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Oxidative discolouration in whole-head and cut lettuce: biochemical and environmental influences on a complex phenotype and potential breeding strategies to improve shelf-life
Lettuce discolouration is a key post-harvest trait. The major enzyme controlling oxidative discolouration
has long been considered to be polyphenol oxidase (PPO) however, levels of PPO and subsequent development of discolouration symptoms have not always correlated. The predominance of a latent state of the enzyme in plant tissues combined with substrate activation and contemporaneous suicide inactivation
mechanisms are considered as potential explanations for
this phenomenon. Leaf tissue physical properties have
been associated with subsequent discolouration and
these may be influenced by variation in nutrient
availability, especially excess nitrogen and head maturity at harvest. Mild calcium and irrigation stress has
also been associated with a reduction in subsequent
discolouration, although excess irrigation has been
linked to increased discolouration potentially through
leaf physical properties. These environmental factors,
including high temperature and UV light intensities,
often have impacts on levels of phenolic compounds
linking the environmental responses to the biochemistry
of the PPO pathway. Breeding strategies targeting the
PALand PPOpathway biochemistry and environmental
response genes are discussed as a more cost-effective
method of mitigating oxidative discolouration then
either modified atmosphere packaging or post-harvest
treatments, although current understanding of the
biochemistry means that such programs are likely to
be limited in nature and it is likely that they will need to be deployed alongside other methods for the foreseeable future
Consumo alimentar, estado nutricional e nÃvel de atividade fÃsica em comunidade universitária brasileira
OBJETIVO: Este estudo teve como objetivo avaliar a variabilidade e a frequência do consumo alimentar, o estado nutricional e o nÃvel de atividade fÃsica em uma comunidade universitária brasileira. MÉTODOS: A amostra constitui-se de 303 voluntários (130 homens e 173 mulheres) pertencentes à comunidade universitária do interior de São Paulo e avaliada por meio da disponibilização pela Internet do Questionário de Frequência Alimentar do International Physical Activity Questionaire e por meio da coleta da descrição autorreferida do peso e da altura. Foi realizada análise descritiva dos dados, análise de frequência alimentar e teste do coeficiente de correlação de Spearman. RESULTADOS: Foram observados inadequação dos hábitos alimentares, sobrepeso e obesidade na amostra estudada. As correlações entre os grupos alimentares apresentaram valores de magnitude maiores no grupo de mulheres que se alimentam de forma mais adequada do que os homens, mas não foram observadas diferenças entre os sexos no nÃvel de atividade fÃsica. Não houve correlação significativa entre grupos de alimentos consumidos, Ãndice de massa corporal e nÃvel de atividade fÃsica em ambos os sexos. CONCLUSÃO: A comunidade universitária estudada apresentou baixo consumo de frutas, legumes e verduras, bem como consumo insuficiente de alimentos do grupo de cereais e leguminosas
Mechanisms and efficacy of dietary FODMAP restriction in IBS
IBS is a debilitating condition that markedly affects quality of life. The chronic nature, high prevalence and associated comorbidities contribute to the considerable economic burden of IBS. The pathophysiology of IBS is not completely understood and evidence to guide management is variable. Interest in dietary intervention continues to grow rapidly. Ileostomy and MRI studies have demonstrated that some fermentable carbohydrates increase ileal luminal water content and breath hydrogen testing studies have demonstrated that some carbohydrates also increase colonic hydrogen production. The effects of fermentable carbohydrates on gastrointestinal symptoms have also been well described in blinded, controlled trials. Dietary restriction of fermentable carbohydrates (popularly termed the 'low FODMAP diet') has received considerable attention. An emerging body of research now demonstrates the efficacy of fermentable carbohydrate restriction in IBS; however, limitations still exist with this approach owing to a limited number of randomized trials, in part due to the fundamental difficulty of placebo control in dietary trials. Evidence also indicates that the diet can influence the gut microbiota and nutrient intake. Fermentable carbohydrate restriction in people with IBS is promising, but the effects on gastrointestinal health require further investigation