Influence of nonfermented dairy products containing bacterial starter cultures on lactose maldigestion in humans

The effect of nonfermented dairy products containing yogurt or acidophilus cultures on lactose utilization by lactose-maldigesting humans was investigated. Yogurt and acidophilus milk containing 10(7) or 10(8) of Streptococcus thermophilus and Lactobacillus bulgaricus, or Lactobacillus acidophilus, respectively, were prepared using commercially processed 2% low fat milk. Immediately following inoculation, products were refrigerated. Lactose maldigestion was monitored by measuring breath hydrogen excretion at hourly intervals for 8 h following consumption of 400 ml of each test meal containing approximately 20 g of lactose. The yogurt milk containing 10(8) cfu/ml was shown to contain significant concentrations of microbial beta-galactosidase (EC 3.2.1.23; approximately 3 U/ml), which remained stable for at least 14 d at refrigerator temperatures. Breath hydrogen peaks were delayed and significantly lower (approximately 20 ppm at 5 to 7 h) than control values (approximately 70 ppm at 4 h), and intolerance symptoms were eliminated in all subjects. Yogurt milk containing 10(7) cfu/ml demonstrated intermediate breath hydrogen values and was marginally significantly different from control values. Lactobacillus acidophilus strains with varying resistance to bile and total beta-galactosidase-producing potential were also tested. Only one strain, LA-1, which demonstrated low bile resistance and intermediate beta-galactosidase activity, was capable of significantly decreasing breath hydrogen values when 10(8) cfu/ml of milk was consumed.     

Lactose absorption by postweaning rats from yogurt, quarg, and quarg whey

Lactose-intolerant postweaning rats were fed experimental diets including yogurt, quargs prepared from yogurt culture and buttermilk culture, and two types of whey obtained from quarg processing. After feeding each diet for a period of 7 d, absence of blood glucose elevation and occurrence of diarrhea were used as indicators of lactose malabsorption. Blood glucose assays and absence of diarrhea indicated that yogurt and quargs prepared from yogurt and buttermilk culture were well tolerated by the rats. Wheys containing the same levels of viable organisms and lactose as the quargs caused severe symptoms of diarrhea and poor lactose absorption as indicated by no changes in blood glucose levels. Plate counts and enzyme assays of gastrointestinal contents confirmed presence of viable culture organisms and beta-galactosidase activity after feeding the two types of quarg. The availability of viable organisms, the exogenous lactase activity, and especially the slow gastric emptying may all have contributed to more efficient hydrolysis and digestion of lactose from quargs and yogurt than from the wheys.     

生物技术在乳糖不耐受防治中的应用

原发性乳糖酶缺乏和乳糖不耐受（吸收不良）是全球性的健康问题。从基因工程技术生产乳糖酶、利用生物反应器生产低乳糖奶、基因治疗等3个方面介绍了生物技术在乳糖不耐受（吸收不良）防治中的应用，并提出口服经改造的益生菌制剂，从根本上解决乳糖酶缺乏的新思路。     

Effect of viable starter culture bacteria in yogurt on lactose utilization in humans

Breath hydrogen production was used as a measure of lactose malabsorption in human test subjects following the consumption of both heated and unheated cultured yogurt. Less hydrogen was produced when the subjects consumed the unheated cultured yogurt than when they consumed the heated product, indicating that lactose hydrolysis was improved in the small intestine of the individuals consuming the unheated cultured yogurt. Lactase activity in yogurt samples was increased in the presence of bile. Yogurt starter bacteria growing in milk normally do not hydrolyze more lactose than needed for their growth. However, the increased lactase activity in the presence of bile indicates that these bacteria could function as a source of lactase to hydrolyze lactose in the small intestine even though the organisms themselves are not expected to grow in that environment.     

Optimization and shelf life of a low-lactose yogurt with Lactobacillus rhamnosus HN001

Lactose intolerance results in gastrointestinal discomfort and the malabsorption of certain nutrients, such as calcium. The replacement of milk with low-lactose and probiotic-enriched dairy products is an effective strategy of mitigating the symptoms of lactose intolerance. Lactobacillus rhamnosus HN001 (HN001) is a safe, immunity-stimulating probiotic. We have developed a process to increase the hydrolysis of lactose and HN001 growth in yogurt versus β-galactosidase (βG) concentration and enzymatic hydrolysis time (EHT) before bacterial fermentation. The objective of this study was to optimize the conditions by which yogurt is processed as a function of βG and EHT using a multifactorial design, with lactose content, HN001 growth, process time, and sensory quality as dependent variables. Further, the shelf life of the optimized yogurt was evaluated. In the optimization study, polynomials explained the dependent variables. Based on Pearson correlation coefficients, HN001 growth correlated positively with the hydrolysis of lactose. However, low lactose content and high HN001 count increased the fermentation time and lowered the sensory quality. The optimized conditions-using polynomials to obtain yogurt with >1 × 10(7) cfu of HN001/mL, <10 g of lactose/L, and a minimum overall sensory quality of 7 on the Karlsruhe scale-yielded a theoretical value of 910 neutral lactose units/kg for βG and 2.3h for EHT, which were validated in an industrial-scale assay. Based on a shelf-life study at 3 temperatures, the hydrolysis of lactose and the growth of HN001 continue during storage. Arrhenius equations were developed for the variables in the shelf-life study. Our results demonstrate that it is feasible to develop a low-lactose yogurt to which HN001 has been added for lactose-intolerant persons who wish to strengthen their immune system.     

Influence of viable yogurt microflora on digestion of lactose by the rat.

Laboratory rats were fed experimental diets including yogurt, pasteurized yogurt, and simulated yogurt with sucrose or lactose for 7 days followed by a single experimental meal of yogurt, pasteurized yogurt, or simulated yogurt. Assays of blood galactose demonstrated that animals fed natural yogurt containing the viable culture microflora were able to absorb galactose more efficiently. Intestinal lactase activity of yogurt-fed animals was greater than in animals fed other experimental diets including pasteurized yogurt. Gastrointestinal survival of culture organisms was demonstrated in vivo up to 3 h after feeding, and thus, the viable cells resulted in more efficient hydrolysis which favored lactose digestion in natural yogurt.     

Influence of lactose concentration of milk and yogurt on growth rate of rats

Growth rates of rats fed lyophilized diets of yogurt, milk, 100% lactose-hydrolyzed milk, and 100% lactose-hydrolyzed yogurt were compared. No differences were significant in weight gains between the animals fed lactose-hydrolyzed diets over 3 wk. Further more, rats fed the lactose-hydrolyzed diets had significantly larger weight gains during the 1st wk than those fed unhydrolyzed diets. This may have been from the deleterious effect of lactose, which was in concentrations of 43% in milk and 36% in yogurt. However, by the 2nd wk, rats fed yogurt had growth rates similar to those fed lactose-hydrolyzed diets, and by the 3rd wk, no differences of growth rates were significant. Continued consumption of high concentrations of lactose improved digestion of lactose. Yogurt fermentation produced growth benefit as compared to the milk from which it was made by reducing the lactose content and by supplying microbial lactase activity.     

Dietary and biological factors influencing lactose intolerance

The number of Americans affected by lactose intolerance is estimated to be between 30 and 50 million people (NDDIC, 2005). Lactose intolerance is the symptoms experienced when the dose of lactose exceeds the digestive capacity of intestinal lactase (lactose maldigestion). Symptoms of intolerance typically include stomach discomfort, excessive flatulence and soft stool or diarrhea and are dependent on dose of lactose, transit time (influenced by meal composition), and colonic flora adaptation. Modest doses of lactose consumed with a meal on a regular basis are often very well tolerated. Lactose maldigestion may be caused by primary (most common), secondary, or congenital lactase non-persistence. Lactose maldigestion should not be thought of as a disease and is not a reliable indicator of lactose intolerance. The hydrogen breath test has become the most reliable method to diagnose lactose maldigestion.     

No difference in symptoms during challenges with homogenized and unhomogenized cow's milk in subjects with subjective hypersensitivity to homogenized milk

It has been hypothesized that certain consumers tolerate untreated cow's milk, but react to processed (i.e. homogenized and pasteurized) cow's milk although they do not suffer from IgE-mediated cow's milk allergy or lactose intolerance. The aim of the study was to compare the tolerance of unhomogenized and homogenized cow's milk in lactose tolerant adults who had repeatedly experienced better tolerance of unhomogenized than homogenized milk. Forty-four subjects were challenged with homogenized and unhomogenized cow's milk for five days in a randomized, double-blind, cross-over study. No differences in the symptoms during the challenges were found. Roughly half the subjects tolerated the homogenized milk better and the other half tolerated the unhomogenized milk better. The results of this study show no difference in the tolerance of homogenized and unhomogenized milk in adults with self-reported symptoms suggestive of hypersensitivity to homogenized milk.     

Lactase Activity of Cultured and Acidified Dairy Products

A method was standardized for determining lactase activity in cultured and acidified dairy products such as cottage cheese, sour cream, and yogurt. Cottage cheese and sour cream prepared by both the cultured and acidified processes and yogurt prepared by the direct acidification process did not possess lactase activity. However, cultured yogurt possessed considerable enzyme activity mainly due to lactase as an endoenzyme in the yogurt culture (Lactobacillus bulgaricus and Streptococcus thermophilus). Enzyme in yogurt increased with time of incubation, reaching a maximum of 8 orthonitrophenol β-d-galactopyranoside units per gram of yogurt in 4 h. S. thermophilus contained approximately three times more lactase than did L. bulgaricus. Also, an in vitro digestion process appeared to enhance the release of lactase from the composite yogurt culture. It was felt that cultured yogurt would be beneficial to individuals suffering from lactose intolerance not only because of reduced lactose but also because of lactase.     

Production of low-dosage lactose milk using lactase immobilised in hydrogel

A hydrogel based on chitosan was employed for the immobilisation of lactase with the aim of hydrolysing lactose and producing low-dosage lactose milk. The degree of swelling of the hydrogel was affected by the type of aqueous solution, pH and temperature. The lactase immobilisation capacities at pH 4.0 and pH 7.0 were 257.12 ± 3.18 and 157.87 ± 1.96 mg enzyme per g dried hydrogel, respectively, after 1440 min at room temperature. The activity of immobilised lactase ranged from 97.91 to 56.04 and 97.91 to 71.80% from the first to the tenth cycle of hydrolysis of standard lactose and lactose contained in UHT milk, respectively. Immobilised lactase in hydrogel could be applied for the production of low-dosage lactose milk for at least ten successive hydrolysis cycles. Moreover, hydrogels containing immobilised lactase could also be useful for the enzyme release in individuals with lactose intolerance.     

β-Galactosidase activity of commercial lactase samples in raw and pasteurized milk at refrigerated temperatures

Many consumers are unable to enjoy the benefits of milk due to lactose intolerance. Lactose-free milk is available but at about 2 times the cost of regular milk or greater, it may be difficult for consumers to afford. The high cost of lactose-free milk is due in part to the added cost of the lactose hydrolysis process. Hydrolysis at refrigerated temperatures, possibly in the bulk tank or package, could increase the flexibility of the process and potentially reduce the cost. A rapid β-galactosidase assay was used to determine the relative activity of commercially available lactase samples at different temperatures. Four enzymes exhibited low-temperature activity and were added to refrigerated raw and pasteurized milk at various concentrations and allowed to react for various lengths of time. The degree of lactose hydrolysis by each of the enzymes as a function of time and enzyme concentration was determined by HPLC. The 2 most active enzymes, as determined by the β-galactosidase assay, hydrolyzed over 98% of the lactose in 24 h at 2°C using the supplier's recommended dosage. The other 2 enzymes hydrolyzed over 95% of the lactose in 24 h at twice the supplier's recommended dosage at 2°C. Results were consistent in all milk types tested. The results show that it is feasible to hydrolyze lactose during refrigerated storage of milk using currently available enzymes.     

低乳糖奶粉的研制

研究了低乳糖奶粉的制作,通过乳糖酶的添加量、乳糖酶的水解温度、水解时间及水解时的pH对乳糖水解率、牛乳中微生物的影响,确定了低乳糖奶粉的水解条件;并对工艺条件进行了讨论。     

Organoleptic and physical properties of yogurt made from lactose hydrolysed milk

Low-lactose yogurt has been manufactured by using two commercial lactase enzymes: Lactozym and Maxilact. For each lactase enzyme two different enzyme treatments were examined: hydrolysing before fermentation and hydrolysing during fermentation.
When evaluated by the triangle test it was not possible to detect any significant difference in organoleptic properties, including sweetness, between the control yogurt and the yogurt samples made from hydrolysed milk. The addition of fruit and sugar made it possible to detect a difference in sweetness when triangle tested.
When lactase was added to evaporated milk (approx. 10% S N F) together with the starter culture, the results showed that addition of an amount equal to 500 - 700 LAU/litre resulted in a yogurt with about 2% lactose. A technology based on these results seems applicable to industrial manufacture.     

Recent advances on lactose intolerance: Tolerance thresholds and currently available answers

The genetically programmed reduction in lactase activity during adulthood affects 70% of the world adult population and can cause severe digestive disorders, which are the sign of lactose intolerance. Lactose intolerance symptoms vary depending on the residual lactase activity, the small bowel transit time, and especially the amount of ingested lactose. To formulate dairy products suitable for the vast majority of lactose intolerants, it is essential to define lactose intolerance threshold. A recent meta-analysis permitted to show that almost all lactose intolerants tolerate 12 g of lactose in one intake and approximately 18 g of lactose spread over the day. The prevalence and severity of lactose intolerance are probably overestimated by the general public. This misconception usually leads to an unnecessary reduction of dairy foodstuff consumption. Nevertheless, dairy products are essential for health mainly due to their calcium content and the positive influence of probiotic bacteria. The formulation of dairy products suitable for most intolerant and suspicious subjects seems necessary. The use of exogenous enzyme preparations, as well as the consumption of lactose-free products or products rich in probiotic bacteria are proposed as symptom-reducing strategies.     

DIRECT ENZYMATIC CONVERSION OF LACTOSE TO ACID: GLUCOSE OXIDASE AND HEXOSE OXIDASE

The conversion of lactose directly to an acid by glucose oxidase and hexose oxidase as a method of milk acidification was studied. Under the appropriate conditions, both enzymes demonstrated the capability to catalyze the conversion of sugar in milk to an acid, producing coagulation. A uniform distribution of oxygen under quiescent conditions was essential for the reaction and could be accomplished with the addition of hydrogen peroxide in the presence of catalase. Commercial samples of glucose oxidase caused a gradual decrease in pH of skim milk containing added glucose or lactase, (beta-galactosidase). Hexose oxidase, which can react with galactose and lactose as well as glucose, produced acid at a very slow rate in skim milk alone. When lactase was incorporated into the milk, the rate of reaction increased significantly.     

Evolution of carbohydrate fraction in carbonated fermented milks as affected by beta-galactosidase activity of starter strains

The influence of carbonation on the evolution of lactose, galactose and glucose in fermented milks with added probiotic bacteria (Lactobacillus casei, Lactobacillus acidophilus and/or Bifidobacterium bifidum) was evaluated and related to beta-galactosidase activity of starter strains. During incubation and first days of refrigeration, lactose hydrolysis resulting in the liberation of galactose and glucose occurred in CT (Streptococcus thermophilus/Lb. casei), AT (Str. thermophilus/Lb. acidophilus) and ABT fermented milks (Str. thermophilus/Lb. acidophilus/Bifid. bifidum). Levels of galactose were higher than those of glucose and could be related to the preferential consumption of glucose by actively growing bacteria. Through the incubation, lactose and monosaccharide levels were not affected by milk carbonation. However, during refrigerated storage the presence of this gas was associated with slightly lower content of lactose and higher levels of galactose and glucose in AT and ABT products but not in CT fermented milks. Through the refrigeration galactose was moderately utilised by Lb. acidophilus in AT products whereas the presence of Bifid. bifidum seems to prevent the consumption of this sugar in ABT fermented milks. Glucose remained constant, with minor variations in CT products but a continuous increase of this sugar occurred in carbonated AT and ABT fermented milks during storage. Beta-galactosidase activity displayed by Str. thermophilus strains was similar at pH 6.5 (initial pH of non-carbonated samples) and pH 6.3 (initial pH of carbonated samples) whereas Lb. acidophilus LaA3 showed greater beta-galactosidase activity at pH 6.3 than at higher pH values. Thus, the enhanced metabolic activity of Lb. acidophilus caused by the low initial pH of carbonated milk also promoted higher cellular beta-galactosidase activity that could have released greater amounts of galactose and glucose from lactose in AT and ABT fermented milks through the refrigerated period. In CT fermented milks, similar beta-galactosidase activity levels of Str. thermophilus at pH 6.5 and 6.3 together with the absence of beta-galactosidase activity in Lb. casei could explain the lack of differences on glucose and galactose content between carbonated and non-carbonated samples.     

乳糖在人体内的营养特性

乳糖是乳中惟一的碳水化合物,最易被人体吸收,被人体吸收后可变成多肽、氨基酸和脂肪酸,从而提高乳蛋白和乳脂的利用率。由于乳糖酶的缺乏,许多患有乳糖不耐受的人不能食用乳制品。从乳糖的含量、乳糖的消化代谢过程和乳糖不耐受的分类以及乳糖的营养功能进行阐述。     

The effects of probiotics in lactose intolerance: A systematic review

Over 60 percent of the human population has a reduced ability to digest lactose due to low levels of lactase enzyme activity. Probiotics are live bacteria or yeast that supplements the gastrointestinal flora. Studies have shown that probiotics exhibit various health beneficial properties such as improvement of intestinal health, enhancement of the immune responses, and reduction of serum cholesterol. Accumulating evidence has shown that probiotic bacteria in fermented and unfermented milk products can be used to alleviate the clinical symptoms of lactose intolerance (LI). In this systematic review, the effectiveness of probiotics in the treatment of LI was evaluated using 15 randomized double-blind studies. Eight probiotic strains with the greatest number of proven benefits were studied. Results showed varying degrees of efficacy but an overall positive relationship between probiotics and lactose intolerance.