Drying is the process of reducing moisture, increasing shelf life, and potentially combating pathogens by using time and temperature. The drying process is also important for achieving the desired product characteristics and sensory combinations.

Historically, dehydration has been used on potato tubers in the form of cubes, in order to boost preservation and shelf life – something that is still applied today. When it comes to technology, the multiple-stage dryer has been the standard technology for hot air convection drying cut, non-pulp forms of a wide variety of vegetables. This equipment provides maximum process flexibility because the drying air temperature, velocity, and humidity are variable throughout the drying cycle. Multi-stage machines provide the best process control, are the easiest to clean, and allow for the greatest bed width, but at the same time have the largest footprint and the highest capital cost. With entry cost being a major consideration for a new processor, multiple-pass and single-stage arrangements are options, particularly for dedicated product and/or low-capacity lines.

A multi-stage, single-pass conveyor dryer can efficiently process potatoes for every application imaginable for drying, roasting, and dehydration. As the product moves through multiple temperature zones with individually controlled temperature, humidity, and airflow, the air is used to transfer heat and remove moisture.

A multi-stage dryer with transfer sections between stages will gently reorient the product during dehydration to provide a uniform drying process at each stage of processing. The multi-stage processing of the pre-formed product allows flexibility where extended cooling time is required for starch gelatinization. A multi-stage configuration provides the operating flexibility required to control process air, humidity, airflow rate, and retention time at different stages of processing for dehydro-frozen products where the focus is on flavor concentration and water removal.

Impingement processing ensures consistent color at high capacities by delivering uniform airflow across the entire conveyor during roasting and color development. High-velocity impingement air tubes transfer high heat quickly and uniformly across the conveyor bed, eliminating the oven edge effect. Impingement systems remove the boundary layer around the product by pinging at high speeds against the surfaces. When compared to lower velocity convection or air systems, this greatly accelerates heat transfer, reducing process time by at least 50%. Airflow and temperature from above and below the conveyor are precisely controlled by dual impingement systems. Single impingement systems only supply air from above the conveyor.

You can read the rest of this article in your complimentary e-copy of Issue 2 of Potato Business Dossier 2022, which you can access by clicking here.