Study of physical and chemical properties of spray drying whey powder

Background Making powder from whey is one of themost challenging parts of whey processing. The presentstudy investigates the performance of a spray dryer for thepreparation of whey powder. Its main objective is to categorizeunknown samples using analysis of discriminationfunction between the operating variables and powderproperties in two or more naturally occurring groups. Inthis work, spray drying was performed in a pilot-scale cocurrentspray dryer. The amount of solid content, inlet, andoutlet air temperature was chosen as independent variables.The titratable acidity, PH, EC, TDS, analytical elements,particle size diameter, ingredients, and morphology werethe response variables that quantify the powder quality.Results The PH of whey powder with 15 % solid contentwas lower than the PH of whey powder with 30 % solidcontent. Furthermore, the PH of the whey dried at inlet(outlet) air temperature of 180 C (106 C) was lower thanthe whey dried at 145 C (87 C). Substances with higheracidity had higher electrical conductivity (EC) as well. Themean particle diameters of the powders produced by pilotplantspray dryer were in the range of 11.26–18.23 lm.SEM picture showed that in pilot-plant spray dryer, therewere a few shallow holes on the particle surfaces as well asa few wizened particles.Conclusions It was observed that in the materials withhigher acidity, the EC was high and the PH was low. Moresolid content caused higher viscosities in the feed, whichincreased the droplet size and consequently, the particlesize. By increasing the temperature and heating duration,the amount of PH reduced and the diameter of the particlesincreased. Moreover, by increasing the percentage of thesolid content, the PH increased, while the solid mass carriedaway by the outlet air decreased. Small particlessprayed by the two-fluid nozzles, led to less amount ofTDS. From the morphological point of view, as theindustrial samples were exposed to heat longer as comparedto pilot-plant samples, they produced spherical andsmoother particles.