Thermal Conductivity and Heat Capacity of Dulce de Leche,a Typical Argentine Dairy Product

Dulce de Leche (caramel jam) is a typical Argentine dairy product similar in composition to sweetended condensed milk. Thermal conductivity and heat capacity of Dulce de Leche were measured to obtain suitable models for predicting these properties at different stages of cooking and for different initial formulations. Thermal conductivity was measured by probe method, and the Maxwell-Eucken model was adequate for prediction purposes. Heat capacity was measured by the calorimetry method for mixtures; data were checked by differential scanning calorimetry. A simple linear correlation between heat capacity and percent solids is proposed for this product. Using uncooked mixtures of powdered milk, sugar, and water, it was shown that chemical changes during cooking do not affect thermal conductivity or heat capacity.     

Chemical and Microbiological Studies on "Duke de Leche" a Typical Argentine Confectionery Product

“Dulce de leche” (milk sweet) is a typical Argentine confectionery product prepared with milk which is concentrated by evaporation in the presence of added sucrose. Its sugar composition, water activity (a_w) and pH values of commercial samples were studied. Water activity varied between 0.80 and 0.85 and pH between 5.6 and 6.3. The effects of practicable modification in a_w pH, storage temperature and addition of potassium sorbate on the growth of an osmotolerant yeast was studied. The best way of inhibiting the growth of the test microorganism at room temperature (25°C) was the addition of sorbate (500 ppm as sorbic acid) together with a pH adjustment to 5.5.     

Advantages of using ohmic heating in Dulce de Leche manufacturing

Ohmic heating (OH, 0, 2, 4, 6, 8, or 10 V cm⁻¹, 72 °C/15 s, 60 Hz) at Dulce de leche processing was investigated. The equipment consisted in an ohmic heating chamber, and rectangular 316 stainless steel electrodes positioned 10 cm apart. OH-treated milk resulted in improvements in the quality parameters of Dulce de leche, with a decrease in energy expenditure (69.85–141.86 vs 1260 kJ) and hydroxymethylfurfural (HMF) levels (7.64–8.54 vs 9.53 μmol L⁻¹), an increase in product homogeneity, and formation of volatile compounds important for the sweetness of Dulce de leche (butanoic acid and 2-furan methanol). In addition, the physicochemical composition, fatty acid profile, and health indices (atherogenic, thrombogenic, desired fatty acids, and hypercholesterolemic saturated fatty acids) of the products remained without changes. In particular, the use of higher electric field (> 6 V cm⁻¹) led to a 14–78% decrease in process time, and improved volatiles profile. OH has proven to be a suitable technology for milk treatment, resulting in improvements in the quality parameters of Dulce de leche with positive impact at the process time and energy expenditure.Industrial relevanceThe Dulce de Leche processing is characterized by long cooking times to acquire its typical characteristic color and flavor. Normally, it is used pasteurized milk as raw material. Ohmic heating decreased the total time of processing in Dulce de leche manufacturing, providing an economy at the in the energy costs without significant change at the quality parameters of the final product.     

Simultaneous Estimation of the Thermophysical Properties of Selected Liquid Dairy Products by a Transient Heat Flow Probe Method

The thermophysical properties of reconstituted whole milk, skim milk, and whey were measured at various temperatures and concentrations. A new method for the simultaneous determination of thermophysical properties using a modified version of current probe theory method was proposed. Two new correction coefficients were introduced, and using the values of these coefficients and an approximate solution of the heat conduction equation, the thermal conductivity and thermal diffusivity of each sample were determined. The specific heat of each sample was estimated from the definition of thermal diffusivity. These properties were expressed as a function of concentration and temperature.     

Silter Cheese,a Traditional Italian Dairy Product: A Source of Feasible Probiotic Strains

Silter cheese is a traditional hard cheese, produced in Valcamonica, Brescia, Italy. A total of 426 lactic strains isolated from Silter were analyzed to determine their probiotic characteristics. 274 out of 426 strains were found to produce bacteriocins against at least one of eight different pathogens (Salmonella enterica, Listeria monocytogenes, Salmonella derby, Salmonella thyphimurium, Salmonella napoli, Staphylococcus aureus, E. coli O157:H7, Salmonella enteritidis). In addition, 211 of 274 bactericin-producer strains adhered to Caco-2 cells and were characterized by RiboPrinter, revealing predominance of Enterococcus faecalis (26%) and Enterococcus durans-faecium (22%). These findings suggest that Silter may qualify as an important source of feasible probiotic strains.     

Sogurt, a Yogurt-like Soybean Product: Development and Properties

Two sogurt products were prepared by fermenting a formulation containing soymilk, 0.15% calcium acetate, 0.5% gelatin, and lactose (0 or 2%) with Lactobacillus casei and Streptococcus thermophilus. Commercial plain yogurt was used as a control. Sogurts were evaluated for aroma, taste, texture, titratable acidity, pH, and color. Sogurts had beany and raisin aromas, more bitter and astringent tastes than yogurt, and slightly sandy mouth- feel. Sogurts and yogurt did not differ (P < 0.05) in intensity of butter aroma. Sogurt with lactose did not differ (P < 0.05) from yogurt in acidity. Sogurts were yellower and firmer than yogurt.     

2007年酿酒、饮料机械行业大事记

一月 广东轻工业机械有限公司经过不断创新，在新产品开发领域取得了卓越的成绩，部分产品还获得了专利。其中，公司自主创新开发的机械阀纯生灌装机（专利号：ZL200420094384．X）、杀菌机（专利号：ZL200710026349．2）、国内最大的码垛机器人（专利号：ZL200420095897．2）获得了用户的一致好评。     

2012年中国酿酒、饮料、乳品机械行业大事记

1月1日,汀苏星A包装机械集川有限公司二二期工程胜利竣工,拥有国际化标准厂房30,000m2,占地面积120亩。不但扩大了生产规模,捉高了生产能力与效率,还改善了生产环境与办公环境。     

大豆分离蛋白在乳制品中的应用

阐述了大豆分离蛋白在乳制品中应用的可行性,介绍了大豆分离蛋白在奶粉、酸奶、冰淇淋、液态奶和乳饮料等产品中应用的现状,提出大豆分离蛋白在奶粉中添加可以与糖混合加入,添加量为1%～5%,同时介绍了分离蛋白在其他乳制品中的应用方法,目前国内外有一些大豆分离蛋白的相关报道,但总体上分离蛋白产品还不够成熟,需要进一步的完善。     

高通量测序技术在乳制品研究中的应用

高通量测序技术以一次并行对几十万到几百万条DNA分子进行序列测定为标志,目前已广泛应用于各个领域,对整个生命科学的发展起到极大的推动作用。本文结合前期开展的一些工作,综述高通量测序技术在乳制品微生物基因组和生物多样性中的应用情况。     

2008年中国酿酒、饮料机械行业大事记

壹月 广东轻工业机械有限公司继续成为嘉士伯啤酒集团供应商，为该集团的马拉维及越南等国外项目提供了优质的啤酒灌装设备产品，同时为新疆乌苏完成二条生产线的安装并进入试运行阶段。2008年广轻产品不只立足于国内市场，还扩大了国外市场的出口，并且得到国际市场的认可，受到国际用户青睐。     

Gelling Properties of Tyrosinase-Treated Dairy Proteins

Protein-based viscous gels can augment or replace carbohydrate-based ones for specific nutritional formulations such as in reduced calorie or low-fat food applications. In this study, slurries of whey protein isolates and calcium caseinate mixed with alginic acid (20% T.S.) were subjected to high-shear homogenization (microparticulation) at 27,000 rpm for 2, 3, 4, and 6 min. The resulting slurries were incubated with mushroom tyrosinase (E.C. 1.14.18.1) at levels of 3, 6, and 9 mg/100 g for 15, 30, and 60 min to facilitate gel formation of the alginic acid with the homogenized dairy proteins. The results indicate that the time of high-shear homogenization had significant (P < 0.05) effect on the viscosities of the gels. Highest gel viscosity was obtained with 6 mg tyrosinase at 60 min, but increases in gel viscosity depended on time of shear, with 2 and 4 min shear resulting in higher viscosity (484 and 6,143 cP) and stronger complex viscosity (49 and 38 Pa.s at 1 rad/s), respectively, compared to the control (69 cP) and (12 Pa.s at 1 rad/s). Gels were stable in refrigerated storage up to 240 h, strengthened with time of refrigeration storage, and became significantly more viscoelastic. Optimal viscous properties were obtained at 4 min microparticulation, 60 min incubation, and 6 mg tyrosinase treatment.     

Q303根霉种曲中高活性凝乳酶特性及新型乳制品的研究

通过Q303根霉三级种、3866根霉三级种、冷干Q303根霉三级种、Q303根霉四级种及其对应产品所酿醪糟浸出液与奶粉发生凝乳反应的各种因素试验发现,高活性凝乳酶活力除了与温度、pH值、添加量等因素有关外,还与制成曲的干燥工艺有关,同时利用酿醪糟浸出液的凝乳特性开发新型风味乳制品,可为凝乳酶生产菌种的选育提供资源及制备方法.     

乳制品与糖尿病的饮食防控

本文综述了乳制品与糖尿病之间关系的研究进展。流行病学研究表明,乳制品对糖尿病的发生风险无不良影响,甚至有一定降低风险的作用。乳制品中的乳糖不会快速升高血糖,其反式脂肪成分并不是糖尿病的风险因子,而其中的乳清蛋白对于糖尿病患者是有利的。因此,乳制品是糖尿病患者饮食的有益组成。     

展望我国未来乳品与饮料研发——主题与方向

<正> 乳品和饮料行业的迅猛发展是改革开放大环境下的必然趋势,随着人们生活水平的不断提高,乳品和饮料逐渐成为了人们日常生活中的必需品。我国是一个13亿人口的泱泱大国,市场持续性的巨大需求,显示了乳品和饮料行业的发展潜力和美好前景。但还要清醒的认识到,乳品饮料市场     

Chemometrics Classification of Argentine Clover and Eucalyptus Honeys According to Palynological,Physicochemical, and Sensory Properties

Palynological, physicochemical, and sensory methods were applied to ascertain the most discriminant variables for honey characterization. Fifteen physicochemical parameters, six indicators of antioxidant capacity and eight sensory attributes were considered. Clover and eucalyptus honeys were differentiated when the linear discriminant analysis was applied. Electrical conductivity, sugars, ferric ion reducing, and Trolox equivalent antioxidant capacity were the most discriminant variables. Odor and color intensities were the sensory attributes scoring the major differences between honeys. The canonical correlations technique pointed out that differences were related primarily to the content of pollen from Trifolium, Medicago sativa, and Lotus. These standards of quality provide a differentiating tool to classify unifloral honeys.     

Physical Properties of Mixed Dairy Food Proteins

Foods may contain more than one type of protein, and food formulators sometimes combine different proteins for desired synergistic textural benefits. Egg albumin, fish protein isolate, or soy protein isolate were blended with calcium caseinate or whey protein isolate and mixed in water adjusted to pH 2.5, 6.8, and 9.0 at 25 or 60°C. The effect of pH and temperature on solubility, viscosity, and the structure of the resulting gels were determined. The viscosity at the most soluble concentration at 25°C were: egg albumin (175.2 mPa.s/35 wt%), fish protein isolate (2207.4 mPa.s/30 wt%), soy protein isolate (2531.5 mPa.s/10 wt%), calcium caseinate (1115.8 mPa.s/15 wt%), and whey protein isolate (161.2 mPa.s/35%). In mixed protein systems viscosity values were reduced. The values for calcium caseinate or whey protein isolate with egg albumin, at the protein level of 15 g/100 g were: calcium caseinate/egg albumin (10:5 wt%) 535.1 mPa.s and whey protein isolate/egg albumin (10:5 wt%) 8.7 mPa.s. Microscopy imaging revealed changes in protein aggregation clusters during heating of calcium caseinate, egg albumin, and whey protein isolate. Egg albumin acted synergistically to increase viscosity, while fish protein isolate acted antagonistically to reduce viscosity. This knowledge is useful to manufacturers who may seek to enhance food texture by blending different proteins.     

Properties of Mixed and Filled-type Dairy Gels

Skim milk powder (SMP), a whey protein concentrate (WPC) and fat globules with modified membranes were used for the fabrication of mixed and filled dairy gels. Firmness and syneresis of pure gels varied broadly with pH and total solids (TS). Mixing SMP and WPC at 10% TS showed synergistic effects on gel firmness, particularly for 50:50 blends, and addition of fat provided further reinforcement. Syneresis of gels and their appearance changed from high and clear to low and turbid, respectively, as the WPC content was increased. Microstructural studies revealed the porous structure of the parent gels, compatability between both protein sources and between fat globules and the protein matrix.     

乳清蛋白在发酵乳制品中的应用

乳清蛋白具有良好的功能性,被广泛应用在各种食品中。本文综述了乳清蛋白产品的组成成分和功能特性,以及乳清蛋白对发酵乳制品的风味、质构、益生菌生长及功能营养的影响。指出乳清蛋白在发酵乳制品中具有良好的适应性和广阔的应用前景。