Resfriamento a vacuo de alfaces hidroponicas (Lactuca sativa L.) cv. Salad bowl : avaliação do processo e da vida pos-colheita. / Vacuum cooling of the alfaces hydroponics lettuces (Lactuca sativa L.) cv. Salad bowl: process evaluation and of the life postharvest time.

AUTOR(ES)
DATA DE PUBLICAÇÃO

2005

RESUMO

The principle of vacuum cooling process is based on the evaporation of water. The water evaporation occurs under low pressure and the boiling point temperature of water is lowered. Refrigeration systems are used for the condensation of the water vapor. For the condensation of water vapor, the adsorption appears as a good technological alternative. The vacuum cooling presents some advantages over other cooling techniques: cooling time and uniformity of the final temperature. In this work, a vacuum cooling system was made and the hydroponics lettuces (Lactuca sativa L.), Mimosa group, cv. Salad Bowl, were vacuum cooled. By experimental design, the influence of pumping rate of flow, mass lettuce and postharvest time (before vacuum cooling) on the mass loss, shelf life, operation time and energy consumption were investigated. The lettuces had been storage in cooling room with average temperature of 1oC. Before the storage, different periods of time between the harvest and the cooling were adopted. The determination of the shelf life was made through sensorial evaluation of the lettuces. The degree-hour (DH) was calculated and models were adjusted to relate the DH with the shelf life. In the characterization of the silica-gel, both equations showed good agreement with experimental data, the coefficients of regression (R2) were 0.991 on the Dubinin-Astakhov equation and 0.993 on the Freundlich equation. The mass lettuce and the pumping rate of flow had significant influence (p <0.05) on the operation time, the energy consumption and the lettuce mass loss. The operation time ranged from 16.9 to 79 minutes, the energy consumption changed from 0.59 to 1.52 kWh, the mass loss varied from 3.01% to 5.44% and the shelf life from 19 to 23 days. The degree-hour model that showed good agreement with the experimental data had a regression coefficient (R2) 0.957 and calculated F 360.5 (p <0,05).

ASSUNTO(S)

lettuce cooling adsorção adsorption resfriamento alface

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