Drying and radial shrinkage characteristics and changes in color and shape of carrot tissues (<i>Daucus carota</i> L) during air drying

Abstract

Drying and radial shrinkage characteristics and changes in color and shape of carrots tissues during air drying were studied. Slices dimensions were obtained by computer vision and the color was quantified by chroma, hue, whitening index and total carotenoids contents. The drying time became shorter of 1 h when temperature increased from 60 to 80°C, but sample scorching was observed at 80°C. Blanching pretreatment accelerated the drying process as a result of tissue softening. Two empirical models fitted very well to drying data (R² ≥ 0.99525) and five among reported shrinkage models highly fitted to the data with R² ≥ 0.99752. A new simple model, the Nahimana et al. model gave excellent fit to shrinkage data (0.99525 ≤ R² ≤ 0.99981) and was then proposed as an additional shrinkage model. Blanched samples underwent higher radial shrinkage compared to non-blanched; the highest radial shrinkage was 63.49 ± 4.73%. The cortex tissue of fresh and dried carrot samples showed better color than the core due to its higher chroma and lower whitening index. Total carotenoids were also higher in cortex and ranged from 15.80 ± 0.02 to 2.27 ± 0.00 mg/100g sample. Samples’ color and main shape descriptors underwent significant changes during drying.

Key words: Carrot, drying, shrinkage, model, shape, color, carotenoid.