Evaluation of product quality produced by vacuum drying compared with other drying methods.

Maltodextrin solutions involving minute amounts of acetone are dried by vacuum drying and by freeze drying. The higher the initial solids content of the feed, the higher is the retention of acetone in both methods.With the increase of initial solids content in freeze drying, freezing points of feed are lowered so that true freeze-drying is attained by using liquid nitrogen. (Above 50% T.S., feed is not frozen even at 233K.) As for quality, product made by freeze-drying is the most superior, followed by vacuum drying and practical spray-drying in turn.