Ability of surfactant hydrophobic tail group size to alter lipid oxidation in oil-in-water emulsions.

Oxidation of oil-in-water emulsion droplets is influenced by the properties of the interfacial membrane surrounding the lipid core. Previous work has shown that an important factor in the oxidation of oil-in-water emulsions is surfactant properties that impact interactions between water-soluble prooxidants and lipids in the emulsion droplet. The purpose of this research was to study the impact of surfactant hydrophobic tail group size on lipid oxidation in oil-in-water emulsions stabilized by polyoxyethylene 10 lauryl ether (Brij-lauryl) or polyoxyethylene 10 stearyl ether (Brij-stearyl). The ability of iron to decompose cumene peroxide was similar in hexadecane emulsions stabilized by Brij-stearyl and Brij-lauryl. Oxidation of methyl linoleate in hexadecane emulsions containing cumene peroxide was greater in droplets stabilized by Brij-lauryl than in those stabilized by Brij-stearyl at pH 3 with no differences observed at pH 7.0. Oxidation of salmon oil was greater in emulsions stabilized by Brij-lauryl than in those stabilized by Brij-stearyl as determined by both lipid peroxides and headspace propanal. These results suggest that surfactant hydrophobic tail group size may play a minor role in lipid oxidation in oil-in-water emulsions.

Ability of surfactant headgroup size to alter lipid and antioxidant oxidation in oil-in-water emulsions.

Oxidation of oil-in-water emulsion droplets is influenced by the properties of the interfacial membrane surrounding the lipid core. To evaluate how surfactant headgroup size influences lipid oxidation rates, emulsions were prepared with polyoxyethylene 10 stearyl ether (Brij 76) or polyoxyethylene 100 stearyl ether (Brij 700), which are structurally identical except for their hydrophilic headgroups, with Brij 700 containing 10 times more polyoxyethylene groups than Brij 76. Fe(2+)-promoted decomposition of cumene hydroperoxide was lower in Brij 700-stabilized than in Brij 76-stabilized hexadecane emulsions. Fe(2+)-promoted alpha-tocopherol oxidation rates were similar in hexadecane emulsion regardless of surfactant type. Brij 700 decreased production of hexanal from methyl linoleate and the formation of lipid peroxides and propanal from salmon oil compared to emulsions stabilized by Brij 76. These results indicate that emulsion droplet interfacial thickness could be an important determinant in the oxidative stability of food emulsions.

Culture, coping, and context: primary and secondary control among Thai and American youth.

Do cultural values and traditions influence the development of coping styles ? To address this question, we compared self-reports of coping by 6-14-year-olds in Thailand and the U.S. One hundred and forty-one children were interviewed about six common stressors: separation from a friend, injection in a doctor's office, adult anger, peer animosity, school failure, and physical injury. Children's self-reported coping methods were coded as overt or covert. Coping goals were coded as reflecting primary control (attempts to influence objective conditions), secondary control (attempts to adjust oneself to objective conditions), or relinquished control. Although findings revealed numerous cross-national similarities, there were also multiple main and interaction effects involving culture, suggesting that sociocultural context may be critical to our understanding of child coping. Consistent with literature on Thai culture, Thai children reported more than twice as much covert coping as American children for stressors involving adult authority figures (i.e. adult anger, injection in doctor's office). Thai children also reported more secondary control goals than Americans when coping with separation, but American children were five times as likely as Thais to adopt secondary control goals for coping with injury. The findings support a model of coping development in which culture and stressor characteristics interact, with societal differences most likely to be found in situations where culture-specific norms become salient.

A multimethod study of problem behavior among Thai and American children in school: teacher reports versus direct observations.

Previous literature describes Thai children as unusually polite, deferent, and behaviorally restrained. Yet, in a recent study employing teacher reports, Thai children were reported to show many more behavior problems than American children. Such a finding may reflect culture-linked differences in the perspective of Thai versus American teachers. To explore this possibility, we used trained observers to conduct direct observations of Thai and American children's school behavior, and we obtained teacher reports on the same children. Observational results were precisely the opposite of previous and present teacher-report findings: Observers reported twice as much problem behavior and off-task behavior in American children as in their Thai age-mates. This pattern may reflect Thai-U.S. differences in teachers' style, societal values and practices, even child temperament. The finding support the value of direct behavior observation in cross-national research on child problems.

Behavioral and emotional problems among Thai and American adolescents: parent reports for ages 12-16.

We studied adolescents' behavioral and emotional problems in the United States and in Thailand, a Buddhist country in which, reportedly, aggression is discouraged and self-control, emotional restraint, and social inhibition are encouraged. Standardized parent reports on 118 problems revealed 45 Thai-U.S. differences. Thai adolescents were reported to show more overcontrolled problems (e.g., shyness, compulsivity, inhibition of talking, fearfulness, and constipation) than American adolescents (p < .0001). The two groups did not differ reliably in total undercontrolled problems, but Americans showed higher levels of direct, overt, and interpersonally aggressive undercontrol (e.g., fighting and bullying), whereas Thais showed more indirect and subtle undercontrol that was not interpersonally aggressive (e.g., sulking and sullenness). The findings suggest that different cultures may be linked to different styles of adolescent problem behavior.

Adult attitudes toward over- and undercontrolled child problems: urban and rural parents and teachers from Thailand and the United States.

In a study of adult attitudes, urban and rural parents and teachers in Thailand and the U.S. made judgments about two children, one with overcontrolled problems (e.g. shyness, fear), one with undercontrolled problems (e.g. disobedience, fighting). Consistent with previous literature, Thais (vs Americans) rated problems of both types less serious, less worrisome, less likely to reflect personality traits, and more likely to improve with time. Urban-rural differences and parent-teacher differences had negligible impact. The findings suggest that certain cultural differences in adult attitudes toward child problems may be robust across parents and teachers and across urban and rural settings.

Epidemiology of behavioral and emotional problems among Thai and American children: teacher reports for ages 6-11.

As a sequel to comparison between reports by parents, we compared behavioral/emotional problems of 6-11-yr-old Thai and American children reported by teachers. These revealed higher ratings for Thai than for American children on nearly all problems showing significant cross-national differences. Thai children were rated higher on both overcontrolled and undercontrolled behavior and had more overcontrolled than undercontrolled problems (p less than 0.0001). Boys were higher than girls on all 48 problems than showed significant sex differences. The findings underscore (1) the impact of culture on children's problems in the school setting and (2) the importance of surveying teacher as well as parent perspectives.