Flavor Retention During Drying

Abstract

The influence of spray dryer operating conditions (drying temperatures, extract solids content, nozzle orifice size, and in- feed spray pressure) and of variations in the proportions of individual skin~- milk components in the extract to be dried, upon flavor retention during drying, was investigated. The influence of those variables upon flavor retention was evalu- ated by adding either acetoin, acetone, or diacetyl to skimmilk (10 to 50% total solids), drying the skimmilk plus the added flavor under the desired operating condi- tions, and then colorimetrically analyzing the skimmilk powder for residual amounts of the added flavor compound. Total solids content of the infeed skim- milk was found to be the major factor influencing the amount of added flavor retained during drying. Diacetyl reten- tion was found to be independent of the particle size of the skimmilk powders. The highes:t exit air temperatures (about 100 C) and lowest inlet air temperatures (about 160 C) used in this study were found to result in optimum retention of added flavors. Milk protein extracts retained diacetyl better during drying than lactose solutions of equivalent concentration (48% versus 34% retention). This occurrence may be partially caused by a snbstantial reduction in the vapor pressure of diacetyl upon addi- tion of milk protein to a diacetyl-water solution. Addition of lactose to a diacetyl- water solution increased the vapor pressure of the diacetyl. The drying of food extracts is generally accompanied by large losses of volatile flavors. For example, Sivetz and )~oote (11) have re- ported that a spray-dried coffee retains only about 10% of the aromas which were present in the brewed coffee. Extract concentration has