Lactose intolerance is becoming a health state that requires the restriction of dairy products in the diet of people suffering from this condition. But milk and dairy products, due to a well-balanced composition in th...Lactose intolerance is becoming a health state that requires the restriction of dairy products in the diet of people suffering from this condition. But milk and dairy products, due to a well-balanced composition in the main macro and micronutrients, cannot be missing from the diet of the consumer of any age. For these reasons, in recent years, in the milk processing industry, the production of low-lactose or lactose-free dairy products is explored. To reduce the lactose content of dairy raw materials, various industrial and biotechnological methods were used: enzymatic hydrolysis of lactose, baromembranous methods, bioconversion of lactose by lactic bacteria and others. The most widely used lactase enzymes in the industry are mesophilic enzymes from filamentous fungi <span>(<i>Aspergillus</i> <i>spp</i>.)</span> and yeasts <span>(<i>Kluyveromyces</i> <i>spp</i>.). </span>Therefore, the aim of this study was to evaluate the effect of the commercial enzyme <i>β</i>-galactosidase on the hydrolysis of cow’s milk at different enzyme <span>con</span><span>centrations, temperatures and pH. Two commercial enzymes <i>β</i>-galactosi</span><span>dase</span> obtain<span>ed from <i>Bacillus</i><span> <i>licheniformis</i></span> and <i>β</i>-galactosidase obtained from <i>Kluyve</i></span><i>romyces</i><span> <i>lactis</i></span>, were used in this study, according to information provided by the manufacturer. The thermal stability of lactose, the effect of milk pH, the effect of temperature, duration of hydrolysis and the amount of enzymes on the lactose hydrolysis degree and the sweetness degree of milk were determined. Research has identified the optimal parameters for obtaining a high degree of lactose hydrolysis in the use of these enzymes. Therefore, to ensure a high lactose hydrolysis degree (over 80%), the following lactose hydrolysis regimens were identified: temperature 4°C - 6<span style="white-space:normal;">°</span>C, 0.3% <i>Bacillus</i><span> <i>licheniformis</i></span> enzymes, duration 4 hours;temperature 4<span style="white-space:normal;">°</span>C - 6<span style="white-space:normal;">°</span>C, 0.3% enzymes from <i>Klavyromyces</i><span> <i>lactis</i></span>, duration 12 hours and temperature 38<span style="white-space:normal;">°</span>C - 40<span style="white-space:normal;">°</span>C, 0.15% enzymes from (<i>Bacillus</i><span> <i>licheniformis</i></span> or <i>Klavyromyces</i><span> <i>lactis</i></span>), duration 2 - 3 hours. The results obtained allow the efficient use of <i>Bacillus</i><span> <i>licheniformis</i></span> and <i>Klavyromyces</i><span> <i>lactis</i></span> enzymes in industrial processes for the manufacture of “lactose-free” or “low-lactose” drinking milk and fermented dairy products for people with lactose intolerance.展开更多
To determine lactose metabolism and lactase activity in Chinese children of different ages, prevalence of lactase deficiency (LD), and lactose intolerance (LI) Methods All 1168 healthy subjects between ...To determine lactose metabolism and lactase activity in Chinese children of different ages, prevalence of lactase deficiency (LD), and lactose intolerance (LI) Methods All 1168 healthy subjects between 3 and 13 years were recruited from schools in four large cities in China They were screened by a 25?g lactose tolerance test Some subjects were challenged with 50?g milk powder on different days Both indicators, the expiratory H 2 concentration and intolerance symptoms, were analyzed Results LD occurred in 38 5% of children in the 3-5 year age group, and 87% of the 7-8 year and 11-13 year old groups The age of occurrence for LD may be at 7-8 years among Chinese children The prevalence of LI among Chinese children was 12 2% at age 3-5 years, 33 1% at age 7-8 years, and 30 5% at age 11-13 years, respectively Conclusion The results demonstrate that LD is very common in Chinese children from these four cities LD and LI have a dose dependent response: lactose absorption and symptoms are based on lactase activity The relationship between breast feeding history (or the history of cow milk intake) and lactase activity among Chinese children has not been established展开更多
The analysis of any kinetic process involves the development of a mathematical model with predictive purposes. Generally, those models have characteristic parameters that should be estimated experimentally. A typical ...The analysis of any kinetic process involves the development of a mathematical model with predictive purposes. Generally, those models have characteristic parameters that should be estimated experimentally. A typical example is Michaelis-Menten model for enzymatic hydrolysis. Even though conventional kinetic models are very useful, they are only valid under certain experimental conditions. Besides, frequently large standard errors of estimated parameters are found due to the error of experimental determinations and/or insufficient number of assays. In this work, we developed an artificial neural network （ANN） to predict the performance of enzyme reactors at various operational conditions. The net was trained with experimental data obtained under different hydrolysis conditions of lactose solutions or cheese whey and different initial concentrations of enzymes or substrates. In all the experiments, commercial 13-galactosidase either free or immobilized in a chitosan support was used. The neural network developed in this study had an average absolute relative error of less than 5% even using few experimental data, which suggests that this tool provides an accurate prediction method for lactose hydrolysis.展开更多
AIM: To evaluate the prevalence of lactose intolerance (LI) following a load of 12.5 g in patients diagnosed as high-grade malabsorbers using the hydrogen breath test (HBT)-25.METHODS: Ninety patients showing high-gra...AIM: To evaluate the prevalence of lactose intolerance (LI) following a load of 12.5 g in patients diagnosed as high-grade malabsorbers using the hydrogen breath test (HBT)-25.METHODS: Ninety patients showing high-grade malabsorption at HBT-25 were submitted to a second HBT with a lactose load of 12.5 g.Peak hydrogen production,area under the curve of hydrogen excretion and occurrence of symptoms were recorded.RESULTS: Only 16 patients (17.77%) with positive HBT-25 proved positive at HBT-12.5.Hydrogen production was lower as compared to HBT-25 (peak value 21.55 parts per million (ppm) ± 29.54 SD vs 99.43 ppm ± 40.01 SD; P < 0.001).Symptoms were present in only 13 patients.The absence of symptoms during the high-dose test has a high negative predictive value (0.84) for a negative low-dose test.The presence of symptoms during the first test was not useful for predicting a positive low-dose test (positive predictive value 0.06-0.31).CONCLUSION: Most patients with a positive HBT-25 normally absorb a lower dose of lactose and a strict lactose restriction on the basis of a "standard" HBT is,in most instances,unnecessary.Thus,the 25 g lactose tolerance test should probably be substituted by the 12.5 g test in the diagnosis of LI,and in providing dietary guidelines to patients with suspected lactose malabsorption/intolerance.展开更多
文摘Lactose intolerance is becoming a health state that requires the restriction of dairy products in the diet of people suffering from this condition. But milk and dairy products, due to a well-balanced composition in the main macro and micronutrients, cannot be missing from the diet of the consumer of any age. For these reasons, in recent years, in the milk processing industry, the production of low-lactose or lactose-free dairy products is explored. To reduce the lactose content of dairy raw materials, various industrial and biotechnological methods were used: enzymatic hydrolysis of lactose, baromembranous methods, bioconversion of lactose by lactic bacteria and others. The most widely used lactase enzymes in the industry are mesophilic enzymes from filamentous fungi <span>(<i>Aspergillus</i> <i>spp</i>.)</span> and yeasts <span>(<i>Kluyveromyces</i> <i>spp</i>.). </span>Therefore, the aim of this study was to evaluate the effect of the commercial enzyme <i>β</i>-galactosidase on the hydrolysis of cow’s milk at different enzyme <span>con</span><span>centrations, temperatures and pH. Two commercial enzymes <i>β</i>-galactosi</span><span>dase</span> obtain<span>ed from <i>Bacillus</i><span> <i>licheniformis</i></span> and <i>β</i>-galactosidase obtained from <i>Kluyve</i></span><i>romyces</i><span> <i>lactis</i></span>, were used in this study, according to information provided by the manufacturer. The thermal stability of lactose, the effect of milk pH, the effect of temperature, duration of hydrolysis and the amount of enzymes on the lactose hydrolysis degree and the sweetness degree of milk were determined. Research has identified the optimal parameters for obtaining a high degree of lactose hydrolysis in the use of these enzymes. Therefore, to ensure a high lactose hydrolysis degree (over 80%), the following lactose hydrolysis regimens were identified: temperature 4°C - 6<span style="white-space:normal;">°</span>C, 0.3% <i>Bacillus</i><span> <i>licheniformis</i></span> enzymes, duration 4 hours;temperature 4<span style="white-space:normal;">°</span>C - 6<span style="white-space:normal;">°</span>C, 0.3% enzymes from <i>Klavyromyces</i><span> <i>lactis</i></span>, duration 12 hours and temperature 38<span style="white-space:normal;">°</span>C - 40<span style="white-space:normal;">°</span>C, 0.15% enzymes from (<i>Bacillus</i><span> <i>licheniformis</i></span> or <i>Klavyromyces</i><span> <i>lactis</i></span>), duration 2 - 3 hours. The results obtained allow the efficient use of <i>Bacillus</i><span> <i>licheniformis</i></span> and <i>Klavyromyces</i><span> <i>lactis</i></span> enzymes in industrial processes for the manufacture of “lactose-free” or “low-lactose” drinking milk and fermented dairy products for people with lactose intolerance.
文摘To determine lactose metabolism and lactase activity in Chinese children of different ages, prevalence of lactase deficiency (LD), and lactose intolerance (LI) Methods All 1168 healthy subjects between 3 and 13 years were recruited from schools in four large cities in China They were screened by a 25?g lactose tolerance test Some subjects were challenged with 50?g milk powder on different days Both indicators, the expiratory H 2 concentration and intolerance symptoms, were analyzed Results LD occurred in 38 5% of children in the 3-5 year age group, and 87% of the 7-8 year and 11-13 year old groups The age of occurrence for LD may be at 7-8 years among Chinese children The prevalence of LI among Chinese children was 12 2% at age 3-5 years, 33 1% at age 7-8 years, and 30 5% at age 11-13 years, respectively Conclusion The results demonstrate that LD is very common in Chinese children from these four cities LD and LI have a dose dependent response: lactose absorption and symptoms are based on lactase activity The relationship between breast feeding history (or the history of cow milk intake) and lactase activity among Chinese children has not been established
文摘The analysis of any kinetic process involves the development of a mathematical model with predictive purposes. Generally, those models have characteristic parameters that should be estimated experimentally. A typical example is Michaelis-Menten model for enzymatic hydrolysis. Even though conventional kinetic models are very useful, they are only valid under certain experimental conditions. Besides, frequently large standard errors of estimated parameters are found due to the error of experimental determinations and/or insufficient number of assays. In this work, we developed an artificial neural network （ANN） to predict the performance of enzyme reactors at various operational conditions. The net was trained with experimental data obtained under different hydrolysis conditions of lactose solutions or cheese whey and different initial concentrations of enzymes or substrates. In all the experiments, commercial 13-galactosidase either free or immobilized in a chitosan support was used. The neural network developed in this study had an average absolute relative error of less than 5% even using few experimental data, which suggests that this tool provides an accurate prediction method for lactose hydrolysis.
文摘AIM: To evaluate the prevalence of lactose intolerance (LI) following a load of 12.5 g in patients diagnosed as high-grade malabsorbers using the hydrogen breath test (HBT)-25.METHODS: Ninety patients showing high-grade malabsorption at HBT-25 were submitted to a second HBT with a lactose load of 12.5 g.Peak hydrogen production,area under the curve of hydrogen excretion and occurrence of symptoms were recorded.RESULTS: Only 16 patients (17.77%) with positive HBT-25 proved positive at HBT-12.5.Hydrogen production was lower as compared to HBT-25 (peak value 21.55 parts per million (ppm) ± 29.54 SD vs 99.43 ppm ± 40.01 SD; P < 0.001).Symptoms were present in only 13 patients.The absence of symptoms during the high-dose test has a high negative predictive value (0.84) for a negative low-dose test.The presence of symptoms during the first test was not useful for predicting a positive low-dose test (positive predictive value 0.06-0.31).CONCLUSION: Most patients with a positive HBT-25 normally absorb a lower dose of lactose and a strict lactose restriction on the basis of a "standard" HBT is,in most instances,unnecessary.Thus,the 25 g lactose tolerance test should probably be substituted by the 12.5 g test in the diagnosis of LI,and in providing dietary guidelines to patients with suspected lactose malabsorption/intolerance.
