The effects of glass transition and stickiness on the direct spray drying of reconstituted skim milk (RSM) fermented with Lactobacillus rhamnosus GG (LGG) were investigated. The fermented RSM did not spray dry properly due to severe wall depositions; however, it dried well (comparable to the control; RSM with resuspended LGG cells) when skim milk powder (SMP) was added. Adding SMP significantly increased the glass transition and sticky point temperatures of spray-dried powder, ranging from 18.2 to 72.4 °C and 34.5 to 78.5 °C, respectively, in a water activity range of 0-0.33. By adding SMP, droplets quickly shifted from a sticky plastic to a non-sticky glassy state during drying, resulting in reduced wall deposition. Although this spray-dried powder exhibited relatively high moisture sorption and lactose crystallization, the correlations between glass transition, stickiness, and moisture sorption suggested that its storage stability at 25 °C may be on par with the control powder.
Keywords: Glass transition; Lactobacillus rhamnosus GG; Reconstituted skim milk; Spray drying; Stickiness.
© The Korean Society of Food Science and Technology 2024. Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.