Kinetics and Quality Aspects of Canadian Blueberries and Cranberries Dried by Osmo-Convective Method

Abstract

Blueberries and cranberries were dried using a hybrid technology consisting of pretreatment, osmotic dehydration, and convective drying. The performance of this hybrid technology was evaluated in terms of quality attributes such as color, taste, rehydration ratio, water activity, as well as sugar and anthocyanins content. Of thirteen different pretreatment methods tested for cranberries, cutting the berries in halves was the simplest and the best one. No pretreatment was needed for blueberries. Osmotic dehydration was performed in batch and continuous modes using sugar solution of 67.5–70°Brix. Convective drying was then carried out in a fluidized bed, a pulsed fluidized bed, or a vibrated fluidized bed. Quality profiles for both berries were determined after each step of such a hybrid technology and compared with quality of berries dried in the vibrated fluidized bed and freeze dryer. Recommendations for full-scale processing are given.

Keywords:

• Fluidized bed
• Hybrid technology
• Osmotic dehydration
• Pretreatment
• Pulsed fluidized bed
• Small fruits
• Vibrated fluidized bed

ACKNOWLEDGMENT

The assistance of Mr. Francois Brunet in HPLC anthocyanins content measurements and Mr. Marcel Tanguay in VFB drying tests is highly appreciated. This study was supported by the Program of Energy Research and Development (PERD) in Ottawa.

Notes

^∗Ten holes (1 mm diameter) per berry.

^∗∗Chemical and thermal treatments.