Towards more efficient intermittent drying of fruit: Insights from combined hygrothermal-quality modelling

• Intermittent drying leads to a reduced (net) residence time of the fruit in the dryer.
• Intermittent drying resulted in similar final fruit quality as continuous drying.
• Hygrothermal simulations are combined with kinetic fruit-quality modelling.
• Longer tempering times reduced residence time, due to the longer moisture relaxation.

Intermittent drying is a promising alternative to continuous drying, as it enables moisture redistribution during tempering periods, leading to higher effective drying rates when the process is started again. This strategy can effectively reduce the net residence time in the dryer, which can help save process energy and increase product throughput. The milder temperature conditions that occur during tempering can also be beneficial for fruit quality. Intermittent drying is analyzed, in a new way, by combining hygrothermal simulations of the drying process with a temperature-dependent kinetic model for fruit quality degradation during drying. This method enabled to quantify the total process time of the fruit, the effective residence time in the dryer but also product quality degradation. By means of a parametric study, we obtained new insights in the impact of tempering time, total cycle time for drying and the ambient humidity conditions during tempering. By intermittent drying, the residence time could be reduced successfully without compromising fruit quality.Industrial relevanceThe modelling strategy provides combined information on the water activity level in the fruit and the fruit quality state during drying. This enables, in a unique way, to optimize the drying process conditions for intermittent drying in order to achieve fast drying and still obtain prime product quality. Thereby a better identification of possible savings in energy and processing time is possible for intermittent drying as well as their relation to the final quality of the fruits.