Eureka! Institutional Repository

In the present thesis, the spray drying of the acidic dairy product - kefir was studied in a laboratory dryer with an inlet temperature of 140 oC, an outlet temperature of 90 oC and using different encapsulation media such as trehalose, fructooligosaccharides (FOS), whey proteins, arabic gum, carrageenan and maltodextrin. In particular, the study focused on the parameters affecting the quality characteristics of the final product in combination with the different encapsulation media. Regarding the parameters, the moisture content appeared lower in the samples with the addition of gum arabic, with the percentage of moisture across the different samples ranging from 2.6% to 5.7%. The acidity measurements showed naturally reduced values ranging from 0.71% to 0.93%, in contrast to solubility, where in the majority of samples the soluble part was higher, with the samples with the addition of maltodextrin being a typical example. Furthermore, the results when measuring hygroscopicity had similar characteristics, since the moisture adsorption had an increasing trend compared to the increase in relative humidity of the environment. Regarding the density and colour measurements, the findings showed that the samples exhibited a similar behavior for bulk/tapped density and whiteness index respectively. The microbiological measurements for the viability of probiotics, lactic bacteria, lactococci and yeasts were not fully successful, as despite continuous efforts, only the presence of lactococci in the kefir powder samples was confirmed. Finally, the maximum particle size was 10 μm with a range from ~2 μm to ~50 μm and the shape was spherical, which is a typical characteristic of materials subjected to spray drying.