Jewe Schröder

Effects Of Spray Drying On Physical Properties, Total Phenolic Content And Antioxidant Activity Of Carob Molasses

Abstract In the present study carob molasses (pekmez) was spray dried to obtain a powder with desired improved handling properties. Maltodextrin with dextrose equivalent (DE) values of 8.6, 15.3 and 18.6 was used as a drying agent. Different molasses to maltodextrin ratios (25:75, 50:50), and dryer air inlet temperatures (160 °C, 210 °C) were additional parameters. The spray dried powders were analyzed for glass transition temperature, moisture content, water activity, wetting behavior, particle size, color, total phenolic content and antioxidant activity. The expected increasing effect of decreasing DE value on the glass transition temperature was obscured by different moisture contents. The glass transition temperature was mainly lowered by increasing the pekmez to maltodextrin ratio but also by increasing the air inlet temperature resulting in increasing moisture content. Wetting behavior was strongly influenced by the DE value. Total phenolic content was reduced in general by about 10 % and antioxidant activity changed by about 20 % independent from the investigated parameters. It can be concluded that spray drying of pekmez with addition of maltodextrin is a suitable method to improve and adjust handling properties of pekmez without loss of its nutritional value.

Investigation on the Usage of Effervescent Atomization for Spraying and Spray Drying of Rheological Complex Food Liquids and on the Resulting Particle and Product Properties

The effervescent atomizer is an internal mixing pneumatic atomizer in which a two-phase flow prior to the nozzle orifice is created by adding gas in a mixing chamber. The resulting flow pattern is responsible for atomization of the liquid feed. In this study, two different single-phase and two multiphase model feeds were employed. Research was focused on the influence of the flow pattern inside the atomizer and the air-to-liquid ratio by mass (ALR) on the spray performance. The flow pattern inside the mixing chamber of the atomizer was recorded by high-speed cameras, while the one inside the nozzle orifice was determined by an optical sensor. Plug and annular flow was found in the mixing chamber, while a bubbly flow—reported for low viscous liquid feeds in literature—could not be formed due to the feed viscosity investigated in this study. The spray morphology investigations (shadowgraphy imaging and time-resolved spray drop size measurement) showed a clear connection of flow pattern and spray fluctuations. The latter are found for plug flow and have to be avoided for spray drying applications. Annular flow was found to be suitable for fine and stable spray characteristics and consequently atomizer geometry and ALR conditions for annular flow were determined. Moreover, the models of Lund and Geckler [J Fluids Eng 130:61303, 2008, Atomization Sprays, 3:77–89, 1993] were used to predict spray drop sizes. The comparison of these values to measured data gave additional insight in the spray mechanism. To investigate the influence of the atomization process on an inner phase of a multiphase feed, oil-in-water-emulsions were atomized and changes in the oil drop size were determined. Oil drop breakup and coalescence was found and could be described by classical emulsification theory. Finally, the investigated effervescent atomizers were used for spray drying experiments with single-phase feeds. The particle characteristics of the dried products were determined and showed a good agreement with the literature.