The objective of this work was to study the effect of osmotic drying, using different hypertonic solutions (sucrose and sodium chloride), on physicochemical characteristics of pansies (Viola Ö wittrockiana). The same treatments were applied to lettuce to compare the behavior of flowers with other vegetables. Pansies’ superhydrophobic surface structure, called papillae, increased the resistance to exchanges with hypertonic solutions. No weight loss was observed after most treatments (sucrose: between 2.2 and 6.8 %; NaCl: between -23.0 % and 1.5 %), aw maintained high values (> 0,94) and monomeric anthocyanins were preserved (fresh 0.10 and 0.19 mg Cy-3glu/g fresh matter for 20%/1 h in NaCl and 60%/1 h in sucrose). When applying more drastic conditions, as sodium chloride for more than 1 hour, undesirable textural and color changes were observed. For lettuce, all treatments caused osmotic dehydration, weight loss (ranged between -9.3 to -30.3 % for 80%/1 h in sucrose and 15%/1 h in NaCl) and a reduction in aw (< 0,97) and carotenoids, with sodium chloride causing more damage in visual appearance than sucrose. Therefore, immersion in osmotic solutions can be applied to lettuce but the desired effect was not achieved for pansies due to the morphological structure of the flowers’ epidermis.

Osmotic dehydration of chestnut slices in sucrose was optimized for the first time by Response Surface Methodology (RSM). Experiments were planned according to a three-factor central composite design (α=1.68), studying the influence of sucrose concentration, temperature and time, on the following parameters: volume ratio, water activity, color variation, weight reduction, solids gain, water loss and normalized moisture content, as well as total moisture, ash and fat contents. The experimental data was adequately fitted into second-order polynomial models with coefficients of determination (R2 ) from 0.716 to 0.976, adjusted-R2 values from 0.460 to 0.954, and non-significant lacks of fit. The optimal osmotic dehydration process conditions for maximum water loss and minimum solids gain and color variation were determined by the “Response Optimizer” option: 83% sucrose concentration, 20 °C and 9.2 hours. Thus, the best operational conditions corresponded to high sugar concentration and low temperature, improving energy saving and decreasing the process costs.