Kinetics of the pulsed vacuum osmotic dehydration of green fig (Ficus carica L.)

Abstract

The fig (Ficus carica L.) is a fruit native to the Mediterranean region. However, it has spread worldwide. Osmotic dehydration is used to reduce the moisture content in food, preserving its main characteristics. This study aimed to obtain the kinetics of the water loss, solid gain and water activity of green figs that were cut transversely and osmotically dehydrated in different sucrose solutions (40, 50 and 60 °Brix). The osmotic dehydration occurred at 40 °C, with a vacuum pulse of 74 mmHg in the first 5 min of the process in a total time of 240 min. The ratio of sample:solution was kept constant at 1:10 (weight/weight). Periodically, the samples were weighed to calculate the kinetics of water loss, solid gain, and water activity. The increase in the concentration of the sucrose solution from 40 to 60 °Brix promoted a percentage increase of water loss from 8.14 ± 0.80 to 12.80 ± 0.50%, of solid gain (0.89 ± 0.31 to 1.42 ± 0.70%), and the reduction of water activity (0.93 ± 0.02 to 0.91 ± 0.01). The mathematical models of Peleg and Azuara were tested for fitting the kinetics of water loss and solid gain. Both the mathematical models of Peleg and Azuara presented good fitness to the experimental data. However, the latter was more adequate (higher r2 and lower error), with predicted equilibrium conditions closer to the experimental values.