FUNCTIONAL, RHEOLOGICAL AND MICROSTRUCTURAL PROPERTIES OF FREEZE-DRIED YOGHURT POWDER
Articles > Article · 2022
Authors: Pınar BALKIR
Gıda, International, 2022, vol 47, pp 457-467
Summary
In this study, functional, rheological, and microstructural properties of freeze-dried yoghurt powder produced at -49°C and 0.0035 mBar conditions from pre-concentrated non-fat yoghurt were investigated. The sample showed good reconstitutional properties with 204 s, 192 s for wettability and dispersibility respectively and 74% for solubility index. Bulk density value was lower, as 285.71 kg/m3, which may be due to the deformation of casein micelles by freeze drying. The water activity of the yoghurt powder sample was 0.1125, much lower than the critical water activity value. The colour of the original yoghurt, yoghurt powder and reconstituted yoghurt were almost white. Reconstituted yoghurt showed better flow behaviour and consistency when compared to original yoghurt. Loss of soluble dry matter in pre-concentration of original yoghurt may have resulted in high hygroscopic powder. The microscopic imaging of original and reconstituted yoghurt demonstrated homogeneous structures for both, however the latter showed a coarser gel network.