Estimation of drying parameters in rotary dryers using differential evolution

Effects of dehydration methods on quality characteristics of yellow passion fruit co-products

BACKGROUND

The production and processing of fruits generate a large amount of residues, which are usually disposed of or under-used, representing losses of raw material and energy. The present paper investigates the effect of four dehydration techniques (convective, infrared, microwave and freeze-drying) on yellow passion fruit (Passiflora edulis f. flavicarpa) co-products and the influence of the main variables on moisture removal and bioactive compounds. The compounds analyzed were total phenolics, total flavonoids, ascorbic acid and pectin.

RESULTS

The content of phenolics and flavonoids increased after dehydration in all techniques investigated and the process temperatures directly affected the ascorbic acid content. Microwave dehydration showed the best results for most bioactive compounds analyzed, if performed in suitable process conditions. However, the highest levels of pectin content were obtained by freeze-drying and convective dehydration.

CONCLUSION

This study reinforces the importance of the adequate use of passion fruit co-products due to the high levels of bioactive compounds in this material. Microwave dehydration presented the best results, which indicates the potential use of this technique for a better exploitation of fruit co-products. Larger quantities of pectin were extracted from samples dehydrated through methodologies with long-time process and low temperatures, such as convective drying and freeze-drying. © 2017 Society of Chemical Industry.

Modeling the Total Residence Time in a Rotary Dryer

A mathematical model for the rotary dryer that determines the total residence time is developed. Experiments were performed in a laboratory-scale direct contact rotary dryer with the gas flowing concurrently with the solids. The model predictions depicted that the total residence time decreases with increasing the inclination of the rotary drum, the speed of rotation and the radius of rotary drum. The validation of the model was carried out experimentally for maize while varying the inclination of the rotary drum and the speed of rotation. The experimental results were observed to be in good agreement with the model predictions.