Cinthya Bertoldo

Efeito do processo de desidratação osmótica a pulso de vácuo na transferência de massa e nas propriedades reológicas e de cor de fatias de manga

O presente trabalho teve como objetivo estudar as propriedades reologicas, de cor e a cinetica do processo de desidratacao osmotica, a pulso de vacuo, de fatias de manga. As fatias de manga foram imersas em solucoes hipertonicas de sacarose, nas concentracoes de 45, 55 e 65 oBrix com temperatura controlada (20 e 30 oC). No inicio do processo, aplicou-se ou nao um pulso de vacuo, utilizando as pressoes de 50 e 100 mbar por 10 minutos. As frutas foram desidratadas por 5 horas, sendo avaliadas em diferentes tempos em relacao a perda de peso, perda de agua, ganho de solidos, aw, cor e propriedades reologicas (tensao e deformacao na ruptura). O aumento da concentracao e da temperatura da solucao causou um aumento na perda de peso e de agua enquanto que a incorporacao de solutos foi favorecida em baixas concentracoes e altas temperaturas e com a aplicacao do pulso de vacuo. O amaciamento do produto, caracterizado pela diminuicao da tensao maxima de ruptura, e o aumento da deformacao na ruptura da amostra ocorreram nas condicoes de maior incorporacao de solutos. Nao houve alteracao dos parâmetros de cor das mangas durante o processo de desidratacao.

Moisture-related adjustment factor to obtain a reference ultrasonic velocity in structural lumber of plantation hardwood

ABSTRACT Wave propagation techniques based on ultrasound for timber grading are influenced by the moisture content (MC) of wood. The ultrasound velocities at an equilibrium MC (V12) and above saturation point (Vsat) were used to calculate moisture-related adjustment factors (kH). Tests were conducted using plantation hardwoods (Corymbia citriodora, Eucalyptus grandis and Eucalyptus pellita) grown in Brazil. Below the fiber saturation point (FSP), kH values were between 0.66% and 0.83%, which concurred with intervals proposed in existing literature for softwoods. However, the kH inferred from the velocities obtained at MCs above the FSP increased (from 10% to 30%) with increasing density. The sound velocity under saturated conditions (Vsat) obtained by adjustment equations was 2–9% lower than the actual Vsat obtained from the tests. The obtained adjustment factors may be useful for the standardization of nondestructive timber grading based on ultrasound propagation.

Influence of Measurement Position, Tree Diameter, and Bulk Wood Density on Models that Predict Wave Propagation Velocity in Logs According to the Velocity in Trees

Abstract The propagation velocity of ultrasonic waves from measurements in trees is numerically different from the velocity obtained from measurements in logs, even in freshly felled logs, and the ...

Aplicações do método de ensaio esclerométrico em peças de eucalipto saligna sm

In this paper the trend of correlations between compressive strength parallel and perpendicular to fibers is studied, obtained by standard destructive tests, and parameters of the esclerometer tests. For purposes of comparison with other non-destructive ultrasound tests were also carried out. Three series of specimens were taken from a log of Eucalyptus saligna and tested in wood saturated condition. Results of the esclerometer impacts for the three directions evaluated (parallel to fiber, radial and tangential) coefficients of variation less than 9% were observed. From the analysis of trend of correlations of compressive strength with the results of esclerometer and ultrasound, better adjustments for the direction parallel to the fibers were observed. Considering the results, it can be concluded that the esclerometer technique was able to identify the homogeneity of the batch tested, justifying to have possibilities of applications to the timber.