乳化法—火焰原子吸收光谱法测定奶粉中的锌

用乳化剂ＯＰ将奶粉乳化成稳定的乳浊液，喷入空气－乙炔火焰中，以标准加入法测定锌，测定结果与灰化法一致，方法简便，准确。     

Comparison of chemical properties of food products processed by conventional and ohmic heating

The effect of ohmic and conventional heat processing of different food products on their chemical and physical parameters was studied. Depending on the food being analysed, parameters such as pH, total solids, ash, titratable acidity, ascorbic acid, total sugars, total fatty acids, total phenolic compounds, and anthocyanins content were determined before and after ohmic and conventional pasteurization techniques and the results were compared using one-way analysis of variance. In goat milk samples treated by ohmic technology the pH value (6.58) and total fatty acids content in milk fat (86.5 mass %) were comparable to those found in milk treated by conventional process, however, ohmically treated samples presented a lower content of lactic acid, 0.13 %. In cloudberry jam samples treated by ohmic technology the results of some of the main parameters tested, such as total sugar content 46.1 mass %, ascorbic acid content 2.83 mass %, and titratable acidity 6.01 mass % (as citric acid) did not show significant differences when compared with samples treated by conventional technology. Presented at the 33rd International Conference of the Slovak Society of Chemical Engineering, Tatranské Matliare, 22–26 May 2006.     

钙黄绿素蓝荧光法测定食品中的微量锌（Ⅱ）

本文研究了在ＣＴＭＡＢ存在下，用钙黄绿素蓝荧光法测定食品中的微量锌（Ⅱ）的实验条件。在本实验条件下，Ｚｎ（Ⅱ）与钙黄绿素蓝生成１：１的配合物使钙黄绿素蓝的荧光增强，最大激发波长和最大发射波长分别为３５３ｎｍ和４４０ｎｍ。     

A new procedure for bovine milk digestion in a focused microwave oven: gradual sample addition to pre-heated acid

Milk samples can be efficiently digested using a focused microwave oven, however the conventional procedure of addition of concentrated acids to the liquid sample leads to digestates with elevated acidity and residual carbon concentrations. In this work a focused microwave oven was applied for acid digestion of bovine milk samples using a conventional and an alternative procedure based on gradual sample addition to hot and concentrated acids. A two-level 2³ full factorial design experiment with eight runs was carried out to evaluate the optimum experimental conditions for reducing both the residual carbon and the final acidity of digestates. The three studied parameters were: temperature of the digestion medium for sample addition, addition of sulfuric acid before the sample or during the first step, and number of aliquots of the sample gradually added. The best conditions were attained by adding small aliquots of milk (ten-fold a volume of 0.5 ml added during 5.0 min) to a digestion mixture containing 3.0 ml nitric acid plus 1.0 ml sulfuric acid heated at 105 °C. It was demonstrated that the digestion efficiency of the alternative procedure was better than the conventional procedure, i.e. 98 and 80%, respectively. The alternative procedure was applied for determination of Ba, Ca, Cu, K, Mg, Na, P, and Zn in whole and non-fat bovine milk. The accuracy was proved using two certified reference materials (whole and non-fat milk powder).     

Thermal transitions and fat droplet stability in ice-cream mixmodel systems

We studied thermal transitions and physical stability of oil-in-water emulsions containing different milk fat compositions, arising from anhydrous milk fat alone (AMF) or in mixture (2:1 mass ratio) with a high melting temperature (AMF–HMT) or a low melting temperature (AMF–LMT) fraction. Changes in thermal transitions in bulk fat and emulsion samples were monitored by differential scanning calorimetry (DSC) under controlled cooling and reheating cycles performed between 50 and –45°C (5°C min^–1). Comparison between bulk fat samples and emulsions indicated similar values of melting completion temperature, whereas initial temperature of fat crystallization (T_onset) seemed to be differently affected by storage temperature depending on triacylglycerols (TAG) composition. After storage at 4°C, T_onset values were very similar for emulsified and non-emulsified AMF–HMT blend, whereas they were lower (by approx. 6°C) for emulsions containing AMF or mixture of AMF–LMT fraction. After storage at –30°C, T_onset values of re-crystallization were higher in emulsion samples than in bulk fat blends, whatever the TAG fat composition. Light scattering measurements and fluorescence microscopic observations indicated differences in fat droplet aggregation-coalescence under freeze-thaw procedure, depending on emulsion fat composition. It appeared that under quiescent freezing, emulsion containing AMF–LMT fraction was much less resistant to fat droplet aggregation-coalescence than emulsions containing AMF or AMF–HMT fraction. Our results indicated the role of fat droplet liquid-solid content on emulsion stability.     

柱后衍生-荧光检测高效液相色谱法快速测定鲜牛奶中链霉素残留量

牛奶样品经磷酸溶液提取，提取液用苯磺酸阳离子交换柱和C18固相萃取柱净化，链霉素残留液用甲醇从C18固相萃取柱上洗脱，经旋转蒸发器减压蒸干，残渣用0．01mol／L庚烷磺酸钠溶液溶解，用柱后衍生-高效液相色谱荧光检测器在激发波长263nm和发射波长435nm测定．方法线性范围为0.01～0．10mg／kg；在0．01～0．10mg／kg范围，三个添加水平的回收率为78．3％～80．2％，变异系数(CV)为7．4％～12．4％，方法检出限为0．005mg／kg．     

Comparison of two methods for the extraction of fat from human milk

We compared two methods for the extraction of fat from human milk. Pure fat extraction techniques are necessary for qualitative and quantitative analysis of milk fat, of which triglycerides account for more than 98%. Method I was a conventional liquid-liquid system for the fat extraction while method II was a faster approach using a haematocrit technique. No significant differences were observed between both methods neither in the fat content determined gravimetrically, nor in qualitative and quantitative analysis of triglycerides by high-performance liquid chromatography (HPLC) with evaporative light-scattering detection (ELSD). We conclude that method II offers substantial advantages over the conventional method (method I). The former requires less reagents and material and is simpler and less time-consuming (approximately 30 min instead of 90 min). Therefore, a new method will make it possible to extract fat of more human milk in the same time.     

蛋白质组学在人乳蛋白质研究中的应用

人乳是新生儿最理想的天然食物，蛋白质是人乳中最主要的营养成分之一。随着蛋白质组学技术的发展，利用蛋白质组学的方法研究人乳蛋白质也取得了一些研究成果。本文综述了近年来蛋白质组学技术在人乳蛋白质研究中的应用，分别从人乳蛋白质的组成研究、动态变化、人乳与其他来源乳汁的蛋白质差异比较、人乳磷酸化蛋白和糖基化蛋白研究、人乳内源肽的研究及人乳蛋白与疾病等几个方面进行了阐述。蛋白质组学技术使人乳蛋白质的研究进入了微量营养研究的时代，人乳蛋白质组学的研究成果将为母婴健康提供更好的保障。     

The Selection of the Optimal Impregnation Conditions of Vegetable Matrices with Iodine

This study aimed to determine the use of selected vegetables (pumpkin, cauliflower, broccoli, carrot) as carriers of potassium iodide (KI) and potassium iodate (KIO₃) by determining changes in iodine content under various conditions of impregnation as the degree of hydration, impregnated sample temperature, and impregnation time. The influence of these conditions on iodine contents in vegetables after their fortification and storage (21 °C/230 days) was analyzed. The results showed that all selected vegetables could be efficient iodine carriers. However, the conditions of the impregnation process are crucial for fortification efficiency, particularly the degree of hydration and the temperature of the impregnated samples before drying. The results showed that the lowest iodine content was in samples fortified at 4 °C and 1:4 hydration. On the other hand, the highest reproducibility of iodine was for the following fortification conditions: temperature of −76 °C and hydration of 1:1. The studies confirmed the higher stability of iodine in KIO₃ form compared to KI. To increase recovery of the introduced iodine in the product after drying, using the conditioning step at 4 °C is not recommended. We recommend freezing vegetables immediately after the impregnation process     

Extractability of Curcuminoids Is Enhanced with Milk and Aqueous-Alcohol Mixtures

In this study, we evaluated the extractability of three curcuminoids (curcumin, demethoxycurcumin, and bisdemethoxycurcumin) from turmeric powder in several solvents using high-performance liquid chromatography (HPLC) with the diode-array detection method. These solvents include water, milk (homogenized, 2% reduced fat, low fat, fat free, soy, almond, coconut, and milkadamia), and aqueous ethanols (0%, 4%, 10%, 20%, 30%, 40%, 50%, and 100%). Ambient water was able to extract only 0.55 mg/g of curcuminoids, whereas warm water extracted more than four-fold higher amounts (2.42 mg/g). Almond, coconut, and milkadamia milk were able to extract only small amounts of curcuminoids at ambient temperatures (0.01–0.07 mg/g). The extractability of curcuminoids in these milk types did not improve, even in warm conditions (0.08–0.37 mg/g). Whereas dairy and soy milk extracted 6.76–9.75 mg/g of curcuminoids under ambient conditions, their extractability increased significantly in warm conditions by 30–100% higher (11.7–14.9 mg/g). The solubility of curcuminoids also varied remarkably in different proportions of aqueous-alcohol mixtures. With 4% ethanol, only 1.7 mg/g of curcuminoids were extracted, and the amounts improved with the increase in ethanol content up to 50% (32.2 mg/g), while 100% ethanol extracted a similar amount as 50% ethanol (34.2 mg/g). This study suggests that the extractability of curcuminoids from turmeric will be dependent on the type of diets consumed with the turmeric supplements.