Preparation of Potato Granules Powder by Superheated Steam Drying Combined with Hot Air Drying

Potato granule powder was prepared by superheated steam drying and hot air drying. The starch ripening and partial dehydration were completed by superheated steam drying in the front section(moisture content 50%~78%)and hot air drying at 65℃ in the back section(moisture content 7%~50%). In the superheated steam drying experiment,the superheated steam temperature,steam velocity and potato chip thickness were selected as the experimental factors,and three-dimensional quadratic regression orthogonal combination experiment was designed to study the effects of superheated steam temperature,steam velocity and slice thickness on the drying characteristics of potato superheated steam and subsequent hot air drying characteristics,as well as the relationship between the bulk density and hydration capacity of potato powder and the drying parameters of superheated steam drying stage. Results showed that,superheated steam drying rate increased with the increasing of steam temperature and velocity while it decreased with the increase of slice thickness;Differences of hot air drying character among all potato chips pre-dried with superheated steam were not significant,but compared with conventional operating,the total drying time of the combined drying method in this study was shortened remarkably;Mathematic models between potato granule bulk density,water holding capacity and superheated steam drying parameters were significant,and their decision coefficients R² were 0.820 and 0.662,respectively;Relative errors between verification experiment values and calculated values from models of bulk density and water holding capacity were 19.93% and 29.07%. Study results indicated that,combined drying method provided in this paper could reduce operating procedure and total drying time,and it had potential industrial application.