高效液相色谱法测定乳粉中异构化乳糖的含量

建立乳粉中异构化乳糖高效液相色谱的测定方法.采用盐酸沉淀蛋白,氨基色谱柱分离,流动相为80％乙腈溶液,示差检测器检测.每100 g乳粉中异构化乳糖添加量为0.3～2.0 g时,回收率97.4％～103.0％.定量检出限为0.3 g/100 g.该方法操作简便,检测准确,可用于乳粉中异构化乳糖的检测.     

乳糖不耐受和低乳糖奶

本文介绍了乳糖的生理功能,乳糖不耐受及其克服途径以及开发低乳糖奶的重要意义.指出利用乳糖酶解技术开发低乳糖奶和低乳糖乳制品,对提高牛奶和乳制品的营养价值,增加乳制品的销量将起到很大作用,其市场潜力巨大,经济、社会效益显著.     

新型去糖牛乳制品的加工技术

无论是液态奶还是固态奶,乳糖是其中最主要的成分.研究中的去糖牛奶采用最新发明技术,能有效去除牛奶中的乳糖,使奶中的总糖含量低于0.5%,其它各项指标符合国家相关标准,达到国家对无糖食品的指标.以本产品为原料可配制成多种低糖和无糖乳制品,外观、口感和营养价值与原乳配制的基本相同.     

帝斯曼乳糖酶产品为乳糖不耐受的中国消费者带来福音

乳制品是人体获取蛋白质及钙的良好来源，但由于我国乳糖不耐症人群所占比例较高，阻碍了乳制品的推广。世界健康组织数据表明，乳糖不耐症或乳糖酶缺乏的人群在中国占85%以上。乳糖酶可以使乳糖水解为葡萄糖和半乳糖，通过降低乳糖含量使乳糖不耐症人群能够少量或正常地摄入乳制品。     

乳糖酶的作用及其在乳品工业中的应用

乳与乳制品是营养成分十分丰富的天然食品，其营养价值早已得到了世人的公认，然而美中不足的是由于部分人体内缺乏乳糖酶导致的乳糖不耐受现象，影响了他们对乳制品的正常摄入，这在很大程度上制约了乳制品在人们日常生活中的普及和人体对乳制品营养成分的消化吸收。随着现代生物科学技术的发展，人们利用乳糖酶定向水解牛乳中大量的乳糖，从而使得从根本上解决乳糖不耐受这一困绕世人多年的医学难题成为可能。本文就乳糖酶在乳制品加工业生产中的应用作一简要论述，以期对大家有所启迪和帮助。     

乳糖酶的特性及其在乳品工业中的应用

乳和乳制品的营养价值早已得到世人的公认,然而由于部分人群体内缺乏乳糖酶导致的乳糖不耐受现象,影响了人们对于乳制品的正常摄入,这在很大程度上也就制约了乳制品在人们日常生活中的普及和人体对乳制品营养成分的消化吸收.随着现代生物技术的发展,人们可利用乳糖酶定向水解牛乳中大量的乳糖,使得从根本上解决乳糖不耐受这一难题成为可能.本文就乳糖酶的来源、     

从牛奶乳清液中提取乳糖与异构化乳糖的研究

本文详细介绍了在实验室中从牛奶乳清中提取乳糖与异构化乳糖的方法,并分析了实现产业化的可能。同时还介绍了超滤、纳滤设备在乳品工业上的不同用途及设备的选型和采购。     

乳糖不耐症及低乳糖奶的发展现状

由于乳糖酶缺乏而导致的乳糖不耐症,极大地制约了中国乳业的发展。而低乳糖奶的开发既能满足乳糖不耐症患者的乳品消费需求,又改善了一些乳制品的品质,是促进我国乳品工业发展的重要途径。     

日粮中添加乳糖可提高仔猪采食量

乳糖是一种能显著影响断奶仔猪采食量的重要营养物质,谷物和植物蛋白型日粮中添加干乳清和脱脂奶粉等乳制品可以提高仔猪的生长性能。不同来源乳糖的推荐量不同,同时部分其他形式的单糖也具有与乳糖相当的功效。     

荷斯坦奶牛乳腺发育中的乳糖变化研究

目的:研究荷斯坦奶牛乳腺发育中乳糖的变化规律.方法:高效液相色谱法测定荷斯坦奶牛乳腺发育中乳糖的含量.结果:围产期,乳腺中才出现可检测到的乳糖;泌乳期乳糖含量增高,泌乳140d达到峰值;退化期乳腺乳糖含量迅速降低,退化30d含量很少.结论:不同生理时期,荷斯坦奶牛乳腺中的乳糖含量不同.     

Use of the in vitro cumulative gas production technique for pigs: an examination of alterations in fermentation products and substrate losses at various time points

An experiment was conducted to examine changes in VFA and ammonia concentrations at different time points using 4 fermentable carbohydrate-rich feed ingredients as substrates and feces of unweaned piglets as inoculum. Fecal inoculum was collected, pooled, and mixed from 9 specially raised (no creep feed or antibiotics) crossbred piglets at 3 wk of age. Inulin, lactulose, molasses-free sugar beet pulp, and wheat starch were used as substrates and were fermented in vitro for 72 h (3 replicates per substrate). Cumulative gas production was measured as an indicator of the kinetics of fermentation. In addition, 3 bottles of substrate per time point with similar contents (amounts of substrate, inoculum, and media) were incubated but were allowed to release their gas throughout incubation. For these latter bottles, fermentation fluid was sampled at incubation time points including every hour between 1 and 24 h and at 48 h, and fermentation end products (VFA, lactate, and ammonia) and OM disappearance were measured. Dry matter and ash were analyzed from the postfermentative samples. The pH of the contents from these bottles was also recorded. The correlation in time between fermentation end products and cumulative gas produced was determined. The results showed that the prolongation of fermentation to 72 h, especially in the case of fast-fermenting inulin and lactulose, may lead to a different end product profile (P < 0.001) compared with the profile observed at the time at which most of the substrate has disappeared. Therefore, we concluded that the fermentation product profile at the end of in vitro fermentation at a specific time point cannot be used to compare fermentability of carbohydrate sources with different fermentation kinetics in terms of gas production.     

Kinetics and postmucosal effects on urinary recovery of 5 intravenously administered sugars in healthy cats

The objective of this study was to describe the kinetics of urinary recovery and to evaluate the effects of postmucosal factors on urinary recovery of 5 intravenously administered saccharides. Ten cats received an isotonic sugar solution containing lactulose, rhamnose, xylose, methylglucose, and sucrose intravenously. These sugars were selected because of their prior use for intestinal permeability and mucosal function testing in humans and dogs. Urethral catheterization with a closed collection system was used for collection of cumulative urine samples prior to and 2, 4, 6, 8, 10, 12, and 24 h after administration of the sugar solution. High-pressure anion exchange liquid chromatography with pulsed amperometric detection was used to measure the concentrations of each sugar in the urine and calculate urinary recovery. Twenty-four hour cumulative urinary recovery for each sugar from the cats, was lower than expected compared to dogs and humans. All 5 sugars had the highest percentage of urinary recovery during the first 2 h after administration. Mean sugar elimination rate constants and half-lives ranged from 0.268/h for methylglucose to 0.415/h for lactulose and 1.67 h for lactulose to 2.59 h for methylglucose, respectively. Metabolism and incomplete urine collection are possible reasons for lower cumulative urinary recoveries of these 5 sugars in cats compared with dogs. Although these 5 sugars are not ideal marker molecules, they may still be useful for intestinal permeability and mucosal function testing in cats.     

乳果糖制备方法的研究进展

乳果糖又名乳酮糖、异构化乳糖,是以乳业副产物乳糖为原料制备的一种还原性二糖,其浓缩液形式是一种重要的非处方药物,对急慢性便秘、肝性脑病等疾病具有显著疗效。乳果糖的生产方法包括化学法、β-半乳糖苷酶法、差向异构酶法等。近年来差向异构酶法因其高转化率受到广泛关注,是极具潜力的新一代乳果糖制备方法,但目前存在副产物依匹乳糖比例高、酶活力偏低等瓶颈问题。本文针对乳果糖制备方法的研究历史与现状进行综述,为该领域的基础理论及产业化研究提供借鉴。     

Possible interesting dietetic effects of lactulose as a feed additive in pig feed

In reared piglets (n = 10), fattening pigs (n = 20) and sows (n = 8) the effects of lactulose as feed additive on the quality and composition of chyme and faeces were tested to find out potential dietetic advantages of its use. The lactulose concentration in the diets varied between 27-29 g/kg dry matter in piglets and fattening pigs and 55-140 g/kg dry matter in the diet of sows. In piglets and fattening pigs the lactulose intake did not alter the dry matter content and pH in faeces; in spite of the higher concentration lactulose did not result in diarrhea in sows or adult minipigs, there was only a slight decrease in the dry matter content of faeces. In contrast to findings in human beings only traces of lactulose reached the hind gut, although higher lactulose concentrations were measured at the end of the small intestine (in piglets: 10-40 g, in fattening pigs 40-70 g lactulose per kg dry matter of chyme). The oral intake of lactulose did not increase the concentration of lactic acid or volatile fatty acids in the content of the small intestine and did not reduce the pH in the chyme, but in the contents of cecum and colon ascendens higher concentrations of volatile fatty acids were measured (in piglets: significantly higher values, in fattening pigs slightly increased concentrations). In piglets as well as in fattening pigs lactulose resulted in reduced concentrations of ammonia in the content of small and large intestine, further more the concentrations of lipopolysaccharides were increased in the colonal chyme, when pigs ingested the lactulose containing diet. Due to the fact that only small amounts of lactulose reached the hind gut there are doubts, whether lactulose has comparable dietetic effects in pigs as known from human beings (for example laxative effects, forced elimination of bacteria like salmonella). The results obtained here in pigs underline the necessity of experimental studies in the target species (including parameters of digestive physiology, chemical/microbial composition of the chyme) before substances are used and recommended for dietetic purposes in feeding practice. In spite of generally adopted similarity of the alimentary tract in pigs and human beings there are eventually some important differences within the intestine, its digestive capacity or in reactions on ingested substances leading to unexpected results.     

Dietary lactulose decreases apparent nitrogen absorption and increases apparent calcium and magnesium absorption in healthy dogs

To study the effect of lactulose on the route of nitrogen excretion, we fed six healthy, adult dogs on diets containing either 0, 1 or 3 g lactulose/MJ metabolizable energy according to a 3 × 3 Latin square design. The results were analysed to identify statistically significant linear trend effects of lactulose. Faecal pH was significantly lowered by lactulose. Faecal ammonium and nitrogen excretion tended to be raised by lactulose feeding whereas urinary urea excretion was significantly reduced. Lactulose feeding significantly lowered apparent nitrogen digestibility. It is concluded that lactulose feeding shifts nitrogen excretion from urine to faeces in dogs which may be beneficial for liver patients. The data are in line with the concept that lactulose stimulates bacterial growth in the colon which in turn enhances faecal nitrogen excretion and lowers the entry of colonic ammonia into the bloodstream, leading to a lesser workload for the liver and less urinary nitrogen excretion. Lactulose consumption was also found to produce a dose-dependent increase in the apparent absorption of calcium and magnesium, but not phosphorus.     

Evaluation of intestinal carbohydrate malabsorption in the dog by pulmonary hydrogen gas excretion

Breath H2 was measured for the assessment of intestinal carbohydrate absorption in healthy, fasted dogs before and after the ingestion of carbohydrate test meals. The dogs were fed lactulose, xylose, glucose, a hypoallergenic diet, or the hypoallergenic diet supplemented with rice, corn, or wheat flour. Breath samples for H2 analysis were collected by an interval-sampling technique during tidal breathing and were analyzed by thermal conductivity gas chromatography. Pulmonary H2 excretion in fasted dogs never exceeded 1 part per million (molecules of H2 per 10(6) molecules of air). Breath H2 excretion after the ingestion of 12.5 g of glucose, a completely absorbed monosaccharide, was not significantly different (P greater than 0.05) from that during fasting; however, ingestion of 12.5 g of xylose, an incompletely absorbed pentose, significantly increased (P less than 0.001) breath H2 excretion. After ingestion of 12.5, 25, or 50 g of lactulose, a nonabsorbable disaccharide, pulmonary H2 excretion increased significantly (P less than 0.001) over fasting amounts and the increases were different (P less than 0.001) from one another. Increases in breath H2 excretion correlated (r = 0.97) with increases in lactulose dose. Breath H2 excretion after the ingestion of the hypoallergenic diet did not significantly (P greater than 0.05) differ from that after fasting. The addition of rice flour to this diet did not significantly (P greater than 0.05) increase H2 production. However, the addition of wheat or corn flour to this diet significantly (P less than 0.001) increased breath H2 excretion.(ABSTRACT TRUNCATED AT 250 WORDS)     

Evaluation of carbohydrate malassimilation and intestinal transit time in cats by measurement of breath hydrogen excretion

Techniques for the measurement of breath hydrogen excretion have been evaluated in dogs and the breath hydrogen test has been shown to be useful for clinical diagnosis and as a research tool. A simple method was developed for collection of expired air and measurement of breath hydrogen concentrations in cats, which enabled demonstration of carbohydrate malassimilation. Breath hydrogen concentrations were measured in healthy cats after food was withheld and after xylose and lactulose administration. Breath samples were collected by use of an open flow system with the cat confined in an acrylic plastic chamber. Breath hydrogen excretion did not exceed 0.53 ml of hydrogen/h in cats not fed. Breath hydrogen concentrations after the ingestion of xylose, a pentose sugar given orally at 0.75 g/kg of body weight, were not significantly higher from those of cats not fed. After ingestion of 3.35 g of lactulose, a nonabsorbable disaccharide, breath hydrogen excretion increased and breath hydrogen concentrations were significantly higher by 45 minutes (P less than 0.05) and 60 minutes (P less than 0.01) from breath hydrogen concentrations measured in cats not fed and after xylose administration. Administration of lactulose at an increased dosage resulted in further significant (P less than 0.01) increases in breath hydrogen excretion. In this study, mouth-to-cecum transit times were variable. A mean +/- SEM mouth-to-cecum transit time of 86 +/- 6 minutes was calculated from measurement of breath hydrogen excretion after oral administration of 3.35 g of lactulose.(ABSTRACT TRUNCATED AT 250 WORDS)     

Kinetics of urinary recovery of five sugars after orogastric administration in healthy dogs

OBJECTIVE: To describe the kinetics of urinary recovery (UR) of 5 sugars used for gastrointestinal permeability and mucosal function testing following orogastric administration of lactose, rhamnose, xylose, methylglucose, and sucrose. ANIMALS: 7 healthy male Beagles. PROCEDURES: A sugar solution containing lactulose, rhamnose, xylose, methylglucose, and sucrose was administered by orogastric intubation to healthy dogs. Urine samples were collected immediately before sugar solution administration (baseline) and at 2-hour intervals thereafter. The UR of the 5 sugars was determined from urine concentrations measured by high pressure liquid chromatography and pulsed amperometric detection. Percent urinary recovery (%UR) of the total UR up to 12 hours after sugar solution administration was calculated for each sugar at 2-hour intervals. RESULTS: Mean %UR exceeded 85% for all 5 sugars at 6 hours after orogastric administration of the sugar solution and exceeded 90% after 8 hours. CONCLUSIONS AND CLINICAL RELEVANCE: In healthy dogs, a urine collection period of 6 hours is sufficient for gastrointestinal permeability and mucosal function testing following orogastric administration of lactulose, rhamnose, xylose, methylglucose, and sucrose.     

复原乳鉴别指标的研究进展

复原乳是炼乳和全脂乳粉与水勾兑成的原料乳,随着乳制品需求的增加,往其中掺入复原乳现象日益严重,因此复原乳的检测成为牛乳质量的重要指标之一,被广大生产厂家和消费者所重视。本文重点介绍乳制品中荧光物质、热处理产物、乳果糖含量和蛋白质理化性质等4类复原乳鉴别指标的研究进展。