Two new sensitive spectrophotometric methods are reported for determination of tartrazine (Tz) (E102) in some commercial food samples. The first method involves two coupled reactions, the reduction of Cu(II) to Cu(I) ...Two new sensitive spectrophotometric methods are reported for determination of tartrazine (Tz) (E102) in some commercial food samples. The first method involves two coupled reactions, the reduction of Cu(II) to Cu(I) by the analyte in acetate buffer medium (pH = 5.9) at 30°C and the complexation reaction between Cu(I) and Tz oxidized form to yield Cu-Tz complex (method I). The other method is based on oxidation of Tz by alkaline KMnO4. These reactions are monitored spectrophotometrically at maximum absorbances 332 and 610 nm for methods (I and II) respectively. Variables affecting these reactions are carefully studied and the conditions are optimized. The stability constants are calculated at 293, 303, 313 and 323 K. The thermodynamic parameters, Gibb’s free energy change (ΔG), entropy change (ΔS), and enthalpy change (ΔH) associated with the complexation reaction are calculated and discussed. Under optimized conditions the proposed methods (I, II) obey Beer’s law 10.69 - 85.50, 5.34 - 34.12 μg·ml<sup>-1</sup> of Tz respectively. The molar absorptivity, sandel sensitivity, detection and quantification limits are calculated. Matrix effects are also investigated. The methods are successfully applied to the quantification of Tz in different commercially food samples. The results obtained are in good agreement with those obtained by the reported methods at the 95% confidence level.展开更多
Various opinions have been presented on the merits and demerits that breastfeeding gives for the allergic onset of the babies. In this report, we focused on whether food proteins eaten by mother mice and secreted into...Various opinions have been presented on the merits and demerits that breastfeeding gives for the allergic onset of the babies. In this report, we focused on whether food proteins eaten by mother mice and secreted into breast milk as IgA-immune complexes contribute to the allergy prevention through oral tolerance in infants who ingest the milk. BALB/c mice were divided into two groups;E-group fed only egg white proteins and M-group fed only cow’s milk proteins as a dietary protein source. After immunizing M-group infants fed their own mother’s milk with ovalbumin/alum, diarrhea associated with experimental Th2 intestinal inflammation was induced by oral administration of ovalbumin. The diarrhea was dramatically suppressed in E-group infants. Concomitantly, low level of serum anti-ovalbumin- and ovomucoid-IgG1 and IgE, suppression of IL-4 synthesis by spleen cells, and low incidence of anaphylactic death after intravenous injection of ovalbumin were observed preferentially in E-infants. Immune complexes of respective dietary proteins and IgA were found in the breast milk obtained from each group of mother. Oral administration of pseudo immune complex chemically synthesized with ovalbumin and monoclonal mouse IgA in advance effectively suppressed anti-ovalbumin-IgG1 synthesis in adult mice after immunization with ovalbumin. The tolerance induced by the pseudo immune complex of ovalbumin diminished spontaneously while mice did not take egg white proteins. Thus, immune tolerance and then prevention of allergic disorder against dietary proteins were acquired via breastfeeding by mothers feeding the relevant proteins, probably through the immune complexes of dietary proteins and sIgAs secreted into breast milk.展开更多
This paper reviews literature on the relationship between food supply and obesity. The focus is on the supply, cost, and variety of food through various types of food outlets and the impact of these factors on obesity...This paper reviews literature on the relationship between food supply and obesity. The focus is on the supply, cost, and variety of food through various types of food outlets and the impact of these factors on obesity in developed countries. The article reveals complex relationships between food supply factors and obesity. A numer of factors related to lifestyles including the mobility of populations and the use of motor vehicles greatly reduce the impact of the local environment on family and individual eating patterns. However, obesity is also affected by factors such as the type and density of food outlets, the cost of food, the travel distance and means of transport to the food outlet. While the relationship between food supply and obesity in the literature reveals complex and mixed findings, this paper concludes obesity is complex and food supply is only part of this phenomenon’s predictors. Because the relationship between food supply and obesity is mediated by such multiple and complex factors including population behaviours, beliefs, lifestyles, knowledge and both food and physical environments;multiple strategies including policy development and other strategies aimed at manipulating food environments, physical environments, populations’ beliefs, behaviours and practices must be considered in searching for evidence to effectively combat obesity.展开更多
Exploring how food web complexity emerges and evolves in island ecosystems remains a major challenge in ecology.Food webs assembled from multiple islands are commonly recognized as highly complex trophic networks that...Exploring how food web complexity emerges and evolves in island ecosystems remains a major challenge in ecology.Food webs assembled from multiple islands are commonly recognized as highly complex trophic networks that are dynamic in both space and time.In the context of global climate change,it remains unclear whether food web complexity will decrease in a monotonic fashion when undergoing habitat destruction(e.g.,the inundation of islands due to sea-level rise).Here,we develop a simple yet comprehensive patch-dynamic framework for complex food web metacommunities subject to the competition-colonization tradeof between basal species.We found that oscillations in food web topological complexity(characterized by species diversity,mean food chain length and the degree of omnivory)emerge along the habitat destruction gradient.This outcome is robust to changing parameters or relaxing the assumption of a strict competitive hierarchy.Having oscillations in food web complexity indicates that small habitat changes could have disproportionate negative efects on species diversity,thus the success of conservation actions should be evaluated not only on changes in biodiversity,but also on system robustness to habitat alteration.Overall,this study provides a parsimonious mechanistic explanation for the emergence of food web complexity in island ecosystems,further enriching our understanding of metacommunity assembly.展开更多
介绍了一种复杂基质的食品中甜蜜素的快速气相色谱检测方法(GC-FID).样品通过水提取后离心,用正己烷对提取液进行净化.取25 mL水相,先后加入5 mL 50 g/L的亚硝酸钠和5 mL 100 g/L的硫酸,密闭冰浴衍生0.5 h.经GC/MS定性,最终衍生产物为...介绍了一种复杂基质的食品中甜蜜素的快速气相色谱检测方法(GC-FID).样品通过水提取后离心,用正己烷对提取液进行净化.取25 mL水相,先后加入5 mL 50 g/L的亚硝酸钠和5 mL 100 g/L的硫酸,密闭冰浴衍生0.5 h.经GC/MS定性,最终衍生产物为环己烷亚硝酸酯.对于10 g样品的检测限为1.5 mg/kg (信噪比>3.0),4个水平添加甜蜜素的回收率,范围为62.55%～106.71%,平均回收率为(80.89±9.63)%,平均变异系数为12.10%.本方法满足复杂样品中的低浓度的甜蜜素监测.展开更多
文摘Two new sensitive spectrophotometric methods are reported for determination of tartrazine (Tz) (E102) in some commercial food samples. The first method involves two coupled reactions, the reduction of Cu(II) to Cu(I) by the analyte in acetate buffer medium (pH = 5.9) at 30°C and the complexation reaction between Cu(I) and Tz oxidized form to yield Cu-Tz complex (method I). The other method is based on oxidation of Tz by alkaline KMnO4. These reactions are monitored spectrophotometrically at maximum absorbances 332 and 610 nm for methods (I and II) respectively. Variables affecting these reactions are carefully studied and the conditions are optimized. The stability constants are calculated at 293, 303, 313 and 323 K. The thermodynamic parameters, Gibb’s free energy change (ΔG), entropy change (ΔS), and enthalpy change (ΔH) associated with the complexation reaction are calculated and discussed. Under optimized conditions the proposed methods (I, II) obey Beer’s law 10.69 - 85.50, 5.34 - 34.12 μg·ml<sup>-1</sup> of Tz respectively. The molar absorptivity, sandel sensitivity, detection and quantification limits are calculated. Matrix effects are also investigated. The methods are successfully applied to the quantification of Tz in different commercially food samples. The results obtained are in good agreement with those obtained by the reported methods at the 95% confidence level.
文摘Various opinions have been presented on the merits and demerits that breastfeeding gives for the allergic onset of the babies. In this report, we focused on whether food proteins eaten by mother mice and secreted into breast milk as IgA-immune complexes contribute to the allergy prevention through oral tolerance in infants who ingest the milk. BALB/c mice were divided into two groups;E-group fed only egg white proteins and M-group fed only cow’s milk proteins as a dietary protein source. After immunizing M-group infants fed their own mother’s milk with ovalbumin/alum, diarrhea associated with experimental Th2 intestinal inflammation was induced by oral administration of ovalbumin. The diarrhea was dramatically suppressed in E-group infants. Concomitantly, low level of serum anti-ovalbumin- and ovomucoid-IgG1 and IgE, suppression of IL-4 synthesis by spleen cells, and low incidence of anaphylactic death after intravenous injection of ovalbumin were observed preferentially in E-infants. Immune complexes of respective dietary proteins and IgA were found in the breast milk obtained from each group of mother. Oral administration of pseudo immune complex chemically synthesized with ovalbumin and monoclonal mouse IgA in advance effectively suppressed anti-ovalbumin-IgG1 synthesis in adult mice after immunization with ovalbumin. The tolerance induced by the pseudo immune complex of ovalbumin diminished spontaneously while mice did not take egg white proteins. Thus, immune tolerance and then prevention of allergic disorder against dietary proteins were acquired via breastfeeding by mothers feeding the relevant proteins, probably through the immune complexes of dietary proteins and sIgAs secreted into breast milk.
文摘This paper reviews literature on the relationship between food supply and obesity. The focus is on the supply, cost, and variety of food through various types of food outlets and the impact of these factors on obesity in developed countries. The article reveals complex relationships between food supply factors and obesity. A numer of factors related to lifestyles including the mobility of populations and the use of motor vehicles greatly reduce the impact of the local environment on family and individual eating patterns. However, obesity is also affected by factors such as the type and density of food outlets, the cost of food, the travel distance and means of transport to the food outlet. While the relationship between food supply and obesity in the literature reveals complex and mixed findings, this paper concludes obesity is complex and food supply is only part of this phenomenon’s predictors. Because the relationship between food supply and obesity is mediated by such multiple and complex factors including population behaviours, beliefs, lifestyles, knowledge and both food and physical environments;multiple strategies including policy development and other strategies aimed at manipulating food environments, physical environments, populations’ beliefs, behaviours and practices must be considered in searching for evidence to effectively combat obesity.
基金J.L.is supported by the Natural Science Foundation of China(No.32271548&31901175).
文摘Exploring how food web complexity emerges and evolves in island ecosystems remains a major challenge in ecology.Food webs assembled from multiple islands are commonly recognized as highly complex trophic networks that are dynamic in both space and time.In the context of global climate change,it remains unclear whether food web complexity will decrease in a monotonic fashion when undergoing habitat destruction(e.g.,the inundation of islands due to sea-level rise).Here,we develop a simple yet comprehensive patch-dynamic framework for complex food web metacommunities subject to the competition-colonization tradeof between basal species.We found that oscillations in food web topological complexity(characterized by species diversity,mean food chain length and the degree of omnivory)emerge along the habitat destruction gradient.This outcome is robust to changing parameters or relaxing the assumption of a strict competitive hierarchy.Having oscillations in food web complexity indicates that small habitat changes could have disproportionate negative efects on species diversity,thus the success of conservation actions should be evaluated not only on changes in biodiversity,but also on system robustness to habitat alteration.Overall,this study provides a parsimonious mechanistic explanation for the emergence of food web complexity in island ecosystems,further enriching our understanding of metacommunity assembly.
