Drought is one of the main factors affecting the productivity of agricultural crops, and plants respond to such stress by activating various physiological and biochemical mechanisms against dehydration. The present study investigated two varieties of sugarcane (Saccharum spp.) with contrasting responses to drought (RB867515, more tolerant; and RB855536, less tolerant) and subjected them to progressive drought conditions (2, 4, 6 and 8 days) followed by rehydration. Drought caused a decrease in water potential (ψw) and osmotic potential (ψos) in the leaves, which recovered to normal levels after rehydration only up to the fourth day of drought. Water stress changed the carbon metabolism of leaves by reducing starch and sucrose contents and increasing glucose and fructose contents in both varieties. Water deficit caused a significant reduction in the maximum quantum efficiency of photosystem II (Fv/Fm) and effective quantum yield (ΦPSII) in both varieties; however, RB867515 recovered faster after rehydration. Under water stress, the more tolerant variety RB867515 exhibited increased activity of the antioxidant enzymes catalase, ascorbate peroxidase and superoxide dismutase compared with the RB855536 variety. The results suggest that RB867515 is more tolerant to drought conditions because of a more efficient antioxidant system, which results in reduced photosynthesis photoinhibition during water stress, thus revealing itself as a potential physiological marker for drought tolerance studies.

Drought is one of the major climatic factors that reduce crop yields in cultivated areas around the world, and studies on physiological responses may help in the selection of drought tolerant genotypes. Thus, this work aimed to correlate gas exchange, photosynthetic efficiency, carbon isotope discrimination (Δ13C) and antioxidant activity in sugarcane varieties submitted to water stress under field conditions. Six sugarcane varieties were submitted to drought stress in three development stages: tillering, intense growth and ripening. In all varieties, the photosynthetic apparatus was severely affected by drought, with a reduction in photosynthetic rate and chlorophyll content. During the tillering stage, reductions in gas exchange and increase in Δ13C and bundle sheath leakiness (φ) were observed. In the intense growth stage, water stress caused increases in leaf temperature, intrinsic water use efficiency, antioxidant enzyme activity and lipid peroxidation, and reductions in stomatal conductance and transpiration in the RB72454, RB855113 and RB855536 varieties. However, the RB92579 variety maintained a better physiological homeostasis at all development stages and presented higher stalks yielding when submitted to drought. This work suggests that screen sugarcane genotype to drought stress should be performed during the intense growth stage, when plants are more sensitive to drought conditions.

No abstract

ÁGUA DE COCO: ASPECTOS NUTRICIONAIS, MICROBIOLÓGICOS E DE CONSERVAÇÃORESUMO: Este artigo é uma revisão que apresenta aspectos importantes sobre água de coco: composição química, aspectos nutricionais, microbiológicos e processos de conservação. Para industrialização e comercialização da água do coco como produto de conveniência, existe a necessidade de aplicação de processos que garantam a estabilidade microbiológica do produto, aumentado sua vida útil e a segurança alimentar. Existem diferentes formas de extrair, conservar e embalar a água de coco. Pode-se fazer uso de tratamento térmico a médias e altas temperaturas, refrigeração ou congelamento. A água no interior do fruto é estéril, no entanto, no momento da abertura, dependendo das condições higiênicas dos utensílios utilizados para abrir o coco, estes podem incorporar microrganismos ao conteúdo interno. Devido às características do produto, à presença de contaminantes e ao aumento no consumo da água do coco no país, é necessário um maior rigor na produção, comercialização e distribuição deste produto.

Eggs and their products have been implicated in food-borne disease outbreaks due to contamination with Salmonella Enteritidis. Irradiation, as a food preservation technology, could minimize such contamination. The aim of this study was to determine the effects of irradiation in powdered egg yolk, egg white, and whole egg samples spiked with Salmonella Enteritidis. The powdered egg samples were exposed to doses of 0.5, 1.0, 1.0, 2.0, 2.5, 3.0, 3.5, or 4.0 kGy irradiation. Odors and tastes of raw and cooked non-inoculated, irradiated samples, and non-irradiated samples, were analyzed by a trained panel. A dose of 2.0 kGy resulted in slight to moderate changes in powdered egg yolk samples, compared to non-irradiated controls, while minimal differences were observed in powdered egg white samples. The dose of 3.5 kGy, when applied to samples of powdered egg white, resulted in taste and odor slightly stronger than the non-irradiated control. The maximum irradiation threshold before changes in flavor and odor occurred was 2.28 kGy, for powdered yolk and whole eggs, and 2.58 kGy, for powdered egg white. Those thresholds were enough to reduce S. Enteritidis to safe levels.Index terms: Bacteria; elimination; powder food. RESUMOOs ovos e os seus produtos derivados têm sido implicados em doenças de origem alimentar devido à contaminação com Salmonella Enteritidis. A irradiação é um método tecnológico de preservação de alimentos que pode minimizar esse tipo de contaminação. O objetivo do presente estudo foi determinar os efeitos da irradiação nas amostras de gema de ovo em pó, clara de ovo em pó e ovo integral em pó contaminadas artificialmente com Salmonella Enteritidis. As amostras de ovo em pó foram expostas a doses de 0,5, 1,0, 1,5, 2,0, 2,5, 3,0, 3,5 ou 4,0 kGy de irradiação. As amostras não contaminadas irradiadas e não irradiadas foram avaliadas por um painel de especialistas que avaliaram odor e sabor cru e cozido não inoculados, amostras irradiadas e não irradiadas. A dose de 2,0 kGy resultou em alterações leves a moderadas nas amostras de gema de ovo em pó em comparação aos controles não-irradiados, enquanto diferenças mínimas foram observados em amostras de ovo em pó. A dose de 3,5 kGy quando aplicada às amostras de clara de ovo em pó resultou em sabor e odor mais fortes do que no controle não irradiado. O limite máximo da dose de radiação sem causar alteração significativa no sabor e odor foi 2,28 kGy para gema em pó e ovos inteiros e 2,58 kGy para clara em pó e suficiente para reduzir S. Enteritidis para níveis seguros.Termos para indexação: Bactéria; eliminação; alimento em pó.