Evaluating spray drying for probiotic preparation
Certain scientific and technological obstacles influencing the performance of functional foods caused by the interactions between probiotics and prebiotics needed to be overcome in order to better understand their significance. In order to achieve this, one of the main goals was to carefully examine the effect that processing has on the performance of probiotic and prebiotic functionality. Therefore, the applicability of spray-drying in the production of skim milk-based preparations containing probiotic bacteria was evaluated. Certain prebiotic substances were taken into account so that their protection capability could be assessed and the possibility of generating synbiotic powder products could be examined. At first, the thermal tolerance, an indicator of probiotic survival during spray-drying, of three strains of probiotic lactobacilli were compared. As such, it was found that thermal tolerance was not a sufficient predictor of performance during spray-drying. Furthermore, other phenomena like dehydration can affect cell viability during drying. In the cases where reconstituted skim milk was employed as spray-drying carrier, a microbial survival rate of 60% to 80% was achieved at an outlet temperature of 80°C. What this means is that probiotic powders contain high numbers of microorganisms caused by stationary phase cultures. Furthermore, it was shown that integrating commercial prebiotic substances or polydextrose in the skim milk powder did not cause any harmful effect on bacterial survival upon spray-drying. Spray-drying was also qualified in terms of glass transition temperatures in order to assess the contribution of glassy state on the containment of bacterial endurance during storage.
