高钙奶中不同钙剂对其稳定性的影响

本文重点研究了钙强化剂的种类、不同用量和不同的稳定剂对高钙奶稳定性的影响.结果表明以碳酸钙为代表的电离度较小的分子钙,其电离产生的钙离子对乳状液体系的稳定性的影响相对较小,因此主要通过提高乳状液的悬浮效果,可解决由于加入碳酸钙而引起的体系出现沉淀的问题;以乳钙为代表的有机分子钙,由于乳钙自身在水溶液中具有很好的分散性,电离度较碳酸钙大,乳钙对高钙奶体系稳定性的影响主要是游离的钙离子与乳状液中界面上的乳蛋白通过桥连作用,引起体系絮凝,可通过加入螯合剂螯合体系的钙离子来解决.     

“合诚”高钙奶稳定剂对高钙奶体系的稳定作用

全国第三次营养调查结果表明，我国居民缺钙现象比较普遍，利用高钙奶进行补钙是一种既科学又经济方便的方法。目前高钙奶中添加的钙剂主要为碳酸钙和乳钙等分子钙剂，容易出现沉淀、絮凝和乳析等问题，添加合适的乳化稳定剂有助于解决这些困扰乳制品生产商和消费者的问题。为此，我们分析了几种高钙奶稳定剂在高钙奶体系中的作用。高钙奶的制作参照谢继志等的方法进行，     

高钙甜牛奶饮料的研制

对高钙甜牛奶饮料生产中不同钙剂和稳定剂对产品品质 的影响进行了研究。结果表明,以乳钙为钙强化剂,添加 量为3.65g/L,稳定剂为0.15％(高钙奶稳定剂与甜牛奶稳 定剂之比为2:1),高钙奶乳化剂为0.15％,柠檬酸钠为 0.08％,精制白糖为8％时产品较好,钙离子含量可迭 1.5mg/mL。本文针对配料的特点,确定了合理、可行的配 方及生产工艺,产品具有钙含量高、稳定性好、口感佳等 特点。     

快速分析卡拉胶与结冷胶对高钙奶的稳定性影响

研究了卡拉胶及结冷胶对以碳酸钙为钙剂的中性巴氏高钙奶的稳定性影响。借助TURBISCAN Lab型分散稳定性分析仪进行稳定性快速分析,同时通过离心分离及传统观察分析法比较两种胶体的悬浮效果。传统观察结果表明,结冷胶在中性巴氏高钙奶中具有良好的悬浮稳定性,随着用量的提升,底部沉淀明显改善,卡拉胶悬浮效果不佳;而通过稳定性分析可以得出,卡拉胶及结冷胶对巴氏奶中的蛋白絮凝起到一定作用,随着用量提升,体系颗粒向下迁移,底部沉淀增加,对改善顶部浮油效果作用不大。     

天门冬氨酸钙溶液的电离度的研究

通过使用钙离子选择电极用电极电位法测量了在不同深度和不同ＰＨ溶液下的天门冬氨醋钙的电离度情况，研究了天门冬氨酸钙的结构。结果表明，当天门冬氨酸钙的深度大于焊，它呈分子钙结构，反之，呈离子钙结构。     

低脂高钙奶的热稳定性

乳蛋白对钙较敏感，游离钙含量过高则会导致乳受热凝固，为了提高乳中钙的含量，增加高钙奶的热稳定性，本文对钙盐进行了筛选，并探讨了钙盐在乳中添加方法。     

高钙奶苦味原因分析

通过有苦味的高钙奶样品中的细菌总数、蛋白质水解度、寡肽含量、游离氨基酸含量、蛋白酶活性等指标的测定,对高钙奶在保质期末出现苦味的原因进行分析。结果表明苦味高钙奶和无苦味牛奶样品中的细菌总数无显著差异(p≥0.05),苦味高钙奶中的寡肽、游离氨基酸含量,特别是苦味氨基酸含量显著高于无苦味牛奶样品(p<0.05),苦味牛奶样品中的蛋白酶活性显著高于无苦味牛奶样品(p<0.05),同时高钙奶中添加的碳酸钙和稳定剂中的蛋白酶也有较高活性。高钙奶苦味主要是由于牛奶中的内源或外源性蛋白酶水解酪蛋白,生成苦味的游离氨基酸、寡肽等造成的,针对这一原因,可通过提高原料乳和添加剂的卫生质量、控制生产加工过程中的卫生、调整和改进杀菌工艺等方法,以避免高钙奶的苦味问题。     

马尾松化机浆DCS中潜在黏性物质稳定性的研究

首先采用GC/MS技术对马尾松化机浆DCS中潜在黏性物质进行了表征,结果表明,黏性物质中的主要树脂组分为脱氢枞酸、亚油酸、油酸和棕榈酸等.接着,探讨了中性和酸性聚糖对树脂模型物(树脂酸R,脂肪酸O)稳定性的影响,结果表明,在没有钙离子存在的条件下,胶态的树脂可以通过静电机理自我稳定.乳液中一旦加入钙离子,胶态树脂颗粒就会迅速聚集,当钙离子与R、O的浓度比分别达到0.6∶1和1.6∶1时,胶态树脂颗粒会完全聚集.中性聚糖可以稳定胶态树脂颗粒,当加入的中性聚糖与R、O的浓度比分别超过0.2∶1和1.0∶1时,钙离子的加入不会引起颗粒的聚集.加入酸性聚糖会进一步恶化胶态树脂颗粒的稳定性;当体系中已存在的中性聚糖足以包裹胶态树脂颗粒时,酸性聚糖的负面效应会限定在一定范围内,体系保持一定的稳定性.     

浅谈填料级重质碳酸钙的生产

随着中性造纸技术的发展，碳酸钙做为一种优良的填料在造纸工业中的应用越来越普遍。按照制造方式的不同，碳酸钙的生产可分为研磨碳酸钙（重钙，ＧＣＣ）和合成碳酸钙（轻钙，ＰＣＣ）两大类。与轻钙相比，重钙由于其颗粒形状呈球状，且比表面积小，对纸张强度和辅料的用...     

羧甲基纤维素钠对高钙液态乳稳定性的影响与机制

以酪蛋白酸钠、羟基磷灰石和羧甲基纤维素钠作为乳蛋白、钙增强剂和增稠稳定剂的模型组分,研究了增稠稳定剂对高钙液态乳体系稳定性的影响,通过优化添加工艺改善钙增强剂在产品中的分散稳定性,并探讨其分子机制,提出了通过由静电相互作用驱动和层层自组装方式构建"多糖/蛋白双壳层"改善无机钙盐在溶液体系中分散稳定性的分子模型。     

高钙液态奶中试加工工艺的研究

对高钙液态奶中试加工工艺进行了研究。通过向原料奶中添加乳钙、奶油粉、酪蛋白磷酸肽、维生素D3等物质，在一定条件下生产高钙液态奶。通过中试试验确定了各种物质的添加量和生产工艺。生产的高钙牛奶具有比普通牛奶更好的口感和香味．没有一般高钙类产品常见的涩味，产品在保质期内稳定性好。     

Impact of source and level of calcium fortification on the heat stability of reconstituted skim milk powder

Calcium enrichment of food and dairy products has gained interest with the increased awareness about the importance of higher calcium intake. Calcium plays many important roles in the human body. Dairy products are an excellent source of dietary calcium, which can be further fortified with calcium salts to achieve higher calcium intake per serving. However, the addition of calcium salts can destabilize food systems unless conditions are carefully controlled. The effect of calcium fortification on the heat stability of reconstituted skim milk was evaluated, using reconstituted skim milks with 2 protein levels: 1.75 and 3.5% (wt/wt) prepared using low and high heat powders. Calcium carbonate, phosphate, lactate, and citrate were used for fortification at 0.15, 0.18, and 0.24% (wt/wt). Each sample was analyzed for solubility, heat stability, and pH. The addition of phosphate and lactate salts lowered the pH of milk, citrate did not have any major effect, and carbonate for the 1.75% protein samples increased the pH. In general, changes in solubility and heat stability were associated with changes in pH. Calcium addition decreased the solubility and heat stability. However, interestingly, the presence of carbonate salt greatly increased the heat stability for 1.75% protein samples. This is due to the neutralizing effect of calcium carbonate when it goes into solution. The results suggested that the heat stability of milk can be affected by the type of calcium salt used. This may be applied to the development of milk-based calcium enriched beverages.     

胶原肽螯合钙的吸收试验研究

以胶原肽螯合钙为受试物,碳酸钙(CaCO3)作为阳性对照,检测受试动物的血清钙、股骨钙含量及股骨指数,评价胶原肽螯合钙对缺钙模型小鼠的补钙功能。结果显示,各试验组小鼠体重增长无显著性差异(P>0.05),胶原肽螯合钙高剂量组和低剂量组血清钙含量及股骨钙含量均高于模型组且差异具有极显著性(P<0.01),同时胶原肽螯合钙高剂量组股骨钙含量高于CaCO3组且差异具有显著性(P<0.05),胶原肽螯合钙高剂量组股骨指数高于模型组及CaCO3组其差异具有极显著性(P<0.01)。说明胶原肽螯合钙具有一定的补充钙质的功能。     

我国人口的缺钙现状及改善措施

钙是人体健康和长寿不可缺少的重要元素,钙的生理功能及缺钙对人体健康的影响日益受到重视。由于国民膳食结构、饮食习惯、营养状态、生理因素等的影响,我国人口的缺钙状况令人忧虑,合理补钙正受到关注。乳和乳制品中的钙最易被肌体吸收,因此食物中增加乳和乳制品,以及含钙较多的豆制品、海产品非常重要。同时,为改变国民膳食结构中钙含量偏低的缺陷,应加强对钙强化食品的研究和开发,增加食物的含钙量。     

Association of low serum calcium concentration after calving with productive and reproductive performance in multiparous Jersey cows

Consequences of postpartum low blood calcium (Ca) concentration are still under study and literature describing this condition in Jersey cows is scarce. A prospective cohort study was conducted to evaluate the association of low serum Ca concentration shortly after calving with milk and energy-corrected milk yields, somatic cell count linear score, and pregnancy to first service and within 150 d in milk in multiparous Jersey cows from 2 commercial herds. Blood samples for serum Ca determination were collected on average at 3 h 10 min postpartum from 352 multiparous Jersey cows. Productive data up to the 10th monthly test were obtained from the Dairy Herd Improvement Association and reproductive data were obtained from herd records. Multiple linear, log-binomial, and Cox's proportional hazards regressions were used to evaluate the association of low serum Ca concentration with productive and reproductive outcomes. Serum Ca concentration ≤2.18 mmol/L was associated with 1.43 and 1.85 kg/d more milk and energy-corrected milk. However, lower serum Ca concentrations were associated with a 0.28-unit-higher somatic cell count linear score per monthly test (Ca ≤2.00 mmol/L), and decreased pregnancy risk at first service (risk ratio = 0.64; Ca ≤1.94 mmol/L) and hazard of pregnancy within 150 d in milk (hazard ratio = 0.40; Ca ≤1.90 mmol/L). The present study is based on a convenience sample of multiparous Jersey cows from 2 commercial herds; further research including more herds and additional blood Ca determinations is needed to describe postpartum blood Ca dynamics and its association with productive and reproductive outcomes for the Jersey breed.     

中性高钙液体奶的钙剂筛选及稳定性研究

对中性高钙液体奶生产中不同钙剂和稳定剂对产品稳定性和品质的影响进行了研究。结果表明,以乳钙为钙强化剂,添加量为6g/L,微晶纤维素复配卡拉胶(1∶1)为稳定剂,添加量为3g/L,制备的中性高钙液体奶对热稳定,口感不会明显增稠,钙含量(以钙元素计)可达2.64g/L。     

Changes in the proportions of soluble and insoluble calcium during the ripening of cheddar cheese

In cheese, the concentration and form of residual Ca greatly influences texture. Two methods were used to determine the proportions of soluble (SOL) and insoluble (INSOL) Ca in Cheddar cheese during 4 mo of ripening. The first method was based on the acid-base buffering curves of cheese and the second was based on the extraction of the aqueous phase ("juice") of cheese under high pressure and determining the concentration of SOL Ca in the juice using atomic absorption spectroscopy. When cheese was acidified there was a strong buffering peak at pH approximately 4.8, which was due to the solubilization of residual colloidal calcium phosphate (CCP) of milk that remained in cheese as INSOL Ca phosphate. The area of this buffering peak in cheese was expressed as a percentage of the original area of this peak in milk and was used to estimate the concentration of residual INSOL Ca phosphate in cheese. There were no significant differences between the 2 methods. The proportions of INSOL Ca in cheese decreased from approximately 73 to approximately 58% between d 1 and 4 mo. These methods will be useful techniques to study the role of Ca in cheese texture and functionality.     

Natural variations of citrate and calcium in milk and their effects on milk processing properties

Natural variations among milk constituents, and their relations to each other as well as to processing parameters, represent possibilities for differentiation of milk to produce high-quality natural products. In this study, we focused on natural variations in milk citrate and its interplay with calcium distribution in milk, in relation to processing properties. Milk samples from individual cows from farms varying in feeding and management practices were collected from April to June 2017 to maximize natural variations in citrate and calcium. Chemical composition, rennet coagulation properties, and ethanol stability were analyzed for all milk samples. We focused particularly on calcium distribution and citrate content and the correlation of these to other milk parameters. No significant change in citrate content was observed during the sampling period, which suggests that mechanisms other than feeding affect citrate levels in milk. Several significant correlations were found, including a positive correlation between complexed serum calcium and citrate, and a negative correlation between urea and ionic calcium. These are both of interest in relation to further processing, as with regard to the stability of UHT milk and in cheese making. Although the correlation between complexed serum calcium and citrate may be explained by their affinity, the underlying driver for the negative relationship between natural milk urea and ionic calcium needs to be clarified by further studies. Furthermore, milk from the different farms varied not only with regard to organic versus conventional farming systems; feeding practices between farms also play an important role in milk composition and functionality. However, none of the differences in milk composition between farms were found to decrease milk functionality and thus would probably not cause any processing problems.     

Influence of calcium salt supplementation on calcium equilibrium in skim milk during pH cycle

Calcium is a mineral essential for humans, especially for bone constitution. Yet most of the worldwide population does not satisfy their Ca needs. Hence, Ca supplementation is of major importance, even in western countries where some specific populations at risk do not satisfy the recommended daily intake of Ca. More than 70% of dietary Ca comes from dairy products. Calcium supplementation of naturally Ca-rich sources such as skim milk is then of special interest. To our knowledge, few data are available concerning milk Ca (MC) supplementation of milk, particularly when followed by pH cycle. In this paper, MC supplementation is studied and compared with Ca chloride (CC) supplementation as a well-known source of Ca. The effect of Ca salt supplementation followed by pH cycle was studied in reconstituted skim milk. Calcium supplementation was carried out with CC and MC at 25 mmol of Ca/kg of skim milk. Ionized Ca concentration and turbidity variations were followed in situ by Ca ion selective electrode and turbidimetry using light reflection. From normalized data on ionized Ca concentration and turbidity vs. pH, it appeared that hysteresis areas were smaller for CC-supplemented milk, whereas unsupplemented milk and MC-supplemented milk behaved similarly. For these 3 dairy systems, pH cycles to pH 5.0 led to a larger hysteresis area than pH cycles to pH 5.5. The shrinkage of the hysteresis area could be interpreted as a reinforcement of casein micelles with Ca ions over the pH cycle.