萃取,氮气吹干。液相色谱条件是以YWG—C_(18)(4.6mm×250mm)作色谱柱,甲醇为流动相,流速2ml/min,在UV325nm检测。样品整个分析周期为25～30min。该方法简便快速,重现性好,回收率95%～102%,变异系数小于3.5%。     

Preliminary study of saffron (Crocus sativus L. stigmas) color extraction in a dairy matrix

Saffron spice has been used for decades as an ingredient in many dairy products but changes in its coloring properties related to milk characteristics have not been paid appropriate attention. Saffron color was studied in ewes’ milk at different fat levels and saffron concentrations using tristimulus colorimetry. In order to evaluate saffron extraction, different temperatures and extraction times were tested. Color changes were demonstrated to be statistically significant when increasing the fat content in milk, as well as saffron concentration. The higher milk fat content, turned the extracts brighter and yellower, while less red and vivid, opposite to results obtained by increasing saffron concentration. Extraction time was not significant for color extraction. Milk extracts resulted slightly brighter and yellower when increasing temperature, probably due to crocetin esters degradation or isomerization from trans to cis configuration. Temperatures between 37 and 70 °C are recommended to avoid structural changes in milk or saffron. Color changes could be due to interactions mediated by phospholipids between milk fat globules and crocetin esters, as well as minor saffron carotenoids.     

Effect of processing conditions on physical properties of a milk fat model system: Rheology

The effect of processing conditions on rheological behavior of three blends of 30, 40, and 50% of high-melting fraction [melting point measured as Mettler dropping point (MDP)=47.5°C] in low-melting fraction (MDP=16.5°C) of milk fat was studied. The effects of cooling and agitation rates, crystallization temperature, chemical composition of the blends, and time of storage on complex, storage and loss moduli were investigated by dynamic mechanical analysis (DMA). Compression tests were performed on samples using frequency values within the linear viscoelastic range (1 to 10 Hz). Loss modulus was, on average, 10 times lower than elastic modulus and was generally not affected by processing conditions. Samples showed a more solid-like behavior that was better described by storage modulus. Storage modulus varied with all processing conditions used in this study, and even for the same solid fat content, different rheological properties were found. Storage and complex modulus increased with temperature of crystallization (25 to 30°C), even though solid fat contents of samples measured after 24 h at 10°C were the same. Moduli were higher for samples crystallized at slow cooling rate, decreased with agitation rate, and were lower for the 30–70% blend at all processing conditions used. Storage moduli also increased with storage time. Shear storage modulus was calculated from the DMA experimental data, and the results were in agreement with the values reported in literature for butter systems. Fractal dimensions calculated for these systems showed a significant decrease as agitation rate increased in agreement with the softening effect reported for working of butter.     

微多蛋白素饲喂产奶牛生物活性试验

微多蛋白素饲喂产奶牛试验,通过对试验组和对照组在各阶段产奶量变化的比较及乳品质量指标的测定表明,微多蛋白素饲喂产奶牛具有明显的增奶效果,其奶质量亦得到改善,产奶牛日粮添加微多蛋白素 １００ｇ／头,可增奶 １．７９ｋｇ／头,替代豆饼组饲喂微多蛋白素 １００ｇ／·日,可增奶 ０．２７ｋｇ／头·日。     

高密度二氧化碳技术对牛奶杀菌效果动力学分析

Inactivation kinetics of total bacteria counts in the milk exposed to dense phase carbon dioxide (DPCD) was investigated.Stronger inactivation of total bacteria counts was achieved at higher pressure and exposure time (p<0.05）.Treatment temperature had synergistic effects with pressure and expose time on the inactivation of total bacteria counts,and lg(N/N₀) significantly decreased when increasing the temperature (p<0.05）.The maximum reduction was 5.082-log at 30 MPa and 50℃ for 70 min.The survival curves of total bacteria counts in the milk against pressure or temperature were fitted by the Weibull model with high regression coefficients,and model parameters,a value (scale factor) and b value (shape factor) changed regularly with increasing pressure or temperature.     

Partial Agonistic Actions of Sex Hormone Steroids on TRPM3 Function

Sex hormone steroidal drugs were reported to have modulating actions on the ion channel TRPM3. Pregnenolone sulphate (PS) presents the most potent known endogenous chemical agonist of TRPM3 and affects several gating modes of the channel. These includes a synergistic action of PS and high temperatures on channel opening and the PS-induced opening of a noncanonical pore in the presence of other TRPM3 modulators. Moreover, human TRPM3 variants associated with neurodevelopmental disease exhibit an increased sensitivity for PS. However, other steroidal sex hormones were reported to influence TRPM3 functions with activating or inhibiting capacity. Here, we aimed to answer how DHEAS, estradiol, progesterone and testosterone act on the various modes of TRPM3 function in the wild-type channel and two-channel variants associated with human disease. By means of calcium imaging and whole-cell patch clamp experiments, we revealed that all four drugs are weak TRPM3 agonists that share a common steroidal interaction site. Furthermore, they exhibit increased activity on TRPM3 at physiological temperatures and in channels that carry disease-associated mutations. Finally, all steroids are able to open the noncanonical pore in wild-type and DHEAS also in mutant TRPM3. Collectively, our data provide new valuable insights in TRPM3 gating, structure-function relationships and ligand sensitivity.     

Composition and crystallization of milk fat fractions

Milk fat was fractionated by solvent (acetone) fractionation and dry fractionation. Based on their fatty acid and acyl-carbon profiles, the fractions could be divided into three main groups: high-melting triglycerides (HMT), middle-melting triglycerides (MMT), and low-melting triglycerides (LMT). HMT fractions were enriched in long-chain fatty acids, and reduced in short-chain fatty acids and unsaturated fatty acids. The MMT fractions were enriched in long-chain fatty acids, and reduced in unsaturated fatty acids. The LMT fractions were reduced in long-chain fatty acids, and enriched in short-chain fatty acids and unsaturated fatty acids. Crystallization of these fractions was studied by differential scanning calorimetry and X-ray diffraction techniques. In this study, the stable crystal form appeared to be the β′-form for all fractions. At sufficiently low temperature (different for each fraction), the β′-form is preceded by crystallization in the metastable α-form. An important difference between the fractions is the rate of crystallization in the β′-form, which proceeds at a much lower rate for the lower-melting fat fractions than for the higher-melting fat fractions. This may be due to the much lower affinity for crystallization of the lower-melting fractions, due to the less favorable molecular geometry for packing in the β′-crystal lattice.     

Polymorphism of milk fat studied by differential scanning calorimetry and real-time X-ray powder diffraction

The crystallization behavior of milk fat was investigated by varying the cooling rate and by isothermal solidification at various temperatures while monitoring the formation of crystals by differential scanning calorimetry (DSC) and X-ray powder diffraction (XRD). Three different polymorphic crystal forms were observed in milk fat: γ, α, and β′. The β-form, occasionally observed in previous studies, was not found. The kind of polymorph formed during crystallization of milk fat from its melted state was dependent on the cooling rate and the final temperature. Moreover, transitions between the different polymorphic forms were shown to occur upon storing or heating the milk fat. The characteristic DSC heating curve of milk fat is interpreted on the basis of the XRD measurements, and appears to be a combined effect of selective crystallization of triglycerides and polymorphism.     

Argazol NF活性染料对牛奶/棉混纺织物的染色研究

针对牛奶纤维不耐碱的特点,选择雅格素中性固色活性染料对牛奶/棉混纺织物进行染色研究。研究结果表明:染色温度对上染率的影响较大;染料浓度2%时,75℃保温90分钟、85℃保温60分钟、95℃保温45分钟染色的上染率相当,约为77%;低温长时染色条件更适宜对牛奶/棉混纺织物染色,75℃保温90分钟的染色效果最好;雅格素中性固色活性染料对牛奶纤维/棉混纺织物染色适宜染淡、中色,牢度较好。染料浓度低于4%时,提升性较好。     

A Newly Developed Synbiotic Yogurt Prevents Diabetes by Improving the Microbiome–Intestine–Pancreas Axis

The prevalence of type 2 diabetes mellitus (T2D) is increasing worldwide, and there are no long-term preventive strategies to stop this growth. Emerging research shows that perturbations in the gut microbiome significantly contribute to the development of T2D, while microbiome modulators may be beneficial for T2D prevention. However, microbiome modulators that are effective, safe, affordable, and able to be administered daily are not yet available. Based on our previous pro- and prebiotic studies, we developed a novel synbiotic yogurt comprised of human-origin probiotics and plant-based prebiotics and investigated its impact on diet- and streptozotocin-induced T2D in mice. We compared the effects of our synbiotic yogurt to those of a commercially available yogurt (control yogurt). Interestingly, we found that the feeding of the synbiotic yogurt significantly reduced the development of hyperglycemia (diabetes) in response to high-fat diet feeding and streptozotocin compared to milk-fed controls. Surprisingly, the control yogurt exacerbated diabetes progression. Synbiotic yogurt beneficially modulated the gut microbiota composition compared to milk, while the control yogurt negatively modulated it by significantly increasing the abundance of detrimental bacteria such as Proteobacteria and Enterobacteriaceae. In addition, the synbiotic yogurt protected pancreatic islet morphology compared to the milk control, while the control yogurt demonstrated worse effects on islets. These results suggest that our newly developed synbiotic yogurt protects against diabetes in mice and can be used as a therapeutic to prevent diabetes progression.