RESUMO Para facilitar os ensaios de atmosfera controlada em laboratórios que estudam condições experimentais de armazenagem de frutas e hortaliças, desenvolveu-se o fluxcentro portátil de restrições, que agrega facilidade de confecção, baixo custo e economia no uso de gases. Sua funcionalidade é propiciada pelos distribuidores e misturadores de gases. Cada componente gasoso proveniente de um cilindro de gás através de uma válvula diferencial de controle da pressão é regulado, geralmente a 6 kPa, e forçado através de 13 restrições padronizadas acopladas a cada saída do distribuidor. A seguir, em 13 misturadores afixados na base, formam-se as atmosferas controladas com 1, 2 ou 3 componentes, que são conduzidas por tubo flexível a minicâmaras de armazenamento, que servem também para estudos de consumo e produção metabólica de componentes gasosos. As restrições para aplicar os mencionados fluxos especificados de componentes gasosos foram produzidas a partir de tubos capilares de vidro para exame de micro-hematócrito, pelo método da moldagem a quente sob fluxo continuado. O fluxcentro portátil é um equipamento simples e de baixo custo, que possibilita a preparação de atmosferas controladas em sistema aberto de composição e fluxos estáveis, de maneira similar aos tradicionais fluxcentro de controle com escape de gás através de barostatos.

ABSTRACT A portable flow board system was developed in the present study with the aim to facilitate lab-scale experiments of controlled atmosphere (CA) with fruits and vegetables. This sturdy flow board combines ease fabrication, low cost and gas economy. Its functionality is provided by manifolds and gas mixers. Each gaseous component is supplied by a gas cylinder through a differential valve of adjusted pressure control, generally at 6 kPa, and forced through 13 standardized restrictors coupled to each manifold output. Controlled atmospheres are then formed with one, two or three gases in 13 gas mixers affixed to the flow board base, which are further conducted through flexible tubes to storage mini-chambers that can also be used to study metabolic consumption and production of gaseous components. The restrictors used in the flow gaseous components were manufactured from microhematocrit test-type capillary glass tubes following the hot forming method under continuous air flow. The portable flow board showed to be low cost and simple post-harvest equipment that allows preparing controlled atmospheres in open systems with stable composition and flow, in a manner similar to traditional flow boards with control of gas escape by barostats.

Hydration indexes are practical variables for quantifying plant water stress and can be useful for agronomic purposes. Three adapted hydration indexes based on relative water content, volumetric hydration, and leaf turgor pressure were evaluated in kale (Brassica oleracea var. acephala) leaf segments. Relative water content and volumetric hydration were measured in leaf segments after a water infiltration procedure with the aim of filling its large intercellular volumes (@18%v/v). The infiltration was done using a hydrostatic weighing procedure and with the aid of vacuum to fully hydrate the leaf segments. These two relative indexes were proportional to the transpiration-induced leaf water loss. The third index, turgor pressure, was measured with a Wiltmeter® instrument. Similarly, the turgor pressure was proportional to the leaf water loss, and it decreased from @310kPa in recently harvested leaves to zero in dehydrated leaves, after a total water loss of @23%. Turgor pressure was correlated with the other two hydration indexes using approximations of leaf volumetric elastic modules. Similar estimates were obtained because the decline between turgor pressure and the natural logarithm of these relative leaf hydration indexes was numerically similar (@900kPa). However, the volumetric hydration index seemed to be more suitable as a model, not only for being more concise but also because it showed a clearer biomechanical representation of the leaf water deficit effects.

Obtiveram-se estimativas da altura máxima tolerável em embalagens para frutas e hortaliças usando métodos para medir a firmeza dependente do turgor em produtos hortícolas. As medidas de firmeza foram realizadas na região equatorial dos produtos. Estabeleceu-se em 5% a superfície da base da caixa em contato com a superfície amassada dos órgãos vegetais como o limite máximo de deformação do produto que não causa perda para a aceitabilidade comercial. Para o cálculo da altura da pilha que causa esta deformação, considerou-se o peso do produto e as acelerações de impacto observadas durante o transporte. A altura, associada a outras características serão utilizadas para o dimensionamento de uma família de tipos de caixas, para o transporte e armazenamento paletizado de frutas e hortaliças no Brasil. A técnica de aplanação e o firmômetro geraram resultados próximos para tomate, batata, cebola, cenoura, chuchu, pimentão, inhame, jiló, batata-baroa, rabanete, laranja, maçã, limão, pera, uva para mesa, mamão, goiaba, ameixa e nectarina. Devido aoa princípio de funcionamento, apenas o firmômetro foi capaz de avaliar a firmeza de produtos com superfície pouco regular, como abobrinha, maxixe, kiwi, pepino, vagem e quiabo.

An estimate was made of the maximum tolerable height for piling boxes of fruit and horticultural products using ways of measuring the firmmess of the turgor of horticultural products. The flattening method and the firmometer generated similar results for tomato, potato, onion, carrot, chayote, bell pepper, yam, gilo, Peruvian carrot, radish, orange, apple, lemon, pear, grape, papaya, guava, plum and nectarine. Only the firmometer was able to measure the firmness of zucchini, kiwi, gherkin, cucumber, okra and green beans, because of the less regular surface. Firmness was measured in the equatorial part of these organs. It was assumed that 5% of the box base in contact with the flattened surface of the studied organs was the highest tolerated compression allowable during commercial use. To estimate the pile height that causes this deformation, the product weight and the usual impact acceleration, encountered during the transportation, were considered. This information along with specific product characteristics are being used to dimension a new box family, for palletized transport and commercialization of fruits and vegetables in Brazil.