Spray Drying: Retention of Volatile Compounds Revisited

Retention or loss of trace volatile compounds during spray drying can be vital for product quality. Examples of cases where loss or retentions of volatile substances are important include retention of balanced flavor and aroma in food products, removal of odiferous substances, and control of the release of volatile organic compounds to the atmosphere. Factors and mechanisms determining losses of these substances are reviewed. Losses can occur during atomization, from undisturbed drops and as a result of morphological development. On the basis of this insight, several avenues for controlling the retention of volatile substances are identified and analyzed. These include control of atomizer pressure or rotation speed, choice of spray angle, configuration of air input, lteration of the air temperature profile, feed concentration, the presence of an oil phase and/or suspended solids, foaming of the feed, feed composition, and steam blanketing of the atomizer.

The quality of a spray-dried product can be strongly affected by the presence or absence of volatile compounds that were present in the feed to the spray dryer. For example, spray-dried coffee and tea have suffered from a air and thereby avoid bubble formation, expansion and bursting for deaerated feeds (20). This approach produces a product with high bulk density. If that result is cceptable, then it should also be a way of precluding volatiles loss due to morphological development.