山羊奶粉蛋白质营养价值的评价

本文以成分分析、大鼠实验评价国产山羊奶粉蛋白质的营养价值,并与牛奶粉蛋白质和大豆蛋白进行比较。山羊奶粉蛋白质的主要限制氨基酸是含硫氨基酸,氨基酸分(AS)和化学分(CS)分别为0.91和0.52,其氨基酸模式与牛奶粉蛋白质相近,稍优于酪蛋白,远优于大豆蛋白;蛋白质功效比值(PER)、净蛋白质比值(NPR)、表观消化率(AD)、真消化率(TD)、生物价(BV)和蛋白质净利用率(NPU)分别为3.01、4.62、90.49％、96.75％、86.02和83.22％,除AD稍高外,其他指标均与牛奶粉蛋白质无差别,除PER外各项指标均高于酪蛋白,所有指标均远高于大豆蛋白质。实验结果证实山羊奶粉蛋白质具有和牛奶粉蛋白质一样优良的营养价值。     

Changes in protein nutritional quality in fresh and recombined ultra high temperature treated milk during storage

The objective of this study was to determine the changes in nutritional quality of protein in stored UHT milk. Commercial fresh and recombined ultra high temperature (FUHT and RUHT respectively) treated milk samples were used. Pasteurized milk (P-milk) samples were used for comparison. Milk samples were freeze-dried for the use in diet formulation. Pasteurized milk samples were freezedried within 24 h of production. FUHT and RUHT milk samples were freeze-dried after production (zero time), 3 and 6 months of storage at 37°C. Three nitrogen balance experiments were done at zero time, after 3 and 6 months of storage. The diet used in all experiments were similar in composition except for protein source. In each experiment egg white (low protein), casein (control), P-milk, and either 0, 3 or 6 months old FUHT and RUHT milk samples were used as the source of protein in the diets. In each experiment 30 (six for each diet) male Sprague-Dawley rats were used. Apparent digestibility (AD), true digestibility (TD), biological value (BV), and net protein utilization (NPU) were calculated for protein in casein and all milk samples. The nutritional quality of protein in FUHT milk before storage was similar to that of protein in pasteurized milk, but it decreased during storage for 3 months and then remained at the same quality up to 6 months of storage. BV and NPU of protein in FUHT milk after storage for 3 and 6 months were lower than that of protein in pasteurized milk by 4% (not significant) and 5% respectively. On the other hand, the nutritional quality of protein in RUHT milk before storage was lower than that of protein in pasteurized milk and remained at the same level after storage for 3 months: however, it decreased significantly after storage for 6 months. AD and TD of protein in RUHT milk stored for 6 months were lower than that of protein in pasteurized milk by 5% and BV and NPU were lower than that of protein in pasteurized milk by 9 and 12% respectively. The above reduction in nutritional quality of protein in UHT milk may be of significant value in feeding young children who might be dependent on this type of milk in their diet.     

Changes in protein nutritional quality in fresh and recombined ultra high temperature treated milk during storage

The objective of this study was to determine the changes in nutritional quality of protein in stored UHT milk. Commercial fresh and recombined ultra high temperature (FUHT and RUHT respectively) treated milk samples were used. Pasteurized milk (P-milk) samples were used for comparison. Milk samples were freeze-dried for the use in diet formulation. Pasteurized milk samples were freeze-dried within 24 h of production. FUHT and RUHT milk samples were freeze-dried after production (zero time), 3 and 6 months of storage at 37 degrees C. Three nitrogen balance experiments were done at zero time, after 3 and 6 months of storage. The diet used in all experiments were similar in composition except for protein source. In each experiment egg white (low protein), casein (control), P-milk, and either 0, 3 or 6 months old FUHT and RUHT milk samples were used as the source of protein in the diets. In each experiment 30 (six for each diet) male Sprague-Dawley rats were used. Apparent digestibility (AD), true digestibility (TD), biological value (BV), and net protein utilization (NPU) were calculated for protein in casein and all milk samples. The nutritional quality of protein in FUHT milk before storage was similar to that of protein in pasteurized milk, but it decreased during storage for 3 months and then remained at the same quality up to 6 months of storage. BV and NPU of protein in FUHT milk after storage for 3 and 6 months were lower than that of protein in pasteurized milk by 4% (not significant) and 5% respectively. On the other hand, the nutritional quality of protein in RUHT milk before storage was lower than that of protein in pasteurized milk and remained at the same level after storage for 3 months: however, it decreased significantly after storage for 6 months. AD and TD of protein in RUHT milk stored for 6 months were lower than that of protein in pasteurized milk by 5% and BV and NPU were lower than that of protein in pasteurized milk by 9 and 12% respectively. The above reduction in nutritional quality of protein in UHT milk may be of significant value in feeding young children who might be dependent on this type of milk in their diet.     

Protein evaluation in growing rats of breast milk and breast milk substitutes with special reference to the content of non-protein nitrogen.

The levels of individual proteins and other nitrogen containing substances differ considerably between cow's milk and human milk. Therefore, during manufacture of infant formulas, attempts are made to simulate the protein composition of human milk. However, the composition and nutritional characteristics of human milk protein are incompletely known. In this paper, the protein quality of breast milk protein with and without the non-protein-nitrogen (NPN) substances present in human milk was studied with growing rats and compared to two formulas, one "adapted" commercial infant formula and a suggested further modified, possibly improved, infant formula. Detailed examinations of protein and amino acid composition of the test diets are given. Breast milk protein with added NPN substances showed a lower protein quality than all other test proteins. Breast milk protein without NPN substances and the protein of the suggested infant formula were of similar quality while the protein of the commercial adapted formula was significantly better than all other test proteins. The use of rat growth assays in the evaluation of protein quality of infant formulas is discussed.     

比较牛奶激发试验与血清特异性抗体诊断婴幼儿牛奶蛋白过敏的临床研究

目的 通过对牛奶激发试验与血清特异性抗体的比较,明确牛奶激发试验诊断婴幼儿牛奶蛋白过敏的临床意义。方法 收治苏州大学附属儿童医院2015年2-11月共57例疑似牛奶蛋白过敏的婴幼儿住院进行牛奶激发试验,并进行血常规检测,采用酶联免疫方法(ELISA)进行血清总IgE抗体、血清特异性牛奶蛋白IgE检测;采用免疫印迹法进行特异性牛奶蛋白IgG检测,比较和分析与激发结果的关系。结果 57例婴幼儿中牛奶激发试验阳性者占40.4%(23/34)。比较阳性组与阴性组的白细胞数、嗜酸性粒细胞比率、中性粒细胞比率、血小板计数变化,差异均无统计学意义(P＞0.05);仅有阳性组激发后中性粒细胞比率较激发前增高,差异有统计学意义(P=0.02);阳性组与阴性组的血清总IgE、特异性牛奶蛋白IgE及特异性牛奶蛋白IgG检测结果比较,差异无统计学意义(P＞0.05)。结论 对疑似牛奶蛋白过敏婴幼儿行血清总IgE及血清特异性牛奶蛋白IgE检测的临床意义不大,不推荐特异性牛奶蛋白IgG用于诊断牛奶蛋白过敏。应提倡牛奶激发试验应用于临床诊断婴幼儿牛奶蛋白过敏。     

Compartmentalization and quantitation of protein in human milk

Human milk protein was determined by three colorimetric methods and by Kjeldahl analysis. The distribution of nitrogen (N) and protein was determined within various milk compartments. Total N, whey, casein, nonprotein nitrogen (NPN), cell N and N in the fat fraction were analyzed by micro-Kjeldahl analysis after a series of centrifugation and ultracentrifugation separations. Fresh milk samples (colostrum, transitional milk and mature milk) were centrifuged at 500 X g to separate milk cells and at 5000 X g to skim the milk. Decelled milk and skimmed milk were ultracentrifuged at 189,000 X g to separate fat and casein micelles from whey. NPN was analyzed after trichloroacetic acid precipitation. Whole milk, decelled milk, skimmed milk and whey were analyzed for protein with the Lowry method, modified for fat-containing samples, the Bradford dye-binding assay (Bio-Rad) and the Pierce bicinchoninic acid (BCA) assay. Cell nitrogen had a tendency to be lower in mature milk than in colostrum. Colostrum contained only 6% casein protein, whereas mature milk contained 13%. Fat from skimming was lower in N than fat from ultracentrifugation. Average NPN levels were similar for milk from all three lactation periods, and constituted 10% of colostrum N and 25% of mature milk N. Protein determined by the Bio-Rad method on whole milk samples had the lowest variability (square root MSE) when correlated to Kjeldahl values. All three assays had lower variability when analyzing whey and skimmed milk than when analyzing whole milk. The Lowry method and the Bio-Rad method had low variability for whey and skimmed milk samples, but the Lowry method yielded analytical values closest to Kjeldahl protein values. The BCA method consistently overestimated Kjeldahl protein by 30%.     

Relationships between the amount of total protein in human milk, the volume of produced milk and perinatal factors

The concentrations of total protein in human milk on the 5th or 6th day after full-term delivery were measured on 184 women, and the amount of protein per 24 hours was calculated by multiplying protein concentration by 24-hour milk production for the same day. Relationships between the amount of protein, milk volumes and perinatal factors were investigated. 1. The mean values (and standard deviations) for total protein concentration and amount per 24 hours, and milk volumes were 1.89 (0.37) g/dl, 6.60 (2.71) g/24h, 353 (144) ml/24h respectively. A significant negative correlation was found between the concentration of protein and milk volumes. The amount of protein per 24 hours showed a considerably high positive correlation with milk volumes rather than with total protein concentration. 2. Among perinatal factors, the age of the mother and whether the delivery was abnormal affected significantly both the amount of protein and milk volumes. The amount of protein and milk volumes of women 30-39 years old, who delivered abnormally were both significantly reduced. The amount of protein for women who had hemoglobin concentrations less than 11.5 g/dl in the latter period of pregnancy was significantly high. However, significant difference disappeared when those women who had both abnormal delivery and birth weight of their baby was more than [mean + 1SD] were excluded.     

Milk ingestion in athletes and physically active individuals

Milk is a cheap drink that naturally contains nutrients in similar amounts as found in typical carbohydrate‐electrolyte sports drinks, as well as providing some protein (36 g/l). While there is little information about the ingestion of milk during exercise, the available evidence suggests that milk might enhance certain aspects of recovery when ingested after resistance and endurance exercise. The protein content of milk means that ingestion of milk immediately after resistance exercise acutely increases muscle protein synthesis, and if used chronically during a resistance training programme, milk ingestion enhances lean mass gains and fat mass losses compared with other protein sources (e.g. soy protein) or ingestion of carbohydrate. Ingesting milk after muscle damaging exercise also appears to alleviate some of the symptoms of exercise‐induced muscle damage, while the electrolytes naturally occurring in milk, as well as the milk protein, appear to enhance rehydration after endurance exercise. In summary, milk appears to be an appropriate post‐exercise drink for athletes and physically active individuals that are not intolerant to lactose and/or dairy. Milk might enhance some aspects of recovery after exercise and it appears that the proteins contained in milk are responsible for most of these enhancements.     

宜昌市2005～2007年乳制品与植物蛋白食品检测结果分析

目的:了解宜昌市乳制品与植物蛋白食品卫生状况,为食品卫生安全监管提供依据。方法:在宜昌市主要的集贸市场和超市随机采集乳粉、鲜乳、豆浆等乳制品与植物蛋白食品,并对菌落总数、大肠菌群、脂肪、蛋白质、铅、砷等项目进行检测。结果:植物蛋白饮料类产品菌落总数超标率较高,达44.4%;乳粉、蛋白粉类产品中蛋白质和脂肪不合格率达到了22.7%和19.1%。结论:宜昌市植物蛋白类食品合格率较低,乳粉、蛋白粉类产品中蛋白质和脂肪不合格率较高,危及食品卫生安全,需加强监督管理。     

Infant formulas with increased concentrations of alpha-lactalbumin

Human and bovine milk differ substantially in the ratio of whey to casein protein (approximately 60:40 in human milk and approximately 20:80 in bovine milk) and in the proportions of specific proteins. Although current infant formulas closely mimic the ratio of total whey to casein inhuman milk, the concentration of a-lactalbumin (the dominant protein in human milk) is relatively low in formula, whereas beta-lactoglobulin, a protein not found in human milk, is the most dominant whey protein in formula. Because of the differences in the protein profiles of human milk and infant formula, amino acid profiles also differ. To meet all essential amino acid requirements of infants, formula concentrations of protein must be higher than those in human milk. Recently, whey sources with elevated concentrations of alpha-lactalbumin have become available, which permitted the development of formulas with increased concentrations of this protein and decreased concentrations of beta-lactoglobulin. alpha-Lactalbumin is rich in tryptophan, which is typically the limiting amino acid in formula, and as a result, formulas have been developed with lower protein but higher tryptophan concentrations. This type of formula may offer a number of advantages to the neonate, which include producing plasma tryptophan concentrations equal to those found in breastfed infants and obviating the need for the body to dispose of excess nitrogen loads.     

Relationships between the amount of total protein in human milk, the volume of produced milk and food intake

The concentration of total protein in human milk on the 5th or 6th day after full-term, normal delivery was measured in 145 women, and the amount of protein per 24 hours was calculated by multiplying protein concentration by 24-hour milk production for the same day. Relationships between the concentration and amount of protein, milk volumes and food intake during the latter period of the pregnancy were investigated. Quantification theory III statistical analysis was applied to analyze food intake patterns. While no individual food item was shown to be effective in improving quality and quantity of mother's milk, the results suggest that mothers who consumed meat, fish, food prepared with oil, seaweed, cow's milk and fruits frequently, and rarely used coffee; or mothers who consumed confectioneries and food prepared with oil frequently, rarely used coffee and alcohol beverages and disliked spices produced greater volumes of milk or milk containing a greater amount of protein.     

Consumption of fluid skim milk promotes greater muscle protein accretion after resistance exercise than does consumption of an isonitrogenous and isoenergetic soy-protein beverage

BACKGROUND: Resistance exercise leads to net muscle protein accretion through a synergistic interaction of exercise and feeding. Proteins from different sources may differ in their ability to support muscle protein accretion because of different patterns of postprandial hyperaminoacidemia. OBJECTIVE: We examined the effect of consuming isonitrogenous, isoenergetic, and macronutrient-matched soy or milk beverages (18 g protein, 750 kJ) on protein kinetics and net muscle protein balance after resistance exercise in healthy young men. Our hypothesis was that soy ingestion would result in larger but transient hyperaminoacidemia compared with milk and that milk would promote a greater net balance because of lower but prolonged hyperaminoacidemia. DESIGN: Arterial-venous amino acid balance and muscle fractional synthesis rates were measured in young men who consumed fluid milk or a soy-protein beverage in a crossover design after a bout of resistance exercise. RESULTS: Ingestion of both soy and milk resulted in a positive net protein balance. Analysis of area under the net balance curves indicated an overall greater net balance after milk ingestion (P < 0.05). The fractional synthesis rate in muscle was also greater after milk consumption (0.10 +/- 0.01%/h) than after soy consumption (0.07 +/- 0.01%/h; P = 0.05). CONCLUSIONS: Milk-based proteins promote muscle protein accretion to a greater extent than do soy-based proteins when consumed after resistance exercise. The consumption of either milk or soy protein with resistance training promotes muscle mass maintenance and gains, but chronic consumption of milk proteins after resistance exercise likely supports a more rapid lean mass accrual.     

西安市主城区健康乳母产后不同时期乳汁成分分析

目的研究人乳成分在不同时期的动态变化规律,以指导婴儿合理喂养。方法选取121名健康乳母,分别在其产后1~6、8、10、12月采集前乳和后乳,采用MIRIS HMA型人乳分析仪检测其中的蛋白质、脂肪、糖类、干物质含量以及能量。结果前乳和后乳中蛋白质含量在产后前3个月明显高于其它月份。乳汁中脂肪和能量的变化是一致的,前乳中脂肪、能量在产后12月内无差异,后乳中脂肪及能量10、12月组高于其它各组。产后1月前、后乳蛋白质含量差异无统计学意义,之后各组前乳均高于后乳。各个时期脂肪含量、能量、干物质后乳均明显高于前乳,而糖类含量前乳均高于后乳。结论人乳在产后不同时期有其自身的变化规律。     

Milk production and nitrogen utilization in response to postruminal infusion of sodium caseinate in lactating cows.

Five lactating, rumen-fistulated Holstein cows were used to obtain additional information concerning the effects of postruminal infusion of sodium caseinate on milk production and amino acid utilization. A 7-day continuous abomasal infusion of approximately 450 g/day of sodium caseinate was preceded and followed by 7-day infusions of an isonitrogenous-isocaloric solution of glucose, monosodium glutamate, and urea. Total collections of milk, urine, and feces were obtained during the last 5 days of each infusion period. On the last day of each period, arterial and mammary venous blood samples were obtained for analysis of plasma free amino acids. During infusion of sodium caseinate, milk production, milk protein (N times 6.38) production, and efficiency of nitrogen utilization for milk crude protein production were increased. Arterial plasma concentrations of free histidine, isoleucine, phenylalanine, valine, and total essential amino acids were elevated above control levels during infusion of sodium caseinate, while ornithine and tryrosine were decreased. Calculation of the relative concentration of essential amino acids in arterial plasma and in milk protein indicated that methionine and lysine were least abundant in plasma relative to their requirement for milk protein synthesis. A high precentage extraction from arterial plasma by the mammary gland also suggested that methionine and lysine may have been the essential amino acids in most critical supply for milk protein synthesis. Calculation of uptake to output ratios of individual plasma amino acids by the mammary gland suggested that significant quantities of extracted arginine, isoleucine, leucine, threonine, and valine were utilized in pathways other than direct incorporation into milk protein.     

The importance of alpha-lactalbumin in infant nutrition

The ideal "humanization" of milk substitutes should include the creation of an amino acid pattern closely resembling that of human milk. Because the mixture of proteins in human milk is particularly rich in tryptophan and cysteine and low in methionine, this pattern is difficult to achieve with commercially available proteins. Even whey-predominant formulas only approximate human milk. Human milk has a high concentration of whey protein (70% of total protein). Of this, alpha-lactalbumin, a component of the lactase synthetase complex, accounts for 41% of the whey and 28% of the total protein. Only 3% of the protein in bovine milk is alpha-lactalbumin. Human and bovine alpha-lactalbumin share a 72% amino acid sequence homology. Both proteins contain (wt/wt) 6% tryptophan and 5% cysteine but only 0.9% methionine. Thus the differences in the amino acid compositions of bovine and human milks are largely attributable to differences in their alpha-lactalbumin contents. Commercial availability of bovine alpha-lactalbumin would allow the construction of infant formulas with amino acid compositions that are very close to that of human milk. alpha-Lactalbumin would also be a valuable constituent of diets for patients whose protein intake must be restricted.     

乳粉中蛋白质测定条件的改进

目的对乳粉中蛋白质测定条件进行改进,以便于实验的操作和控制。方法参照中华人民共和国国家标准《食品中蛋白质的测定》（GB／T5009．5—2003）对《婴幼儿配方食品和乳粉蛋白质的测定》（GB／T5413．1—1997）中的试样前处理和消化液的蒸馏2个重要步骤用同一乳粉进行蛋白质含量的测定比对。结果测定条件改进前后所测同一乳粉中蛋白质含量结果无差异性。结论改进后的测定条件在乳粉中蛋白质测定时容易操作和控制,不易导致测定实验失败。     

富硒蛋白对小鼠免疫功能影响

目的观察富硒蛋白对正常小鼠免疫功能的影响作用。方法选用48只继康的ICR小鼠，随机分成4组，在饲料中分别加入贫硒蛋白、贫硒蛋白与亚硒酸钠混合物、富硒牛奶、富硒蛋白，进行30d的喂饲后测定小鼠淋巴器官指数、迟发型变态反应、溶血空斑形成数。结果富硒蛋白能够促进小鼠溶血空斑的形成，刺激迟发型变态反应，作用优于相同硒含量的富硒牛奶或者贫硒蛋白与无机硒的混合饲料（P〈0．05）。结论该富硒蛋白产品有提高小鼠体液免疫、细胞免疫功能的作用。     

牛奶及奶粉中蛋白质的快速测定法

目的:建立一种牛奶及奶粉中蛋白质的快速测定方法。方法:在试管中以双氧水-硫酸加热,快速消解牛奶及奶粉中的蛋白质,使用纳氏试剂比色法测定。结果:快速消解只需5分钟即可完成。两个品种牛奶中蛋白质各测定8次,相对标准偏差分别为3.9%和1.3%,用甘氨酸标准溶液做回收试验,回收率99.4%。用本法测定奶粉标准物质(GBW10017)6次,与标准值比较结果无显著性差异。结论:该方法操作简单,结果可靠。     

牛乳蛋白过敏儿童肠道优势菌群多样性的分析

目的 探讨牛乳蛋白过敏儿童肠道优势菌群多样性的规律, 为缓解或治愈牛乳蛋白过敏提供理论依据。方法 以7例牛乳蛋白过敏儿童和5例健康儿童为研究对象, 采用细菌的16S rDNA V3区通用引物, 以研究对象的粪便总DNA为模板进行PCR扩增, PCR产物进行变性梯度凝胶电泳(denaturing gradient gel electrophoresis, DGGE)分析, 结果应用Quantity One软件分析。结果 牛乳蛋白过敏儿童和健康儿童的肠道优势菌群多样性差异有统计学意义, 且牛乳蛋白过敏组的多样性高于健康对照组。牛乳蛋白过敏组和健康对照组分别能聚类到不同簇中, 说明两组样本的肠道优势菌群结构不同。相似性分析结果显示过敏组相似性范围为27%~72%, 健康组相似性范围为28%~64%。结论 牛乳蛋白过敏儿童肠道优势菌群多样性相比较健康儿童肠道优势菌群多样性发生明显变化, 揭示肠道微生态平衡可能是造成牛乳蛋白过敏的潜在原因。     

Hyperinsulinaemia, supplemental protein and branched-chain amino acids when combined can increase milk protein yield in lactating sows

The aim of this study was to determine whether dietary supplementation with branched-chain amino acids, and the infusion of insulin and dextrose, would increase milk protein secretion in the sow. The experiment involved sixteen lactating sows fed either a normal lactation diet (162 g/kg crude protein, n 8) or a high-protein diet (230 g/kg crude protein, n 8) supplemented with branched-chain amino acids (valine, isoleucine and leucine). Sows were either infused with insulin and dextrose or not infused at all during mid (day 5-10) and late (day 17-22) lactation in a single reversal design. Blood samples were analysed for glucose, and the dextrose infusion rate was adjusted to maintain the blood glucose level within 15 % of pre-infusion levels. Milk (10.1 v. 11.1 kg/d; P=0.014) and lactose (628 v. 727 g/d; P=0.002) yield increased with insulin infusion, whereas milk protein content (5.0 % v. 5.5 %; P=0.007) was increased in diets supplemented with protein and branched-chain amino acids. Piglet growth was increased by feeding the higher-protein diet (237 v. 273 g/d; P=0.05) but not significantly increased by insulin infusion (245 v. 265 g/d; P=0.11). These effects were additive such that the combined treatment resulted in a 24 % (56 g/d; P<0.05) increase in piglet growth rate. These data demonstrate that increasing the dietary protein/branched-chain amino acid content can increase milk protein secretion but not milk yield. The infusion of insulin and dextrose increased milk and milk lactose yields, and tended to increase milk protein yield but not milk protein content. These effects are additive and translate to increased protein yield and piglet growth.